[Collins] Re: Re: SYNTHESIZER FOR DRAKE RECEIVER BY HAGEMAN

[Dr. Gerald N. Johnson]

On Tue, 2006-10-17 at 05:58 -0400, kiyoinc at attglobal.net wrote:
> <geraldj at ispwest.com> wrote:
> 
> > 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.
> 
> That's my read too. The SSENG DDS kit looks like it would do what I want 
> but, and this is why I haven't ordered it, I don't know the details.
> 
> How do I program the steps and the end points?
> 
> It's like in the moo-vies, how do they always know what to type on the 
> keyboard or what knob to turn to open the hidden door?  And, conversely, 
> how come there's a command interface that obeys, "Run fortress 
> self-destruct sequence."  that doesn't ask for 2 or 3 different 
> passwords like the timecard system at a previous employer.
> 
> I don't have a pic programming set up here.  Well maybe I do, if I knew 
> what to download and could find my RS-232 break out box, etc.  Point is, 
> just sitting here, I don't know what to do.
> 
> Then, there's the issue of SSENG's shrinking product line.  It looks 
> like they are retired engineers and are scaling back their business. 
> They've moved from Maryland to a retirement place in Arizona.  Seems to 
> be a lot of that going on.

I think you ascribe fortune 500 size to a mom and pop operation. Maybe
one engineer and one order taker, kit assembler, packer, and shipping
clerk. Pop does the kit assembly for the completed items. I don't think
Sam and Susie Engineering has ever been bigger.
> 
> I'm not really interested in transmitting.  I haven't put a signal on HF 
> in 10 years, no, 15 years.  So the FCC's concept of spectrum purity 
> isn't an issue for me.
> 
> I listen.
> 
> In any case, I have transmitting crystals for the amateur bands.  What I 
> don't have is a convenient way to tune across the bands with the 75S-1.
> 
> Why not add a DDS 1st oscillator to it?
> 
> Speculation that there will be phase noise or spurs is not a reason to 
> avoid trying.  Somehow the AOR DDS2A works.
> 
> Even if the SSENG DVFO II is noisy and not suitable for transmitting, 
> perhaps it could be improved, cleaned up.  Perhaps it would work well 
> enough that a 75S-1/75S-3 would be an adequate general coverage receiver.
> 
> We won't know until someone tries.
> 
> The one thing that holds me back is that I don't know if the kit will 
> meet the gross specs, start at an x55 frequency, step 200 kHz, display 
> the S-line offset, and there's the issue of the reverse offset.
> 
> I also don't know exactly what it takes to "program" it.
> 
> If I could get it working, and stepping, and displaying, but it made an 
> S-5 "ssssssshhh" across the band and there were occasional birdies, 
> that's fine.
> 
> The bands sound worse than that on all my receivers.
> 
> It passes proof-of-concept and someone might be able to refine it. Even 
> if that's not possible, it'd be good-enough for general coverage listening.
> 
> de ah6g/4
> 
In the November 2006 QST there is a vector impedance meter that uses a
couple DDS chips for signal creation and detection. There are many
details glossed over but there might be more information in the links
from the footnotes. Maybe you could build your own.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer