[SECC] Upcoming activity

[Gary Breed]

> Gary,
>
> Is the 2L 40 full sized or ??? Details ???
>
> TU !
> 73 Billy AA4NU
______________________________________________

Here it is...Gary, K9AY


Antenna description:  K9AY 2EL 40M Beam

Boom: 18 ft. 2" OD x .093" wall

Elements: 52 ft long; each side of center is 7 ft 1-1/2" tubing (insulated
from boom), a 2-1/2" diam. loading coil (10-12 turns), 20 ft graphite
fishing pole with 3/16" braid inside, less trimming and overlap.

Weight: 25-30 lbs. max. No boom truss needed, not much element droop.

Tuning: CW band, min. SWR at 7020, 1.5:1 at 7065, 2:1 about 7090.

Matching: Direct feed with approx 50 deg. electrical length 25 ohm line (2x
RG-8), driven element is theoretically 18 +j14 ohms. No balun - feedline is
taped to boom, to the mast and routed on the inside of the tower. I think
it's well enough isolated.

Tune up procedure:  Started with EZNEC model.  "Disassembled" antenna in
EZNEC to see that the reflector would be resonant by itself at about 6990
kHz at 50 ft and driven element somewhat lower in frequency (remeber, it's
inductive).

Each element was assembled and raised on a rope and pulley for tuning.
Loading coils were adjusted for desired resonance.  Loading coils lightly
taped to allow future adjustment.

Entire antenna was assembled and hoisted pointing upward until the reflector
was about 20 feet off the ground.  The driven element was adjusted for 1:1
match at 7025, which took four iterations of hoisting and lowering.  The
match was 1:1, which inferred that the reflector was already tuned properly
(Murphy cut me a break!).

Mounted horizontally on the tower at 35 ft., the 1:1 match was at 7000.
Raising the antenna to 75 feet raised the frequency to 7020 with about 1.1:1
SWR.

A few comments:

1. Pre-tuning using modeled dimensions works well (I've done this before).
2. Tuning with antenna at low height and pointing upward works well.
3. Fiberglass or graphite crappie poles are great antenna elements (I did
this before, too).
4. I missed slightly on reflector tuning, but the error is on the side of
gain rather than pattern -- I'll take it like it is!



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