HF Radio Propagation Modeling

Today's antenna modeling programs, like EZNEC and 4nec2, use the decades-old NEC program code to calculate the electric and magnetic fields produced by an antenna in 3 dimensions. (They also model parameters like impedance to assess the power efficiency of the antenna and transmission line combination.) We normally look at the radiation pattern results for the far field, considered to be greater than 2 wavelengths away from the antenna. NEC-based software is not equipped to model the fields at a great distance. The software does not model what happens to the electromagnetic energy as it propagates over a long distance.

To complete the picture of radio communication between two HF transceivers we need to look at radio propagation tools. Here are two links that list some of the available resources:

• Real-Time HF Propagation Prediction
• High Frequency Propagation Models

Both links make reference to VOACAP, which I became aware of while using 4nec2. I have not yet tried to use it, but I saw that VOACAP has both online and downloadable versions. 4nec2 has a utility for exporting an antenna design in the format required by VOACAP to model the propagation. Common pre-built antenna models can also be used as inputs to VOACAP. For point-to-point propagation modeling the design of the antenna at each end should be known. The first link above has a nice primer on VOACAP and a quick guide with lots of information.

The second link above also lists a program HFWIN32 which is said to contain 32-bit versions of three published propagation modeling tools: ICEPAC, VOACAP and REC533. Some more recent instructions and links are available at this web site.

A newer, freeware program HamCAP is designed to interface with VOACAP to predict HF radio propagation.

Playing with these propagation models may contribute to a better understanding of which antenna types should work best for a given frequency, time of day, geographic locations and solar conditions.
 

The History of Southern Regional Center (SO) and the WEDIXIE ARC

by G. Warren Coleman / WD4NIT

The WEDIXIE Amateur Radio Club began in 1968 at the Western Electric Southern Regional Engineering Center in Atlanta, GA. WEDIXIE was a prefix that applied to all of the corporately-sponsored employee clubs at the site, including an active scuba club, a personal computer club, an indoor and outdoor recreation club, and of course, the ham radio club. The WE in WEDIXIE stands for the Western Electric Company. The DIXIE portion of the name of course refers to the location's southern heritage.

Western management provided the club with a room in the facility to serve as a ham shack. It was located on the first floor and was about 12-15 ft square. The antennas were located on the roof, and included both wire and beam antennas fed with runs of coax and 7/8 inch Andrews Heliax cable.
In 1984 the American Telephone & Telegraph Company (AT&T), the original owner of Western Electric, changed the WE-CO name to AT&T Network Systems. In 1996, AT&T spun off the company, which then became Lucent Technologies. Around 2002, a greatly downsized Southern Regional Center moved from 6701 Roswell Rd in Sandy Springs, GA, to Alpharetta, about 15 miles to the north. The original property was sold and most of it was eventually demolished. In 2006, Lucent was purchased by and merged into the French-based company Alcatel, which changed its name to Alcatel-Lucent.

By the time the Regional Center was moved to Alpharetta, only two active employees of the radio club remained and the company decided they would not sponsor a club there. Not wanting to let their beloved club call WB4MZO be reassigned elsewhere, the club's retired members reincarnated the WEDIXIE ARC as a retiree club and received permission from Lucent management to continue to use the WE trademark in its name. We still fondly remember the "Good Old Days," and strive to keep the club active and to preserve the Western Electric Company spirit.
Our members, though still active amateurs, now move a little slower than they once did, but we remain ready and able to assist the community in times of need. We have elected club officers and a trustee, and our club members especially look forward to participating in the annual Field Day exercise each year, a contest which has had a WB4MZO presence since well before the turn of the millennium.

Google Hangout Setup for Radio Patch

This document presents the steps for setting up a Google Hangout for voice patching to a transceiver or other applications. It assumes that you have already established the required transmit and receive audio interfaces between a transceiver and a computer that runs the Google Hangout Internet application. It is convenient for the control operator of the transceiver to join the Hangout with a separate computer, tablet or smart phone for the purpose of monitoring the patch audio and speaking to other participants on the Hangout.
Updated 11/02/2015

TPWINLOG File Locations

If you are using Windows 7 or Windows 10, and:

• if you directed the TPWINLOG 2015 program to install in C:\TPQ then all the files you need (including TPLogOut.txt if you print to file) will be located in that folder.
• if you allowed TPWINLOG 2015 to install in the default folder:
  C:\Program Files (x86)\TPQ
  then your files (including TPLogOut.txt if you print to file) will be located at:
  C:\Users\name\AppData\Local\VirtualStore\Program Files (x86)\TPQ
  where 'name' is the Windows user name under which the program was run.

