The Bell Ringers

SWR: Does it matter?

2011-12-20T21:59:00.000-06:00

SWR and baluns were discussed during several of our recent morning QSOs. We combined personal experiences and many on-line references in order to better appreciate the topic.

Understanding SWR by Example by K5DVW is a must-read article. (You can skip the Smith Chart section.) The article illustrates how transmission line loss can easily be a greater issue than SWR when trying to transfer maximum power to the antenna.
VSWR Myths includes a similar set of examples and goes on to discuss various common myths.
The Easy Way is a wordy article that also makes the case for non-resonant antennas and tuners to operate across multiple HF bands. Four topics covered in separate sections of the article are: Antennas of non-resonant length, Line attenuation,the Transmatch, and the Balun.

A few online calculators enable you to estimate the losses due to SWR:

SWR Loss Calculator
Types of Coax Cable and Line Loss
Misunderstanding VSWR misleads - This article discusses some pitfalls of such calculators and provides a link to a more sophisticated calculator. Look for TWLLC on that page.

Many articles explore the use of baluns in all sorts of HF antennas:

Choosing the Correct Balun by W8JI provides guidelines for several antenna types. An area of particular interest in our group discussions is the multi-band dipole with balanced feeder. A table in this article includes recommended element and feed line dimensions. I found a second version of this article that has a copy of Table 1 with data for both 300-ohm and 450-ohm feeders.W8JI has lots of other content on his web site.
Baluns in Antenna Systems by VK1OD analyzes several balun usage scenarios and compares their modeled behaviors, with conclusions for each. Other references are provided. The author's home page has links to lots of content.
Baluns: What They Do and How They Do It by W7EL gives a detailed explanation, with sketches, of what issues a balun is intended to solve. The article includes the results of field experiments to support conclusions about balun use, but also with further questions. W7EL is the author of EZNEC software.

Finally, from G4NVH comes HF Balanced Transmitting Systems, a 75-page compilation of materials from various sources. See the table of contents and pick your favorite topics!

John

Visit to KB4LWT

2011-12-13T15:21:00.001-06:00

Here are photos from Gary N4OLN's visit to Larry KB4LWT. The outdoor photos show some views of Larry's loop antenna.

Hunter Bandit Linear Refurb by N4MYT

2011-12-12T09:44:00.001-06:00

Click here for a report from N4MYT about the power supply refurbishment of his Hunter Bandit linear amp.

2011-11-09T14:31:00.002-06:00

Here are photos from W4BBW taken at this summer's reenactment festivities at Ider, AL.

Contest Resources from W4EA

2011-11-08T12:56:00.000-06:00

During recent morning discussions of ham radio contests, Dan W4EA, an enthusiastic contest operator, shared some resources for our consideration. His emails provided web links to various contest calendars, operating tips, and logging software (i.e. N1MM). I've added these links as two new groups in our Bell Ringers Links page. You'll see them in the third row of the matrix there.

Thanks, Dan!

Six Meter Beacon at NØSAP

2011-11-08T11:49:00.001-06:00

Here is the announcement from NØSAP about his new beacon:

As of Saturday, November 5th, 2011 I have a new Six Meter Beacon on the air. The frequency is 50.063.5 running 8 watts to a J-Pole with a Alinco DX-70. I think this is the only six meter beacon in the State of Missouri. Any reports will be appreciated. "SAP" NØSAP

There is a posting on QRZ.com with many comments.

Pioneers award to TPARCA in 1995

2011-10-12T10:42:00.000-05:00

Here is a bit of TPARCA history from 1995.

KE4ID's article in October CQ magazine

2011-10-12T10:39:00.001-05:00

Jack's article about restoration of a National NC-81X has been published in the October 2011 issue of CQ Magazine. Congratulations, Jack!

Huntsville Hamfest 2011

2011-08-22T06:19:00.002-05:00

Here are two photos from our traditional gathering at noon on Saturday at the Huntsville Hamfest. Thanks to N4OLN for the photos! Click on the photos for an expanded view. A captioned copy of the first photo is posted at the group photos page.

VoIP Phone Patch

2011-07-13T21:01:00.004-05:00

Below is a drawing of the VoIP phone patch configuration that I have been using for a few months. Click on the image for a full-sized view.

I'm using the phone patch audio input & output jacks of the transceiver. Modern transceivers should work in a similar manner with their line audio input & output jacks. A RIGblaster Pro forms the interface between transceiver and the PC sound card. Many other forms of audio interface can serve the same function.

The vintage SoundBlaster sound card has 4 audio jacks: line in, line out, speakers, and microphone. The line in and line out jacks connect to their corresponding jacks on the RIGblaster. My headset microphone connects to the microphone jack. I've been using the convenient headphone jack on the RIGblaster with my headset earphone(s), but I need to try the sound card speaker jack to see if its performance is any different. This setup provides ample audio levels, except for the audio from the distant phone to my earphones.

The Windows-based audio mixer associated with the sound card provides the ability to combine and adjust the level of my voice along with the distant phone voice when transmitting. I'm able to hear the distant caller's voice and my own (i.e. sidetone), but I'd like to be able to reduce the latter a bit. I can mute my own voice with a mouse click in the Windows audio mixer.

In the receive direction, I can supply as much audio as needed for the distant phone party, using the transceiver's audio gain. This tends to provide more audio than needed for my local earphone(s).

For the VoIP connection to the distant phone, which is connected to the public switched telephone network (PSTN), I've been using the Google Call Phone feature in Gmail. It is free again this year, and does not max-out the 600 MHz CPU in my ham shack PC. A PC with adequate CPU power can use Skype for the same function, but calls to PSTN phones require a paid Skype subscription. Group voice chat / calls are apparently not supported on the Google platform at this time. Skype has good capabilities for conferencing multiple participants on PC-based Skype clients or on PSTN phones.

Doublet antenna for 7-30 MHz

2011-06-21T07:08:00.002-05:00

Yesterday our discussion on 3740 kHz included the characteristics of a wire doublet antenna for 7 thru 30 MHz, based on recommendations (see page 8) from W8JI. Below are links to screen shots from NEC-based analysis of the antenna, for two lengths: 55 ft and 66 ft. Analysis used 3/8 wavelength of 300 ohm feeder, to conform to the article's recommendation to use odd multiples of 1/8 wavelength for the feeder.

55 ft antenna, with radiation patterns in horizontal plane and a plot of impedance for the 7 ham bands. The data points in the latter are the frequencies where computations were done. For the impedance plot, connecting lines drawn thru the intervening non-ham frequencies should be ignored.

W8JI 55 ft doublet

Click on individual thumbnails when the album opens, or select the slideshow mode.

66 ft antenna, with same plots and same feeder & height above ground.

W8JI 66 ft doublet

Radiation patterns for vertical plane are not included here, but are readily available.

John

W4S Special Event Station

2011-04-12T06:32:00.004-05:00

Here is some pictures from the special event station W4S April 9th and 10th from Pigeon Forge, Tennessee.

The four people in the above photo from left to right are

Paul WA0BAG, Sap N0SAP, Steve WA9JNM and Smitty KB4BW.

Above is a picture of Jim KC4RD operating the Ten-Tec Eagle.

73's Steve WA9JNM

Video by WA9JNM

Thanks, Steve!

Pigeon Forge and TenTec factory

2011-04-07T20:16:00.002-05:00

Here are some pixs from Pigeon Forge and TenTec factory with their new
radio. KB4BW & KC4RD were with me.

Bruce
K4CMC

Titanic Special Event - April 9 & 10

2011-04-07T20:09:00.001-05:00

Remember the Titanic April 9th and 10th in Pigeon Forge, TN.

Hope to see you there. N0SAP "SAP"

This Special Event is to honor the two brave radio operators Jack Phillips and Harold Bride for the 99th Anniversary of the Titanic tragic sinking. The WØS at the World's Largest Titanic Museum in Branson, MO. and the W4S World's Second Largest Museum in Pigeon Forge, TN. will be held as an open event for all hams and non-hams to operate. The "W" and "S" is for White Star the shipping company of the Titanic. Ten-Tec will display the new "Eagle" Transceiver for all to use in the Pigeon Forge, TN. location. We will be operating around the clock from both locations. Come experience being chased by stations from around the world at this International Famous Special Event Station.

Operating frequencies will be as follows for SSB and CW.
14.260 ssb +/- 3KC
7.260 ssb # +/- 3KC
3.860 #ssb #+/- 3kc

CW will be running split
14.060 CW UP 2kc
7.060 CW UP 2kc
3.560 CW UP 2kc

For more information and future updates the websites are:
www.w4sspecialevent2011.bravehost.com
www.wzeros.com

Antenna party at Zamora

2011-03-18T09:48:00.001-05:00

Here is a set of photos from the antenna party organized by KE4ID at the Zamora Temple site used during Field Day in recent years. The objective was to compare the performance of several antennas in advance of Field Day. Click on the slide show thumbnail if you wish to view individual photos in the web album.

