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Strong Rd feedback in mh3

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Edouard Lafargue

Strong Rd feedback in mh3

I was operating portable today, with a long wire in a tree and
counterpoise on the ground, and no matter what I did, every time I pushed
the mic button, I got super strong RF feedback in audio monitoring,
apparently picked up by the MH3 cable - things got slightly better if I
tried to bunch/coil the MH3 cable. Is this common?

I only managed to work one station in Indiana in the time I tried, most of
the time what I heard in my headphones while transmitting was
unintelligible garble, so it is no surprise others didn't hear me, I
guess...

My KX3 has got an internal ATU and it managed to match the long wire
perfectly at each frequency I tried to operate...

Any advice?

Ed
W6ELA

(phone)
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Don Wilhelm

Re: Strong Rd feedback in mh3

Ed,

Yes, that can be common with long wire antennas - that can happen with
any transceiver, it is not unique to the K3 or KX3.

Change the length of your long wire by 1/8 wavelength at the frequency
you are having trouble with.

The situation is that you have a high RF voltage on that antenna near
the shack end.
Even though the tuner can match it, it can produce a strong RF Field in
the shack.

73,
Don W3FPR

On 5/28/2016 11:17 PM, Edouard Lafargue wrote:

> I was operating portable today, with a long wire in a tree and
> counterpoise on the ground, and no matter what I did, every time I pushed
> the mic button, I got super strong RF feedback in audio monitoring,
> apparently picked up by the MH3 cable - things got slightly better if I
> tried to bunch/coil the MH3 cable. Is this common?
>
> I only managed to work one station in Indiana in the time I tried, most of
> the time what I heard in my headphones while transmitting was
> unintelligible garble, so it is no surprise others didn't hear me, I
> guess...
>
> My KX3 has got an internal ATU and it managed to match the long wire
> perfectly at each frequency I tried to operate...
>
>

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wayne burdick

Re: Strong Rd feedback in mh3

Administrator

Also try a QRP balun at the radio, such as our BL1 or BL2.

73,
Wayne
N6KR

On May 28, 2016, at 8:43 PM, Don Wilhelm <[hidden email]> wrote:

> Ed,
>
> Yes, that can be common with long wire antennas - that can happen with any transceiver, it is not unique to the K3 or KX3.
>
> Change the length of your long wire by 1/8 wavelength at the frequency you are having trouble with.
>
> The situation is that you have a high RF voltage on that antenna near the shack end.
> Even though the tuner can match it, it can produce a strong RF Field in the shack.
>
> 73,
> Don W3FPR
>
> On 5/28/2016 11:17 PM, Edouard Lafargue wrote:
>> I was operating portable today, with a long wire in a tree and
>> counterpoise on the ground, and no matter what I did, every time I pushed
>> the mic button, I got super strong RF feedback in audio monitoring,
>> apparently picked up by the MH3 cable - things got slightly better if I
>> tried to bunch/coil the MH3 cable. Is this common?
>>
>> I only managed to work one station in Indiana in the time I tried, most of
>> the time what I heard in my headphones while transmitting was
>> unintelligible garble, so it is no surprise others didn't hear me, I
>> guess...
>>
>> My KX3 has got an internal ATU and it managed to match the long wire
>> perfectly at each frequency I tried to operate...
>>
>>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Edouard Lafargue

Re: Strong Rd feedback in mh3

Thanks everyone! Good advice. Now that I have better Internet access
again (btw I meant "RF" not "Rd" in the subject line, of course), I
discovered this article on ... elecraft.com :
http://www.elecraft.com/Apps/eliminating_tx_rf_feedback_probl.htm :-)

I will experiment with less random lengths for my random wires, and
better counterpoises, and a small balun if necessary.

73 de ed w6ela

On Sun, May 29, 2016 at 2:05 PM, Wayne Burdick <[hidden email]> wrote:

> Also try a QRP balun at the radio, such as our BL1 or BL2.
>
> 73,
> Wayne
> N6KR
>
>
> On May 28, 2016, at 8:43 PM, Don Wilhelm <[hidden email]> wrote:
>
> > Ed,
> >
> > Yes, that can be common with long wire antennas - that can happen with
> any transceiver, it is not unique to the K3 or KX3.
> >
> > Change the length of your long wire by 1/8 wavelength at the frequency
> you are having trouble with.
> >
> > The situation is that you have a high RF voltage on that antenna near
> the shack end.
> > Even though the tuner can match it, it can produce a strong RF Field in
> the shack.
> >
> > 73,
> > Don W3FPR
> >
> > On 5/28/2016 11:17 PM, Edouard Lafargue wrote:
> >> I was operating portable today, with a long wire in a tree and
> >> counterpoise on the ground, and no matter what I did, every time I
> pushed
> >> the mic button, I got super strong RF feedback in audio monitoring,
> >> apparently picked up by the MH3 cable - things got slightly better if I
> >> tried to bunch/coil the MH3 cable. Is this common?
> >>
> >> I only managed to work one station in Indiana in the time I tried, most
> of
> >> the time what I heard in my headphones while transmitting was
> >> unintelligible garble, so it is no surprise others didn't hear me, I
> >> guess...
> >>
> >> My KX3 has got an internal ATU and it managed to match the long wire
> >> perfectly at each frequency I tried to operate...
> >>
> >>
> >
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> > Message delivered to [hidden email]
>
>