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K3 Distorted Audio On Transmit

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dave_w0ru

K3 Distorted Audio On Transmit

I have a K3, P3 and KPA500. Last night I was encountering some high SWR. The K3 has the KAT3 internal 100 watt antenna tuner. I do not have the KAT500 tuner. If the SWR was too high, the KPA500 indicated a fault and I went back to 100 watts with the K3. I tried bypassing the KAT3 to see how the SWR looked. The K3 started producing extremely distorted audio when I transmitted (I was listening with my headphones). The audio sounds like a loud roar. This only occurred on 20 and 30 meters at about 50-100 watts output using upper sideband (yes, I know we can't legally use USB on 30 meters, I just briefly keyed the PTT). The other bands were fine. Today I found the problem does not happen when I use a dummy load. The K3 schematic shows`there is a low-pass filter for 20/30 meters. I am just trying to figure out if the high SWR caused damage.

73,
Dave W0RU

Don Wilhelm-4

Re: K3 Distorted Audio On Transmit

Dave,

Audio distortion on only 1 or 2 bands is usually a symptom of RF in the
Shack.
That is confirmed by the fact that all is well on a dummy load.
The best place to cure it is on the antenna feedline.
If you do not have a good current balun at the antenna feedpoint, add one.
If you have a few feet of slack in the feedline, I would make 5 turns of
the coax through a stack of 5 or 6 FT240-31 ferrite toroids. Do that at
the shack entry point or just inside the shack. See the information in
K9YC's paper on RFI for a photo - http://audiosystemsgroup.com/RFI-Ham.pdf
The toroids are available at Mouser or from Diz at
http://www.partsandkits.com

73,
Don W3FPR

On 3/1/2014 12:08 PM, dave_w0ru wrote:

> I have a K3, P3 and KPA500. Last night I was encountering some high SWR. The
> K3 has the KAT3 internal 100 watt antenna tuner. I do not have the KAT500
> tuner. If the SWR was too high, the KPA500 indicated a fault and I went back
> to 100 watts with the K3. I tried bypassing the KAT3 to see how the SWR
> looked. The K3 started producing extremely distorted audio when I
> transmitted (I was listening with my headphones). The audio sounds like a
> loud roar. This only occurred on 20 and 30 meters at about 50-100 watts
> output using upper sideband (yes, I know we can't legally use USB on 30
> meters, I just briefly keyed the PTT). The other bands were fine. Today I
> found the problem does not happen when I use a dummy load. The K3 schematic
> shows`there is a low-pass filter for 20/30 meters. I am just trying to
> figure out if the high SWR caused damage.
>
>

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dave_w0ru

Re: K3 Distorted Audio On Transmit

Don,

Thanks for the insight and references. This is the first time I have encountered this type of problem. The temperature here in Minnesota is -3 degrees F. Any outside modifications may have to wait awhile.

73,
Dave W0RU

Don Wilhelm-4

Re: K3 Distorted Audio On Transmit

Dave,

Don't you know antenna work is best done during the winter. :-)
The colder it is, the more efficient that antenna will be!

73,
Don W3FPR

On 3/1/2014 1:41 PM, dave_w0ru wrote:
> Don,
>
> Thanks for the insight and references. This is the first time I have
> encountered this type of problem. The temperature here in Minnesota is -3
> degrees F. Any outside modifications may have to wait awhile.
>
> 73,
> Dave W0RU
>

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Bruce Rattray

Re: K3 Distorted Audio On Transmit

Hello Don. Then I must have the world's most efficient antennas with wind
chills in the minus 50s and minus 60s this time around. Hihihi 72/73
Bruce ve5rc love my K2!

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Don Wilhelm
Sent: March 1, 2014 12:50 PM
To: [hidden email]
Subject: Re: [Elecraft] K3 Distorted Audio On Transmit

Dave,

Don't you know antenna work is best done during the winter. :-) The colder
it is, the more efficient that antenna will be!

73,
Don W3FPR

On 3/1/2014 1:41 PM, dave_w0ru wrote:
> Don,
>
> Thanks for the insight and references. This is the first time I have
> encountered this type of problem. The temperature here in Minnesota is
> -3 degrees F. Any outside modifications may have to wait awhile.
>
> 73,
> Dave W0RU
>

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KD8NNU

Re: K3 Distorted Audio On Transmit

Efficiency applies when the work on said antenna is performed in the cold weather.

Thanks
Don
Sent from my iPad

> On Mar 1, 2014, at 10:20 PM, "Bruce Rattray" <[hidden email]> wrote:
>
> Hello Don. Then I must have the world's most efficient antennas with wind
> chills in the minus 50s and minus 60s this time around. Hihihi 72/73
> Bruce ve5rc love my K2!
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Don Wilhelm
> Sent: March 1, 2014 12:50 PM
> To: [hidden email]
> Subject: Re: [Elecraft] K3 Distorted Audio On Transmit
>
> Dave,
>
> Don't you know antenna work is best done during the winter. :-) The colder
> it is, the more efficient that antenna will be!
>
> 73,
> Don W3FPR
>
>> On 3/1/2014 1:41 PM, dave_w0ru wrote:
>> Don,
>>
>> Thanks for the insight and references. This is the first time I have
>> encountered this type of problem. The temperature here in Minnesota is
>> -3 degrees F. Any outside modifications may have to wait awhile.
>>
>> 73,
>> Dave W0RU
>
> ______________________________________________________________
> 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
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html