BirmingHAMfest Group Photo

2011-03-06T16:20:00.001-06:00

A photo of our group's gathering at the 2011 BirmingHAMfest joins the many that appear on the Group Photos page linked to our home page.

When you arrive at that page you'll also see reference to W4AXO's presentation. A link to his new logging program is included there and also on the Telephone Pioneer QSO Party page that is linked to our home page.

Java update breaks chat room copy/paste

2011-03-02T12:07:00.004-06:00

UPDATE: See comments at bottom of this posting for a solution that works for all versions of Java.

Regular users of the Bell Ringers chat room know that it requires Java to be loaded by the web browser so the addonChat applet can run. Recently I accepted the latest update -- Java 6 Update 24. I considered this worthwhile since the update patched multiple vulnerabilities.

On the next morning I noticed that I could not paste a web link or any other text into my outgoing chat message bar. If you never have the urge to paste a URL or other text into your message bar, you can ignore the rest of this post.

Pasting URLs, etc. has become a popular way of sharing diverse discussion topics and sources of additional information during our morning QSOs. I soon suspected the Java update as a trigger for the trouble. Through the addonChat support page I submitted the issue and got a speedy response. I assume that the paying business customers of addonChat brought up the issue right away. Here is an excerpt from their reply:

We've just recently been made aware of apparent bugs in the latest build of Java 1.6. This security release appears to have unintentionally disabled both copy and paste using CTRL/CMD commands as well as hot-linking to remote images using the IMG tag.

We're currently awaiting further information from Oracle regarding this and hope their next build resolves these issues.

In the meantime, we recommend uninstalling Java from your system and downgrading to Java 1.6.0_23 (Java 1.6 build 23). You may download a copy from http://www.oldapps.com/java.php

Below you will find the steps to uninstall Java update 24 and reinstall Java update 23. Java defaults to notify (or update) you automatically, so you will want to disable this action until we determine that a subsequent Java update resolves this issue.

For Windows XP:

First, use Control Panel, Add or Remove Programs and remove Java 6 Update 24
Go to: http://www.oldapps.com/java.php and download Java 6 Update 23
Install Java 6 Update 23
Disable updates:

Go to Control Panel, open Java Control Panel
On the Update tab, Un-check the Check for Updates box
On the Warning page that pops up, choose never

For Windows 7:

First, use Control Panel, Programs and Features and remove Java 6 Update 24
Go to: http://www.oldapps.com/java.php and download Java 6 Update 23
Install Java 6 Update 23 (I chose the x64 version for my Win 7 laptop)
Disable updates:

Go to Control Panel, open Java Control Panel
On Advanced tab, expand JRE Auto-Download
Check Never Auto-Download
Click OK

If, during the Java update 23 installation you get an offer to add the Yahoo! toolbar, I suggest that you decline it (un-check box), unless you really want it.

That should cover it. When I get word of Java 6 Update 25, I'll test it for chat copy & paste and advise.

(This blog entry updated 4/6/11)

75 m Voice & Video Party

2011-02-03T19:19:00.000-06:00

This morning we had quite a crowd on 3740 LSB and occasional CW. We also tried out Carl's expanded Adobe Acrobat.com account with ConnectNow web conferencing.

Carl shared his desktop, showing TRX-Manager software, with a multitude of our participant log-ins and web cams. Below is one of the screen shots I captured during the peak of activity. Click on the thumbnail below for a full size image.

Recently we've used the desktop sharing feature to share live demonstrations of SDR software (by KE4ID) and antenna modeling software (by WA5MLF). Carl has used the desktop sharing on numerous occasions to demonstrate TRX-Manager, Ham Radio Deluxe, and Master Commander software for local and remote control of ham radio systems.

ConnectNow is a powerful and fun tool for sharing knowledge among members of the group.

Antenna radiation patterns - 220 ft dipole

2011-02-02T15:28:00.002-06:00

Here are some radiation patterns for this antenna for 160 thru 10 m bands, using 40 ft height above rocky ground. No feedline was used for this analysis; the source was located at the mid-point of the antenna.

Each slide identifies the frequency and orientation (vertical plane or horizontal plane). The maximum gain (red line) and -3 dB gain points (green lines) are marked. A short horizontal red line near the center of most plots represents the antenna structure, oriented broadside to the viewer. For 40 - 10 m, 3D color plots are also included. A white line in those plots represents the antenna structure. x, y and z axes (barely showing) are in green.

Click on the image below to access the slide set where you can play a slide show or view individual slides.

Dipole, 220 ft, 160 - 10 m

Bell Ringers on Skype Video

2010-12-30T06:27:00.002-06:00

Here are two views that I captured during yesterday's Skype video conference, which included a walking tour of Dave's new QTH. Click on each image to see the full-size copy.

The image below shows a close-up of the SoftRock SDR transceiver that Jack is now building.

Happy New Year 2011 to all!

Frequency Analysis of On-Air Audio Recordings

2010-11-17T06:55:00.003-06:00

I used the FFT frequency analysis feature in my audio editing software to produce some views of audio from several members' transmissions as received on my Heathkit SB-104A. The results are presented in this photo album. Click on the first thumbnail image to display it full size with its caption. You can use the two arrowheads above the image to go backward and forward to compare images. Or you can select the slide show mode and navigate using controls below the photo. All graphs were made with the same settings in the audio software. Two overlay images show a pair of curves on a single slide.

Here are some additional notes:

All audio recordings are influenced by the receive passband and audio filtering of my SB-104A
A local peak appears around 3 kHz in all graphs. This is a birdie in my receiver and should be ignored.
Each horizontal line represents a 3 dB amplitude step -- a factor of 2 power ratio
Each graph is the result of FFT analysis of the speech sample that was recorded, and the frequency content varies according to what slice of time you choose to analyze. Speech is a complex, continuously changing waveform. Pure, steady tones would give more consistent results.
My software can present a real-time FFT of the audio as it plays. In that case the frequency display varies continuously as expected for a complex, continuously changing waveform.
Increasing the FFT size from the 1024 used in these graphs to higher numbers (2048, 4096, etc.) reveals increasingly fine details, but does not affect the overall shape of the response shown in the lowest (1024) setting.

John

Antique Telephone

2010-09-28T16:43:00.002-05:00

Here are some photos from George KW7GAM showing his antique phone. Click on the slide show thumbnail to view the photos full size. George said:

The old Western Electric telephone needed a few drops of oil on the generator shaft. I had to open it up so I took a couple of pictures.

My Dad brought it up from South Alabama when we were kids in the 1950s. I'm sure it must have been when my future company, GTE, was converting to dial in its Alabama properties. My brother and I had it working back then, and I restored it in the 1970s.

See the little key hanging on a loop of the battery wire that the telephone man used to open the compartment with the secret electronics.

Ten-Tec Hamfest 2010

2010-09-27T14:22:00.000-05:00

Phil KB4XX and Tim WA4PTZ attended the Ten-Tec Hamfest on 9/25/10. Here's an excerpt from Phil's email report:

"For those who have never been, this is what I would consider an “old-fashioned” hamfest… free parking… free admission… free outdoor flea market (bring your own tables (or just open your tailgate) and set up shop). The flea market takes place in a small gravel parking lot behind the building with overflow up the grassy hillside behind that. Ten-Tec has a big tent set up in front of the building where they show off their wares… with demo stations you can operate."

Click here to see a nice photo set by KE9V. One topic of discussion on this morning's 3740 QSO was the new Ten-Tec Model 599 Eagle transceiver that appeared at the hamfest. Gee, I wonder how they came up with that model number?

Huntsville Hamfest Photos

2010-08-25T12:10:00.001-05:00

Photos from the Huntsville Hamfest are on the Bell Ringers web site. You can reach that page by going to Group Photos from the Bell Ringers home page, or click here for a shortcut.

You'll find the group photo previewed here, along with other small group and individual photos from N4OLN. A thumbnail below the group photo will take you to a set of 81 photos by W4BXI. These include both people and radio gear. Also featured are a few shots taken at some of the excellent forums. SDR and the FlexRadio display seemed to be popular. I noted that FlexRadio's web site includes a link to the W9OY Software Defined Ham Radio blog. A few of John's photos show slides from the ever-popular forum by David Hathaway on Solar Cycle Prediction.

Also included is this link to the extensive collection of people photos from MCARS.

QSO on 3740

2010-08-02T13:53:00.001-05:00

Today's QSO on 3740 kHz included KB4XX and KB4PYR operating from the Smokemont camp at the the Great Smoky Mountains National Park. I captured some of the receive audio at my station south of Birmingham. I did not have my recording software running correctly when KB4PYR was on, but I did capture some of KB4XX, along with W4UOA and KE4ID.

Here are MP3 copies of selected audio clips of the QSO. These are compressed to 32 kb/s and are stored on Google docs, where you can open each file directly or download for listening. My transceiver was not tuned in exactly, so the voice pitch is not quite correct in some cases.

KB4XX at 0852 CDT, starting out Q5, but fading later in the clip
W4UOA at 0854 CDT operating at Mentone
KB4XX at 0857 CDT
KE4ID at 0858 CDT

KB4XX occasionally reached S9 at my station, but was mostly in the range of S2 to S6. According to Google Earth, the distance from Smokemont to Birmingham is about 249 miles.

73, John

More Field Day Photos

2010-07-22T10:25:00.001-05:00

Bell Ringers have shared additional Field Day photos for your enjoyment.
Click here to visit a very nice collection provided by Tom KC5UN from the DeKalb Co. ARC event.
Click here to see a report and photos provided by Warren WD4NIT from the Wedixie Club event.

Thanks to Tom and Warren!

Field Day 2010 at Zamora Temple

2010-06-27T18:54:00.004-05:00

Here are some photos from Saturday afternoon. Click on the slide show at any time to see the photos full size in the web album.

Also click here for photos by Carl.

Let me know if you have photos from other Field Day sites that may be of interest to our group.

73,
John WA5MLF

Hank's HF mobile antenna

2010-05-15T13:10:00.001-05:00

Here are some photos that show what Hank uses to talk to us while traveling around the southeast.

Bell Ringers on Google Map

2010-05-11T09:50:00.004-05:00

Here is the most recent version of the Google Map that I assembled using Google Earth. You can click on the link below the small map to get a large view where it is easier to pan and zoom and click on the placemarks.

With the Google Earth version of this map you can also get distance and bearing between any two points. Click here to download a copy of the Google Earth map for use within the Google Earth program on your PC.

View Bell Ringers - 02-2010 in a larger map

Audio Recordings on 75 m

2010-05-05T22:16:00.003-05:00

Here are some audio clips from our QSO on 75 m this morning. Click on each call sign to access the MP3 audio file.

W4BXI using Skype audio bridge to connect KB4XX and WA4PTZ
KE4ID
WA4PTZ
KB4PYR
KF4RCY
W4UOA
WB4PDD

These are short segments from a much longer recording. Let me know if you want to hear more.

250 mW Tuna Tin into a 730-ft. doublet

2010-04-28T12:55:00.000-05:00

This item caught my attention when skimming KB6NU's Ham Radio Blog. See the April 14 article here and scroll down to the topic "Another QSO of note".

W3TIM is the operator of that QRP rig with broadcast-style balanced antenna tuner. His page on QRZ.com includes the same photo of the tuner and a nice photo of his Tuna Tin rig.

SSB Audio Compression

2010-04-27T11:12:00.001-05:00

This morning George KW7GAM asked for reports about how his audio sounded on 3740 kHz with and without compression. Click here for the audio recording made from my transceiver. The screen shot above shows the audio waveform as displayed in Cool Edit 2000, with text labels added to identify the two compression states. Click on the image for a larger view.

The appearance of more black space in the right-hand, uncompressed portion of the audio waveform supports the expectation that average audio power is lower for that state. The software allows for selecting a portion of the waveform for statistical analysis. Here are some data for the two portions of the overall waveform:

Compression	ON	OFF
Minimum RMS Power:	-37.89 dB	-39.54 dB
Maximum RMS Power:	-10.5 dB	-11.23 dB
Average RMS Power:	-17.56 dB	-19.63 dB
Total RMS Power:	-16.48 dB	-18 dB

The two histograms below also show the difference. The graph for compression ON (lower left) shows a greater number of samples near the high amplitude (right-hand) side of the graph, while the graph for compression OFF (upper right) shows more samples spread across the amplitude range. The X-axis of these graphs provides the amplitude scale in dB relative to some reference not explicitly stated by the program.

W3DZZ Multi-band Antenna 80-40-20-15-10m

2010-04-20T10:06:00.000-05:00

This antenna has been discussed several times since W4BXI tested it at his antenna farm. Click here for a nice short article by G8ODE that covers the physical and electrical properties, including some radiation pattern plots. A detailed analysis of the antenna by ON9CVD (with discussion of trap component values, impedance and performance) is available here.

Antenna Tuner Matching & Feedline Lengths

2010-04-02T12:33:00.001-05:00

This is a recurring popular topic in our morning QSOs on 75 m. Multiband operation of a single antenna system results in a wide range of impedance at the transmitter end of the feedline. The Hamuniverse web site provides this article with a discussion of some common scenarios that can result in a very high impedance being presented to an antenna tuner. A few good thumb rules are provided along with a table of feedline lengths to avoid and lengths that are acceptable.

The table focuses on the 160, 80, and 40 m bands. It is worth noting that the listed lengths to avoid are computed for one frequency on each band. For example, the 130 ft and 260 ft lengths to avoid on the 160 m band relate to 1.8 MHz (assuming a feedline velocity factor of 0.95). At 2.0 MHz you may want to avoid feedline lengths of 117 ft and 234 ft. Thus, considering the entire 160 m band you may want to avoid feedline length ranges of 117 - 130 ft and 234 - 260 ft. Similarly, on the 80 m band you may want to avoid length ranges of 58 - 67 ft, 117 - 135 ft, and 175 - 200 ft. On the 40 m band you may want to avoid 32 - 33.5 ft, 64 - 67 ft, 96 - 100 ft.

A table footnote says that "some trimming or adding of line may be necessary to accommodate higher bands". If one desires to use the antenna on ALL bands through 10 m, the set of feedline lengths needed to satisfy the guidelines on all bands may become more restrictive. Careful testing on all desired frequency neighborhoods should reveal any problem areas for matching. Then, hopefully, minor adjustments of the feedline length can accommodate the range of the antenna tuner.

W4AXL Tour

2010-03-31T08:05:00.001-05:00

Thanks to W4BXI for the great pictures!

Dayton Hamvention 2010 “Amateur of the Year"

2010-03-20T15:48:00.005-05:00

Congratulations to Jim Stafford, W4QO, BellSouth retiree (1993) and Bell Ringer # 164, public service advocate and well-known QRP enthusiast, who has been named Dayton Hamvention 2010 Amateur of the Year.

Thanks to Phil, KB4XX, for notifying us of Jim's award.

N0SAP Mobile

2010-03-07T23:09:00.003-06:00

Here are a few photos sent by N0SAP, showing his mobile CW setup. Sap did not explain if he has a hands-free adapter for the CW rig! Hi.
Reply from Sap: 'I am working on the hands-free adapter next using mind control. "SAP" N0SAP'

Bell Ringers & TPARCA at BirmingHAMfest 2010

2010-03-07T22:55:00.004-06:00

Here are a few photos from the BirmingHAMfest. I'll post a copy of the group photo with names and callsigns in the group photos section of the Bell Ringers web site. Many other photos are available on the MCARS web site at this link.

Attendees at our Saturday forum included: David KC4SBP, George KW7GAM, Carl W4UOA, Bob WA4PWA, Pat W4QAT, Ed W4DGH, Fletch W4BBW, John W4BXI, Hank K4HM, Selene KG4RMT, Ron N4DLE, Dennis N4NR, Hjordis KI4TVB, Ben W4CT, Bill KB4PYR, Phil KB4XX, Myra K3PGH, John WA5MLF.

Bob WA4PWA told us about a fascinating new device that interfaces his cell phone with his hearing aids. It is the iCom communications interface from Phonak.

David KC4SBP was looking for folks who worked for Southern Bell at the Hurt Building. I suggested that he should also explore the MaBellHams group on Yahoo.

Dennis N4NR gave us a brief history of the WireNet, a bulletin board predecessor to TPARCA.org. The active community from all continents of the world enjoyed sharing information and programs on WireNet, which also provided Internet email before the RBOCs started their ISP units. We are indebted to Dennis and Jerry Pruett (SK) for establishing the foundation of today's TPARCA.org.

130' vs 110' for Multiband Doublet Antenna

2010-02-24T23:10:00.001-06:00

See this document for a first pass analysis of the antenna choices that W4BXI is considering.

W1TP Telegraph & Scientific Instrument Museums

2010-02-13T12:32:00.000-06:00

Friday's snow in Birmingham was not sufficient to keep folks away from an excellent presentation by Bell Ringer #263 about the history and technology of the German Enigma cipher machine. A reference in Keith's presentation contains a video that reenacts the use of the machine during WWII.

A visit to the W1TP home page reveals a treasure trove of information and photos of interest to collectors and historians. The focus is on telegraph equipment and scientific instruments and the Enigma. One of his web pages contains some nice photos from the 2009 Dayton Hamfest.

Enjoy!

