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Topband: Somebody mentioned Quads

To: topband <>
Subject: Topband: Somebody mentioned Quads
From: Herb Schoenbohm <>
Date: Fri, 26 Jul 2013 17:33:06 -0400
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I need your help on this: Recently my top mast snapped with the passage of Hurricane Chantal. Amazing the fiberglass three element Tri-band Cubex Quad survived with the spreaders bent like noodle soup into the tower guy wires. I took the quad down and decided to restring it since the #14 bare stranded did not look that good. I replaced all the quad loop wires with exactly the same measurement but used #14 solid insulated wire. Everything remained the same but now the quad has the lowest VSWR at the lower band edge and no longer covers 14 or 21 entirely without a 3:1 VSWR. Ten meters however works fine with a broad dip at 28.3 which is the same as before. I have made four unanswered calls to Cubex's voice mail with no reply. This brings up my question could the velocity factor of bare stranded #14 copper to insulated #14 solid have that much impact on the driven element is frequency and bandwidth. I can probably restring the quad driven element on the tower on each band....or....should I simply feed it with a gamma match on each band. My plan this weekend is to take the MFJ 259B up the tower and measure what is there on each band.

I bought a Cubex Quad so the entire bands could be covered without the VSWR default on by Alpha kicking in. On the antenna I use a 3/4 wave RG-11 matching transformer. I had the also a 3/4 wave RG-11 matching piece on 15 but when i went to sa direct 52 ohm coax feed I can operate on CW . However the VSWR shoots up to 2:1 above 21.100. I can not shorten the 15 meter section anymore with out the whole thing looking like a Hex beam. This brings up the question: Can I put in a series capacity (I could start with a variable) small door knob to shorten the self resonant frequency of the loop. I have never seen this done before but if I cancel out the residual inductance and have the impedance near to 50 ohms plus or minus i could reduce the VSWR at least?

I know I should have done all this on the ground before raising the monster quad....but I thought if I kept all the measurements the same the antenna would perform the same. Thus your help and suggestions are needed.


Herb Schoenbohm, KV4FZ

P.S. To get this back on Top Band subject....with the quad I lost nearly 25 per cent of the top loading my A4S provided before on 160 meters. Something to consider when deciding what to buy.... as my only top loading now is the quad's 18 foot boom. I still have a 30 foot stinger on the top but even connecting the quads feed lines with a ground strap to the boom did not amount to being worth the effort. My tuning box at the base of the cage feed just does a bit more adjustment for a slightly less efficient 160 meter vertical.
Topband Reflector

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