Drake TR-7 question

Garey Barrell k4oah at MINDSPRING.COM
Fri Sep 22 09:22:54 EDT 2006

George -

It's strictly a guess, but I would guess around 7500. I've seen quite a 
few TR-7s, and so far I've not run into one below 7500 that had the 
Version 2, 2nd IF/Audio board.

It's pretty easy to spot if you can see inside the card cage. The 
Version 1 has four "aluminum" IF cans along the top edge. Looking down 
from the front of the transceiver the Version 1 has a square, black 
transformer at the far right. Version 2 has an IC (MC1496) there. Easy 
to spot even in a small photo.

Someone has modified a Version 1 with a small "daughter" board mounted 
in that corner holding the MC1496 and a very few components. There are a 
couple of changes needed on the PassBand Tuning board to adjust the BFO 

Another one has replaced the active mixer with a DBM, again bumping up 
the LO (BFO) level to compensate. Even simpler to implement.

Personally, I've never been able to tell any significant difference 
between the two boards by listening to the receiver. The signal level is 
held constant by the AGC, so any dynamic range advantages of either 
"alternative" detector are not realized, and the discrete mixer does a 
reasonable job of suppressing the LO feedthrough. I doubt anyone could 
tell you which board was in a transceiver by just listening to the receiver.

73, Garey - K4OAH

Drake 2-B, 4-B & C-Line Service CDs

George Maier wrote:
> Does anyone know, by approximate serial number range, when Drake changed the
> TR-7 product detector from diodes to an MC-1496.
> Thanks & 73
> George - W1LSB

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