I am very pleased with a sample build I have of an MLTL
(Mass Loaded Transmission Line) as given by the designer
who goes by the handle of GM.

I get some cone breakup when listening to an over the air
FM signal. If I change from stereo to mono the noise goes
away. What is the answer to this?

The details are: FE127e in the MLTL w/no stuffing or internal
damping at all.

So you're saying ot could be the source?

Never had the problem on tv. Or cd that I recall. So that
would explain why flipping to mono cured the problem?

What would cause that at a broadcast source?

Apparently you can tune a straight wire antenna by adding resistance. Playing around one day I found that terminating a piece of coax I'm using as a TV antenna with a 75 ohm load and then adding R to suit helped quite a bit. I'm sure there's formulas to calc the required resistance for each frequency or BW, but I don't know them. FWIW, 5m ohms works for most of my local TV stations, though I have to fine tune it by moving the coax around since horizontal/vertical orientation affects it. With the other stations, just attaching the 75 ohm termination to a good ground is sufficient.

Attaching the shield at the open end to a good ground helps too, or at least it does with my TV. I couldn't tell any difference when I had it attached at the TV's input, but haven't delved into why it would make any difference since the antenna is only ~6.6ft long. Mine is a huge old metal drafting table/desk 'L' unit, but you can just run a 10 ga solid copper wire from an outdoor grounding rod or in-door cold water pipe.

After seeing how superior an OTA HD TV broadcast is compared to what the local satellite or cable service offers, I think it's time I learned about antenna design...........

HTH,

GM