Author Topic: Mobile Anrtenna off the charts. And possible fix?  (Read 2561 times)

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jdh

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Re: Mobile Anrtenna off the charts. And possible fix?
« Reply #15 on: April 30, 2017, 05:55:42 PM »
Extend the bottom, trim the top.


spacecase0:
Depends on what the glob in the middle really is.  It can be three things, a loading coil (not likely in this case), a phasing section, or a wave trap.  If it is a wave trap then UHF stopped at the trap while the section below the trap acts like a quarter wave on that band the trap would be invisible to VHF allowing the whole antenna to act as a quarter wave on that band.

BTPost

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Re: Mobile Anrtenna off the charts. And possible fix?
« Reply #16 on: May 01, 2017, 01:08:36 AM »
When I have run into these type of issues, I get out the Spectrum Analyzer With a Tracking Generator, and an Impedance Bridge... then connect the antenna in question...  This gives you a visual picture of where the antenna is resonate, and where the edges are... It then becomes easy to adjust the lengths to get things where they should be...  Works really well on multi and HF Antennas...
Bruce in alaska AL7AQ