FreqCarl

That's odd. The swr's on the 1477 I have are higher on the higher frequencies. I was checking swr's with both my Surecom and a NanoVNA which were very similar. The original top piece on mine is 7 15/16", 202mm if you want to go back.

The Tram 1477 is a pre tuned antenna, just not for GMRS.

Just setting up a GMRS base and purchased a Tram 1477 from a friend of mine. I'm running around 90' of LMR400 to it and SWR's on all GMRS channels were a little over 2:1. Probably ok, but I wanted to take the 1477 apart to see if I couldn't get it a little lower, but couldn't find any info on how to disassemble it. The setscrew on the base that holds the element inside the antenna is covered with a glue that I scraped out as much as I could, and gave it a couple seconds of a propane torch to soften up the glue. That set screw is a 3mm Allen, and the other setscrews on the element takes a 2mm Allen wrench. Once that setscrew on the base is backed out enough, the whole element pulls out. There are 3 pieces of foam on the element, covering a coil, a union (or another coil, not sure), and another piece of foam on the upper portion. This foam snugs up the element in the fiberglass/plastic piece, but will pull out. I first tried extending the element by using some heat shrink over the tip and a piece of 3/32 welding rod. SWR's were higher on both ch1 & 22. I then took some foam off of the union to loosen the 2mm set screw and removed the top portion of the element and experimented with different length's of welding rod. I have the original uncut top piece to put back on just in case. I found the lowest swr readings from a 120mm/4.75" piece of welding rod. The original SWR readings on ch1/ch22 were 2.14/2.26, and with the shorter top element they are 1.28/1.82. Haven't checked 467.xxx yet. I'm not a seasoned ham or gmrs user, but messed with CB's 50 years ago. So take my findings with a grain of salt, but this is how I disassembled my 1477 if anyone was wondering.