First a short story. There’s a Florida Ham Man who frequently offers antenna advice on his YouTube channel. Coincidentally, that advice often reflects yhe most recent newsletter advice from a Belgian RF guru, who so happens to be an antenna manufacturer. Yes, of course, we’ve seen these collaborations from many ham influencers on YouTube. I point this one out because the Florida Ham Man and his RF guru friend have several times advised that the best way to measure antenna performance is with “far field” measurements. They are right. Yet, the guru offers no far field measurements for the antennas he sells (hmmmm?), and the Florida ham suggests the far field measurements require expensive equipment making them difficult to do.
BS! That story ends now! Perhaps these two guys don’t realize we already have an extensive collection of WSPR and RBN stations that act as our far field measurement equipment. These receivers listen for our tests and report them to easily accessible databases. In earlier articles, I described how a couple of us have used WSPR for our A:B comparisons.
The little ZachTek WSPR transmitter is my far field tool.
Well friends, Tim Hale, K5OHY, just made it A LOT EASIER to do objective far field A:B antenna comparisons. The process is straightforward:
- Set up the A and B antennas. In this comparison A is an inverted vee, at 20 feet, EFHW on the left. B is the KJ6ER Challenger on the right.
- Use a WSPR transmitter, either the desktop unit I like, or your own rig properly configured.
- Alternately transmit from antenna A, then B. Repeat the alternations a number of times to level out ongoing propagation changes. (more is better – this time I used 7 pairs)
- Compare the results. Compare number of spots, signal strengths, distances, etc.
Until now, that last bit was where it gets very tedious. Tim has flattened that tedium with an online tool that collects the results from the WSPR or RBM database and runs a number of analyses. The results are simply spectacular. You’ll see comparisons of the number of spots heard, signal strength, distance reach, and directional favoritism. The summary text is informative, and the illustrations are outstanding.
Go see it at: FarField Lab. The Compare antennas page offers several examples of real comparisons. Walk through any of them and check every detail.
Do It Yourself: Read the lower part of the Compare antennas page (it’s short) to quickly learn how to run your own tests, and then fill the form in the lefthand column to get your comparison started. The tool dynamically gathers the data from the online databases, and then produces far field reports for those antennas standing in your own field. I’m sure you will learn things about your antennas.
Be aware, the tool stores none of your data, but builds reports in real time, dynamically. As such, it might take a couple of seconds to respond.
Dig Deeper: Tim offers very extensive help about conducting your own comparisons and interpreting the results. Learn how to run either short comparisons, or longer running comparisons. Learn, if you want, the detailed math he uses and the way the reports are derived. Once again, you’ll learn more about your antennas.
Tim: MANY THANKS for such a powerful FAR FIELD tool!
Below are snippets from a recent comparison. I pitted my everyday use inverted vee EFHW against a new KJ6JER Challenger. It was run as a series of 14 two minute WSPR runs alternating A,B,A,B …. These give you a small glimpse of what Tim’s Far Field tool can do. Explore it yourself at FarField Lab.
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