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K3 Problem during transmission on SSB

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Luigi Casari

K3 Problem during transmission on SSB

Ragards to all,
I have just discovered a problem, 28 MHz or 21 MHz SSB, during transmission
the power drop down to abt. 10/15W.

This after few second of transmission, the power staies low for some seconds
and then increases again. No question of microphone, I have tried with MC85
and Pro set, also change the levels of the mic gain and compressor without
result.

I have tried on other frequencies and have not been able to recreate the
problem, only in 21 and 28 MHz.
Don't believe is a problem of SWR and some protection what limits the power,
the antenna is the same from the 10m to the 40m, Opti Beam, and the SWR
where have done the tests are low. Also the internal SWR meter of the K3
give me low SWR.
Even in 160m, 80m or 6m with others antennas no problem.

In FM mode I don't notice any decrease of power, 110W constant.

Some idea?

73, Luigi HB9CXZ

[hidden email]
http://web.ticino.com/hb9cxz/

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Scott Ellington

Re: K3 Problem during transmission on SSB

Sounds like RF feedback. Do you see the same problem with a dummy load?

73,

Scott K9MA

Scott Ellington
Madison, Wisconsin
USA

On Oct 14, 2010, at 2:37 PM, Luigi Casari wrote:

> Ragards to all,
> I have just discovered a problem, 28 MHz or 21 MHz SSB, during transmission
> the power drop down to abt. 10/15W.
>
> This after few second of transmission, the power staies low for some seconds
> and then increases again. No question of microphone, I have tried with MC85
> and Pro set, also change the levels of the mic gain and compressor without
> result.
>
> I have tried on other frequencies and have not been able to recreate the
> problem, only in 21 and 28 MHz.
> Don't believe is a problem of SWR and some protection what limits the power,
> the antenna is the same from the 10m to the 40m, Opti Beam, and the SWR
> where have done the tests are low. Also the internal SWR meter of the K3
> give me low SWR.
> Even in 160m, 80m or 6m with others antennas no problem.
>
> In FM mode I don't notice any decrease of power, 110W constant.
>
> Some idea?
>
> 73, Luigi HB9CXZ
>
> [hidden email]
> http://web.ticino.com/hb9cxz/
>
>

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Luigi Casari

Re: K3 Problem during transmission on SSB

In reply to this post by Luigi Casari

Tnx Wes and Scott for your replay,

I connect a dummy load and I transmit on different bands.
The problems is on 21,24 and 28 MHz band.

To times when I push the PTT of the microphone the power is low and then gets up.

Don't believe is a problem of return RF as Scott suggests me.
When I have seen the first time the problem were doing DX in 21MHz, I used the PA and I get lots of compliments for the modulation.
If they had been a RF problems with 1 KW the modulation has been distorted or with strong noises.

Seem more a false contact from some part.

This evening after the work I will try with K3 Utlility and I will check the connectors.

73 to all.

Luigi HB9CXZ
----- Original Message -----
From: Wes Stewart
To: Luigi Casari
Sent: Thursday, October 14, 2010 11:33 PM
Subject: Re: [Elecraft] K3 Problem during transmission on SSB

Luigi,

You might try running into a dummy load and see what happens. If you still have the issue use the utility program and run the TX power calibration. If that fails, then you may have an intermittent issue the same as several of us have had.

One issue seems to be the "2D connector" at the right rear of the radio that connects the output filter board to the chassis. This is the only ground return for the output connector. Make sure the screw is tight. It is the one that runs from the side panel completely though the 2D connector to the circuit board.

Wes

--- On Thu, 10/14/10, Luigi Casari <[hidden email]> wrote:

From: Luigi Casari <[hidden email]>
Subject: [Elecraft] K3 Problem during transmission on SSB
To: [hidden email]
Date: Thursday, October 14, 2010, 1:37 PM

Ragards to all,
I have just discovered a problem, 28 MHz or 21 MHz SSB, during transmission
the power drop down to abt. 10/15W.

This after few second of transmission, the power staies low for some seconds
and then increases again. No question of microphone, I have tried with MC85
and Pro set, also change the levels of the mic gain and compressor without
result.

I have tried on other frequencies and have not been able to recreate the
problem, only in 21 and 28 MHz.
Don't believe is a problem of SWR and some protection what limits the power,
the antenna is the same from the 10m to the 40m, Opti Beam, and the SWR
where have done the tests are low. Also the internal SWR meter of the K3
give me low SWR.
Even in 160m, 80m or 6m with others antennas no problem.

In FM mode I don't notice any decrease of power, 110W constant.

Some idea?

73, Luigi HB9CXZ

[hidden email]
http://web.ticino.com/hb9cxz/

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
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Please help support this email list: http://www.qsl.net/donate.html

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Scott Ellington

Re: K3 Problem during transmission on SSB

I agree that, if the same problem exists with the dummy load, it's not RF feedback. (Especially the audio is OK with an amplifier and antenna.) A poor connection is the must likely suspect.

73,

Scott K9MA
On Oct 14, 2010, at 11:28 PM, Luigi Casari wrote:

> Tnx Wes and Scott for your replay,
>
> I connect a dummy load and I transmit on different bands.
> The problems is on 21,24 and 28 MHz band.
>
> To times when I push the PTT of the microphone the power is low and then gets up.
>
> Don't believe is a problem of return RF as Scott suggests me.
> When I have seen the first time the problem were doing DX in 21MHz, I used the PA and I get lots of compliments for the modulation.
> If they had been a RF problems with 1 KW the modulation has been distorted or with strong noises.
>
> Seem more a false contact from some part.
>
> This evening after the work I will try with K3 Utlility and I will check the connectors.
>
> 73 to all.
>
> Luigi HB9CXZ

Scott Ellington
Madison, Wisconsin
USA

______________________________________________________________
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Joe Subich, W4TV-4

Re: K3 Problem during transmission on SSB

I'd more likely suspect an error in performing the wattmeter
and TX Gain calibrations. Check the user manual.

73,

... Joe, W4TV

On 10/15/2010 2:06 PM, Scott Ellington wrote:

> I agree that, if the same problem exists with the dummy load, it's not RF feedback. (Especially the audio is OK with an amplifier and antenna.) A poor connection is the must likely suspect.
>
> 73,
>
> Scott K9MA
> On Oct 14, 2010, at 11:28 PM, Luigi Casari wrote:
>
>> Tnx Wes and Scott for your replay,
>>
>> I connect a dummy load and I transmit on different bands.
>> The problems is on 21,24 and 28 MHz band.
>>
>> To times when I push the PTT of the microphone the power is low and then gets up.
>>
>> Don't believe is a problem of return RF as Scott suggests me.
>> When I have seen the first time the problem were doing DX in 21MHz, I used the PA and I get lots of compliments for the modulation.
>> If they had been a RF problems with 1 KW the modulation has been distorted or with strong noises.
>>
>> Seem more a false contact from some part.
>>
>> This evening after the work I will try with K3 Utlility and I will check the connectors.
>>
>> 73 to all.
>>
>> Luigi HB9CXZ
>
> Scott Ellington
> Madison, Wisconsin
> USA
>
>
>
> ______________________________________________________________
> 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
>

Ignacy

Re: K3 Problem during transmission on SSB

In reply to this post by Luigi Casari

Look at supply current and see whether the current increase with time? I have heard that some PA suffer from overheating IF trap.
Ignacy, NO9E