[Drake] preselector

[Misic, George J.]

The basic reason that the RF front-end tuning is a separate knob from the frequency tuning is that receivers like the Drakes and the S-Lines have a different tuning rate for the RF front end circuits than they do for the frequency control.  All bands on the Drake are 550 KHz, and 200 KHz on the Collins S-Line; the RF tuning rate is a percentage of the frequency, so a single knob would create a huge tracking problem, and much mechanical complexity [think Collins R-390 or 51J-4 here].  73.

George KE8RN

-----Original Message-----
From: drake-bounces at mailman.qth.net
[mailto:drake-bounces at mailman.qth.net]On Behalf Of DJED1 at aol.com
Sent: Thursday, May 04, 2006 7:18 PM
To: eberbari at indy.rr.com; dcsfree at comcast.net; drake at mailman.qth.net
Subject: Re: [Drake] preselector


I'm not sure if Drake was the first, but it's interesting how the  
preselector function came about.  Back before 1950, in the days of  Hammarlund and 
National, all the preselection circuits were gang-tuned with the  tuning dial of 
the radio.  My SP-600 has one knob tuning for all circuits,  for example.  So 
there was no separate preselector knob. Then, Collins went  to the separate 
linearly tuned oscillator, with a crystal controlled  downconversion (75A2,  75A4, 
etc).  Interestingly, these had  integrated tuning, so that the preselection 
circuits were driven by cams from  the tuning dial- still one-knob tuning.  
The ultimate example of integrated  one-knob tuning is the R-390A, with a 
stunningly complex set of gears and  cams to tune both the RF preselector and the 
variable IF stages. Collins  undoubtedly decided this was too expensive for 
consumers, because the 51S and  75S series were the first Collins designs to use a 
separate preselector  knob.  Similarly, in that time frame, Drake also used 
this approach.   It's obviously a cheaper solution, which comes at the expense 
of having  another knob to tweak.
Anyway, the answer to the question depends on when the 75S Collins rigs  came 
out versus the Drake 2 line.
Ed  WB2LHI  
______________________________________________________________
Drake mailing list
Home: http://mailman.qth.net/mailman/listinfo/drake
Help: http://mailman.qth.net/mmfaq.html
Post: mailto:Drake at mailman.qth.net