[NLRS] DEMI transverter LO question..

[Ed Marciniak]

Your crystal is probably starting up as 7th overtone instead of 5th or vice
versa You could try adding/removing a half to one turn from the coil nearest
the xtal (L2 on microlok) and retuning capacitor for max output.

----- Original Message ----- 
From: <W0ZQ at aol.com>
To: <nlrs at mailman.qth.net>
Sent: Sunday, June 20, 2004 6:36 PM
Subject: Re: [NLRS] DEMI transverter LO question..


> In a message dated 6/20/2004 1:24:10 PM Central  Standard Time,
ray at w9ray.org
> writes:
> I have a DEMI 902-28 transverter  problem..  I net the LO frequency to
> 874.000 but when I shut off the power,  turn it back on immediately, the
LO
> Frequency moves...to 874.032 and I have to  retune it every time! it
appears to quite
> repeatable...   Any ideas  what the problem is...
>
>
>
> Hmmm, not sure, but the oscillator circuit "likes" 874.032  better.   My
> (minor) experience with DEM LO's is not to tune them to  frequency (in
your case
> 874.000) put rather to its strongest signal (which is  "close" to its
primary
> freq) ... I think on the DEM you tune the  small capacitor for maximum
voltage
> on a detector.   By tuning to  the maximum signal I find that the LO is
more
> stable, provides a better signal  level to the mixer, and assures startup
with
> both low voltage and when cold much  better than when you tune it for an
exact
> match (ie; 874.000).   You  can then compensate for frequency with your IF
> rig.   For example, my  2304 DEMI is 2304.100 when my IF rig is 144.123.
>
> If you are to much of a purest to accept this, you can dither with the LO
> tank circuit in and around the xtal.  Try compressing or expanding the
windings
> on the (series ?) coil that is in the tuned circuit with the xtal, or
> perhaps change the fixed capacitor values by a couple of pf.
>
> I just remembered that DEM has a tech note on this subject ..... here is
the
> link
> _http://www.downeastmicrowave.com/PDF/Dn016.PDF_
> (http://www.downeastmicrowave.com/PDF/Dn016.PDF)
>
> 73, Jon
> W0ZQ
> _______________________________________________
> NLRS mailing list
> NLRS at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/nlrs
>