Assumed setup: A is Challenger and B is TW2010, switched after every transmission (16 transmissions from 14:36 UTC, order A B A B A B A B …)

Summary

Too close to call. Reach leans Challenger, heard by 103 receivers against 96, but not enough to call, and Challenger looks ahead by about 0.7 dB, but it could be anywhere from Challenger ahead by 2.6 dB to TW2010 ahead by 1.1 dB.

• 📡 Reach: 103 receivers heard A and 96 receivers heard B (10 only A, 3 only B, 93 both) — A heard by more receivers in 5 of 8 pairs, B in 3: within normal variation. Challenger leads, but if the two really reached equally, a split this lopsided in that direction would still happen about 36% of the time: suggestive, not enough to call it.
• 📶 Strength: Inconclusive: at the 80 shared receivers, Challenger looks ahead by about 0.7 dB, but it could be anywhere from Challenger ahead by 2.6 dB to TW2010 ahead by 1.1 dB. Challenger leads, but if the two were really equal, a lead this big would still show up about 21% of the time: suggestive, not enough to call it. A was stronger at 41, B at 28, tied at 11.
• 🌍 Similar farthest reach. Farthest receiver: A 4,815 mi (HB9ZHK), B 4,815 mi (HB9ZHK).
• 📏 By distance: no distance range stands out.
• 🧭 By direction: no direction stands out.
• 🔁 Consistency: over 8 rounds of A then B, A was stronger in 2 and B in 5. A mixed record: propagation moved around more than the antennas differ.

⚠️ Only receivers that were on the band during both sides’ transmissions are counted (106 of 142): they decoded other stations in your transmission slots. Many WSPR receivers hop between bands and are on this band only in some time slots, which would otherwise look like one side reaching more.

First a short story. There’s a Florida Ham Man who frequently offers antenna advice on his YouTube channel. Coincidentally, that advice often reflects the 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.

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 KJ6ER 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.

How about those YouTube influencers who shout into their SSB rigs “Can you hear me now?” “I’ll switch to the other antenna, and let me know which is better.” Can we trust our ears? Maybe in the cases with very notable signal differences. Yet, within a few minutes, the sun is likely to change the propagation enough to fool our ears.

Our analog hearing is very subjective. That’s why audiologists use sound proof booths and calibrated instruments to objectively measure how well we hear.

Being a data driven geek (40 years in the Information Technology business) I prefer more objective measurement. Let’s use some actual instrumentation rather than subjective judgement … and don’t get me started about bouncing S-meters.

My objective comparisons use results from far field WSPR receivers as measurement instruments. The method is to put both antennas on an A:B switch, to feed a WSPR signal to the switch, and to switch between the two antennas every two minutes (the normal WSPR cycle), and to continue switching back and forth while each antenna has 5, 6, or more cycles. The minute-to-minute changes get averaged into a longer timespan. Then, compare results.

A series of 3 articles described the process. Start here.

BETTER YET… Coming SOON, a less tedious approach to objective far field comparisons.

A/B antenna testing is always plagued with the “propagation constantly changes” remark that suggests the tests at different times are never equivalent. The technique I use here compares 2 antennas over the SAME timeframe, not two separate timeframes. I do this by switching the antennas back and forth for multiple 2 minute WSPR cycles as shown in part 1. That closes the gap on the changing propagation argument. THANKS to Lord Callum McCormick, M0MCX, for showing this technique.

Then, I Take the results from those runs and use AI (Grok is my AI choice) to do the grunt work of separating the 2 minute runs and analyzing the results. See part 2 for how that is done.

This post describes how the antennas are setup and points to complete results for tests run on 3 bands: 20M, 15M, and 10M.

EFHW

This EFHW is my everyday multi-band choice here at the Casa Easton Antenna Test Range. It consists of a wire approximately 62 feet long poised in an inverted vee form with the apex at about 20 feet, supported by a carbon fiber mast. There is a small coil (about 1uH) 7 feet from the feed end to balance the resonant nulls to where I expect them, the CW portions of the bands. It is fed by a home-built 49:1 autotransformer and that is preceded by a home-built Common Mode Choke.

