August 16, 2017
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Here is 24 hours of WSPR data collected from the 20m Vertical Dipole:
There were 114 unique receive spots and 90 unique heard from spots with 1W transmit. This seems low compared to N5Cey’s 20m 1/4 wave vertical which typically receives 180 to 200 unique spots from his QTH near Los Fresnos.
I did some A vs. B tests on SSB yesterday switching between the 1/4 wave vertical and the vertical dipole. This time I used a remote receiver using Websdr.org. I connected to a station in the San Fransisco area and monitored my voice transmissions. In this case the vertical dipole came in about 1 S units stronger. I then switched to a station in New Jersey and the opposite was true!
I am going to do some additional testing on various 20m vertical configurations using WSPR over the next couple of days.
August 12, 2017
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Here in South Texas you hear a lot about the Canicula. July 14 through August 24th is considered to be the hottest part of the year. It’s 94° F here today but when you add the 54% humidity we get a heat index of 106° F. So naturally I choose today to play with a new antenna!
I built a vertical dipole for 20m today using two Workman Hamsticks. I thought this would be fairly easy as I didn’t have to get it too far off the ground. More on that later…
I read that one ham had pretty good luck with the stinger set at 38″ so I set that as a starting point. I set it up vertically on a painters pole with the bottom stinger about a foot off the ground and found the SWR minimum was in the 13.5 Mhz range. I shortend the stingers and the SWR went down to the 13 Mhz range. I played with this for some time until the whole mess collapsed in the breeze. Arrrgh!
I came inside and after re-hydrating played around with the antenna again. Nothing I did seemsed to work in getting it to tune in the 14m band. I got it back to the original configuration and ventured outside again. I set it up as before and the SWR was in the 13.5Mhz range again. This time I guyed the painters pole and sent it up a few feet. The SWR started going down with the minimum frequency going up into the 20m band…Aha! I raised it up so the feed point was about 15 to 16 ft off the ground. This put the end of the stinger at about 8 feet. Now the SWR response looked good with 2:1 or less across most of the 20m band.
Inside again now I started to tune around and found the SWR swinging again. Suspected Common Mode Currents again so went outside and lowered the antenna to 8 feet, redressed the coax so that it comes out away from the feed point at 90° for about three feet. Now everything is working out fine. I made an SSB contact to Chile and to Guatemala right off.
So here is what I learned today:
- It is too hot in South Texas in August to play with antennas…wait till early morning or very late in the afternoon next time.
- A vertical dipole needs to be a few feet off the ground to tune properly
- It is vitally important that the coax feed line in a vertical dipole come out at at 90° angle for several feet to avoid common mode currents.
Here is a view of the antenna:
Here is the SWR plot:
Will run 1W WSPR for 24 hours and compare data with the 1/4 Wave vertical.