In Windows 7, if you navigate to the program's folder C:\Program Files (x86)\TPQ
you can reach the data folder by clicking on Compatibility files, as shown in the screen shot below.

click above to enlarge

The Compatibility files button shown above for Windows 7 does not appear to be available in Windows 10, but you can open the file explorer at C:\Users and 'drill down' to 
C:\Users\name\AppData\Local\VirtualStore\Program Files (x86)\TPQ
where 'name' is the Windows user name under which the program was run.

Another option is to search for tpqsolog using the search box near the upper right corner of the file explorer in either version of Windows. However, since AppData is a hidden folder, you may need to start your search there, rather than at a higher level in the folder (directory) tree. I found that a standard (non-admin) user search starting at C:\Users would not find the file tpqsolog.txt, but the same search starting from C:\Users\name\AppData does find the file.

Map of Members on Saturday Net

Here are two views from Google Earth that show the locations of Bell Ringer members who have checked into our Saturday morning net during the past two years, according to records kept by W4BXI. The first view covers a wide area to show all station locations. Four circles show a range in miles from W4BXI's location. The legend at top right gives the radius for each circle.

Click on map for enlarged view.

The second view covers a smaller area to expand the view of the many stations located in Alabama and Georgia. Three circles show the range in miles from W4BXI's location.

Click on map for enlarged view.

These map views may help us to better understand the variation in reception among our members according to their ranges and the radio propagation experienced by frequency band and time of day.

I can easily add and remove stations and generate range circles centered on any point on the map.

Short Dipole & Horizontal Loop for 3.5 - 30 MHz

A recurring discussion topic during our morning QSOs involves two of the multi-band HF antennas presented in the article Choosing the Correct Balun, by W8JI. The antennas are:

• Multi-band Dipole / Doublet - described on pages 7-10
• Horizontal Loop - described on pages 16-19

The focus of our discussions has been on versions of these antennas that are sized for 3.5 - 30 MHz. To gain some additional insights about how these antennas compare, I modeled each with antenna analysis software. I used a height of 70 ft above average ground conditions, to be consistent with some of the data presented by W8JI. The following PDF documents present the analysis results:

• Radiation Patterns
• SWR and Impedance

The radiation pattern graphics show only the total gain views. The software can also present the gain views for horizontal polarization or vertical polarization separately. I limited the radiation pattern analysis to the 80, 40, 20, 15 and 10 m bands, but any frequency can be entered to generate any desired patterns. Would anyone like to see what the patterns look like for an 80 m loop on 1296 MHz?

The SWR and impedance results cover the full range from 3.5 to 30 MHz. The last page shows the impedance for selected frequencies within the ham bands. Only the points are plotted on that graph.

Further analysis will compare the SWR and impedance results for 300 ohm and 450 ohm feedlines. I believe that the software can also provide an overall efficiency figure for the combination of feedline and antenna.

Update 7/4/15: Below is a graph of impedance (for the shortened dipole) calculated at selected frequencies within the HF ham bands (3-30 MHz). These points are for the transmitter end of a 300-ohm feedline for 3 different lengths: 1/8 wavelength, 1/4 wavelength and 3/8 wavelength (at 3.5 MHz).  The 1/8 and 3/8 wavelength cases correspond to the recommendations of the W8JI article referenced above.  I was a bit surprised at the high impedance values for the 3/8 wavelength case in the 75/80 m band, and turned to the venerable Smith Chart to double check the impedance transformation of the 3 feedline lengths. Its results agreed with the results of the NEC software. I can provide a table of the graph data to anyone who is interested.

It was interesting to see that the 1/4 wavelength feeder gave reasonable impedance levels on some of the bands, and that the 1/8 wavelength case was sometimes better than the 3/8 wavelength case. Impedance levels for a 5/8 wavelength feedline should be similar to those for the 1/8 wavelength case.

I plan to analyze 3 lengths of 450-ohm feedline in the same manner to include in this article. Also planned are studies of 300-ohm and 450-ohm feedline impedance for the loop antenna.

