[Milsurplus] OT: Amelia Earhart

[Hue Miller]

There are many interesting radio related aspects to Earhart's final flight, 
and in that
connection I'd heartily recommend Ric Gillespie's book, which goes into the 
putative
post-landing messages at length.
Some of what are called "post-loss" transmissions were claimed to be heard 
totally
out of the 3105 and 6210 channels that her radio was equipped with. I was a 
member
of the  TIGHAR forum several years ago and confess I was probably 
instrumental in
furthering the claims to veracity of those reported receptions, when I 
pointed out the
harmonic-liberating ability of the minimal tuned circuits in the W.E. 
transmitter. The
tuned circuit in the transmitter was only a single tapped coil, something 
like in our
BC-230/430 transmitter but without any resonating variable cap. Plus in 
those years,
late 1930s, DX was really, and I mean really, in and working. So it is 
possible that
people heard AE on some odd harmonic of one of her channels. However, TIGHAR
credulously accepted one or two reception reports that I thought lacked 
logic to
them - in one, AE is heard seemingly having a conversation with her 
navigator,
even when listening to the receiver at the same time. Which sounded to me a
bit too much like a "broadcast", as in "program".  I questioned the 
"harmonic
theory" but was attacked by TIGHAR's resident physicist advisor, who 
marshaled
the ICEPAC ( I think it was ) propagation prediction software to silence me. 
I don't
have the math to work this program and I don't have time to learn it now, 
even if
I wished to. I did point out that the "harmonic theory" depended on analysis 
of the
whole transmitter from tube plate to wire antenna resonances - that there 
was no
such thing as "broadly resonant" single wire antenna ( that description 
still survives
in the TIGHAR "Research Reports" but my objection was blithely ignored. 
Basically
I am saying that an antenna match at 6210 to a nonresonant wire antenna will
NOT automatically guarantee an effective transfer of power to the wire 
antenna
at some harmonic of 6210. It so much depends on the antenna impedances.
However that point was disregarded in their physicist advisor's power 
calculations,
which I would call "best, best, best case".
A couple other points. There was NO CW transmitting facility provided. No 
key
was taken along. The only way possible to key the transmitter would have 
been
to disconnect the antenna feeder and send by touching it to the transmitter 
antenna
post. You might have an opinion on how likely that was to have been done, by 
two
non-technical people not particularly schooled in telegraph sending.
Also, apparently, altho we do not know for certain, NO RDF receiver of any 
kind
was onboard. There was a photo of AE with a Bendix representative posing 
with
a "DF Coupler" for use with any HF receiver; this was clearly a prototype of 
a model
Bendix sold the the U.S. Navy, which became the DU, later produced in larger
numbers as the DU-1. The DU itself tuned up to 8 MHz. The Navy later 
abandoned
the idea of HF DF for aircraft as just not workable; hence the more limited 
freq
range of the DU-1, up to 1500 kHz. AE was supposedly to DF on the USCG ship
Itasca on 7000 kHz but could not get a null, for whatever reason, skywave
interference or unfamiliarity with using the DU, plus the possible added 
difficulty
of tuning back and forth on the receiver from 7000 to one of the comms 
channels.
Truly, the communications arrangements were poorly and sketchily worked out
and that was probably a major factor in her missing the landing island.
It has seemed to me for a long time that this would have been an ideal 
project
for someone like Paul Allen to pursue. At last Ric Gillespie has funds for 
another
search.  Climate change conditions mean Nikumaroro is being pounded by
fiercer storms and there was fear whatever scant evidence might remain would
be washed away by higher seas. Ric Gillespie has, altho he would deny it, 
made
this his life's work and certainly for all his devotion to this subject, 
certainly
deserves to learn AE's final chapter, one way or the other.
I did a few years back buy a transmitter of the same type as on AE's 
aircraft.
I thought it would be a kick to restore and use on air, and also to try to 
get
some real numbers as for harmonic output power and emergency CW keying
method. I learned that the W.E. tubes are what I considered fabulously
expensive, slightly better in the last couple years as China has started
reproducing the 205D tube for the audio market - thank you, glass audio
fanatics. Probably I will have to get a BC-375 type dynamotor to run the
transmitter. After a recent surgery it hurts to even think of things such as
heavy dynamotors etc. or lifting anything heavier than a 205D but I'm hoping
given enough months I can bounce back and even move some PE-237s out
of my vehicle at last.
Again, I strongly recommend the Gillespie book. You will get every cent of
your money's worth.
-Hue Miller