[Drake] Re:FS: Frequency Synthesizer for Drake R-4 Series

[Jordan]

In my experience the FS-4 was a very poor substitute for crystals.
My R-4C had very poor sensitivity on bands below 4 mhz, there were spurs
all over each band that was selected, and several bands could be tuned
at the same time using the preselector tuning. And this FS-4 had been
aligned by Drake themselves...!
73 de Jordan...

"Barry L. Ornitz" wrote:

> Bob, W6NBI, offered his frequency synthesizer for the 4-line
> receivers for sale and wrote:
>
> > This frequency synthesizer for the Drake R-4 series
> > receivers was designed and built by me and was published in
> > the August 1972 issue of "ham radio" magazine.  The
> > synthesizer provides complete coverage from 500 kHz to 30
> > MHz.  When the Drake receiver is used as the controlling VFO
> > in transceive mode, full operation is possible from 1.5 to
> > 30 MHz, including the WARC bands.  I will supply an original
> > issue of the magazine (torn cover), as well as schematics of
> > all the circuits which improved performance but were never
> > published.
>
> It has been quite a while since I remember reading the article
> in Ham Radio Magazine.  Does this synthesizer output in 100
> KHz steps (I think it does) or in 500 kHz steps?
>
> I ask because while the receivers can cover 1.5 to 30 MHz with
> the exception of 5 to 6 MHz, in nice 500 KHz bands, the
> companion 4-line transmitters have a number of frequency
> segments where they should not be used, and a number of other
> frequency segments where only portions of the dial range are
> acceptable and crystal frequencies ending in other than 0.1 or
> 0.6 MHz are needed.  These segments are, of course, where
> spurious emissions are likely because of harmonics of the PTO
> or because of the high probability of tuning the radio to the
> incorrect mixer products.  They are all listed in the
> transmitter manuals.
>
> Fortunately only one WARC band is affected, the 30-meter band,
> where a 20.8 MHz crystal is normally needed rather than a 21.1
> MHz crystal.  Sadly the proposed new 60-meter band may not be
> possible with this series of radios.
>
> >From memory again (and since it has been quite a while since I
> read the article, I may be mistaken), I believe this design
> had spurs spaced 100 KHz away from the desired output that
> were of a high enough level to cause some problems with false
> signals.  Do your modifications specifically address these
> spurs?
>
> Please note that this is not to fault Bob's design in any
> way.  I think the Drake FS-4 may have suffered from some of
> the same problems.  Perhaps someone who has owned a FS-4 can
> address this.
>
>         73,  Barry L. Ornitz     WA4VZQ     ornitz@tricon.net
>
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