I use it nearly everyday because it is easy to deploy (my antennas are all daytime-only) and band switching is done from my rig without any physical antenna manipulation. Simple, it works acceptably well for my favorite activity, POTA chasing. It can’t always reach the West Coast from central Florida, but covers a good part of the USA.

POTA PERFormer

Before anyone asks about the power lines in the distance, about 100 yards away, they are operated by Duke Energy and are completely free of any HF RF interference. Now, those plants in the raised bed are a different story. They are victims of an unusual hard frost here in central Florida.

Results: Each of the links below includes the prompt I used for Grok and Grok’s full response to those prompts. Quick bottom line: the PERFormer outperforms the EFHW on 20m and 15m, while the EFHW performs better on 10m. Caveat: 10m is always a crap shoot from here.

• Complete A/B results for EFHW vs POTA PERFormer 20 meters
• Complete A/B results for EFHW vs POTA PERFormer 15 meters
• Complete A/B results for EFHW vs POTA PERFormer 10 meters

There are other A/B comparisons I might run. The physical constraint is both antennas should be different shapes. Running 2 verticals against each other in the confined space of the Casa Easton Antenna Test Range will interfere with each other. Yet, the EFHW vs a Marauder or a Marauder vs a TW2010 might work. Perhaps…

There’s a new technology in town. Let’s persuade ChatGPT or GROK to do the grunge work. That’s what robots are for. Right?!

Lord Callum McCormick demonstrated how he uses AI to do the tedious work and to produce wonderful comparison charts. Basically, he asked ChatGPT to separate results stored in a spreadsheet and do various calculations on the two sets of results. Callum was seeking which antenna is “better.” But, better at what? Well, that’s why we want various calculations; number of stations that heard us, number of times they heard us, distance, and signal strength, etc.

Callum used ChatGPT. I stole his prompt and did the same with Grok. It’s fascinating watching the AI machine, collect the information, learn about how WSPR works, build a program to separate various data and do calculations. It tells you what it is doing as it goes along, and then shows the results you asked for. Be aware: one has to be precise in what we ask for. Some report that AI can sometimes give you more than you expect. Adherents of the AI industry describe these adventures into uncharted, unspecified, territory as “hallucinations.” My antennas are mysterious enough without hallucinations. Just give me only what I asked for. Thank you.

Callum specifies the prompt he used in his video. I copied it and modified it a bit for my own interests, omitting his RX analysis. I simplified the process to need only 2 log file uploads. We arrive at very similar results. Since I use most of my antennas enough to have a feel for them, these tests confirm and solidify what I know about them. They also give me a quick way to compare a newly built antenna with one of my long time favorites. It quickly eliminates the “Is it the antenna, or today’s propagation?” question.

Process:

• Set up both antennas
• Connect them to an A/B switch
• Set up the WSPR transmitter and use a PC to control the transmitter. Set the callsign, grid square, and band for the test.
• Start running.

• Watch the WSPR Transmitter control screen and every time the little red light shuts off, switch the A/B switch. Missing this will spoil the results.
• Continue for as long as you please. I like to go through 6-8 cycles for each antenna
• Collect the results from wsprnet.org. My preference is to sweep the data into a spreadsheet. Name that spreadsheet Transmit log.xlsx
• Create another spreadsheet named Time slots.xlst

• Fetch the prompt from the bottom of this post. NOTE WELL: Edit at least the line which specifies the label for the report.
• Upload the A/B prompt and the two spreadsheets to Grok.
• Sit back and watch it work.

Below is part of what Grok reported. I’ll explain this particular test in the next post. Or, you can go here to see all of what Grok prepared. Note that at the top of the Grok report you can see the actual prompt I used (feel free to steal for yourself) and the data files. Next post: more detail about this particular comparison.

