K3 intermittent RX drop-out

[LA0BY]

Hi gents,

Since fall 2011 I am happy to own the basic version of the K3, with the only
extras being the KXV3A transverter interface, some CW filter and the KDVR3
voice recorder. I have been using the K3 once or twice each month only as IF
unit for a 2 m XVTR. So I am not using the SO-239 rear socket. The K3 worked
very fine for almost 2 years but started then to exhibit intermittent
drop-outs of the RX signal. The path was not completely gone, just had extra
attenuation of 30-40 dB. Transmission seemed never affected. Initially it
resembled a hanging contact of a T/R-relay, and could be cured by pushing
the PTT once or twice.

 

But during the first hilltop operation after the winter the problem was
permanent. Back home in the shack the problem was still there but went away
by itself after some hours of warm-up. I tried to identify the failing stage
but never got to the bottom of it before it disappeared. But I found the
extra insertion loss is way down into the receiver, probably at the second
IF level. During a second hilltop operation the problem surfaced again. Back
in the shack the failure was present only for some minutes before it
disappeared. While it persisted, I could not detect any effect of tapping
somewhere on the chassis.

 

I have read some earlier reports of similar malfunction in this forum, and
will take a closer look at all connectors. I will also try to reproduce the
problem by using freeze spray, because I suspect it could be related to low
temperatures.

 

I would appreciate to hear if anybody else has observed such behavior and
was able to pinpoint the failing part or contact.  

 

73, Stefan (LA0BY)

 

Email la0by >at> darc.de

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[Don Wilhelm-4]

Stefan,

You have not only the K3 in the receive path, but also the transverter,
coax, and perhaps a sequencer.

Have you tried changing the coax to the transverter IN jack?
Often problems of that nature are caused by faulty coax.
Have you ruled out a bad contact in your transverter or other external
switching?
Does the K3 receive at your IF frequency if an antenna is connected to
the SO-239 jack?

If you have an alternate source of 28 MHz signal (signal generator or an
antenna that will receive even noise on 28 MHz), try connecting that to
the K3 transverter input to see if the problem is in the K3 or something
external.

73,
Don W3FPR

On 5/24/2014 4:42 AM, Stefan Heck wrote:

> Hi gents,
>
> Since fall 2011 I am happy to own the basic version of the K3, with the only
> extras being the KXV3A transverter interface, some CW filter and the KDVR3
> voice recorder. I have been using the K3 once or twice each month only as IF
> unit for a 2 m XVTR. So I am not using the SO-239 rear socket. The K3 worked
> very fine for almost 2 years but started then to exhibit intermittent
> drop-outs of the RX signal. The path was not completely gone, just had extra
> attenuation of 30-40 dB. Transmission seemed never affected. Initially it
> resembled a hanging contact of a T/R-relay, and could be cured by pushing
> the PTT once or twice.
>
>  
>

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[LA0BY]

Hi Don,
Thanks for the reply. Yes, I have rules out all other causes but the K3. It
does not receive on any HF band (or only with about 40 dB attenuation) when
the problem is present. My first thought was also the XVTR but it is
definitely not the cause.

73, Stefan (LA0BY)



-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: 24. mai 2014 14:36
To: Stefan Heck; [hidden email]
Subject: Re: [Elecraft] K3 intermittent RX drop-out

Stefan,

You have not only the K3 in the receive path, but also the transverter,
coax, and perhaps a sequencer.

Have you tried changing the coax to the transverter IN jack?
Often problems of that nature are caused by faulty coax.
Have you ruled out a bad contact in your transverter or other external
switching?
Does the K3 receive at your IF frequency if an antenna is connected to the
SO-239 jack?

If you have an alternate source of 28 MHz signal (signal generator or an
antenna that will receive even noise on 28 MHz), try connecting that to the
K3 transverter input to see if the problem is in the K3 or something
external.

73,
Don W3FPR

On 5/24/2014 4:42 AM, Stefan Heck wrote:

> Hi gents,
>
> Since fall 2011 I am happy to own the basic version of the K3, with
> the only extras being the KXV3A transverter interface, some CW filter
> and the KDVR3 voice recorder. I have been using the K3 once or twice
> each month only as IF unit for a 2 m XVTR. So I am not using the
> SO-239 rear socket. The K3 worked very fine for almost 2 years but
> started then to exhibit intermittent drop-outs of the RX signal. The
> path was not completely gone, just had extra attenuation of 30-40 dB.
> Transmission seemed never affected. Initially it resembled a hanging
> contact of a T/R-relay, and could be cured by pushing the PTT once or

twice.
>
>  
>


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[LA0BY-2]

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