[Elecraft] Garbled K2 SSB Signals

[Don Wilhelm]

Dale,

That is an old problem often referred to as WAOF (Weird At One Frequency).
That frequency region is where the PLL frequency and the VFO frequencies 
cross.  Those two signals can couple together producing the condition 
that you observe.  The fix is to reduce the opportunity for those 
signals to couple together.

Make certain that C88 on the bottom of the RF board soldered between 
pins 12 and 13 of U4 is on the correct pins and has the shortest 
possible leads.  Also the length of the leads for RFC15 and C91 should 
be as short as possible at the connection point with U4 pin 16.

If that does not take care of it, flush cut all pins and component leads 
in the vicinity of U4 and U6 including the R-paks to eliminate anything 
that could act as an antenna.  Also above the board make certain the 
varactors and capacitors in the VFO and PLL area are seated completely 
down on the board - long leads will cause the signals to couple together.

The last gentleman who had this problem reported that the above efforts 
did not stop it entirely, but when he covered the U4 area with 
electrical tape, the problem went away.  Now, I can't explain why the 
electrical tape would have that effect, but give it a try.

73,
Don W3FPR


On 5/4/2014 9:11 AM, dale at k4eq.net wrote:
> I completed my K2 earlier this week and everything seems to be working
> great. However, I have discovered one problem. Received SSB signals from
> 7180 to 7185 kHz are garbled even with the NB and preamp off. Thus far I
> haven't observed this problem on any other frequency. Any ideas what may be
> causing this?
>