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KXPA100 SSB Distortion

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KXPA100 SSB Distortion

My KXPA100 transmits distorted audio on SSB, but works normally on CW and RTTY. With 100 watts output, drain current is 11.7 A and supply voltage is 13.1 V, down from 13.7 V on receive. My power supply is a pre-MFJ Astron RS-35A.

The KX3 with which I drive it operates normally on all bands and modes, with good transmit audio. Speech compression is off and mic gain is set to 20.

Should I send the amp back to Elecraft for service, or is there another problem?

73 Ray W2RS
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Kurt Cramer-3

Re: KXPA100 SSB Distortion

Does it work correctly into a dummy load. It sounds like RF in the audio,

73 Kurt W7QHD

> On Apr 23, 2018, at 8:32 AM, Ray W2RS via Elecraft <[hidden email]> wrote:
>
>
> My KXPA100 transmits distorted audio on SSB, but works normally on CW and RTTY. With 100 watts output, drain current is 11.7 A and supply voltage is 13.1 V, down from 13.7 V on receive. My power supply is a pre-MFJ Astron RS-35A.
>
>
> The KX3 with which I drive it operates normally on all bands and modes, with good transmit audio. Speech compression is off and mic gain is set to 20.
>
>
> Should I send the amp back to Elecraft for service, or is there another problem?
>
>
> 73 Ray W2RS
> ______________________________________________________________
> 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]

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Elecraft mailing list

Re: KXPA100 SSB Distortion

Hi Kurt,

It's hard to tell because the monitor plays the KX3 audio, which is good.

Tnx, Ray

-----Original Message-----
From: Kurt Cramer <[hidden email]>
To: rsoifer1 <[hidden email]>
Cc: elecraft <[hidden email]>
Sent: Mon, Apr 23, 2018 8:58 am
Subject: Re: [Elecraft] KXPA100 SSB Distortion

Does it work correctly into a dummy load. It sounds like RF in the audio,

73 Kurt W7QHD

Don Wilhelm

Re: KXPA100 SSB Distortion

Ray,

Do you have a dummy load and another receiver? Borrow the receiver if
necessary.

You can't tell much by the KX3 monitor.
Connect the dummy load to the ANT jack and connect a short wire to the
other receiver. Place that wire far enough away from the dummy load to
obtain about an S-9 signal. Listen with headphones.

Transmit at several power levels. How does the signal sound at each.
If it sounds OK on the dummy load, then look for RF in the shack to be
the problem.
OTOH, if it sounds distorted into the dummy load, contact elecraft
support - [hidden email]

73,
Don W3FPR

On 4/23/2018 12:14 PM, Ray W2RS via Elecraft wrote:

> Hi Kurt,
>
>
> It's hard to tell because the monitor plays the KX3 audio, which is good.
>
>
> Tnx, Ray
>
>
>
>
> -----Original Message-----
> From: Kurt Cramer <[hidden email]>
> To: rsoifer1 <[hidden email]>
> Cc: elecraft <[hidden email]>
> Sent: Mon, Apr 23, 2018 8:58 am
> Subject: Re: [Elecraft] KXPA100 SSB Distortion
>
> Does it work correctly into a dummy load. It sounds like RF in the audio,
>
> 73 Kurt W7QHD
>> On Apr 23, 2018, at 8:32 AM, Ray W2RS via Elecraft <[hidden email]> wrote:
>>
>>
>> My KXPA100 transmits distorted audio on SSB, but works normally on CW and RTTY. With 100 watts output, drain current is 11.7 A and supply voltage is 13.1 V, down from 13.7 V on receive. My power supply is a pre-MFJ Astron RS-35A.
>>
>>
>> The KX3 with which I drive it operates normally on all bands and modes, with good transmit audio. Speech compression is off and mic gain is set to 20.
>>
>>
>> Should I send the amp back to Elecraft for service, or is there another problem?
>>
>>
>> 73 Ray W2RS
>> ______________________________________________________________
>> 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]
>
>
> ______________________________________________________________
> 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]
>

Don Wilhelm

Re: KXPA100 SSB Distortion

In reply to this post by Elecraft mailing list

Ray,

Do you have a dummy load and another receiver? If so, connect the dummy
load to the KXPA100 and put a short antenna wire on the other receiver.
Transmit, and adjust the distance between the dummy load and the other
receiver "antenna" to produce an S-9 signal.
Does the KXPA100 produce a distorted signal?
If not, then look carefully at your antenna system - the likely problem
is RF-in-the-shack.

OTOH, if the KXPA100 output is distorted working into the dummy load,
you should contact [hidden email] with those facts.

One thing that can cause some distortion is low power supply voltage to
the KXPA100. That voltage should be at least 13.8 volts during receive
and drop to no less than 13.2 during transmit at 100 watts. Low voltage
during transmit can cause increase IMD (distortion).

73,
Don W3FPR

On 4/23/2018 11:32 AM, Ray W2RS via Elecraft wrote:
>
> My KXPA100 transmits distorted audio on SSB, but works normally on CW and RTTY. With 100 watts output, drain current is 11.7 A and supply voltage is 13.1 V, down from 13.7 V on receive. My power supply is a pre-MFJ Astron RS-35A.
>
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