[Milsurplus] OT: Amelia Earhart

[David Stinson]

----- Original Message ----- 
From: "Hue Miller" <kargo_cult at msn.com>
Subject: Re: [Milsurplus] OT: Amelia Earhart


> 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. ...  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....

I can give some insight into this, having a lot of time with the 
BC-230
and now also with the U.K. TR9D, which uses an output stage
similar, (but lower power) to the WE transmitter:
tapped PA coil directly connected to the antenna
and no tuning cap, depending on the antenna's "C" to resonate.

The harmonic content of the output of the BC-230
is acceptable for use on the air today.
The output of the TR9D is screaming-alive with harmonics.
I connected the rig to my 140 ft wire antenna
and started the "DF Contactor" clock for tests.
The 2nd is only down about 6 dB,
and the third and fifth harmonic (11.67, 19.45 MC)
were easily detectable a mile away.
And the TR9 only does about a watt out ;-).
I did not detect even harmonics beyond the 2nd.

Important to note that I was tuning the TR9D all the way down
to 3.89 MC, which is far beyond its speced 4.4 MC.
It will resonate there, but with much more "L" than
normal, which means the tank "Q" would be lower.
Doubtless that accounts for some of the harmonic richness,
but certainly not all.   I'm going to pad the tank with some "C"
to raise the "Q" and see what that does to the harmonic content.
I intend to make at least a few contacts
with the TR9D, so will follow it with a low-passed amplifier.

73 DE Dave AB5S