[Boatanchors] Possible VFO???

Bob Groh bob.groh at gmail.com
Mon Apr 10 12:06:27 EDT 2017

Lee, I would second the other opinion that you got - yes, it would work but
there are a lot of hidden problems. To expand on the problems, near in
spectrum purity would be my biggest worry.  Harmonics you can handle fairly
easily with standard LPF's, etc.  The close in phase and amplitude noise -
not so easy to handle. And those close in stuff is what could make it a
poor performer as a receiver LO and a 'not so nice' VFO (for anyone close
to you in frequency). I would not recommend it.  If you want digital
accuracy, there are some nice frequency synthisizer ICs out there and kits
to add a display etc to make a nice VFO. The IC I am thinking of is the
Si570 and a web site to look at a kit to put one to work is:

Go down the page to the 'Si570 Controller and ....' section.  I purchased
one of those kits to build up an HF generator (still a work in progress).
Several links to other sites there also.

So, bottom line, I don't recommend the use a function generator as a VFO.

Bob Groh, WA2CKY

On Sun, Apr 9, 2017 at 8:42 PM, Lee <L at w0vt.us> wrote:

> Could you use this generator as a VFO?  Would you need a low pass filter
> for it?  For 40 meters and above, would you use a 40 meter signal for all
> bands 40 thru 10 meters?  I suspect so as most old boat anchor rigs used 40
> meter crystals for 40 meters and above. Then the next question is how do
> you mute it while receiving.  I'm wondering if there would be a way to move
> the output frequency while receiving.  Possibly a fast acting relay could
> switch in the generator while transmitting and switch it out while
> receiving. I'm not sure how much radiation would come out of the plastic
> box while receiving if it was still on the operating frequency.  (This is
> assuming we are operating on 40 meters and the generator was on 40
> meters.)  It certainly has enough output power to drive a boat anchor.
>  Anyone on here experimenting with this concept?
> Lee, w0vt
> http://www.ebay.com/itm/351825634342?_trksid=p2057872.m2749.
> l2649&ssPageName=STRK%3AMEBIDX%3AIT
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