75 m Loop Antenna at W4UOA

2010-02-09T22:16:00.013-06:00

Corrected version -- original had results for double the intended loop length.
Here is some analysis of a loop antenna proposed by W4UOA. The following slide show presents impedance vs frequency for several bands. Resistance and reactance are plotted in the upper half of each slide, and impedance magnitude and phase are in the lower half. Click on any slide to view it in the source album. Additional magnification is available using the magnifier icon in the Picasa album view.

The radiation patterns below show the typical progression in frequency, with more lobes and lower angle of radiation as frequency increases. There is a large amplitude difference between the peaks and nulls in the patterns at higher frequencies.

The antenna elements and support wires are the silver lines. The feedline is blue. The color-coded radiation pattern was left at original scale to show its relationship to the antenna structure. The program allows zooming the pattern much larger, such that the antenna structure is engulfed. Viewing at any azimuth and elevation angle, in increments of 5º, is available. Standard 2-D plots are also available.

The predicted performance of this antenna seems consistent with other published analyses of loop antennas, and does not appear to be adversely affected by un-grounded metallic support wires.

Radio Estate Sale for Oren Anderson, W4HDF

2010-02-04T10:17:00.000-06:00

KE4ID is in the process of posting items for Oren's estate sale. You can view available items on this page of the Birmingham Crystal Radio Group web site. Check back often to see additional items as they are added.

NVIS Antenna Resources

2010-01-21T10:27:00.003-06:00

NVIS antennas have been a very popular topic among our members recently. A very interesting view of NVIS potential is found in the Hourly Area Predictions web page shared by ki4sgu. Use the pull-down menu under General Charts For Global HF and select Atlanta, then click the display button. The resulting color-coded chart indicates recommended frequency ranges for HF radio communication with the Atlanta area. It seems to conform fairly well with our morning QSO experiences on 75 and 40 m.

There are many published resources about the design and performance of NVIS antennas. Here are a few that we discussed recently on the air:

The Cloud Warmer NVIS Beam - A nice article found by kb4xx.
A Short Study of NVIS - A concise presentation of the design and performance. Includes antenna radiation patterns to show effects of various design choices.
Some Notes on NVIS Antennas - This is a link to several very detailed articles by L. B. Cebik. A free web account provides access to a treasure trove of antenna articles by this author.

We look forward to additional reports from members who are experimenting with these antenna designs.

Impedance of Twisted Pair Wire / Cable

2010-01-11T11:05:00.001-06:00

A recent morning discussion by our group on 75 m included the use of twisted pair wire or cable for certain HF antennas. There were questions about the impedance of twisted pair wire at HF. Since Jack KE4ID is building a 2-conductor Beverage antenna using "field phone wire", Bill KB4PYR suggested that he use a noise bridge to estimate its impedance at the HF range of interest. A good article about Beverage construction is this one by W8JI.

Today Jack advised that his noise bridge measurements show the impedance to be about 100 ohms in the 80 m frequency band. The results were the same whether or not a current balun was included at the source. The 100 ohm value of impedance at radio frequencies is consistent with many web pages that can be found using the search string "twisted pair cable impedance". One example source is the article Twisted pair cables.

Bell Ringers Map

2009-12-30T13:16:00.001-06:00

Here is a snapshot of a map (updated 2/18/2010) that includes most of the Bell Ringers who appear on 40 or 75 m. Click on the image to magnify or to download. In this view I've left off the details of cities and roads to provide a less cluttered view of were our members are located.

The placemarks are defined in a KML file that can display in either Google Earth or Google Maps (for viewing in a web browser). Let me know if you'd like to see a different view or if you want to make some yourself using a copy of the KML file.

Radios with Micromachined Resonators

2009-12-28T10:58:00.002-06:00

An article in the December 2009 issue of IEEE Spectrum describes how precision micromachined mechanical components, especially resonators, can provide performance superior to that of electronic components for key functions in wireless handsets (e.g. cell phones). Two valuable characteristics of such components are:

zero or very low consumption of battery power
very high Q in resonant circuits (e.g. > 10,000 at 1.5 GHz)

Dr. Nguyen argues that electronic solutions, including software defined radio designs, are not likely to be practical for wireless handsets due to their requirements on battery power. He points to the presence, in today's cell phone designs, of certain electro-mechanical components:

thin-film bulk acoustic resonators (FBARs),
surface acoustic-wave (SAW) resonators, and
quartz crystals.

He predicts that future designs will incorporate MEMS components to overcome the challenges of purely electronic approaches to radio front ends. He reports that handset makers and DARPA are funding work in this area. For additional background on this work, with lots of nice illustrations and article links, visit Dr. Nguyen's web site which includes this link to a research summary.

Saturday Net on 7230 kHz

2009-12-27T11:38:00.002-06:00

The signal reports among participants in the Saturday, 26 Dec 2009 net confirmed the continuing lack of propagation at distances of less than about 250 miles. Without a map in front of me that shows the locations of participants, it is hard to visualize the relative distances and directions among stations. Below is a map view showing the participants' locations and a dark shaded area representing the approximate zone of "no copy" (aka donut hole) relative to Birmingham. Click on the image to magnify.

To represent the ability of various stations to hear each other I produced another view with color-coded lines between many (but not all) pairs of stations. Red signifies good copy and blue signifies poor or no copy. In general, stations that are at least 250 miles apart were able to copy each other, although this distance threshold seemed to be growing as time progressed beyond the 0900 CST start of the net. W4BXI reported poor copy of K9JWJ although they are 307 miles apart. I used purple to mark that path.

Hopefully, this picture will improve as sunspot cycle 24 gets going!

Museum of Radio & Technology

2009-12-23T10:40:00.002-06:00

Visit the Museum of Radio & Technology in Huntington, WV. Their web site includes:

A virtual tour slide show with 175 photos that include antique radios and other technology on display
A tour of major display areas that includes captions for many of the items in photos

A local TV news report provides a brief video tour and commentary on some of the exhibits.

Thanks to W8OI and KA4ZCO for sharing the info about this remarkable museum!

Antenna Wire Candidates

2009-12-03T09:17:00.004-06:00

W4BXI recently shared some samples of antenna wire candidates for review and discussion. I've stripped back the tough insulation on the telco wire types to reveal the conductors and check their wire gauge. Below are photos of the samples, with captions. Click on any photo to magnify.

This first photo shows two similar drop wire types, both with copper-clad steel conductors. Telco #1 appears to be 16 ga, based on my adjustable wire stripper. Telco #2 is 19 ga, based on measurement with a telco wire gauge that has calibrated openings for 19, 22, 24, and 26 ga. The insulation is tough, but manageable with a sharp knife. The copper cladding still looked like copper after my scraping with a knife.

This photo shows two identical or very similar drop wire samples. Both have 2 pairs of 24 ga copper wire. Non-metallic (probably Kevlar) strength members are located near the outside edges of the outer jacket. The wires are located between the strength members. The outer jacket insulation is very similar to the that of the first two samples.

This last photo shows two types of single-conductor stranded wire. #4 has 7 strands of 24-ga bare copper, THHN insulation that is resistant to gasoline & oil. #5 has many strands of tinned copper wire.

Lineman's Test Set from 1940's

2009-11-22T15:34:00.003-06:00

From WA9JNM:
You might like these pictures of my grandfather's telephone lineman box. He worked as a lineman during the 1940's in southern Indiana. The darn thing still cranks out the
voltage around 30 volts. 73's Steve

What is that single sideband?

2009-11-17T12:07:00.006-06:00

Today's discussion on the air was good for stimulating the brain cells as we considered what a single sideband RF signal really consists of. The components of a classic AM signal example using a single, steady audio tone are familiar and are well-represented in the ARRL Handbook and numerous textbooks. In my copy of the Handbook, the chapter on Mixers, Modulators and Demodulators derives the result of mixing (multiplying) a carrier and a modulating frequency. The result is shown as:

AM signal =

sin 2f_ct + ½ m cos (2f_c - 2f_m)t - ½ m cos (2f_c + 2f_m)t

where: f_cis the carrier frequency, f_m is the modulating frequency

You recognize the first term as the carrier, the second term as the lower sideband and the third term as the upper sideband.

A simple view of single sideband would discard the carrier term and one of the sidebands. This could be implemented, for example, using a sharp filter. Examining the term that is left shows a constant sinusoid (cosine function) at a frequency above or below the original carrier frequency by an amount equal to the constant modulating frequency.

During our discussion I postulated that if I transmit a pure (single frequency) audio tone on my SSB transmitter and did not tell you where I was tuned (e.g. 3740 kHz), you could not tell, by tuning your receiver, what audio tone frequency I was transmitting. This is supported by an illustration in the Modulating Sources chapter of my copy of the Handbook. It shows a spectrum analyzer display with a single peak and an oscilloscope view of a constant amplitude RF envelope. The caption labels it as “an unmodulated carrier or single-tone SSB signal”.