W4BXI - Net control on RV Service Net

Click here for an audio recording of W4BXI on the RV Service Net on 7191 kHz, as heard on my transceiver in Baton Rouge. This was at 0645 CDT this morning. John's signal was reading S9.

Baluns

Here are a few selected articles that were referenced during our recent on-air discussions of baluns, and voltage vs current baluns in particular:

Balanced - Unbalanced - Balanced, by VK5AJL
Lots of good definitions and illustrations.
See the comment posted below by N4NR. Other sources refute the author's contention that current baluns are only designed for 1:1 ratio.

Baluns: What They Do and How They Do It, by W7EL
An illustrated discussion by the author of EZNEC software.

Choosing the Correct Balun, by W8JI
An article that our group has consulted many times.

Broadband Baluns
Focus on air-core and ferrite-bead choke baluns.

Common Mode Chokes
A chart of impedance measurements

Special thanks to W4PRE who directed me to the Chattanooga Amateur Radio Club website that includes many good antenna-related topics on the Links page.

TPWINLOG Data Files

TPWINLOG 2015 creates the following data files to accomplish logging and scoring for the Telephone Pioneer QSO Party:

• BonusCall.txt
• Chapsworked.txt
• CWchapsworked.txt
• LogInFile.txt
• TPHistory.txt
• TPLogOut.txt
• tpqsolog.txt

If you need to edit any of these files independent of TPWINLOG, you must navigate to where they are stored on your system and use a plain text editor, such as Notepad, to make the edits. Be sure to make a backup copy of a file before editing.

The location of these files depends upon how you installed the program. Section 2.1 of the ReadMe file has the following information and suggestion:

THE INSTALL PROGRAM WILL INDICATE THAT IT IS GOING TO
WRITE THE FILES TO: C:\Program Files\TPQ
The install program will create the TPQ folder in the Program
Files folder. OR .. you can click the Change Directory command
button and install to some other folder. Those using Windows
Vista or Windows 7 may wish to change the path to C:\TPQ to
prevent file redirection. This makes finding program written (data)
files much easier.

CASE 1: If you follow this suggestion you will easily find all of the data files in C:\TPQ, as shown in the Windows Explorer screen shot below.

Click to enlarge.

CASE 2: If you allow the program to install to its default directory, the program and data files will reside in two separate directories. The program will be found in C:\Program Files (x86)\TPQ, along with initial copies of two data files that are write-protected, as shown below.

Click to enlarge.

To access the complete set of data files you must navigate to their directory by clicking the Compatibility files button as noted in red above. This will take you to the view that is shown below.

Click to enlarge.

The examples above are from my installations on Windows 7 PCs.

If you must know, the full path to this directory is:
C:\Users\John\AppData\Local\VirtualStore\Program Files (x86)\TPQ
and AppData is a hidden directory, but is easily reached using the Compatibility files button shown previously. Your username will be where "John" appears. You can edit and save the data files in this directory as discussed in the second paragraph above.

If you only need to add some new entries to TPHistory.txt, you can accomplish that from within TPWINLOG.  Enter the station's CallSign, Chapter and Name in the boxes near the bottom of the TPWINLOG window, then click HistoryFileAdd under the HistoryFile menu. Your new entry will be added to the end of the file.

Click to enlarge.

Send me an email or post a comment if you have any questions.

TPWINLOG 2015 -- History File

Based on some questions about how the history file is updated during contact entries in TPWINLOG, I performed some tests this morning.

When the program is installed, the original, default history file (from the downloaded zip file) TPHistory.txt is put into place. While the program is used, the first contact with new station that is not found in the original history file is added to the end of the history file.

We recommend that you practice using the program well in advance of the event, entering practice contacts. Before you start participating in the event you need to delete the log of practice contacts by choosing File, DeleteLog, as shown below.

My testing confirms that this delete function will clear out the following files:
   tpqsolog.txt
   Chapsworked.txt
   CWchapsworked.txt
It will not clear out the TPHistory.txt file. Subsequent use of the program will make use of any new station history data (not in the original history file) that was entered during your earlier use of the program. I tested this by entering a fictitious call sign that I knew was not in the original history file. 

