I agree. We really don't want the coax shield to be part of the antenna, regardless of whether the antenna is vertical or horizontal. If the coax shield is part of the antenna, it can seriously distort the resonance and the driving point impedance - hence the need for some common-mode isolation.
Regards, Charlie, K4OTV -----Original Message----- From: Topband [mailto:[email protected]] On Behalf Of Robert Harmon Sent: Wednesday, June 03, 2015 4:21 PM To: Top Band Contesting Subject: Re: Topband: Question on common mode chokes Jim, It will be interesting to see what others say but my take on this is that the tuner function is to provide an impedance match to the vertical and doesnt provide any choking. You still should have the choke. 73, Bob K6UJ > On Jun 3, 2015, at 9:42 AM, James Rodenkirch <[email protected]> wrote: > > I seem to recall, while reading up on common mode chokes, where I wouldn't need one if I employ an autotuner at the base of the antenna...is that true/factual? > > I have an LDG Z11ProII autotuner right at the base of my vertical - I did add a common choke at the input to the autotuner (21' of my LMR-400 coax wound around a piece of 4.5" PVC for the low bands) but wonder if that is really necessary. > > 72, Jim Rodenkirch K9JWV > > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband
