Go to
http://wsprnet.org/drupal/wsprnet/map
select MF band (600meters) put in my call WH2XCR
and select past 12 hours.
You will see first hand what propagation on 600M is like in todays
world. Technology has made things a lot different, or leave the
call sign field blank and see all the activity on 600M.
73 Merv K9FD/KH6
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.
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