The Bell Ringers

Radios with Micromachined Resonators

noreply@blogger.com (wa5mlf) — Mon, 28 Dec 2009 16:58:00 +0000

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

noreply@blogger.com (wa5mlf) — Sun, 27 Dec 2009 17:38:00 +0000

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

noreply@blogger.com (wa5mlf) — Wed, 23 Dec 2009 16:40:00 +0000

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

noreply@blogger.com (wa5mlf) — Thu, 03 Dec 2009 15:17:00 +0000

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

noreply@blogger.com (wa5mlf) — Sun, 22 Nov 2009 21:34:00 +0000

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?

noreply@blogger.com (wa5mlf) — Tue, 17 Nov 2009 18:07:00 +0000

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

noreply@blogger.com (wa5mlf) — Tue, 17 Nov 2009 15:59:00 +0000

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

noreply@blogger.com (wa5mlf) — Wed, 11 Nov 2009 19:53:00 +0000

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

noreply@blogger.com (wa5mlf) — Tue, 03 Nov 2009 15:49:00 +0000

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

noreply@blogger.com (wa5mlf) — Tue, 27 Oct 2009 03:17:00 +0000

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

noreply@blogger.com (wa5mlf) — Wed, 21 Oct 2009 11:33:00 +0000

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

noreply@blogger.com (wa5mlf) — Tue, 20 Oct 2009 11:39:00 +0000

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

noreply@blogger.com (wa5mlf) — Tue, 20 Oct 2009 11:33:00 +0000

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

Early telephone multiplex systems & Bell Labs

noreply@blogger.com (wa5mlf) — Sun, 20 Sep 2009 12:26:00 +0000

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

noreply@blogger.com (wa5mlf) — Thu, 03 Sep 2009 12:41:00 +0000

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

noreply@blogger.com (wa5mlf) — Fri, 21 Aug 2009 12:29:00 +0000

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

noreply@blogger.com (wa5mlf) — Thu, 20 Aug 2009 12:16:00 +0000

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

noreply@blogger.com (wa5mlf) — Mon, 17 Aug 2009 19:02:00 +0000

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

noreply@blogger.com (wa5mlf) — Mon, 17 Aug 2009 18:59:00 +0000

Photos by Gary, N4OLN

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

Skype under threat

noreply@blogger.com (wa5mlf) — Tue, 11 Aug 2009 13:42:00 +0000

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

noreply@blogger.com (wa5mlf) — Wed, 05 Aug 2009 23:50:00 +0000

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

noreply@blogger.com (wa5mlf) — Mon, 27 Jul 2009 15:10:00 +0000

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

noreply@blogger.com (wa5mlf) — Fri, 24 Jul 2009 20:10:00 +0000

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

noreply@blogger.com (wa5mlf) — Tue, 30 Jun 2009 14:27:00 +0000

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

noreply@blogger.com (wa5mlf) — Tue, 12 May 2009 14:15:00 +0000

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.