[TowerTalk] TH7 SWR trouble ... Coax balun question

[TexasRF@aol.com]

I guess Hygain products have been out of site so long we have forgotten some 
of the deatails of the TH7DXX. This antenna was designed to be used with the 
BN86 balun (BN4000 is also ok) and the conductors supplied with with the 
antenna. The wires are spaced a few inches apart as they leave the balun and 
connect to the driven element. The spacing and wire diameter is such that a 
short transmission line of a few hundred ohms is formed by these wires. If 
you run the numbers through a transmission line program (or Smith chart) you 
will see a surprising shift in the feedpoint resistance especially on 10 
meters. As K7LXC sez: do what the manufacturer says! The coax choke baluns 
and other nice baluns may work well in most cases but the TH7 is not one of 
them. Check the owners manual for details.

73 de Gerald, K5GW/Texas Towers

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