[MRCG] HF Ground-to-air comms

[Tim]

"A better receiver and antenna directly impacts the ability to hear a weak
signal so I think that does factor in. It has been my experience that with
these WW-2 radio what if/ would it work questions are best answered by
actual field tests. Like when OPE Tom and I tested BC-222 to BC-222 coms
and also operational tests with TBY's and MAB's. So.....who's got a plane
with HF AM capabilities? Let's try it."

Hi!  Hmmmmm   Thinking about all this...Well, I think we already did try it
- except the BC-611 was in the air and the other end was on the ground.
The receiver sensitivity and noise floor of a GRC-9  (with a 100 foot reel
antenna with a good ground) is probably pretty much comparable to an
airborne BC-348 with an aircraft wire antenna.  Atmospheric noise being
constant in each case...

So if a few, maybe tens of milliwatts radiated by the BC-611 was below the
atmospheric noise level received at the time I don't think any improvement
on the aircraft receiver end would matter much, if at all.  As I was trying
to receive it, the BC-611 transmit signal was below my combined
atmospheric/receiver noise floor level.  I know my receiver was working
fine because I could hear the guy in Palo Alto, 25 miles away via ground
wave (and blocked by the east bay hills) calling him (but don't know how
much power he was using)...

The path loss on 3885 Kc (and accounting for antenna capture area) is much
lower than on 145 Mc and even that didn't help... So I'm calling that 19
mile, optical LOS path, air-to-ground  experiment reasonably valid - but
busted.  At least the way I did it....So it's true - that 0.012 wavelength
BC-611 antenna with no significant circuit ground is clearly the problem...
I can hear SOCAL AM QSO's with my '611 - but they can't hear me.

Guys have worked the Space Shuttle with 5 watt HT's on 2 meters using
rubber duck dummy load antennas (let's call them 0 db gain)  The gain of
the BC-611 antenna is very much worse and the power to that antenna is 360
mW - and that ground-to-space path loss is much more on 2 meters than on
75...

So John!  Do you have an HF radio in your L-Bird?  Lets try it and see what
kind ground-to-air range IS possible!  Or is my slide rule rusty.....

[snip]