Another way of saying this is: Suppose another ham tunes up with a carrier at 3738 kHz. What do you hear at 3740 kHz on your SSB receiver on LSB? You hear a 2 kHz audio tone. Now suppose I transmit a 2 kHz audio tone on my SSB transmitter on LSB on 3740 kHz. If you are listening on LSB on 3740 kHz you hear a 2 kHz tone. The effect is the same.

In the absence of more rigorous analysis, I maintain that a constant pure audio tone transmitted on SSB is equivalent to an unmodulated carrier. Of course, the real world equipment generating such a signal will add some distortion, making it not precisely identical to an unmodulated carrier. Also, a voice waveform is highly complex, with multiple varying frequencies and amplitudes.

The more rigorous treatment of SSB (example) uses math that is equivalent to the phasing method of generating SSB. It is a notch up in level of complexity compared to what is presented in the Handbook. It is also the basis of many communications systems that we take for granted today: broadband Internet access, digital TV, cell phones, etc.

Comments?

John WA5MLF

Net Manager - WA5MLF

2009-11-17T09:59:00.001-06:00

WA5MLF (Bell Ringer #17) has assumed the duties of Net Manager for the Bell Ringers Net, effective 11/15/09. He succeeds W4BXI, whose leadership in this role is much appreciated. Any questions or suggestions about the Bell Ringers Net should now be directed to WA5MLF.

Antenna Analysis

2009-11-11T13:53:00.008-06:00

This morning's discussion on 75 m covered the characteristics of a commercially-available doublet antenna of 130 ft total length, center-fed with 75 ft of 450-ohm open line. The following additional parameters were used in analysis performed with the 4NEC2 antenna modeling software:

12-gauge copper conductors
height above ground 30 ft
average ground characteristics

Below is a sequence of horizontal radiation patterns, computed at one frequency for each of the 9 HF bands. The patterns for 80-40 m are very similar in shape. Starting at 30 m, additional lobes appear. You can click on the figure to select and examine any slide more closely.

Using the program's 3D features, the following plot shows the complexity of the antenna's radiation pattern at 28.5 MHz. This is an overhead view, with antenna oriented from left to right. Click on the figure to enlarge.

A frequency sweep from 1.8 to 29.7 MHz was made to investigate the behavior of the antenna's impedance at the transmitter end of the feed line. The following figure shows the calculated values of resistance, reactance, impedance, and phase at increments of 0.2 MHz. Numerical values are available in the program's output file, and one set of numbers (at 7.2 MHz) are shown on the figure. Click on the figure to enlage.

It can be seen that the antenna's impedance (green curve) is fairly high (several hundred ohms) at many of the ham band frequencies, confirming the need for a tuner to achieve matching to a 50-ohm transmitter. The program includes a feature for calculating the needed matching components. This could be used to predict the ability of a given tuner to achieve a match at any given frequency.

John WA5MLF

Poll Results for Saturday Net Operations

2009-11-03T09:49:00.004-06:00

After 7 days the web poll on this topic has closed. Thanks to all who expressed their interest in future operations of the Saturday Net by voting.

The choices, from which a voter could choose one OR more, were:

Use 75 m exclusively until sunspot activity enables a return to 40 m.
Use 75 m with optional Skype and/or phone patch connections for stations who are too distant from the core 75 m participants.
Use 60 m
Use 40 m exclusively, with the aid of relay stations. Remain on 7230 kHz while evaluating the effect of changing back to standard time on November 1.
Implement an RF bridge between 75 m and 40 m, enabling stations to select the band that gives them the best ability to hear and be heard.

The poll recorded 33 participants, with a total of 44 choices selected. Here is a summary of the results, which can also be viewed on the poll gadget, although you must scroll horizontally to see the numbers.

75 m exclusively -- 8 votes - 24% of 33
75 m with patching -- 3 votes - 9%
60 m -- 1 vote - 3%
40 m with relays -- 20 votes - 60%
40 m - 75 m bridge -- 12 votes - 36%

Below is a pie chart showing the results based on the votes for each choice divided by the 44 total selected choices. Click on the image for a magnified view.

Thus, most responders favor the use of 40 m for the Saturday net. There is also clear indication of a desire to have the best of both worlds, combining the long range of 40 m that favors more distant members with the short range of 75 m that favors the Alabama-Georgia core of participating members. With today's technology we have several choices beyond traditional relaying to help bridge the 40 m and 75 m propagation gaps and enable all members to participate. These include a Skype-based VoIP HF Bridge and a Cross-Band Internet Bridge. These may not be available for every Saturday net, since they involve the presence and extra efforts of two members who are equipped to implement these services.

Based on our October 26 conference call, our goal in the near term is to resume a formal Saturday morning members' net with roll-call check-ins, using whatever tools are available. Weekday mornings have and should continue to hold lively, informal QSOs using two bands.

Feel free to post comments below and/or send email to me or to W4BXI.

John WA5MLF

Saturday Net Operations

2009-10-26T22:17:00.004-05:00

In response to John's (W4BXI) call to conference about possible ways to improve our Saturday Bell Ringers Net, the following Bell Ringers met:
John (WA5MLF), John (W4BXI), Carl (W4UOA), Gary (N4OLN), Jorge (KI4SGU), Larry (KB4LWT), and Phil (KB4XX). After discussing our 40 meter propagation problems, here are some ideas we thought might make our Saturday Bell Ringers Net better:

Use 75 m exclusively until sunspot activity enables a return to 40 m.
Use 75 m with optional Skype and/or phone patch connections for stations who are too distant from the core 75 m participants.
Use 60 m
Use 40 m exclusively, with the aid of relay stations. Remain on 7230 kHz while evaluating the effect of changing back to standard time on November 1.
Implement an RF bridge between 75 m and 40 m, enabling stations to select the band that gives them the best ability to hear and be heard.

We invite your feedback about these choices and any others that may be relevant. Please use the poll feature at the upper right corner of this blog to capture your votes for one or several of the choices. One of our goals is to resume a formal Saturday net with check-ins by member number.

The alternatives are listed in brief form in the poll to enable better visibility of the results after your votes are entered. You'll still need to use the horizontal scroll bar to see results. (The poll feature is one that I have not previously used.)

You may also post comments directly to this blog posting for other members to read.

An updated list of Net Control Stations is posted on our web site.

Thanks for your interest and inputs!
John WA5MLF

Map of 75 m Net: 1994-1997

2009-10-21T06:33:00.005-05:00

Following yesterday's discussion of the Net's past operation on 75 m, I looked at my logbook records and found that the Saturday morning net used 3920 kHz in the 1994 - 1997 time frame. Making note of the member stations that checked during that period I produced this Google map showing their locations to reveal the Net's viability on 75 m during the low period of the sunspot cycle. The map supports our understanding of the membership as being concentrated mainly in LA, MS, AL, GA. The highest member number among check-ins at that time was 272.

Click on the link below the map to get a larger view with more navigation features. Many of the member locations shown are only at the city level of detail, not street address. It is interesting to compare this map with the one produced earlier this year that reflects participation in the 2008-2009 time frame.

John WA5MLF

View 75 m Net 1994-1997 in a larger map

VFO Controlled Low Power Transmitter

2009-10-20T06:39:00.002-05:00

The Rockless, a VFO Controlled Low Power Transmitter, is featured in the November 2009 issue of QST. Jimmy K9JWJ contacted the author and was directed to The Rockless QRP web site for more info. Thanks, Jimmy, for the link.

ON8PO Radio Museum

2009-10-20T06:33:00.001-05:00

See this amazing museum of radio equipment! Thanks to W4BXI for the link!

Early telephone multiplex systems & Bell Labs

2009-09-20T07:26:00.004-05:00

During a recent morning QSO on 3968 we talked about early frequency division multiplex technologies for carrying multiple voice channels on individual metallic circuits. Probably the earliest example was the O-carrier system deployed on open wire routes. A few photos are shown at this web site.

Information about these FDM systems is sparse on the web. The above referenced article on FDM does include a link about L-carrier systems deployed on coaxial cable.

N-carrier systems were used on twisted-pair cables starting about 1950. According to two books in my library, N-carrier was used for routes ranging from 15 to 250 miles. They used two frequency bands: 36 to 140 kHz (low group) and 164 to 268 kHz (high group) in opposite directions, on two cable pairs. At successive repeaters the signals were translated between the low group and high group to promote equalization across the entire route. Depending on the version of the system, either 12 or 24 channels were carried on 2 cable pairs.

Searching the web for more information about these carrier systems also yielded a nice article about Bell Labs. Scroll down to find entries grouped by decades.

The Bell Ringers web site also includes some good historical links on the Links page.

Latest W4BXI System Audio Drawing

2009-09-03T07:41:00.005-05:00

Here is a drawing of John's latest audio configuration. It makes use of a second PC to 'mix' a phone line caller via phone patch into a Skype conference call that connects to the transceiver.
Click on the image above for an enlarged view. Drawing is made using the OpenOffice Draw program.

