I thought that those of you were kind enough to advise on my problems- as
well as others- might be interested in progress to date.
I became convinced, largely because of the experiences of others here, that
I was suffering chiefly from a dimensional problem, due to the use of
insulated wire. So I took the bull by the horns, and took the thing down(
quite an adventure single handed, at least for my dysfunctional limbs!), and
having rescaled in EZNEC from the apparent 20.25Mhz "resonance", I chopped 6
inches off each end of the driven element and 6.4 inches off each end of the
reflector. I realised then that my problems were just beginning, because it
was exceedingly difficult to maintain the correct geometry- face and tails
of the elements etc. I did what I could, but it looked ghastly after
re-erecting; however there was no way I was going to take it down again that
day. To boot, the dratted thing had turned, so that it was now firing SW.
In the shack I was gratified to find that the MFJ analyser was now
indicating resonance at about 21.2Mhz. I realised that at the end of an
unknown length of RG213-probably about 30 metres- this was not the be all
and end all. However it was by now the afternoon of the WPX SSB contest, and
there was a goodly number of SSB signals around. It was gratifying that
every signal checked from SA and the Caribbean was now 3-6dB up on the
reference vertical, whereas previously it had been 3-6dB down. The f/b was
clearly poor, but in view of the distorted geometry, this was hardly
surprising. In fact as chiefly a contest operator, this is not the most
important factor to me, forward gain being more significant. So swallowing
my pride as a 99% CW operator, I found a fist mic., fired up with 400 watts
and called all the SA/Caribbean stations that I heard. Most came back first
time, although it took about 3 or 4 calls to raise KG4AA who had a humungous
Eu pile up on him-possibly he was off the nose a bit anyway. This is not too
dusty for an antenna at 20ft a.g.l.
What this does is give me confidence to proceed with reconstruction, using
the fibreglass spreaders to hand. I think that I will use bare wire to avoid
the pitfalls of insulation. I have some nice 1.6mm stranded Copper to hand,
and that should fit the bill I think. This will also enable me to use better
quality insulators, as sag of the wire should be less of a problem. I must
say that I am still rather disappointed that the published literature offers
no caveat about the use of insulated wire, since it is clearly well known to
the cognoscenti. That really could have saved me a lot of aggravation.
73
Clive
GW3NJW
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Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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