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[K3] High SWR when running above 12w on 160,80m

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Ilya

[K3] High SWR when running above 12w on 160,80m

Hi Gentlemen!

Recently I got some strange behaviour in my K3/100 #4413, looking for any
ideas.

When running more than 12 watts on 3.5 and especially 1.8 mhz, the internal
meter shows higher SWR values. The higher the power is set - the higher the
showings are. Like when the power is 20w - it shows smth near 2.0, when the
power is set to 50w - it shows 3.0 and says 'HI SWR'. If I tune antenna
with ATU prior to transmitting - the values are lower, but overall
behaviour is reproduced. Everything looks fine on 40 meters and higher.

But:
1. External meter shows normal SWR like 1.2-1.5 (the real one - the same as
my antenna analyzer shows).
2. If power level is set lower than 11.9 watts - the problem does not
persist (internal meter shows 1 or 2 segments).

Given the description above - I guess something should be wrong in the 100w
amplifier?
Looking for any advice.

Thanks and 73!
Ilya, R3XA
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Bob Wilson, N6TV

Re: [K3] High SWR when running above 12w on 160,80m

A bad coax jumper or a loose coax connector can cause problems like this,
especially if it is in between the radio and the external SWR meter. Can
you try a different coax jumper? Or, can you bypass the external SWR meter
and connect the antenna directly to the K3, perhaps ANT 2 instead of ANT
1? If no difference, I suppose something could be wrong with the low pass
filters inside the K3, but check the coax first.

73,
Bob, N6TV

On Sun, Mar 3, 2019 at 4:40 AM Ilya <[hidden email]> wrote:

> Hi Gentlemen!
>
> Recently I got some strange behaviour in my K3/100 #4413, looking for any
> ideas.
>
> When running more than 12 watts on 3.5 and especially 1.8 mhz, the internal
> meter shows higher SWR values. The higher the power is set - the higher the
> showings are. Like when the power is 20w - it shows smth near 2.0, when the
> power is set to 50w - it shows 3.0 and says 'HI SWR'. If I tune antenna
> with ATU prior to transmitting - the values are lower, but overall
> behaviour is reproduced. Everything looks fine on 40 meters and higher.
>
> But:
> 1. External meter shows normal SWR like 1.2-1.5 (the real one - the same as
> my antenna analyzer shows).
> 2. If power level is set lower than 11.9 watts - the problem does not
> persist (internal meter shows 1 or 2 segments).
>
> Given the description above - I guess something should be wrong in the 100w
> amplifier?
> Looking for any advice.
>
> Thanks and 73!
> Ilya, R3XA
> ______________________________________________________________
> 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
>

______________________________________________________________
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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

Ilya

Re: [K3] High SWR when running above 12w on 160,80m

Thanks Bob!

The coax jumper is not the root cause - I tried connecting the transceiver
directly to amp/antenna (via both ant1/ant2 sockets) and still got the same
swr showings.

First of all I thought of some amplifier issue as it all starts at power
setting at exactly 12.0w (the level when the 100w amp gets enabled, if I'm
not mistaken). When the power is set to 11.9w (highest setting without 100w
amp) - the swr meter shows 1.0.

Will look closer at BPFs, thanks!

On Mon, 4 Mar 2019, 06:10 Bob Wilson, N6TV, <[hidden email]> wrote:

> A bad coax jumper or a loose coax connector can cause problems like this,
> especially if it is in between the radio and the external SWR meter. Can
> you try a different coax jumper? Or, can you bypass the external SWR meter
> and connect the antenna directly to the K3, perhaps ANT 2 instead of ANT
> 1? If no difference, I suppose something could be wrong with the low pass
> filters inside the K3, but check the coax first.
>
> 73,
> Bob, N6TV
>
> On Sun, Mar 3, 2019 at 4:40 AM Ilya <[hidden email]> wrote:
>
>> Hi Gentlemen!
>>
>> Recently I got some strange behaviour in my K3/100 #4413, looking for any
>> ideas.
>>
>> When running more than 12 watts on 3.5 and especially 1.8 mhz, the
>> internal
>> meter shows higher SWR values. The higher the power is set - the higher
>> the
>> showings are. Like when the power is 20w - it shows smth near 2.0, when
>> the
>> power is set to 50w - it shows 3.0 and says 'HI SWR'. If I tune antenna
>> with ATU prior to transmitting - the values are lower, but overall
>> behaviour is reproduced. Everything looks fine on 40 meters and higher.
>>
>> But:
>> 1. External meter shows normal SWR like 1.2-1.5 (the real one - the same
>> as
>> my antenna analyzer shows).
>> 2. If power level is set lower than 11.9 watts - the problem does not
>> persist (internal meter shows 1 or 2 segments).
>>
>> Given the description above - I guess something should be wrong in the
>> 100w
>> amplifier?
>> Looking for any advice.
>>
>> Thanks and 73!
>> Ilya, R3XA
>> ______________________________________________________________
>> 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
>>
>