[Elecraft] K2 rev B low sensitivity

[Wallace, Andy]

> -----Original Message-----
> From: Ron D'Eau Claire [mailto:rondec@easystreet.com]
> 
> Select your narrowest filter. 
> 
> Turn up the gain so you hear "band noise" - the background QRN that is
> always there.
> 
> Disconnect the antenna. 
> 
> If the noise level drops noticeably, you K2 is hearing as well as any
> receiver with a similar bandwidth. 

Great point, Ron. Actually I had thought of your earlier posts on the
subject
when doing the signal tracing. After resoldering the Q22 area and having
good sensitivity again, I did verify that on 80 and 10 I could hear the 
difference with the antenna connected vs. not. 

> SOME K2's seem to have relatively low audio system gain. Ops complain
> that they have to run the Audio Gain control way up - almost 
> full "open" to get adequate gain 

Well with the preamp on, both my K2 and the K1 are comfortable to
listen to -- through their speakers -- at about 9:00. (Before resoldering
the Q22 area, it was more like 12:00.) My difficulty was not having a K2
to compare to -- I would hate to have this rig for years and then discover
it wasn't as nice as it could have been due to a construction error/fault.
Before resoldering Q22/C161/RFC11, it took over 300 uV to get S-9 on 40
with the preamp off. Now it's 120 or so....quite a difference!

>  Using a pre-amp when you don't need one means
> that you are reducing the dynamic range of the receiver. 

Understood -- in my case I am using a terrible antenna, just 35' long,
with no prospect of improvement anytime soon. So I may need to use the 
preamp in most cases. Hopefully the KAT2 will help, as much as the KAT1
helps my K1 on receive. 

> But that is not a good indicator of whether your K2 can
> "hear" weak signals as good as another receiver. 

Of course -- but by calibrating "by the book" and injecting a signal
of x microvolts for S-9, it gives people something to use for comparison.
The best reference would be oscilloscope shots of what to expect in the
signal path for a given input. 

Thanks, Ron. I've stopped worrying and now I can look forward to
filling all the empty connectors inside. :-)

Andy