Topbanders,
Last night I finally hit the frustration point with my anemic TX signal
(for a 4-sq that is). EU finally came in here, and I called Wolf DF2PY
about a dozen times before he heard me. He was armchair copy here.
My 4-sq elements are Gladiator "center loaded" whips, 32' tall, with about
7' of 1-1/4" inductor starting about 6' up; very lossy.
I decided to see if I could make these contraptions better. First, I put
jumpers (1/2" X 1/16" alum. lath, clamped with hose clamps) over the
long, skinny coils. Then I put 3 - 30' loading wires running down from the
top at a 45 degree angle, and added a skirt wire. The skirt wire runs
about 7-8 feet above ground. (I intend to rebuild the whole array next
summer, but for now, I've got to work with what I have)
A trip to the hardware store yielded what I think are decent coil
materials. They had a flexible 4-1/2" drain tile with grooves spaced about
1/2" (I have no idea what the dielectric properties might be). The grooves
are a perfect fit for 3/16" copper tubing. I got 20 feet of the tubing,
and wound it onto the form. This gave me about 16 or 17 turns. So the
coil specs are, roughly, 17 turns of 3/16" tubing spaced 1/2" with a 4-1/2
inch diameter.
I mounted the coil to the bottom of the whip and started tapping for
minimum reactance at 1.820 Mhz. (MFJ 259B) The sweet spot was about 2/3 of
the way down the coil (the top end is attached to the base of the
whip). The 259B says R = 5 and X = 5.
I have a good ground system, with 72 radials per element, over highly
organic, saturated soil (water table a few inches to a few feet down).
The Rrad with the original whips is about 13 ohms. I expected higher Rrad,
but the sloping top hat apparently more than overcomes the
Rrad advantage of top loading. Presumably, the lower Rrad will more than
double my ground losses, right? Wish I knew what they are, but presumably
they are low.
I would like your opinions on the efficiency of this radiator compared to
the originals.
Is my coil design OK?
Are my losses in the new coil more than enough lower than in the old
coils to overcome additional ground losses?
Will the lower impedance work ok with the Comtek box (50 ohm phasing
lines) or will I have to do additional matching
at the antennas?
I'm sure there are other things I'm not considering. Please give me your
thoughts. I need to decided right away if I am going to do the other
elements, with the CQ 160 next weekend.
73,
Ron - WA9IRV
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