Not seen this heater wiring before

[Jebbyman]

Hi all,
Gleaned much while lurking here over the years, but this is my first post. So thanks much for all the great stuff!

I've attached a picture of a heater wiring scheme I've not seen before in the good number of chassis I've been in. This is from a Monitoradio MR-10, but it's the same on a MR-33 I've got. They've wired one side of the heater circuit to chassis ground and one side series connected to all tube heater pins, ala Tweed Champ, etc. Oddly, they've taken the time/effort to coil the hot side of the circuit into an air-core inductor between each tube. Even painted a yellow spot on each coil.

Anyone seen this before? I'd have thought the effort (and wire) better spent on twisting the heater wires. Is this a long-lost, superior noise cancellation technique? Now I gotta know.

Thanks all.

[sluckey]

Stuff like that is not uncommon in old RF equipment.

[PRR]

Yeah, it is an FM radio, not an audio amp. 100MC and 10.7MC radio jiggles will go tube-to-tube on heater wires. Also an FM radio typically gains-up to total-clipping, so really wants to howl-round at MHz.