[Milsurplus] More Earhart scenarios

Hue Miller kargo_cult at msn.com
Sat Apr 28 19:09:13 EDT 2007


I am a subscriber to the TIGHAR list. This is "The International
Group for Historic Aircraft Recovery". This group believes 
Amelia Earhart after missing the Howland field, came down
on Gardner Island (Nikumaroro).  In looking at the record of
supposed signals received after her nonappearance, one 
particular signal which i questioned, is explained with the claim
that well, why couldn't she receive and transmit at the same time.
My statement that this was not possible, nonstandard is dismissed
as not dealing with all cases, hers being maybe an exception.
Unfortunately i have no radio texts on hand. 
So if you are at all interested in WW2 and pre-WW2 aviation, i 
pose these questions. If you can quote chapter and verse, not
just off the top of your head, so much the better. Or even from
experience.

1. Many 2-way HF systems ground the receiver antenna during 
transmit. For medium power, is this necessary?

2. If you have separate aircraft R and T antennas, T on top
the plane in the usual fore-and-aft wire, and receive antenna
on the belly, with 50W transmit power, does the receiver input
circuit need to be protected, or can it handle the voltages
developed? About 8 - 10 foot separation between the two
horizontal wires, frequencies 3-6 MHz, and antenna less than
1/4w on the lower frequency. 

3. If you do not at least switch off the B+ to the receiver front
end, then you would have to either turn off the receiver, or
manually retard the gain control before, and advance it after,
each transmission, right?  Also, if i recall, if not done, the
receiver's AVC charges up enuff that it takes some seconds
to discharge, is this correct?

4. I don't particularly recall the texts, when i had them, addressing
the control and switchover topics. Do you know if the Army's 
"AM Transmitters and Receivers" TM, or if some USAF or 
USN Electronic or radio text addresses this specific issue, that
i could locate and quote?

5. The WE Co. type 13 transmitter carried on the plane does have
an antenna T/R relay, and it does ground the receiver antenna post
during transmit. However on this plane, the topside antenna was not
used for receive. I imagine this was to minimize the antenna wire 
running internal thru the plane to under the pilot seat, where the receiver
was. Sound logical? 

Yes, some of this seems self-evident, but my word alone is
not good enough!  Thanks- Hue Miller 


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