[Collins] Re: SYNTHESIZER FOR DRAKE RECEIVER BY HAGEMAN

[Dr. Gerald N. Johnson]

On Sun, 2006-10-15 at 20:45 -0400, kiyoinc at attglobal.net wrote:
> collins-request at mailman.qth.net wrote:
> 
> > I don't believe you can switch bands like that on the 75S-1. I have
> > the 75S-3 and you have to switch the band switch to change coils and
> > then switch crystals within the passband of the switch setting. The
> > crystal sockets are also selected by the band switch but with the
> > extra sockets you can change crystals within the passband. The mod to
> > add extra crystals from Collins added a second switch deck and
> > another crystal board. This allowed several crystals for each switch
> > position. The 75S series was not designed for SWL type service.

Yet my boss Lloyd Winter who was in charge of the S-Line and 51S-1
receiver group told me (summer of 1964 when he found me in the lab
drooling over a 51S-1) that the S-line performance was better everywhere
than the 51S-1 and that the best way for continuous coverage was a
75S-3B and the crystal pack.
> 
> Yes and no.  Glen's add-on crystal switch board effectively -2's the 75S-1.
> 
> I'm not asking for continuous .3 to 30 tuning by spinning one knob.
> 
> I'm looking for a DDS to control the 1st mixer.  It might integrate with 
> Glen's crystal switch.
> 
> If I get the itch to listen to a frequency, I'd have to switch the 
> S-Line's bandswitch to proper letter band, switch the DDS on and tune it 
> to the band segment, and switch the modified Glen crystal bank expander 
> to engage the DDS.
> 
> Then I'd have peak the front end and tune the PTO.
> 
> I have the Collins crystal pack so I can do that now by lifting the lid 
> and plugging the appropriate crystal.  Glen's crystal switch makes that 
> easier.
> 
> A DDS would make it even easier. The DDS would replace the crystal pack 
> and the act of plugging and unplugging crystals.
> 
> The AOR DDS2A is an elegant, albeit costly solution.  I think it's 
> overkill because part of its magic is to replace the PTO.
> 
> I'm satisfied with the PTO's readout, stability, and feel.
> 
> I could not get the folks at SSENG to understand that I don't want a 
> VFO, I want the 100+ Collins front end crystals.

Looking at SSeng's order blank, that DDS box is their only product that
is available these days. None of the others listed can be bought. So
making changes is probably equally unobtainable. The way I read their
description, step and offset are programmable so 200 KHz steps and 3.155
MHz offset may be achievable. With the way the DDS works, having finer
or grosser steps doesn't change the requirements of the circuits,
especially when the frequency needs to end with .x55 MHz. Its all in the
input to the control register and that's through a microprocessor.
> 
> de ah6gi/4

Spurs 40 dB down won't meet FCC transmit standards and in a noisy
environment could easily add more off frequency trash to the pass band.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer