UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - President Lincoln SWR issue "only" when meter inline.

Richard675 · 14th Jun 2021, 5:09 pm

Sounds like something funny happening on the feeder.

As the aerial is a new-install the positioning of the feeder relative to the aerial may be causing this. (Or other metallic objects nearby) Ideally it should come down vertically for about a half wavelength.

I would suggest trying an RF choke just below the feed point…..wind half a dozen turns of coax about 6” diameter and tape up, or wind on a plastic pipe etc.

A test for currents on the outer of coax is to grip the cable or coil it up while watching the reflected power. If it changes then you know you need to choke off those currents. Make sure the reflected power indicated is not way off the scale on the meter when doing this otherwise you might not see any changes.

The Lincoln’s PA might indeed be a bit touchy and the placing of the SWR meter inline might just be taking it over the edge. Can you try it on a friends aerial?

14th Jun 2021, 5:09 pm	#10
Richard675 Pentode Join Date: Jun 2009 Location: Braintree, Essex, UK. Posts: 170	Re: President Lincoln SWR issue "only" when meter inline. Sounds like something funny happening on the feeder. As the aerial is a new-install the positioning of the feeder relative to the aerial may be causing this. (Or other metallic objects nearby) Ideally it should come down vertically for about a half wavelength. I would suggest trying an RF choke just below the feed point…..wind half a dozen turns of coax about 6” diameter and tape up, or wind on a plastic pipe etc. A test for currents on the outer of coax is to grip the cable or coil it up while watching the reflected power. If it changes then you know you need to choke off those currents. Make sure the reflected power indicated is not way off the scale on the meter when doing this otherwise you might not see any changes. The Lincoln’s PA might indeed be a bit touchy and the placing of the SWR meter inline might just be taking it over the edge. Can you try it on a friends aerial?