Rewinding ferrite core antenna.
 

Hi guys.

Working on a Grundig-Majestic radio, model 8085 I think.

Anyway, the rubber bands holding the ferrite antenna gave out and I'm left with a ferrite core and wire.

Does anyone have *any* tips they can offer on winding these? I've wound coils in the past, which probably won't be as time consuming as trying to get this perfect. The original wire lost a lot of its insulation, so I'm replacing it with magnet wire.

Will being off a little on the winding numbers have that drastic of an impact?

What sort of original wire was it?
If it was litz then you may want to replace it with the same since using magnet wire in place will reduce "Q" of the tuning.

It didn't look like litz, it was some bundle of stranded wire with an almost waxy paper coating. The portions where the wire was missing insulation would short, so I don't think the strands are even lacquer coated, I don't really know. The magnet wire I've got is actually a pinball coil about the same diameter I stole wire from to rewind a jukebox coil.

Sent from my Transformer TF101 using Tapatalk 2

You can get the exact number of turns, when you turn the radio on, with the antenna coil wires connected to the radio (leave an ample amount of wire on the AVC line connection), tune in a station near the bottom end of the dial (around 570KHz) and add or remove turns of wire to get a max amount of signal strength. You can also bunch up or spread the turns of wire along the length of the ferrite core to make fine adjustments.

You may also be able to wrap a piece of paper around the core and wind your wire on that: then the whole coil & paper can slide to tune the coil. Some windings are spaced: if yours was, try to recreate that spacing when you wind. But I have some that are close wound.

The "form" the original wire was wound on is still there. Its loose, but its there. The original windings were very close, no gap at all between them.

Thanks for the advice.

You can probably see the "ghost" of where the winding was, and wind over that. Secure temporarily with tape until you have the right number of turns. And with the form loose you can slide back and forth on the core to tune it. When all is right, a few spots of hot glue will hold the ends of the winding and the form on the core.

Yeah, the rements of the old windings are clearly visible, and the magnet wire is a good fit. I mostly just have to work a section that hasn't gotten kinked, or avoid getting off a bit.

Ill admit, the coils I've solenoids I've wound in the past were far from "perfect" winds. As much as I tried to get everying nicely wound...it'd alwyas jump a wind, but they weren't critical enough that it mattered. First one I ever made ran off line voltage.

One other point of interest: if you ever break a ferrite rod, just superglue it back together fitting the two halves so they nest perfectly. It will work fine.

Well, luckly its not broken.

Gundig didn't secure these things well. Rather than clipping in place, the antenna just sits on a mount in the back with two rubber bands holding it on. Well, one was missing, replaced it with ziptie. Didn't do the other side, it gave and I watched the antenna unroll the largest coil right to the floor.