While doing a lot of station work, moving antennas, updating cable runs, I’ve done a lot of antenna vector analysis, fixing grounds, removed a failed (defective?) AlphaDelta spark arrestor, and also listening to signal quality with my other HF Rig (Yaesu FT-991).
When checking 20m and 40m, I didn’t hear the clear, clean FT8 tone, but what sounds like an overwhelming hum. I recorded an example of this here.
Weird signal on FT8 20m & 40m bands.
Research into what this might be, continues. I’m considering shipping radio in for service, but don’t want to be without my rig for a month or so, and only find out nothing is wrong?
I’ve solicited opinion from other HAMs. Maybe I’ll find a solution that doesn’t involve shipping something to California.
Thanks to the installation of the Ameritron RCS-4 remote antenna switcher, it’s become much easier to compare my two HF antenna installations. With a flick of the rotator, it’s easy determine which antenna is the ‘loudest’ and which is tuning up to a lower final SWR.
The Antennas
G5RV
Mounted roughly 20′ in the air (trees don’t really get tall in Texas Hill Country), with a horizontal ‘L’ configuration, with 1 leg running N-S, and another ENE-SSW. This is fed entirely with repurposed RG6 satellite coax, through the remote switch box outside the house, and another 60′ run from the remote switcher to the ladder line.
Offset Fed Window 80 (OCF80)
Mounted roughly 20′ in the air, with an almost perfect N-S orientation, with the long let on the South side of the run. This fed with a mix of RG6 (shack to antenna switch), and 100′ of cheap RG58 from switcher to the feed elevated feed point in a tree.
RCS-4 Remote Coax Switcher
AMERITRON RCS-4 remote switch mounted and grounded outside shack/house.
Audible – which is the ‘loudest’
This was easy.. flipping back and forth between the G5RV and the OCF80 across various bands showed that the G5RV, was the loudest by roughly double (3db.. give or take). It’s quite obvious both to the ear, and to the scope which was the winner here.
Resonance – which is the most favorable
This is where it got interesting. Using the trusty RigExpert AA-35, I ran scans of both antennas from the shack side coax switch feed (through the switcher).
Ameritron RCS-4 Remote Coax Switch
The results sort of conflicted with my observations regarding which antenna seemed to be working better. I downloaded the scans from the RE and superimposed the two on a chart showing the HAM HF bands:
The OCF80 clearly (at least to me) seems to be markedly better in SWR, especially where it counts, in the grey HF bands. I was surprised to see the OFC80 is (or should be) a little better on 160m than the full-size 160m G5RV. The resonance is shifted to right (high) of most of the bands for the OCF80, and the opposite for the G5RV. I’ve done all I can to lengthen the OCF’s legs to shift the resonance lower, but it’s still not ‘right’.
This chart also explains why I’ve struggled with 80m as of late.. tuning is way off there. 60m is also a mess, but I’ve not tried to work 60 yet, so it’s not been an issue. But I’d like to see much better matching.
Considering that the RG6 most likely is a factor here in the shift and overall SWR, now that I’ve gotten hooked on HF, and gave upgraded radios, time to invest in proper coax. In the next week I’ll be ordering some, once I figure out how much I actually need! Another helpful feature in the RigExpert software is an analysis of the coax, including what I’m guessing is a pretty decent calculation of overall length. If this is right, I think a 500′ roll should get me from the office/shack to the switcher and out to the two antennas, retiring all the RG6.
Glad I could participate in the Costa Rican Bicentennial Special Event during the month of September.
A number of confirmed QSLs were made with the participating stations in Costa Rica. Contacts were made on 10m, 17m, 20m and 40m using FT8 digital protocol. There was a lot of traffic, and more than a couple of pileups, but even at though I’m limited to 100w, we were able to complete some solid contacts.
I’d like to thank the TI2HAS and the TI200I special event team for sending out such a wonderful looking commemorative certificate.
