|
TENNADYNE LPDAs use
a double boom, one above the other, that perform a double duty.
They act as [1] a constant impedance transformer, providing a constant impedance
match between the very high impedance of the LPDA elements and your 50-52 ohm
feedline. They also [2] provide a rigid fore-to-aft structure much
like a truss, giving very strong mechanical support to the antenna
elements. Overall, this boom structure is exceptionally strong!
Each boom is precision machined so that the elements pass directly through them,
continuing with the constant impedance transformation!
One of the things that distinguishes TENNADYNE LPs from those of other manufacturers is this use of a
double boom, and there's more to it than meets the eye. In Chapter
24 of the ARRL Antenna Book, the one on Transmission Lines, the book
states, "In installing parallel-wire line....the line should be kept
away from other conductors, including downspouts, metal window frames,
flashing, etc., by a distance of two to three times the line
spacing. Conductors that are very close to the line will be coupled
to it to some degree, and the effect is that of placing an additional load
across the line at the point where the coupling occurs. Reflections
take place from this coupled "load", raising the SWR. The
effect is at its worst when one wire is closer than the other to the
external conductor. In such a case one wire carries a heavier load
than the other, with the result that the line currents are no longer
equal. The line then becomes unbalanced."
Every LP on the market must use a form of
the open-wire line as a feedline within the antenna structure itself,
whether it is actually made of wire or, in the case of TENNADYNE LPs, the booms themselves. Imagine, if you will, what
happens when you run this feedline, from one end of the antenna to the
other, only inches from the grounded boom of the antenna. A clear
reason why TENNADYNE
LPs are superior....by design.
"I
am pleased with the performance of the T6; it allows me to move through the 20,17,15,12
and 10 meter bands with the simple flick of the band switch."
K9LA Carl Luetzelschwab [T6] |
|
