Back in January 2014, a few of us local hams tried an experiment. The idea was to try VHF/UHF SSB on a local level with vertical antennae, rather than horizontal. Everybody has a vertical antenna for FM, but not very many have a horizontal antenna. So N0YNT (Matt), KD0UIH (Chuck), KD0WZW (Pete), and I tried it out. UHF SSB didn't really work very well, but we got two-metre SSB to work nicely with a vertical antenna.
With the recent tropo ducting affecting even UHF propagation, I began to think about UHF SSB again. Maybe UHF SSB was viable locally at night. After all, people work UHF SSB with 5W and a three-element beam and make it 50 miles. I also wondered if tropo ducting affected polarisation like ionospheric bounces do. Maybe UHF weak-signal modes could work with vertical polarisation if tropo ducting gave it a boost.
I really wanted to get some answers, and that would require other people to help out. So I contrived an experiment. It would have to be something that people could do at their leisure, and something that wouldn't require a lot of time or co-ordination. What I did was set up a propagation beacon and emailed several hams to ask for their participation. A few were willing to give it a try.
A CW beacon was set up on 432.325 from 6:30 PM to about 9 PM, and it fired every three minutes. The Yaesu FT-897D has a built-in CW beacon function, though it only runs 20W on UHF. At 13 wpm, there was more than enough time to hear the beacon signal. I used the same vertical antenna that had worked so well for our 2014 VHF SSB experiment. The beacon would run for three nights, so there would be enough time for everyone to listen for it.
The operators that participated were N0AGI (Nagi), AE0CX (Chuck), and KE0NA (Dave). At various points, Dave also set up his own beacon using a beam to get better results.
The results were disappointing, but that's why you do an experiment. Dave was able to hear the beacon at about nine miles distance, but it was weak. Chuck, in St. Paul, couldn't hear it all. Nagi, in Prior Lake, also couldn't hear it. The others were intrigued enough by this effort to try again on two metres.
A beacon was set up on 144.285 with 20W. Dave heard it at 569, compared to 549 on UHF. This morning, I set up the Yagi to point south and ran 50W in hopes that Nagi would be able to hear it. He did. Here's the video. It's a strong signal and completely readable.
The interesting thing is that Nagi and I can't reach each other with UHF. He runs a repeater on 442.075+ from a tower at his home. I can't even hear it ID with a six-element Yagi pointed straight at it. He can't hear the UHF CW beacon when it's beamed at him, so weak-signal modes don't help. But he can clearly hear a two-metre beacon.
Dave's case is also interesting when comparing the two bands. Here's a video of his reception of the UHF beacon. There's nothing on the S-meter, yet the signal is completely clear. This is what Dave and I also found when experimenting with UHF FM simplex before. The signal itself hardly breaks S1, but it's completely readable. Now look at the video of Dave receiving the VHF beacon. It's S7, but about as clear as the UHF signal was.
I really did expect better results on UHF. I had even thought that there might be a use for a UHF propagation beacon locally. We didn't try horizontal polarisation on either band. I'll leave that for someone else to experiment with. Frankly, I'm bewildered by the poor UHF results. A few FM repeaters in town run with not much more than 20W on FM, and they don't use beams. They reach further than nine miles. Shouldn't weak-signal modes perform better than FM? Is there something about UHF weak-signal modes that requires horizontal polarisation? Remember, we were working vertical-to vertical, so there weren't any cross-polarisation losses.
On the other hand, VHF worked quite well. We used vertical antennae in that case, and that didn't seem to impede propagation. Two-metre weak-signal modes worked in a case where UHF failed in both FM and CW. I can even see a case being made for a two-metre propagation beacon in town, such as exist on HF.
I didn't see any evidence that tropo ducting had any effect on our efforts on either band. During the period that the beacon was operating, I was able to reach several FM repeaters that are unavailable otherwise. For example, the UHF Hugo 444.050 machine opened up at night at S8 levels. None of this translated to greater coverage for the UHF beacon. How is it that I can clearly work an FM repeater 22 miles away with the same rig that fails to reach a station 14 miles away (AE0CX) using CW on the same band? I'm completely baffled. Does tropo work differently for weak-signal modes? Vertical polarisation was used in both cases, FM and CW. It makes no sense, but there it is.
Even stranger was that AE0CX (Chuck) couldn't hear KE0NA's (Dave) UHF beacon at a distance of about six miles. That's almost HT distance for FM. Both were using roof-mounted antennae, and Dave was running 20W. Maybe there's something about UHF weak-signal modes that makes vertical polarisation untenable, but doesn't affect FM. Again, I'm baffled.
Out of the four operators that participated in this effort, we have two Extras and one General; I'm the "dummy". Maybe someone else can make sense of these results.
We proved before that 2M SSB voice is viable with a vertical antenna, provided you are communicating with other vertically-polarised stations. This experiment really drove that point home. CW was used because it eliminated the need for someone to actually talk for hours on end. The point was not to prove that CW was an effective mode for local two-metre communication. Having said that, I could see 2M CW being a viable means for local operators to learn the code in a "hands-on" manner, without requiring anything more than their current VHF vertical antenna.
Somewhere down the line, I'd like to see if QRP power levels (such as the FT-817ND offers) are effective for local two-metre weak-signal work. It might also be interesting to compare horizontal and vertical polarisation, and find out if it makes a dramatic difference for UHF. I'm also intrigued now at the possibility of horizontally-polarised FM, especially on UHF.
Even though this experiment was perplexing and challenged my pre-conceived notions, it was gratifying to find local operators are still willing to experiment and try different things. If someone else wants to try beaconing with different antennae arrangements from different distances or at different power levels, I'm always open to that. Too often, I run into "know-it-all" people that never try different things because they already 'know' what the results will be. That seems counter to the spirit of amateur radio. In this case, though, a few people stepped up and tried something that they hadn't done before -- without 'knowing' what the results would be in advance.
Weak-signal modes aren't for everyone, and there isn't a lot of activity to justify the expense of the equipment needed for VHF/UHF work. I'm not trying evangelise anything, however. It's all about figuring things out and thinking "outside the box".
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