With the drawing produced, one can make copies with overlaid features, such as the one below that illustrates the main flow for a regular phone patch. A series of these can be done to form a slide presentation, if desired.

Larry's Bees

2009-08-21T07:29:00.002-05:00

Larry KB0BH sent me some additional photos of his bee keeping and honey production. Outdoor photos were taken by N4OLN. You can view the complete set in this album on the Bell Ringers web site.

Audio Interconnections at W4BXI

2009-08-20T07:16:00.002-05:00

Here is a draft drawing based on a sketch from W4BXI, for discussion purposes. Click on the image for a full-sized view.

VoIP HF Radio Bridge in QST

2009-08-17T14:02:00.003-05:00

An article on this topic, written by W4UOA with some assistance from W4BXI and WA5MLF, is published in the September 2009 issue of QST, page 40. We welcome your feedback and invite you to also use the vote link for ARRL members.

Huntsville Hamfest Photos

2009-08-17T13:59:00.004-05:00

Photos by Gary, N4OLN

These photos are also posted in the Group Photos section. Click on the thumbnail for Huntsville 2009.

Skype under threat

2009-08-11T08:42:00.003-05:00

The VoIP technology that we like to use for HF radio interfacing to the Internet is under threat due to E-bay's sloppy acquisition of Skype. See this summary from episode 583 of Leo Laporte's show The Tech Guy. The summary includes a link to an article on the British news site The Guardian.

Pioneers award to TPARCA in 1995

2009-08-05T18:50:00.005-05:00

Here is a bit of TPARCA history from 1995. Click on the thumbnail for a better view. Pictured receiving the award is W4AXO, Bell Ringer #187.
Also, see the 1994 group photo.

Updated W4BXI System Audio Drawing

2009-07-27T10:10:00.005-05:00

In an earlier blog posting W4UOA provided a drawing of W4BXI' s overall audio interconnections, and WA5MLF followed with a drawing to focus on the two-way audio paths between transceiver and Internet-connected PC. Since that time W4BXI has added a second audio mixer (colored orange) to the system. An updated draft drawing by WA5MLF is shown below (click to enlarge).

Photos of key hardware elements may be seen here.

Feedback from W4BXI would be appreciated to ensure that this version of the drawing conforms with the "as built" hardware configuration.

This may aid our ongoing discussions of interfacing multiple participants to an HF radio QSO using Skype, and even the 20th century technology called a phone patch. Today's on-air discussion renewed the quest for a system configuration that can connect multiple Skype callers to the host HF transceiver without the use of external hardware mixers or a second PC to host the Skype audio conference.

Electronics Recycling in Birmingham

2009-07-24T15:10:00.004-05:00

If you have old electronic equipment of any kind that you can't or don't want to trade or sell, consider bringing it to a recycling company, such as Technical Knock Out. They are a full-time operation located near US-31 (Independence Dr) and 28th Ave S. The annotated photo below (click to enlarge) shows the TKO location. It is suggested that you call them before going to make sure they are present. Sometimes they are away collecting discards from local businesses.

Last year I took a wide variety of items to a weekend collection that the company sponsored at Whole Foods. A couple weeks ago I took some equipment directly to the TKO warehouse where I found the employees disassembling old computer equipment and other electronic gear. They are glad to accept all kinds of radio, audio, and other equipment. Sheet metal parts are picked up by a local company that uses recycled metals to produce various forms of piping. Circuit boards are shipped to a company in another state that separates the components and materials for recycling.

Call TKO at 205-451-0180 if you have any questions.

John

N0A - Nixa, MO Field Day

2009-06-30T09:27:00.015-05:00

N0SAP - Sap provided the following photos from the Field Day operations of the Nixa Amateur Radio Club. Click on any photo for a larger view.

Click here to view a local TV news video about the event.

Ham Radio Audio and Resources

2009-05-12T09:15:00.007-05:00

During a discussion of online receivers this morning Bruce K4CMC told us about the blog Ham Radio Audio and Resources. If you scroll down there to the section labeled 5) Online Receiver's you'll find a list with many links. (The blog author misuses apostrophes.)

Included among them is the Lebanon, Tennessee Receiver provided by Trish Ray, K4ZE that we were remembering from an earlier QSO.

Thanks, Bruce!

Thanks to Phil KB4XX for sending an updated link the K4ZE receiver. See S-Meter Website Receivers for another listing of receivers. I suspect that these also appear in the blog listed above.

WA4PTZ Loop Analysis

2009-04-23T09:50:00.016-05:00

Using the sketch Tim provided of his loop antenna, I entered the measurements into the 4nec2 program and got the far field patterns shown below. These are calculated with a 50-ohm generator at the feed point -- no feed line included. I expect that the field patterns would be similar with the feed line included.

160 m horizontal gain. Major lobes approximately north-south.

160 m vertical pattern. Mostly straight up, as expected.

75 m horizontal pattern. 4 lobes

75 m vertical pattern. 2 lobes; angle of radiation moving away from vertical.

40 m horizontal pattern. More lobes appearing.

40 m vertical pattern. Lobes continue to move toward lower angle.

20 m horizontal pattern. Lobes increasing rapidly and some nulls are deep.

Here's the 3D color coded version of the 20 m pattern.

20 m vertical pattern. Radiation angles continue to progress lower.

I have not looked at the patterns yet for higher bands. Below are SWR and impedance plots, without feed line included.

Creating a Horizontal Loop Antenna

2009-04-21T21:41:00.005-05:00

Tim WA4PTZ wrote a nice paper to inspire other amateurs to discover the excellence of this simple antenna. Thanks, Tim!

W4BXI System Audio

2009-04-20T09:56:00.004-05:00

W4BXI has gradually built a versatile interconnection of components that enable him to hear audio from two transceivers and to interface two-way audio between a transceiver and his contacts using Skype for VoIP calls via the Internet. Of course, he also incorporates the 20th century phone patch as another option.

As John's system has grown some issues have emerged about how to best interface various components while avoiding ground loops, feedback and level mismatch. Recent email exchanges with W4UOA and WA5MLF led to their developing some system diagrams to aid in discussion and identification of configuration choices. Below is a diagram from W4UOA that gives a complete picture of the capabilities assembled by W4BXI. (Click on it to enlarge.)

This shows that John can access various audio streams at the mixer as well as participate in a Skype VoIP conference via the Bridge Computer. Carl has included a list of control operator procedures describing how the main components are used. In testing today John determined that he can also initiate a Skype conference on the Rig Computer and connect those participants to his FT-1000 transceiver.

In order to focus more closely on the two-way audio paths, WA5MLF prepared the diagram shown below that does not include all components and audio mixer connections. (Click on it to enlarge.)
The audio mixer is shown with its separate left and right channel inputs from the FT-1000 and outputs to a headset. A new input to the headset's right earphone is the Skype caller's talk path (dashed line in the drawing). Phone patch #4 is used to combine the talk and listen (transceiver transmit and receive) audio while avoiding the creation of a feedback path. Phone patch #2 is used primarily for ground loop isolation, and can be replaced by a single transformer.

Comments and suggestions are welcome.

Smith Chart

2009-04-15T10:19:00.006-05:00

Why do we need it? This is answered very well by David J. Jefferies in his article where he says:

"The SMITH chart is a graphical calculator that allows the relatively complicated mathematical calculations, which use complex algebra and numbers, to be replaced with geometrical constructs, and it allows us to see at a glance what the effects of altering the transmission line (feed) geometry will be. If used regularly, it gives the practitioner a really good feel for the behaviour of transmission lines and the wide range of impedance that a transmitter may see for situations of moderately high mismatch (VSWR)."

Many articles about the Smith chart seem to focus first on proving its mathematical validity. It is not necessary to have a rigorous understanding of its mathematical basis to get useful results from it as a tool.

A nice approach to understanding the format and applications of a Smith chart, without getting bogged down in math, is provided in the December 2007 QST, page 48. This is the first of a 3-part series that totals only 6 pages.

Another good introduction is the Smith Chart Tutorial suggested by John W4BXI. This one makes nice use of colors to illustrate the construction of the chart and includes several good simple applications. Don't be put off by the first two pages.

An impressive collection of Smith chart resources was suggested by Phil KB4XX. It includes a list of 20 tutorial articles, including the one referenced in the previous paragraph.

Several web sites provide downloadable copies of the Smith chart that you can print locally for use in working your own transmission line and matching problems. Several are included at the collection link above. My favorite sources are:

Impedance Smith chart at Print Free Graph Paper. Once there, select Smith Chart Graph Paper on the first pull-down menu.
Admittance Smith chart
Combined chart (impedance and admittance scales -- color print is a must!)

