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

[Barry L. Ornitz]

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