[Elecraft] K2 / KX3 receiver observation - need explanation

[Don Wilhelm]

Gernot,

Because you are hearing the same thing (or almost the same thing) on 2 
receivers, give thought to the possibility that the source may be 
outside the receivers.
Even mild corrosion in the antenna system can produce a connection that 
acts like a diode and will mix strange frequencies together and produce 
unexpected results.

Faulty solder connections in the receiver can produce the same results.  
Yes, unwanted mixing products from strong signals can occur in the 
receiver.  I do not think it is a sign of aging.

I have never seen symptoms like you describe when driving a K2 with a 
very large signal from my workbench signal generator.

Does your K2 have the Extremely Strong Signal Handling mod installed?  
If not, install two 1N4148 diodes back to back across the input to RF 
board U12 - those diodes can be installed either between pins 4 and 6 of 
U12 or across leads 3 and 4 of T7.  The newer schematics identify those 
diodes as D40 and D41.  If you have an older K2 with the 2nd Xtal 
Flattening Mod installed, that covers the leads of T7 and you will have 
to install the diodes across the U12 pins.

73,
Don W3FPR

On 6/5/2015 10:07 AM, gt-i at gmx.net wrote:
> Hello everybody,
> during the WPX contest I noticed some weird sounds in the K2 when 
> tuning to strong (>S9+20db) stations.
> The sound was distorted, kind of ripple, but it did not sound like 
> typical ringing.
> I also noticed LZ9W booming in on 80m with S9+40db, producing 3 images 
> in the K2 and the KX3. However, in the K2 the 2 ghost signals were 
> frequency modulated. How could this happen?
> Another big one, LY2W, also produced 3 signals in the KX3 but all the 
> 3 were nice and clean.
>
> I thought these ghost images would depend on the receiver 
> architecture, or am I wrong here?
>
> Regarding the first observation: Since the K2 is already > 10 years 
> old, could component aging already play a role. If so, where to look for?
>
> Thanks for any ideas!
> 73
> Gernot
> DF5RF
>
>
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