Monday, September 5, 2016

TR20 NPOTA activation results

KX2 and tripod-mounted 20m Hamstick
I got up bright and early yesterday morn and drove to a location near Alto, TX to activate the El Camino Real de los Tejas National Historic Trail (TR20). If you know any Spanish at all, you know that any place named Alto would probably be a good choice for radio operations.

Despite the surplus of organic antenna supports exceeding 100-feet in height, my antenna was simply a 20m Hamstick vise-gripped to a camera tripod. To this, I attached two quarter-wave radials. About 10 feet of RG58 attached the antenna to the KX2 and a CQ on 20m CW led to effortless contacts from Cali to Nueva Jersey and many points in between, most with good signal levels.

Then I decided to try 20m SSB - and the mystery began...

The rig's autotuner made for a perfect match but when I called CQ I noticed strange behavior from the KX2's little RF Out meter. It wasn't moving in step with my speech. At times, it lingered at the max side of the scale even when I wasn't speaking. No one answered my CQ's. Then I unhooked the mic and tried using the KX2's internal microphone. All was well and I was able to contact several stations. Switching back to the external mic resulted in the same problems as before despite various settings of the audio input level control.

The KX2 has a "monitor" function which allowed me to hear my own audio as I spoke it. Sounded like crap. A lot of hash but not the squeal of audio feedback that I'd anticipated. Using the internal mic may be handy in some situations but not something I wanted to do in a NPOTA activation, so back to CW.

When I returned home, I hooked the KX2 up to my Yagi and tested it on 20m SSB with the external mic. Perfect. I can only guess that RF was getting into the mic line due to the close proximity of the antenna. I wish now I'd taken the time to deploy the PAR en-fed and see if the results repeated themselves. My point in using the "Hamstick on a tripod" was to see if such a combo is feasible given our current conditions. CW results suggest that it is but how to resolve that SSB-with-external-mic issue? Perhaps try different ground radial configs or use a longer length of RG58 to get the antenna further from the radio.

The best NPOTA-related QSO occurred after I returned home. As I was testing the KX2 on 20m phone, I was called by David N5KWD. I'd never heard of him but it turns out he lives about a mile from me. David has only been licensed a year and is already into ham radio in a big way.- he has activated 16 of the 17 NPOTA locations here in Texas by driving to them all in a loop. And I mean a BIG loop, circumnavigating the state to the tune of 3500-ish miles. Check out details of his NPOTA activations here.

He reported great audio from the KX2.


David Ryeburn VE7EZM and AF7BZ said...

My guess: RF on the outside of your feedline. Moving the GP antenna further away may or may not help (my guess is not). Get two ferrite toroids with large enough inside diameter to let the plugs on the ends of your RG58 pass tbrough. Put one at the base of the antenna after winding say 10 turns of coax through it. Put the other at the KX2 end. I'll bet this fixes it. Why did it behave with your Yagi? I'll bet you have a proper balun up there at the Yagi.

David Ryeburn VE7EZM and AF7BZ

John AE5X said...

I will try that David - and I need to try it in my backyard rather than driving 100 miles away and trying it ;-(
Yes, there is a balun up on the Yagi. Thanks for the suggestion. I'll post here how it goes but I am puzzled as to why operating CW didn't present any problems...

Hank, N8XX said...

You should move closer to your National Park/Trail. It's very easy to get to TR04, North Country National Scenic Trail for me, because it traverses this part of Michigan with closest point 2 miles from where I live. Was great on January 1, and up until about early June. By now we have about 9K contacts from numersous activators, so it's hard to attract attention.

If you don' like the ferrite toroids suggested by VE7EZM you might try carrying a faraday shield with you, and put yourself and the KX2 inside, and the antenna outside. (Well, thinking about it, it wouldn't be very practical, but I'm sure it would solve the problem. :)

72/73 de n8xx Hg
QRP >99.44% of the time

David Ryeburn VE7EZM and AF7BZ said...

You wrote "I am puzzled as to why operating CW didn't present any problems"

RF entering the chassis via the outside of the coax has to leave it somewhere else (Kirchhoff's current law) and one such "elsewhere" could be the mike cable. You could put another toroid on that, near where the mike plugs in. But it would be better to eliminate the common mode current in the first place. The circuitry connected to the paddle probably isn't as sensitive to RF as the circuitry connected to the mike cable.

John AE5X said...

There is a much closer NPOTA to activate but I've been there twice already. I have even more driving ahead for 2 other NPOTAs that I want to activate but will combine the activations with other reasons to be there (fishing, camping).

John AE5X said...

Thanks again, David. I will experiment with the same antenna + an old LDG balun I have around here somewhere.