Electronics > RF, Microwave, Ham Radio

Disimilar metets in an antenna vertical coil


I ran into a problem with a dual-band vertical. Long story short, the 'loading coil' was bad, it affected VHF, not UHF. The problem was a poor connection between the 'coil' and the whip 'fittings' inside the assembly (see the attachment), but in this case it was NOT a 'dissimilar metals issue. The antenna is new, I caught the problem before the antenna was installed (using the separate 'Ground Plane roof mount) on the roof.

There was a plastic build-up inside of the plastic 'sleeve' somehow from manufacturing. Here is the antenna;

My question is, the metal fittings are chrome coated brass or copper and the coil is either brass or copper from what I can tell. Isn't this a issue with dissimilar metals and the chemical action between them?

Spring is likely plated steel.  The copper spring is a close relative to the chocolate teapot as its such a soft metal, for springs beryllium copper alloy is used.  Probably just a poor connection due to oxide film, dirt and or corrosion.  Cheapo construction leads to lacklustre performance...

I did contact them, they sent a replacement and that's fine. I have another one of these, but tuned to the Business Bands that had no problem. Of they I had a spare coil/coupler, that was fine also.  :-+

Tram has a almost identical setup.
Its a  "Tram 1180" dual band antenna and a "Tram 1470" ground plane mount, but their mount has a 'N' connector which the Nagoya doesn't have making it a huge plus (in my book). Also the antenna is cheaper since it doesn't have the flexible right angle base and the longer base coil. If i came across that first I would of choose that with the N connector for UHF. I asked Nagoya about the better connector, but all they sell is the old school SO-239.   :--


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