[Milsurplus] Re: DF-ing & Earhardt/Noonan

[Hue Miller]

----- Original Message ----- 
From: "Al Klase" <skywaves@bw.webex.net>

> Hue,
> 
> Interesting info about the 7500KC DF.  At that freq. you 
> could have a really strong skywave hitting you nearly 
> vertically when you were within 100 miles or so of the TX.
> Hence no null.

I think it depends on how the skywave and direct wave combine.
I have done a very little bit of DFing on 49 meter BC stations,
and you can get a null, even from stations MUCH farther than
100 mi. out, but.....it gets really impossible if propagation is
unstable, moreso even around sunrise/ sunset, when it's 
unusable. I have a manual for the SCR-504 ( i think it is....)
"suitcase DF", serendipitously found in an antique store by
itself, and i was very happy to pay the $15 price,  believe
me, anyway this manual talks about the same thing, the
sunrise/ sunset problem.

Also a note that AE/FN had flown around the Lae, Niu
Guinea airfield a day or so before, trying to get a null on
the airfield's 6 Mcs signal, but couldn't. AE bagged that 
trial, saying that maybe the airfield signal was too strong,
but that sounds not right, don't it? I mean, she could
just have flown out a few miles. Strange. It's still a 
mystery, and if you figure anything out about it, you will
have made a definite contribution to (maybe) understanding
what happened near Howland.

Maybe they just didn't have enuff experience with this.
I found it could be very frustrating to try to get a null
sometimes, as the null depth might constantly change,
but if you were persistent, didn't give up, you could
often tell the general direction of the null within say,
just guessing here, 15 degrees. IF they had gotten
this, then switched to "DIRECTION" on the DU,
to engage the sense circuit, they could have gotten
the right direction too, which would have helped them
at least fly in the right direction and general bearing,
instead of wondering if they were going / coming.
Hue