Ummm ... let's be truthful here. The B&W folded dipole can be found in
radio catalogs from the 50's. We all knew [I was a kid with a new
license then and even I knew] that the doohicky at the center of the top
wire was a 400 or so ohm non-inductive resistor, and half the power [3
dB] heated it up. There was no subterfuge and B&W wasn't "conning"
anyone, it was very clear in the specification sheet. 300 ohms at the
feed point, hams often fed them with 300 ohm TV twinlead of the day to a
balanced link coupled to the final tank circuit. A 4:1 transformer
netted 75 ohms which nicely matched that twinlead too.
Nor did the Nat'l Guard get conned, they had a specific need for an
MF/HF antenna that was light, easy for a couple of troops to erect, and
very broadband ... their operating frequencies are [were] sort of
day/night separated, rarely if ever harmonically related, and required
ranges were in the several hundred miles or so miles. It was a great
antenna for a specific purpose which is why you see [or saw] them at
many military installations, some of which were Nat'l Guard Armories.
For 10 months in high school, I worked coastal marine from So
California. Very large V-Beams on 200 ft towers with two terminating
resistors at the ends. Moderately broad patterns into the Pacific, very
little off the backs [not many ships back there]. 5 KW from the TX, 2.5
KW into the resistors, 2.5 KW to all the ships at sea. Great antenna
for the purpose.
As with all things in Engineering, antenna choice is a basket of
trade-offs. The Nat'l Guard rarely tries to work DX. Broadband however
was near the top of their list.
Incidentally, the "T2FD" [TTFD] acronym arose from the "Tilted
Terminated Folded Dipole" developed by the US Navy during WW2, designed
to have one end hoisted on a ship's mast and the other anchored near the
deck. Lowered the elevation angle of the main lobe, something important
to them. Hams associated it with someone's call which I can't remember
at this point.
73,
Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn
On 8/13/2017 10:28 AM, Ken G Kopp wrote:
The antenna Jim's is referring to (below) is ... I believe ... better known
as
a "T2FD". In a case of conning the unknowing B & W ... and maybe even
themselves ... sold hundreds of them to the Army National Guard. You see
them hanging above every armory here in MT.
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