[Elecraft] Tuning Clunks was:K2 compared to others rigs

[Geoffrey Mackenzie-Kennedy]

This might be a tough nut to crack in terms of the surgery required. From a 
quick thus limited investigation into this "clunk" problem in my K2  I am 
reasonably certain that the lack of shielding to protect the VCO and 
Reference, together with the lack of suitable interface filtering , is 
responsible. I don't think that the BFO is directly involved but I could 
well be wrong. In my K2 the "clunks" appear, as you say, in the presence of 
strong signals, and are found on every band that I have been able to check 
so far, 40m is perhaps the worst case. What appears to happen is that the 
strong incoming signals leak into the VCO / Reference area, and when their 
composite level exceeds some value, which is frequency and leakage 
dependent, attempt to take over control of the VCO which results in 
"clunks". The frequency separation between "clunks" is not always 5kHz but 
does seem to be related to the frequencies of the incoming signals which are 
attempting to take over. I must stress that I have not had the opportunity 
yet to undertake an in depth investigation, but I am very aware of the 
leakage between the front end and the VCO / Reference from earlier work with 
my K2. "Clunks" should not be confused with "Clicks" whose cause(s) are 
quite different!

Here the received individual carrier levels of the BC stations above 7100 
kHz can approach -10dbm / -5dbm with an antenna looking East, and there are 
many of them. It is not uncommon for my K2's LO system to lock onto one of 
these carriers, and only let go after the receiver has been retuned about 1 
kHz.

73,
Geoff
GM4ESD


Darrell Bellerive <va7to at yahoo.ca> wrote:


>I agree that the synthesizer "tuning clunks" every 5 kHz in the presence of
> strong signals needs to be addressed.
>
> I know that Elecraft found that muting the receiver to eliminate these
> noises was worse than the noises, but there must be a solution to at least
> lessen these "tuning clunks."
>
> On March 24, 2007 03:25 am, Dave-Boat Guy wrote:
>> A bare-bones K2 is a fine radio, although there are
>> still a couple of unresolved issues, like the tuning
>> clunks you hear on crowded bands, due to the
>> synthesizer.  I'm still puzzled why it hasn't been
>> addressed.