[Milsurplus] Freq. Coverage of Navy Transmitters

[Hue Miller]

----- Original Message ----- 
From: "howard holden" <holden7471 at msn.com>

> The puzzle to me is why did the TBW have the LF unit? Any antenna they could 
> set up on the beach would be a pretty inefficient radiator in the LF range. 

Well, not on the beach, but this wasn't only a beach radio.
Yes, the shoreside antenna would be pretty inefficient. But the inefficiency
didn't persuade the German and Italian military planners from making use
of LF/ MF, even in armored scout cars.  I think this was for ground wave
coverage in rolling country, even tho i don't think i have yet explicity seen
this idea in print elsewhere. It just popped into my head just now, i recall
reading something in an ARRL mobile book, i think it was, that stated that
for mobile with same power and antenna, 160 actually gave somewhat more
coverage. This just as an example that lower is not automatically "worse".
Sorry, wish i had that reference handy to cite.

> The upper MF and HF would be far more useful and practical for shore-ship 
> comms. Perhaps it was to be able to communicate with merchants involved in 
> landings, who might have had only MF/LF rigs. That could explain the MCW 
> capability on many Navy transmitters.

Landing missions and shoreside portable stations wouldn't be communicating
with cargo type vessels no matter the owner. The comms would be funneled
thru other appointed communication ships. Pretty sure i can back this up, with
some trouble and digging, but that's absolutely the lesson from the actual
landing invasion radio traffic quoted in the book, "Navy Retread".

> The other puzzle is why the Navy used suppressor-grid modulation instead of 
> plate  mod on some transmitters? Typical power output with suppressor mod is 
> about 1/4 of the CW output. Granted, the weight and space savings over plate 
> mod on the TBW might mean something to the guys who had to muscle it ashore, 
> but with a hulk like a TBL, at 700 lbs (not including the MG set), what 
> would another 150 lbs mean, instead of the 75 lbs for the suppressor 
> modulator.
> 
> Howie WB2AWQ

Actually, 150 lbs.  more can be a big deal for aircraft or for portable equipment that
has to be moved around by man power. But here's another great big reason, i 
think:  AM was considered to be the secondary mode for the transmitter, maybe
not the main show with cw as a fallback.
-Hue Miller