[Milsurplus] SCR-183 question

[Kargokult@aol.com]

In a message dated 4/19/02 6:10:35 AM Pacific Daylight Time, 
n4fs@monmouth.com writes:

<< Hue & Group -
 
 Hue you are totally wrong on this one. I never talked about calibration,
 just plain alignment. since the receiver is a TRF, all stages have to tune
 in unison, meaning, all RF stages have to track. 

--Okay- i grant that since the BC-229/ 429  covered the LF band, tracking
there would be important. But recall your experience aligning front ends
of receivers - on HF, inserting a replacement tube is not going to affect
sensitivity of the RF stage, because the bandpass on HF is in the 100s
of kHz before you are well down the selectivity slope.

That is if you want a
 receiver with some sensitivity. With regards to the CW operation, there is
 still one main frequency to which the receiver is tuned even though it may
 be broad. It is that tuned to station that needs to be heterodyned against
 in order to properly demodulate the CW, so, the local oscillator had to
 track the main tuning also for BFO injection. >>

--For the RU, this still didn't matter - on the HF bands. The dial calibration
marks are only something like 0 - 100, so you cannot reasonably use it
to hit, say, 5655 kHz, and the RF is wide enuff that tracking, if you swap
coils between receivers or change tubes, there's no problem. On LF,
the tracking does become important. Without having measured it, i still
suspect swapping even LF coils between receivers could not have any
deleterious effect - the tracking variation is just not that important here.
These receivers were used far from any DX contest environment - i mean
they weren't used for dx'ing in a crowded band, but to tune to a definite
frequency and sit there.
BTW, re the differences RU/GF to SCR-183, the Navy gear looks a lot
more modern, doesn't it? And it has a lot more accessories. But for
AM reception, 3 tuned circuits at HF is *all* you have for selectivity.
Say, this is kinda interesting too, that the SCR-183 also started out
with black wrinkle, then went to plain aluminum. You almost never
see a SCR-183 in black anymore, while the Navy never went to plain
finish, til the post war ARC-3 anyway.
While i'm on color, i've wondered before why the US military went in
so much for black wrinkle. Other countries used grey, green, or
blue in their aircraft equipment, and it didn't seem to hurt the 
aviators eyes or anything.
Hue