K2 receiver problem and signal tracing question

[Robert Greenwalt-2]

Hi

My K2 used to receive nicely.  Good strong signals on various bands, I was
able to use a noise generator and spectrograph program to tune the filters,
etc.  Then I added the ssb kit and receiving seemed to fall way off.  I
removed the kit, re-soldered the jumpers and resistor and still receiving is
bad.  I can hear occasional signals, but nothing makes the S meter move.  I
can hear a slight difference between the noise generator being on and off,
but not enough to get a hump on the spectrograph.  A sad state.

So I'm going to embark on a signal tracing adventure, but I have a question:
 The instructions say the signal generator should be outputting .14 Vrms
according to the RF probe - is that reasonably accurate?  If I use an
oscilloscope instead should I be getting .14Vrms (.2Vp or .4Vpp)?  That
seems high when the s9 reading corresponds to 50 uV..  I just want to make
sure I'm not going to fry something pumping in 200000 uV.

Thanks
Robert K6RJG
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[NQ3RP]

Robert -

I built the noise generator on the Elecraft site and used it, I don't know what it's output is as I don't have an oscilloscope.  Sorry to hear that you have trouble after installing the SSB.  

John
NQ3RP

[Don Wilhelm-4]

Robert,

Yes, the recommended signal level is quite high, and purposely so - it
is high enough to read the levels on an RF Probe.
If you are using an oxcilloscope (with a 10X probe please), you can use
a lower level, just be certain the level is sufficient to be seen above
the noise the probe picks up - if the level does not decrease when you
turn the generator off, your 'scope is only seeing noise.

There is not a lot that the installation of the KSB2 option can do to
kill receive, especially if you restored the jumpers, so the signal
tracing is the way to go, you may find the problem anywhere in the
receive path.  Do check the BFO and VFO injection levels first.  I would
suspect the BFO as the first 'culprit' - the level at U11 pin 6 must be
greater than 200 mV peak to peak.

73,
Don W3FPR

Robert Greenwalt wrote:

> Hi
>
> My K2 used to receive nicely.  Good strong signals on various bands, I was
> able to use a noise generator and spectrograph program to tune the filters,
> etc.  Then I added the ssb kit and receiving seemed to fall way off.  I
> removed the kit, re-soldered the jumpers and resistor and still receiving is
> bad.  I can hear occasional signals, but nothing makes the S meter move.  I
> can hear a slight difference between the noise generator being on and off,
> but not enough to get a hump on the spectrograph.  A sad state.
>
> So I'm going to embark on a signal tracing adventure, but I have a question:
>  The instructions say the signal generator should be outputting .14 Vrms
> according to the RF probe - is that reasonably accurate?  If I use an
> oscilloscope instead should I be getting .14Vrms (.2Vp or .4Vpp)?  That
> seems high when the s9 reading corresponds to 50 uV..  I just want to make
> sure I'm not going to fry something pumping in 200000 uV.
>
> Thanks
> Robert K6RJG
>
>  

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