Loop Antennas

2009-04-15T09:41:00.002-05:00

This morning on 3968 we discussed loop antennas briefly. Phil referenced The Loop Skywire article from QST November 1985. Tim is pleased with the results from his loop antenna and emphasized that it need not be a full wavelength to be usable on 160 m. Larry commented about a recent club presentation about a member's 500+ ft loop antenna fed with high-quality coax and using a remote antenna tuner. The Loop Skywire article seems to emphasize keeping cost low.

N4KC published a detailed article on his loop antenna and its performance relative to other antennas installed at his location.

Another loop design that I found interesting was featured in the March 2008 QST, page 56. The author describes a 187-ft loop of #26 AWG black insulated Copperweld wire. It terminates directly on an SGC SG-237 antenna tuner mounted just below the window sill where the antenna wires enter his antenna-restricted apartment.

160 m Inverted L Antenna

2009-04-14T16:16:00.012-05:00

The other antenna that W4BXI likes to use on 160 m is a center-fed inverted L using ladder line. The sketches below provide the configuration details. Click on the image to enlarge it.

I entered this data into the 4nec2 software as a new model for analysis. Since there is not a convenient way to depict the sloped terrain, I used a level ground terrain. The model structure is shown below as it appears in the program. White lines are the antenna elements, blue lines are the ladder line feeder, and green lines are the xyz axes.

The program's main output window is shown below. It indicates the impedance at the end of the feedline to be 131+j691 ohms (703.31 ohms @ 79.27^o) at 1.8 MHz. The SWR for a 50-ohm source is calculated to be 75.7. For comparison, the impedance at the antenna feedpoint, with feedline removed, calculates to be 38.5-j40.5 ohms (55.88 ohms @ -46.45^o).

The variation of SWR, for a 50-ohm source, is shown in the graph below.

The next set of graphs show the variation of impedance, etc. vs frequency at the end of the feedline. The values at 1.8 MHz are highlighted.

The program is able to calculate the component values for several types of networks to match the feedline impedance to a 50-ohm source. The values for each network type are shown below. Component values for a (C-L-C) high-pass T-network are highlighted in green. This gives an indication of the component ranges that may be used in an antenna tuner to achieve a match for this model approximation.

The next plot shows the far field horizontal radiation pattern for the modeled antenna. Major lobes are seen to be perpendicular to the 130 ft leg that is 60 ft above ground. It is not known how this pattern would differ for a sloped ground terrain.

The final figure shows a 2-dimensional slice of the radiation pattern, color-coded for intensity. The elevated 130 ft leg of the antenna appears as a white line emerging from the pattern. The other leg is seen as a white vertical line that connects to another white line extending to the right, close to ground. Blue lines represent the ladder line feeder.

The program enables one to rotate this pattern in all directions for other views.

ICOM IC-7600

2009-04-06T11:31:00.001-05:00

Also from Phil:
"New ICOM IC-7600 is now shipping – first reviews are starting to come in. Wide dynamic range and many nice features - looks like another winner for ICOM. Gotta’ like that sexy hi-res display and built-in spectrum scope. Add a USB keyboard and work PSK31/RTTY. "

Solar Powered Station

2009-04-06T11:27:00.002-05:00

Phil sends us news about this Australian Solar Powered Station.
"be sure and check out his station and photo gallery web pages – talk about a low noise floor QTH! Note the 670 amp-hour (solar-charged) battery set, his “homemade” antenna rotor/direction indicator and his “neighbors”."

Thanks, Phil.

Plot of Impedance vs Frequency

2009-04-05T14:59:00.002-05:00

For a wider view of W4BXI's 160m antenna properties I used the 4nec2 program's feature that plots impedance vs frequency. The above plot (click to magnify) is from 1.0 to 29.7 MHz in steps of 0.2 MHz. (I started at 1 MHz to get whole numbers on the x-axis.)

The color-coded points and scales identify resistance, reactance, impedance, and phase. A nice program feature is the display of numeric values when you click on a specific point. In the above example I clicked on the 7.2 MHz point before I made the screen capture.

This plot shows the repeating peaks and nulls of impedance, etc. as the program sweeps through the chosen frequency range (with a maximum of 256 steps). The corresponding Smith chart (not included here) shows a series of 16 circles passing through the calculated impedance points plotted around the chart.

Smith Chart Views

2009-04-03T06:55:00.002-05:00

As mentioned in the March 31 posting, I have used the Smith chart to check the calculation of impedance at the transmitter end of the 120' feedline. The starting point was the antenna's feed point impedance that is marked on the chart shown here (click on image to magnify). This calculated impedance is in the neighborhood of a dipole's impedance near resonance. The SWR circle shown is based on connecting with a feedline with characteristic impedance of 450 ohms, which is the reference point at the chart's center. The same results can be seen on a paper copy of the Smith chart when plotting with coordinates normalized to the 450-ohm characteristic impedance.

This second chart shows the location of impedance coordinates at the end of the 120' feedline, which represents 0.24 wavelength toward the generator (transmitter). The blue radial line (spoke) from the center is aligned with the 0.24 wavelength mark on the outer perimeter scale. The intersection of this line with the constant SWR circle gives the approximate impedance at the end of the feedline, as annotated in red. This value agrees, within the margin of positioning the mouse cursor, with the value calculated previously.

This final chart shows the range of impedance values (black dots along orange curve) that the program calculated when sweeping from 1.6 to 2.0 MHz. The 1.6 MHz point is identified with the green spoke line and its values are shown in the lower right-hand corner of the page.

160 m Windom antenna modeling

2009-03-31T21:48:00.015-05:00

Recently W4BXI provided some details (left) of his 160 m Windom antenna, since I had offered to model it with the 4nec2 software.

The screen shot below is a representation of the antenna structure data as entered into the program. Click on any image for an expanded view.The white lines are the wire elements and the blue lines are the feedline. A level ground is used for convenience, but the actual antenna site has some sloping ground as noted in the details sent to me.

Below are some of the results. The main program window shows impedance, etc. at the end of the 450-ohm feedline. Impedance at the transmitter end of the feedline is calculated to be quite high: 3797 + j861 ohms. I intend to check this using alternate tools (e.g. Smith chart). I expect it to be very dependent on the length of the feedline.

A sweep of frequency from 1.6 to 2.0 MHz yields the following SWR and reflection coefficient curves. This is based on a 50-ohm source with no matching. Naturally, the SWR looks better when using a 72-ohm feeder.

The program provides a tool for calculating several types of matching networks for matching to the designated 50-ohm source. Here are the results.

Also available are several forms of far field pattern plots in horizontal and vertical planes. Here is the horizontal gain plot.

3D plots of gain in various forms are also available. Here is one example that uses color coding to represent intensity. The antenna structure is also shown in this plot.

Text output files are also available if you want to examine or separately plot all the results.

Electronics Recycling

2009-03-30T15:10:00.004-05:00

Several web sites enable you to search for companies near you that recycle electronic equipment that you may be unable or unwilling to sell, trade or reuse. Two that I can suggest are:

Earth911 - click on the Electronics tab and search with your address or zip
myGreenElectronics - search with your zip code

An example of a company I found in Birmingham is Technical Knock Out.

Antenna Modeling & Analysis

2009-03-21T14:53:00.004-05:00

Some powerful software tools are available for modeling and analyzing many forms of antennas that are popular among hams. These can be used to guide the designs of home-brew antennas and to gain insight into measurements made on actual antennas that you are using. Models can include antenna elements, detailed in 3 dimensions, transmission lines, matching / loading components, sources, ground surfaces (with various characteristics) and surrounding objects. Program outputs include: impedance, SWR, radiation patterns, current distributions, front/back ratios, impedance matching. Currently available versions of the program can sweep frequency inputs or component values (e.g. antenna height, wire size, loading coil inductance) to produce plots depicting the variation of results with the swept parameters.

The granddaddy of antenna analysis programs is the Numerical Electomagnetics Code (NEC) family of programs originally developed at Lawrence Livermore Labs in 1981, on a contract to the U.S. Navy.

NEC2 was released to the public. Browsing the NEC2 User's Manual reveals the punch-card FORTRAN genesis of this program, and the terminology continues in current versions of the program that hams can run today on their personal computers. Historical documentation and information links are collected at the NEC2 web site.

Among the links at the NEC2 web site is one to the EZNEC versions of the program developed by W7EL. A free demo version of this program is available and it is a very good place to start to learn what this program can do. The free version is full-featured, only limiting the complexity of antennas (20 segments max) that can be modeled. Paid versions of the program permit much greater complexity of antenna systems.

Another implementation is the 4NEC2 program developed by Arie Voors. You can get an appreciation of this program's capabilities from the large collection of screenshots. It is a free program and, like EZNEC, includes a good number of pre-built antenna models, many developed by W4RNL. These are good for getting familiar with the program and as starting points for developing models specific to your needs.

