[TowerTalk] [Force 12 Talk] Mag 240N questions....URGENT
K7LXC at aol.com
Thu Nov 24 13:14:12 EST 2005
In a message dated 11/24/2005 10:00:45 A.M. Pacific Standard Time,
Force12Talk-request at qth.com writes:
> I am TRYING to "tune" a 240N (height is 25') and am not getting
results. Tom is not sure why. He says the factory default lengths for the
reflector and the driver should work but I am much shorter than this (5.5"
on each tip on the reflector and ~3.5" on the driver element) AND the
bandwidth is bad (~ 180 Khz - should be almost 300). Can someone please
> Does anyone know how many turns the hairpin match has? I do not think I
one (or I misplaced it) and I made one that is 2.5" in diameter and 3 turns.
Since the hairpin (made into a coil) is part of the element length, it's not
too critical in length since the jumpers can (will) be adjusted to resonance
anyway, rendering the hairpin length simply relative.
> Did you tune yours or just set it to a length?
You have to tune each element to resonance (the REF and DIR resonances are
in the manual). I have NEVER seen an F12 linear loaded antenna be set
correctly when using the manual dimensions - they're just a starting point.
> What length did you end up with (for the tip sections) on the reflector?
the driven element?
I've always just adjusted the LL jumpers and didn't worry about any other
part of it.
> What is the swr bandwidth for a 2:1?
For the F12 LL antennas I've worked on - a couple of dozen - it's been about
180 khz. I think there were only a couple of N types in there.
> I checked the driver alone (reflector jumper removed) and still the SWR
a 2:1 is only about 180Khz.
Sounds normal to me.
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