MFJ makes an inexpensive kit for the 269 analyzer that turns it into a grid dip
meter that you can then use to test the traps for proper frequency etc.
Here is a good read about rebuilding the A3S including the trap frequency and
also what you should see from the GDO
http://www.para.org.ph/membersarticles/A3S/
Regards, John NA6L
-----Original Message-----
From: John Crovelli <w2gd@hotmail.com>
To: john <john@kk9a.com>; towertalk <towertalk@contesting.com>
Sent: Sun, Oct 23, 2011 3:08 pm
Subject: [TowerTalk] A3/A4 tuning information
ohn KK9A et al.
ome additional information. This is a brand new A4 antenna right out of the
ox from Cushcraft. The direction of the traps was clearly marked with stickers
nd all traps were properly installed in the right direction. And npne of the
raps from the A4 had drain holes (an obvious mfgr error) but the TK traps for
he 40M addon kit did have the holes drilled.
urther, in shipment, over half of the SS hoseclamps were deformed/crushed. Had
o buy six new ones to replace clamps that were not salvageable.
he antenna is mounted in the clear at least 35 feet above a roof on an HDBX 48
oot tower. There are no other antennas nearby.....so we can pretty much
liminate interactions of any kind.
sing the factory dimensions for tuning the DE for either 'center' or 'CW' that
ome with the A744 40M addon kit, the bandwidth was only about 180 khz on 20M,
50 khz on 15M, and maybe 500 khz on 10m, but in no case could I get the minimum
WR where I wanted it so the antenna would provide both cw and phone coverage.
n 40 meters there was 120 khz of bandwidth, what I expected, and it had a
inimum at 7055 which was what I was looking for.
here are four possible points of adjustment on each element half. The maximum
djustment on each element half (between the 'center' and 'CW' options per the
anual ) is 14 inches.
ince I could not hit the desired sweet spot frequencies on any of the bands
sing the factory settings, I strongly suspect the traps are not tuned to the
roper frequency for the dimensions provided. One or both of the TC and TD
raps are potentially defective from the factory. This would account for the
nability to hit the desired mid-point frequencies in the SWR curves, and the
ack of overall bandwidth on 15 and 20, etc. where there should be nearly 500
hz.
have assembled and installed more than a dozen A3/A4 + A744 addon antennas so
'm very familiar with their assembly and installation.
'm looking for info from anyone who might have had this same experience and/or
pinions of others what might be wrong. I have received several off line
esonses so far, one of which confirmed the antenna should have nearly 500 khz
f bandwidth, particularly on 20 and 10 meters.
nd no, I don't have the traps in my possession. They are still on the antenna
hich is currently mistuned in the air at 50'.
3,
ohn Crovelli W2GD/P40W
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