Hello Top Band Antenna Gurus:
Need a little help please. I recently got back on 160m in a small way.
(rec'd my "DXING ON THE EDGE" book <tnx Jeff> the other day and am all fired
up to put out more than a peanut whistle signal, hi)
I'm trying to shunt feed my tower for Topband and am wondering how
electrically "tall" it might appear?
(I don't own a grid dip meter, but do have an older MFJ-259 antenna
analyzer)
<<<(*or is this even possible to load on 160m*?) >>>
It's a 48' tall triangular, Delhi tower that progressively tapers as you go
up. Must be roughly 3' at the base and around 1' at the top. (guesses).
Exiting the top is about 16' of 2" alum. mast with 2 big hombrew 6m beams
stacked vertically on it sitting in a Ham IV rotor... They are both 30'
long - 2" booms with 8 elements horizontally polarized. (All 16 elements are
roughly 9.3' long each) One horizontal antenna sits right on the top of
the tower and the other very near the top of the mast @ the 64' mark. All
elements and booms are mechanically grounded/connected to the mast. No
special effort has previously been made to insure good electrical contact
between antennas, booms, masts, rotors, etc. They are fed with hardline and
also there is a TOP/BOTTOM/BOTH switch between antennas. (doubt this makes a
difference). At the ground level I have 12 x 80'->130' (random length) newly
buried copper radials, also attached to tower base.
I have tried shunt feeding it with the attachment point at the 24' mark up
the tower (and various spacings) and another sort of delta feed connection
at the 30' mark. (this seems a bit better)
The absolute highest I could possibly feed it would be around 42' mark as
the drip/rotor loop for the coax is quite big and hangs down quite far (too
far), so it would get caught up if I installed a feed any higher. Also the
rotor and the phasing switch box below precludes putting a pipe any higher
up with ease. For series matching I do have a roughly(?) ~600pF air
variable that I used successfully for years on a variety of inverted L's @
old QTH . . .not having any luck now. Low slopers always beat out the
tower on RX and can't get it to load anyways.
------------ Top 30' boom , 8el, 6m antenna (@64')
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| 16' of 2" alum mast
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------------ Bottom 30' boom, 8el, 6m antenna (@ 48')
[] top of 48' tower
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[]
[]
[]
[]
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(tower base in huge block of concrete 8 x 8 x 4' deep)
GROUND 12 x 80-130' buried copper radials.
Ideas? Tips? Will it even (ever?) work !? (hi)
My guess would be I need to:
a.. get the attachment point as high as I can go (even if that means just
another 12' up, to 42' mark)
b.. make it larger than a single #12AWG r90 insulated wire (cage??)
c.. and possibly employ an Ohmega match.? (only have a series cap now)
. . . .but as I really HATE to climb (even to only 42' high), I'd rather
get some informed opinions before trying anything more.
Thanks in advance !
Mike VE9AA - - now living in FN66
Mike, Coreen & Corey Smith
699 Rte 616 Keswick Ridge
NB
Canada
E6L 1T1
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