Further testing reveals that changes (e.g. chapter #) made during subsequent contacts with any station will not be saved to the history file. However, TPWINLOG will (apparently) consult the tpqsolog.txt file first when subsequent contacts are made with the station whose details were changed on the previous contact entry. Naturally, those changes will be lost when the practice log file is deleted. Any station details that you wish to preserve need to be entered directly into the history file (using a plain text editor) so that they will be found when you start over with a blank log file. 

Also, if you do make changes to station data during the event, especially chapter changes, you will want to edit your final log file prior to printing results so that you don't end up with something like 2 chapter numbers recorded for the same call sign. 

Please send me email if anything above is not clear or if you have other questions.

Windows Computer Security -- Using a standard user account

By default Windows sets up the initial user account with full admin privileges. This makes it very easy for the user and for malware / spyware / adware publishers to install new programs on your computer. A study reported that of all the security patches issued by Microsoft in 2013, 92% of the vulnerability exploits would have been blocked by use a of standard user account.

Here is the process I have used successfully on 11 Windows 7 computers to convert an existing admin user account to a standard account:

Create a new admin account:

• Log in to your existing user account that has admin privileges
• Go to Control Panel, User Accounts
• Click Manage another account
• Click Create a new account
• Enter a name for the new account (e.g. Admin)
• Click the Administrator button
• Click Create Account
• Click on the new account icon
• Click Create a password
• Enter password (different from normal user password) in the two boxes
• Click the button Create password
• Return to desktop and log out of your normal user account

Downgrade normal user account to standard:

• Log in to your newly created admin account
• Go to Control Panel, User Accounts
• Click Manage another account
• Click on the normal user icon
• Click Change the account type
• Click Standard user
• Click the button Change Account type
• Return to desktop and log out of your admin account

Log in to your normal account and resume use

If you attempt to install a new program or an upgrade (other than Microsoft updates), you will be prompted to enter the password for an admin account. Pay close attention! If this appears for a program you don't recognize or did not choose to install, it may be malware attempting to install.

On rare occasions (in my experience) a program may need to be installed or updated when logged into an admin account. In most, but not all cases, you may be able to simply right-click on the program file and select "Run as administrator". 

Updates 3/27/15: 

• One example of a program that must be run from a logged-in admin account is Evernote. When I am using the program from my standard account and it announces an update available, it tells me to ask my administrator to install the update. It does not make the update available to install by my standard account.
• Many programs allow me to install updates by simply entering my admin password when the UAC pop-up box appears. In some cases the update downloads go to my admin user's download folder rather than to my standard user download folder.

I believe that the same or very similar steps would apply to Windows 8 computers.


Also see these three rules for online security published by Brian Krebs. 

3 Antennas Compared

Recently we discussed the comparative performance of 3 wire antennas, sized for 80 m, on 3.5 MHz and above. I used antenna modeling to compare the following antennas, all at 40 ft above rocky ground:

• W8JI 110 ft dipole
• Horizontal Loop of 287 ft
• 133 ft Off-Center Fed Dipole

I found that the shapes of the radiation patterns vary, but the peak total gain figures are similar among the 3 for the two frequencies I used: 3.5 and 7.2 MHz. Here is a summary of results:

	Maximum Total Gain (dB)
	@ 3.5 MHz	@7.2 MHz
110 ft dipole	5.53	6.59
Horizontal Loop of 287 ft	6.39	5.83
133 ft OCF Dipole	5.74	6.42

Radiation patterns for the 2 frequencies are shown in this PDF file. If you zoom in enough you can read the data on each graph.  Patterns for additional frequencies are easily generated.

I used a similar side-by-side presentation in this 2010 posting when comparing two antennas sized for 160 m (110 ft or 130 ft wire to each side of the feed point).

WA5MLF

Feedline Loss & Other Characteristics

Here are some online resources you can use to calculate the loss and other characteristics for specified feedline types or geometries:

• Cable Loss  (coaxial & ladder line)
• Coaxial Cable Calculator
• Coaxial Cable Power Ratings
• Coaxial Cable Equations
• Coax Cable Impedance Calculator

 If you want to find this and other posts in the future, be sure to use the blog's search feature. Look for this search box at the top left corner of the blog page

and enter your search term there.

In response, one or multiple blog postings will be presented if your search term matches one of the labels attached to a posting. This posting has the following labels attached: antenna, feedline, SWR.