[AMRadio] Any Elmac PMR 6 docs in the house?

[Mark Foltarz]

Charles, as you have seen in the schematic, there is of course no direct coupling methods indicated.I'm guessing there was a simple gimmick like in the Hallicrafters S40 to inject the BFO.  Does the VFO oscillate at all  with or without the s variable cap connected?
Mark

      From: CL in NC via AMRadio <amradio at mailman.qth.net>
 To: amradio at mailman.qth.net 
 Sent: Wednesday, August 15, 2018 6:05 PM
 Subject: [AMRadio] Any Elmac PMR 6 docs in the house?
   
The PMR6 BFO circuit is a mystery to me.  V8 is a 12AT7, one half is the BFO oscillator, the other the audio preamp.  There is no connection shown on the schematic for coupling the BFO into the IF at the last stage, and I don't get it if the plan was for just the intercapacity of the dual triode to couple energy into the audio preamp.  That would seem to be beyond where you would get mixing and a beat note.  The owner of this RX wanted me to remove several mods to make it stock.  One of the mods was a variable cap and series cap from the grid of the BFO into the grid of the last IF, and it worked great.  Now it does not.  The later PMR7 uses both sides of the BFO tube for the oscillator and injects it into the last IF's grid with C82.  So, anybody have a clue as to how Elmac intended this to work, or did they leave something out of the schematic?  Think I will put the mod back in.

Charlie W4MEC in NC
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