[Premium-Rx] RE: Drake R7 sensitivity upgrade

[Warren Ziegler]

Hi Dan & all,

   I have a Drake RR-3 (rack mount marine version of
the R7). I did modify the audio and agc about 10 years
ago when I got the receiver. I unfortunately didn't
document it, but I remember fattening up the audio
coupling caps. In many cases I had to use tantalum
caps to fit bigger value caps on the board. I also
remember removing RC networks that Drake put across
the audio to roll off the high frequency audio
response.
   I just bought a bunch of low voltage drop Schottky
diodes for another project, I'll give your mod a try.
 73 Warren K2ORS

--- Dan Neves <NDan at heinze-institute.com> wrote:
>  
> 
> Hello everyone:
>  
> This weekend was surgery weekend for the R7. The
> 6790GM has been showing
> up the Drake lately. In searching the Internet, a
> suggestion was found
> by Pete Gianakoupolos in hardcoredx.com, that these
> Drake R7 and TR-7's
> could be modified to increase sensitivity and lower
> the noise floor.
>  
> The 1N4148 diodes in the translator board and 2nd
> Mixer were replaced
> with 1N5711 Schottky diodes. This apparently
> improves MDS from the R7's
> .15 to .07 uV, an already superb figure. Please bear
> in mind I do not
> have the equipment necessary to bear this out for
> fact. I do, however
> have a soldering iron...
>  
> The results were apparent in the nightly showdown
> with the 6790GM. The
> Drake showed a significant improvement in weak
> signal performance and
> seems easier to listen to, as the noise floor has
> definitely dropped to
> a new low. These 2 receivers are again most
> definitely on par in my
> humble experience.
>  
> Listening for weak DX with the Drake was made with
> optional 4Khz filter
> in "synchrophase" sideband mode. It is said this
> allows about 3 Khz of
> bandwidth thru, while with the 6790GM the 3.2Khz SSB
> filter is engaged
> for synchrophase detection use. Very much the same
> performance,
> startlingly so..
>  
> Having a little success of course is addictive...and
> now the questions
> turn to the group experience. The audio train
> probably does not have the
> very best capacitors available as fancy types were
> out of reach back
> then. Also electrolytic capacitors in the voltage
> regulation area may
> not impart the best quality to audio.
>  
> The audio on the 6790GM of course is positively
> symphonic, and my half
> deaf 93 yr. old mother in law can listen to Radio DW
> in the evenings in
> German as though the announcer is standing next to
> her yelling in high
> German directly into her good ear...  ; )
>  
> If only the 6790GM had the IF notch and PBT (knob)
> of the R7 and the R7
> had the stability, and ease of tuning of the
> 6790GM...
> It is interesting to note that for around $550.00 a
> cure is available
> for these maladies in the form of the SE-3 for the
> 6790GM and the RV-75
> VFO for the R7. 
>  
> Does anyone in the group have any suggestions for
> further mods as it
> seems the R7 here has just had its claws sharpened
> to good effect...
>  
> I will have some of these hot carrier diodes left
> over, as the mod took
> 8 .If anyone is feeling adventurous just let me know
> off list and I will
> send em over for free...
>  
> Cordially, Dan Seven
>  
> R7 6790GM 6217E  
> 
> > _______________________________________________
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