[Milsurplus] WW2 TRC-10 discussion

[Hue Miller]

I was recently looking at the manual for the AN/TRC-10
2-12 Mcs. cw trans-receiver and read that the plate voltage
on the receiver tubes ( 6SK7, 6SA7 etc. ) was 300 volts.
That's a bit high, isn't it? Doesn't leave much of a safety
margin if the overall B+ goes high. I don't think i have ever
seen any other vac tube receiver pushed this hard, with
this high B+.

BTW, the AN/TRC-10A i don't think got past the 
recommendation stage, in other words, the changes
were agreed on, but i do not think it was ever produced
( I think WW2 was winding down rapidly - TRC-10
improvements were being discussed April 1945 ).
Some of the changes were to change the 6SK7s to
6SG7, even the audio output 6J5 to 6SG7. I can under-
stand the RF tube change, to get more sensitivity out
of the circuit, but i don't get the 6SG7 as audio output.
That seems crazy, because it's much harder to get a 
match to headphones with the pentode voltage 
amplifier tube. This radio wasn't intended as some dx'ers
machine, so i don't get the need to change to 6SG7 at
all, really.
Another interesting thing is that the TRC-10 (no suffix)
came in with a selectivity of something like 2.5 kcs. at 6 db
points ( i assume this is what they mean by "bandwidth
at 2 times input"  ), while the gov't spec called for " 3 to 7
kcs."  Easy, the design committee just changed the called-
for spec to "2 to 7 kcs." and then the radio fit the gov't
specs.  The docs overall seem to indicate a number of
problems with the radio, tracking, drift, regeneration, etc.
My observation seems to come up with the same kinda
conclusion, it seems a bit hasty. The radio innards seem
not up to usual robust combat radio specs, altho maybe
more in line with hastily designed and disposable 
clandestine type radio equipment.
BTW, the TRC-10 is apparently essentially the same radio
as the PRC-1, which has a much higher reputation due to
having an actual wartime track record, plus the civilian
suitcase packaging of the PRC-1 adds the $py radio aura
to it.  Even tho the TRC-10 may be equally uncommon.
( Did i read production of 155 examples? for the TRC-10 ? ).
The difference is that the TRC-10 has a metal case, with
legs like the BC-654, the front cover instead of folding
down, comes completely off and then clamps horizontally
on top as a kind of rain shield. The TRC-10 uses a 2E22
quick heating pentode, which i do not understand either-
this radio was not designed for fast, automatic break-in,
so why not the more common 807? Using the AC supply
with the TRC-10, the cw note hums a pretty good bit,
since the 2E22 was designed for dc filament power. I 
wonder if the PRC-1 used the same 2E22? BTW, the only
actual WW2 use of the PRC-1 i've read about, or am
otherwise aware of, was by Merrill's Marauders guerilla
unit in the CBI war theater.
Hue Miller