Today I took my 60m QCX mini out for it's first run during a SOTA activation.? I was using a QRP Guys EFHW with an Elecraft T1 tuner with? 30ft ground wire laying across the ground.? The Mini kept hanging with a "G" symbol when keying.? Even when I stopped keying it would show a "G", hang, give a quick sidetone DIT, and then show "G" again.? This would repeat 9-10 times without me touching the paddle.



EFHWs typically have RFI due to their design.? This rig is supposed to be designed for portable use.? Most people use a wire or EFHW for portable/SOTA use.? Disappointed at how sensitive it is to RFI under what is considered (by me at least) to be a normal SOTA setup.?

I'm assuming there is no way to disable the GPS interface so that RFI won't cause it to have a seizure?

So an EFHW antenna should be exactly that: END FED HALF WAVE. Unfortunately many of the commercially, overpriced so-called EFHW antennas are not a half wave at all at the frequency of interest, but some random length wire with an overpriced balun at the end of them. Many won't tune certain frequencies even with an auto tuner and the RF at the feedpoint is very high and gets into the radio and other nearby devices.

For a 60m antenna that EFHW needs to be about 88' long and as high as possible. How long and high is yours???

Morning Richard.? My 60m Mini has no problems with my full length 60m EFHW and homebrew 49:1 transformer.? I've had it out on a number of SOTA activations using about 20 feet of feedline.? I've always found it curious that the QRP Guys unit requires an odd length of wire for each band that is not a half wave???

Ken,
W4KAC

On Sun, May 29, 2022 at 12:44 AM, Larry Gagnon wrote:

So an EFHW antenna should be exactly that: END FED HALF WAVE. Unfortunately many of the commercially, overpriced so-called EFHW antennas are not a half wave at all at the frequency of interest, but some random length wire with an overpriced balun at the end of them. Many won't tune certain frequencies even with an auto tuner and the RF at the feedpoint is very high and gets into the radio and other nearby devices.

For a 60m antenna that EFHW needs to be about 88' long and as high as possible. How long and high is yours???

I'm not arguing the fact that most EFHWs are not true EFHWs but the fact that a radio, marketed for portable ops, is so sensitive to RFI that it requires capacitors, choking, toroids, etc to be usable with the normal setups that most portable ops use.? I don't know of any SOTA ops that carry resonant antennas for all bands they work on.? Most carry a multiband EFHW.?

The GPS and WSPR features are nice, but I would prefer a radio that is made to be a radio without the extra niceties, or at least give an option to disable them.? No issues with MTR or Venus radios using the same antenna.

Richard

EfHW aren't miracle wires even with a T1 attached. Always understand the basic properties of a coax fed antenna before tuning it.??

An 80m EFHW is around 130 feet long. It will typically operate well on even and odd harmonics. Note that often this antenna misses 60 and 30 meters, the design of the antenna unravels there.?

Now for 60m operation cut your wire to a half wave and you should do better. You can use the same efhw transformer with different length wires. Perhaps put in your kit a 65 foot wire for 40/20 minutes, then have extensions for 60 and 80 meters.?

Don't get into paradigm of tuning a random length efhw, it wrecks the paradigm.?

Curt

On Mon 30 May Richard - N1RBD wrote:

I don't know of any SOTA ops that carry resonant antennas for all
bands they work on.

I use a link-dipole most of the time. It can be made resonant on 80, 60,
40, 30, 20 and 17 metres. Sometimes I also use it on 15 metres with the
links set to 40 metres and a little help from a tuner. I also have a few
mono-band verticals for the shorter HB bands, but they've not been out
for a while. I expect they'll come out of storage soon...

--
73, Rick, M0LEP

Richard: my EFHW SOTA antenna gets RF into my 40 and 20m QCX+ Mini radios, but not my 15m radio. Neither my 40-15m doublet nor my 40-15m linked dipoles do this and that is solely obviously just a result of high RF at the nearby feedpoint of an EFHW. The dipoles or doublet tend to easily outperform my EFHW in most situations, so I rarely use it.

The RF is probably being picked up by your paddle line and earbuds. I solved the RF problem with a bypass capacitor on the audio out and the two paddle lines right on the board. More details on this via a search here on the forum....

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...yeah that's obvious all right, but many SOTA ops use EFHW wires fed right at the rig so as to reduce the bulk and weight of requiring a coax feed to the wire. Also, if using a pole for wire support on a non-treed summit you normally want to be near the pole base for extra pole support.

On Sun, May 29, 2022 at 08:31 PM, Richard - N1RBD wrote:

I'm not arguing the fact that most EFHWs are not true EFHWs but the fact that a radio, marketed for portable ops, is so sensitive to RFI that it requires capacitors, choking, toroids, etc to be usable with the normal setups that most portable ops use.

It's a $55 radio; it also does not have an internal ATU, speaker, band scope, etc.? I'm not sure that the complaint about its sensitivity to RFI is well founded.? Also, in my limited experience, any radio can suffer from RFI issues if the antenna is a disaster.? I don't even have the metal case for my 40m QCX-Mini but a homemade EFHW cut at 63' does not cause any problems for my radio.? Feedline length has a noticeable difference on RFI coming off an EFHW.? I wrap my RG-58 feedline through a clip-on ferrite 6-7 times at .05 wavelength from the transformer to try and choke off any feed line radiation as well.??

If you are carrying a mono-band radio out for an activation, maybe you can carry a resonant mono-band antenna as well.? Or at lease a multi-band EFHW that resonates at your desired frequency without an ATU.??

My suggestions are only worth what you paid for them.
Joshua

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Nuff sed.