[ARC5] OT? bc-348 bfo question

[Fernando - LU2DFM]

On Mon, Sep 16, 2013 at 12:20:20PM -0700, Kenneth G. Gordon wrote:
> On 15 Sep 2013 at 20:53, Fernando - LU2DFM wrote:
> 
> > Another interesting observation in this radio: the BFO signal comes
> > from the low level end of the oscillator (grid) instead of the plate.
> > I think most other designs take the output at the high level end.
> 
> Over the years, I have seen many oscillators in receivers in which the signal 
> was taken from the grid. I remember this since when I first noticed it, I 
> thought it was very strange. This was at least 50 years ago.
> 
> I suspect now that this was normally done in those circuits in which the plate 
> is "grounded".

Huch sent me a couple of pictures of his receiver. From those pics and
his comments, resulted that there are two gimmick caps there: one from
the grid of the triode BFO to 2nd IF amp plate, and one from the plate of 
the triode BFO to the plate of the 1st IF amp plate.

I completelly missed the 1st IF gimmick.

So, there actually is a feedback loop from plate to grid of the triode
BFO that happens to go through the 2dn IF amplifier pentode. 

The gimmicks in my radio where moved and bended, so the BFO couplig was
poor. The coupling seems to be fine now.

Next weekend I expect to get time to do a complete realignment and
complete a power supply. Once done, I will listen on this receiver to
see how it works.

Thank you very much everyone.


-- 
73 de Fer, LU2DFM