[Milsurplus] tank radio skip?

[Hue Miller]

----- Original Message ----- 
From: "Brooke Clarke" <brooke at pacific.net>
To: <milsurplus at mailman.qth.net>
Sent: Sunday, January 30, 2005 10:56 AM
Subject: Re: [Milsurplus] tank radio skip?


 
> That's an H.F. antenna designed for NVIS use, but may also send some 
> signals into DX paths.  See:
> http://www.tactical-link.com/WWII_NVIS.htm  where there are some 
> drawings showing these H.F. antennas on German armored recon vehicles.
> Brooke Clarke, N6GCE

I'd suggest that it's a wee bit presumptive to call this an "HF NVIS antenna".
For tactical local communications where not using the low-vhf range, the
German communications pretty much topped out around 7 MHz.  Much of
their equipment, even mobile, covered frequencies that don't fit the HF
designation of  3 - 30 MHz. For example, the 100WS transmitter, 200 - 1200
kHz. The 30WS transmitter carried in command tanks and scout cars, in
addition to the vhf gear, covered 1 - 3 MHz.   These antennas, and the antenna
called a "star antenna, which looks like a vertical with 3 capacitive loading rods
about 3 ft long that slant down like an umbrella, seen on the back deck of  "
Command Panzers",  were all intended for use with the LF/MF equipment. 
( I have the "star antenna", and it is really heavy: NOT aluminum at all.
Still waiting to find a panzer - or maybe i should just sell the antenna. )
If they had intended to use only HF, they would not have bothered with such
a fragile and expensive antenna for just HF - they would have used a whip,
just like the rest of the world did. 
The thing that looks like a railing on scout cars or a laundry rack is a purely 
capactive antenna.  Or consider it a top hat  hat with the vertical part of the
antenna shrunk down to nothing. It was resonated with the loading coil inside
the transmitter.  More capacity = less loading coil - and less coil losses. 
I don't think NVIS was in their consideration as such - it was  just a way to get 
current into the antenna at LF. With such a small antenna at LF, you have basically
a point source for RF.  With LF/ MF, good ground wave range was what they 
apparently were after. The crank up tower photo i suspect was not for any
groundplane vhf antenna, i believe it was just a crank up vertical for actual HF 
longrange communications in the range up to 10 MHz most likely.  ( Where the 
KWEa receiver topped out, 10 MHz.)  Communications when parked, of course.
I have not seen an actual German GP antenna in the paper i've looked at, but i'm 
always ready to learn. I think i read that the frame aerials idea was kind of an idea
that was dropped later in the war - i'd suppose these antennas too fragile and
bothersome to maintain.  
Germany was big on capacitive loading of short antennas. You can also find
many photos of infantry and arty spotters using big boxes about the BC-654 
size, with a vertical maybe 3 to 7 ft tall and a capacitive hat with 4 spokes of 
about 14 inches each.  -Hue Miller