John

Antenna Tuner Discussions

2009-03-11T10:19:00.007-05:00

The topic of antenna tuner operation and design was popular today. Here are some links that Phil and I have dug up that may be helpful:
How to User Your Antenna Tuner is a fairly long article with several additional web links and many posted comments. Among the included links are:

Antenna Tuner Operation is a short article by ARRL about how to use a common tuner type.
A T-Network Simulator is a Java application that lets you practice using a software simulated tuner. You can turn the knobs on the tuner to try your solution and then click the autotune button for comparison. The simulator can be run or the web page or downloaded to run locally on your Java-enabled PC.
Antenna Transmatch Tips provides some details of popular tuner designs that are commercially available along with tips for similar homebrew units. It includes some discussion of common component limitations.

Other links provided in Phil's recent email:

An article about the Ten-Tec Model 238B HF Antenna Tuner describes the circuit and how it operates.
Getting the Most Out of Your T-Network Antenna Tuner is an article from the January 1995 issue of QST.

A subtopic of particular interest is the ability to find more than one group of settings in T-network tuners to provide a match. This property is illustrated in the 1995 QST article cited above. See the article's section labeled Practical T-Network Tips for some recommendations on how to avoid overheating inductors and arcing capacitors.

Many additional articles are available at this DX Zone web page.

Your comments are welcome.

John

Dalton Hamfest 2009 Photos

2009-03-11T10:14:00.003-05:00

Photos from this event are available for viewing here. Thanks to N4OLN and W4UOA for their camera work!

Bell Ringers Google Map

2009-02-04T09:24:00.004-06:00

View Larger Map

I've created a new Google map showing 34 selected members of our group. Above is a portion of the map, which you can also view in full size. This initial version is based on coordinates available from QRZ.com. I'm updating locations based on corrections sent to me.

If you click on a placemark (push-pin) the member's call sign, name and member number are displayed.

If you are logged in with a free Google account, you can also find a distance measuring tool under the "Featured content" section on the left side. You can also view this map in Google Earth, if you have installed that free program.

Please send me any corrections or additions for the map. I'll be glad to add more members who may want to be included or remove those who don't. Thanks to Jorge ki4SGU for showing us how to use this Google resource. Enjoy!

John

Amateur Radio SDR

2009-02-02T14:12:00.003-06:00

I found a recently started blog about this topic. It includes information about the SoftRock radio kits that are promoted as a good way to get started with SDR in amateur radio. A companion web site provides some information about how to set up an amateur radio SDR.

John

Nixa Ice Storm 2009 by N0SAP

2009-01-28T14:12:00.006-06:00

Here is a report and photos from Sap N0SAP. Click on any photo below to see it full size.

Here are some pictures of the first ice storm of 2009.  We had about 3/8 inches of ice and four inches of snow.  We have not loss power, so I guess we are lucky for that.  "SAP"

Picture 009 (last) is the permanent building full of radio parts.

PropNET

2009-01-26T15:46:00.003-06:00

This morning on 3968 we learned from ki4SGU a little bit about PropNET, a project that uses PSK31 to create an RF-based digital peer-to-peer network. The link in the preceding sentence will take you to the FAQ for some background info.

A fascinating product of this project is an automated communication circuit quality report, a type of propagation map that displays connections made among stations whose locations are marked on the map. The graphical display is frequently updated, giving a snapshot of propagation conditions at the time of viewing. The results can be displayed for all bands or for a single band of interest. Click on any station's location point for info from QRZ.com.

Enjoy!
John WA5MLF

Bell Ringers on a Google Map

2009-01-14T11:07:00.005-06:00

Yesterday Jorge ki4SGU assembled, in near real time, a Google map that shows the locations of several stations who participated in our QSO on 75 m. You may view it by clicking here. Click on a blue push-pin either on the map or on the left-side listing to reveal details about that QTH.

The locations are based on the public data that is used by Google maps and similar web applications. Some locations are not quite correct, but can be adjusted in the customized map itself. This will not, however, correct the underlying error in the external database that is accessed by Google and other mapping applications.

Using Jorge's map as inspiration, I hope that we will assemble a similar map that shows more of our members and frequent associates who join with us regularly on 75 or 40 m. Let me know if you wish to help as a collaborator who can edit / update our future map.

73, John

HF Noise - Plasma TVs

2008-12-19T09:20:00.003-06:00

This morning's discussion of digital flat screen TVs included a mention of plasma TVs as a source of RF noise that can affect HF radio. An article with comments from 2002 describes this issue. Thanks to KB4XX for this link.

The ARRL hosts an RF noise page that includes audio recordings of various identified noise sources, along with waveform views. There is not one currently labeled as a plasma TV, but there are some entries for TV sets as noise sources.

If you or your neighbors buy plasma TVs and you notice an increased noise level across the HF bands, you may want to see if the noise correlates to operation of the plasma TV. Good luck!

Russian Woodpecker

2008-12-18T15:31:00.004-06:00

Old timers on the HF bands will remember the Russian woodpecker. Go here for a web article with great photos of the antenna array. Thanks to Joe KA4ZCO for the link.

Understanding Antennas

2008-12-08T06:59:00.002-06:00

Smitty KB4BW suggested the web page Understanding Antennas for the Non-Technical Ham. It provides access to a PDF copy of a 74-page book by Jim Abercrombie, N4JA.

Global Tuners

2008-11-14T07:19:00.002-06:00

GlobalTuners is a web site that provides free access to radio receivers around the world. After creating a free account with log-in, you can access a receiver and listen to a frequency of your choice. Since the receivers are being shared by others, you must follow the web site's protocol of requesting permission to change a frequency, if others are listening to the current frequency. A chat window is provided to facilitate communication among concurrent listeners.

Thanks to W4BXI and W1TXT for the info about this site.

Remote Station Control

2008-11-14T07:12:00.002-06:00

Here is a 12 minute video of how Randy K7AGE is using his laptop PC on the road to control his rig at home, operating on several modes and bands. Thanks to W4BXI and W1TXT for the link.
http://www.youtube.com/watch?v=whe9nV9InnQ

Montgomery Hamfest

2008-10-25T16:37:00.002-05:00

Date: Saturday, November 8, 2008
Time: 9:00 A.M. Until 3:00 P.M.
Location: Garrett Coliseum, 1555 Federal Drive, just West of Coliseum Blvd. in North Montgomery, AL
For more information, click here.
Bell Ringers planning to attend are invited to contact WA5MLF to share attendance plans within our group and coordinate an eyeball QSO.

Solar Cycle 24

2008-10-14T09:45:00.003-05:00

This morning one of our members mentioned the SOLARCYCLE24 web site for a source of information about the progress of the new cycle. The appearance of sunspot #1005 seemed to bring some nice short-range propagation on 40 m yesterday, but its fading seemed to relegate us to the usual 200 mile minimum for our morning QSO today.

Vintage Amateur Radio Stations

2008-10-04T07:14:00.002-05:00

Visit this web site for recordings of 1920's era rigs. Photos of VE3BBN's spark-gap transmitter are included. Thanks to Brian N4DKD for letting us know about this site.

Receiver Saver -- Updated Circuit

2008-09-18T09:54:00.010-05:00

I've made two modifications to the circuit that is described in a posting on 6/10/08. Click on the revised schematic below for an enlarged view.

By changing the values of R1, R2, and C1 as noted, the transition from transmit mode (receiver grounded) to receive mode (receiver connected through to its antenna) takes about 1 second. A smaller value of C1 can be used for a shorter time delay. The transition from receive mode to transmit mode is still very quick, IF the transceiver control lead provides a low resistance to ground on transmit, thereby discharging C1.

This circuit change enables an operator using full break-in CW to use the circuit on a spotting receiver without having the circuit's relay chattering in time with each CW character transmitted. Since the status indicator LED has its own switching transistor Q2, it now transitions from red to green a fraction of a second after the relay switches from transmit to receive state. The values of R3 and R4 could possibly be adjusted to change this behavior.

Diode D8 was added to prevent the powered-off circuit from presenting a resistance-to-ground of about 1 megohm or less (R1 in series with base-emitter junction of Q1) to the transceiver control circuit. In one user's application this circuit was connected to the control lead from a transceiver to a linear amplifier. The amplifier apparently interpreted the resistance-to-ground of the receiver saver circuit as a transmit control command from the transceiver. The addition of D8 presents a much higher resistance-to-ground on the control lead that should prevent false keying of the linear amplifier.

Enhanced ARRL Document Services

2008-09-18T09:54:00.007-05:00

Thanks to Tim WA4PTZ for calling attention to the new option for obtaining copies of past QST articles. ARRL members can now access online copies of articles from December 1915 through December 2004 via the ARRL web site. Articles from other publications, as well as QST, can be ordered as paper copies or on CD-ROM. The search feature continues to provide a convenient way of finding those past articles.