[Elecraft] K3 receive on .474.2 kHz - OT MF Gibson Girls

[Mike Morrow]

Some MF propagation variables are illustrated in the miliary manuals for those "Gibson Girls" (GG).  Most were SCR-578/BC-778 units that were 500 kHz A2 only, about 2 watts plate input, connected to a 300-foot wire vertical suspended by kite or balloon and a ground strap dropped into salt-water sea...nominal range was around 300 miles.  In fresh water the range was about **10 percent of that**.  For land use a 300-foot counterpoise was required and expected range was **5 to 10 miles**.

(Very late in WWII the T-74/CRT-3 GG became available, identical to the BC-778 with 8280 kHz A1 HF added.  In early 1954 the T-74A/CRT-3A came out with that new 8364 kHz A1 HF output instead.)

Unlike the post-war merchant-marine crank-operated lifeboat radios operating on those same frequencies, none of these units had receivers, although in late war some USAAF flights over the Arctic were supplied with a dry-cell battery-powered 200 to 400 kHz receiver AN/CRR-1.

IMHO it is interesting to study the very serious use of these low-power marginal antenna emergency sets operating on MF from 75 years ago.  The new 630m band is technically and *historically* fascinating.  It's good to see equipment makers like Elecraft supply support for its use.

Mike / KK5F
(Kept a 500 kHz receiver near bedside for several decades!)

Fred wrote:

>When the WW2 surplus began flooding the market in the US in the early 
>50's, the Gibson Girls already had the 8MHz frequency, 8280 if my memory 
>serves me ... which it often doesn't.  The story says it got changed to 
>8365 because people bought these things dirt cheap and did not know that 
>when they cranked them, they transmit.