I just erected a new MFJ-1982 80/40/20/15/10m trap dipole at 45 feet and I'm seeing some odd behavior on my analyzer. The SWR shows 3.2:1 on 80m at the shack end of 75 feet of RG-8X, but when I move my MFJ-259C analyzer directly to the feed point, it's reading over 8:1 at the same frequency. I understand lossy coax can mask high SWR, but this seems extreme. Has anyone experienced similar issues with trap dipoles where the feedline losses are actually making the SWR look better than it really is? The antenna works on other bands with sub-2:1 readings, so the traps appear functional.

Classic example of feedline loss masking the real problem. RG-8X at HF frequencies has significant loss - if your coax is attenuating 3dB on 80m, that reflected power gets cut in half going back to your radio, making 8:1 look like 3:1. Check your trap connections and element lengths first.

I had the exact same issue with my 80m dipole. To measure true antenna SWR, you need the analyzer right at the feedpoint or use very low-loss coax. My "good" 2:1 reading at the shack turned out to be 6:1 at the antenna due to corroded trap connections.

That math checks out perfectly. With RG-8X having about 3dB insertion loss on 80m for your run length, return loss becomes 6dB, which converts to exactly 3:1 SWR. Your true 8:1 antenna mismatch is being hidden by the lossy feedline - not good for efficiency!