[TowerTalk] Cushcraft XM240 & Shunt fed tower

VE6WZ_Steve ve6wz at shaw.ca
Mon Jun 12 19:35:03 EDT 2006


Don't forget about the driven element.
That driven element may have a DC ground through the coax shield, but
the current balun can get real hot carrying the 160m RF !!

A WORD OF CAUTION when shunt feeding a tower with an XM-240 on top:
There is a very good chance you will "cook" the balun unless you short
the driven element to the boom when TX on 160m.  Here is a photo of what
my XM-240 CC balun looked like after a year of shuntfeeding the tower on
160 without shorting the current balun:
http://www.qsl.net/ve6wz/CCbalun.htm  I came to suspect this problem
when I could see the 160m SWR slowly drift with KW key down as the balun
heated up !!!

It's likely each shunt-fed tower setup may act differently depending on
the top loading configuration (other Yagis etc.) but you may want to put
a small relay at the driver.  I just use a small 12v relay that is
powered in parallel with my tower mounted switch box.

BTW...before I grounded my XM-240 reflector I would here the same
"tick"-"tick" sound, but not only when electrical activity was nearby,
but also on warm breezy sunny days too.  Wind static ???

de steve ve6wz http://www.qsl.net/ve6wz/

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