[Drake] Noise Blanker

[Lars E. Pettersson]

On Saturday 01 March 2003 18:35, Mike Elliott wrote:
> The NB-7 was done before the "woodpecker" and the R7 came along.  The
> NB-7A serves
> both the R7 and TR-7, plus blanks the woodpecker (difff. t.c.)
> Mike

Mike, looking in the 1980 version of the service manual for the Drake TR7 
both versions of NB7 is depicted, and the only difference I can see in the 
schematics of both is that NB7 ver1 uses 3N204, and NB7 ver2 uses TIS-153, 
R841 in ver1 is 1M, and 680K in ver2, C835 is 270 pF in ver1, and 330 pF 
in ver2, NB7 ver2 also have a J310 amplifier before the noise blanker 
gate. The NB7 ver2 is exactly an NB7A but without the filter and 
associated components for impedance matching.

So the question still remains, why did Drake sell two different versions of 
the NB7; one with (NB7A, R7 service manual), and one without the filter 
(NB7 ver2 in the 1980 TR7 service manual)

Adding a filter, and then an amplifer (the J310 mentioned above) make 
sense, but why the NB7 ver2? Why not only NB7A to be used in both TR7 and 
R7?

73 de Lars, sm6rpz
-- 
Lars E. Pettersson, SM6RPZ
Gothenburg, SWEDEN
sm6rpz@home.se
http://www.gbg.bonet.se/cassegrain/