[Milsurplus] Tubes?

[Michael A. Bittner]

John, thanks so much for your definitive reply. That's really interesting.  I recall the same technique being used in the earliest GPS receivers to acquire the satellite signals under various conditions of maneuvering, Doppler, time uncertainty, etc.  Thanks again. Mike, W6MAB

  ----- Original Message ----- 
  From: John Vendely 
  To: milsurplus at mailman.qth.net 
  Sent: Thursday, April 19, 2012 1:57 PM
  Subject: Re: [Milsurplus] Tubes?


  Hi Mike,

  The "pulse sweep generator" was a simple transmit frequency acquisition 
  aid.  This series of radios had a very simple transmitter consisting of 
  a frequency modulated electron-coupled "power" oscillator coupled 
  directly to the antenna.  The radio featured an AFC system to lock the 
  transmitter frequency to that of the receiver by feeding a DC control 
  voltage derived from the receiver's discriminator back to the transmit 
  oscillator, thus holding it on frequency (the receiver remained on while 
  transmitting).  But sometimes, the transmitter was initially far enough 
  off frequency that it fell outside the receiver's IF passband, and no 
  AFC voltage would be developed.  The transmitter would then simply drift 
  around off frequency.  When this occurred, the sweep generator was 
  designed to automatically activate, sweeping the transmit frequency back 
  and forth.  The frequency sweep was made wide enough to ensure that at 
  some point, the transmitter would enter the receiver IF passband, and 
  the AFC could then lock.

  The original PRC-8, 9, and 10 radios did not have the sweep frequency 
  acquisition feature, and evidently experienced problems if 
  transmit/receive frequency tracking wasn't pretty close.  In the "A" 
  model of the radios, they sacrificed one IF amplifier, replacing it with 
  the sweep oscillator.

  73,

  John K9WT

  On 4/19/2012 1:08 PM, Michael A. Bittner wrote:
  > OK, Thanks for the info.  But, why would you need a pulse sweep generator in an FM transceiver?  Mike, W6MAB
  >    ----- Original Message -----
  >    From: David Ross
  >    To: milsurplus at mailman.qth.net
  >    Sent: Thursday, April 19, 2012 9:34 AM
  >    Subject: Re: [Milsurplus] Tubes?
  >
  >
  >
  >
  >    On 4/19/2012 7:18 AM, Michael A. Bittner wrote:
  >    >  What were these replaceable circuit modules use in, especially the pulse sweep generator??  Mike, W6MAB
  >    >  http://www.ebay.com/itm/ASSORTED-SPECIALTY-TUBES-TUBE-CADDY-6-/330719816641?pt=LH_DefaultDomain_0&hash=item4d006febc1
  >    They are used in either PRC-8s&  PRC-9s&  PRC-10s, or PRC-8As&  PRC-9As
  >    &  PRC-10As.  There are about ten different types of these modules, some
  >    have miniature tubes inside and some are passive.
  >
  >    The six of them should ship for just a couple of dollars...
  >
  >    73
  >    Dave Ross    N7EPI
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