[Elecraft] Question Regarding Direct Conversion Receiver

[Don Wilhelm]

The stability of a Direct Conversion receiver is determined solely by 
the Local Oscillator (VFO).
It must be stable both mechanically and electrically.  It sounds like 
yours is suffering from hand capacity effects.
If it uses an air variable capacitor, it should be mounted rigidly and 
behind a metallic panel to reduce the hand capacity effect.
If OTOH the oscillator is tuned with a varactor, the power source to the 
oscillator must be regulated for stability, and that is typically done 
with a zener diode.
Is the inductor a toroid that is mounted rigidly to the board? - the 
toroid turns should be tight - this is not a place for loose windings.

Since you did not give the model of that kit, so I could not look up the 
schematic, so I can only give generalities.

73,
Don W3FPR

On 1/23/2013 12:25 AM, Bernie KF0QS wrote:
> I now have a question about something I did years ago.  When I got the K1, I
> decided to build something smaller first in order to practice soldering.  I
> built a Vectronics (actually, from MFJ) direct conversion receiver for 20
> meters (I also built the companion transmitter, and it works fine).  The
> problem is that merely touching the receiver makes its change frequency, and
> tuning it is an uncertain process.  As a result, it is unstable, and not
> much fun to operate (though it is reasonably sensitive despite its
> simplicity).  There must be some capacitance that it is getting from my
> touch, that is adversely affecting its performance.
>
> Did I do something wrong in building this receiver, or is it just the price
> of a really bare bones design?
>
>