72 de N4REE, Bob

===== Below is PART of the results from Grok =====

Overall Statistics

Metric	POTAPerformer (PERFormer)	EFHW
Total number of reports	384	236
Number of unique reporters	128	95
Median SNR	-17	-18
Median distance (km)	1551	1498
Maximum distance (km)	6599	3949

Distance Bucket Analysis

Bucket	POTAPerformer (PERFormer) Count / Median SNR	EFHW Count / Median SNR
Short haul (0–2000 km)	321 / -15	204 / -17
Medium haul (2000–4000 km)	62 / -18	32 / -19.5
Long haul (>4000 km)	1 / -26	0 / null

Observations on Antenna Behavior

Based strictly on the provided data, the POTAPerformer (PERFormer) generated 63% more total reports and engaged 35% more unique reporters than the EFHW, indicating broader overall reception during the test periods. It also achieved a slightly higher median SNR across all distances (-17 vs. -18) and a marginally higher median distance (1551 km vs. 1498 km), suggesting more consistent signal strength and reach under the tested conditions.

In short-haul distances, the POTAPerformer received…. (See more at the GROK report link)

---

Grok A/B Prompt

I have conducted a controlled A/B antenna comparison using WSPR only.
Both antennas were tested: at the same station on the same band at the same power within clearly defined time windows.
Nothing else was changed.
Find two files attached.
Both files are in Excel format.
1 The Timeslots Log in UTC notes which antenna was in use and exactly what time.
2 The Transmit log downloaded from WSPRnet in UTC.
The logs are accurate and in clear two-minute chunks – there is no need to be concerned about the times. 
My timeslot log includes the antenna label for every 2-minute WSPR slot. 

Your tasks: 
Label this report "A/B EFHW vs. POTAPerformer - 20m"
Identify which antenna was in use for each transmit period.
For each antenna, calculate:
- total number of reports
- number of unique reporters
- median SNR (not maximum)
- median distance
- maximum distance

Group TX results into distance buckets:
- short haul (0–2000 km)
- medium haul (2000–4000 km)
- long haul ([greater than] 4000 km)

For each bucket, show report count and median SNR. 
For each antenna, calculate:
- total decode count
- median distance (if available)
- maximum distance

Output requirements: Present results in clear tables.
Do not declare a single winner.
Explain what each antenna appears to be better suited for - based on the data.
Focus on differences in behavior, coverage, and application rather than preference or opinion.
Base conclusions strictly on the data provided, not on predicted behavior.
Explain how you calculated the results.

A common method of testing antennas uses weak signal propagation reporting (WSPR) to see how far a signal reaches.

OK. Let’s use WSPR to compare two antennas, A/B testing. Being a lifelong nerd, I really really like data driven results. We can run WSPR using one antenna and then the other, and compare results. Sounds simple.

Oh!!! Propagation varies by time of day, by band, and even from minute to minute. This leads many to think that an A/B comparison between 2 antennas using WSPR is not valid, because if I run 20 minutes on one antenna and then take time to switch, and maybe rearrange antennas, and run 20 minutes on the other, propagation will most likely have changed, especially if there is a notable amount of time between the two test periods.

Yes, there are those of you out there who will suggest using 2 different callsigns, one for each antenna. First, good if you have 2 available. Second, you have 8 seconds to pause the transmission, change the callsign, throw the switch, and restart transmission. See how well that works out. It’s a lot less error prone to let the transmitter run continuously and sort out the collected results.

Next, collect the results from wsprnet.org of from wspr.rocks, separate the reports into two buckets, one for each antenna, and analyze things such as number of spots, signal strengths, and distances. Yeah, sounds simple. … until you get this honking large spreadsheet downloaded and tediously try to separate every other line into two separate spreadsheets (one for each antenna). OH SNAP!

Doing this without any other tools is so tedious and error prone that I defy anyone not mix up results between the two antennas.

There is a better way. Lord Callum McCormick led the way recently and I’m stealing directly from him. I’ll show you the technique in the next post. …

72 de N4REE, Bob