The AM Forum

I ended up with some variometers/goniometers, and don't find much on them except old receivers. Really old receivers.

Among them is what looks to my ignorant eye like a large Millen plug-in transmitting coil similar to BC-610 size and with the ceramic bar-plug setup of banana plugs, but it's maybe for 6 meters, or not enough turns for 10 Meters anyway.

Instead of  the usual two air-wound coils with space in the center for a lever-mounted coupling coil, this is a long ceramic form about 2.5" diameter with maybe 3 turns on each side.

Instead of a space for the output link, this form is solid and has a smaller ceramic form in the middle, inside the form, with several turns on it, which can be rotated - so it looks like a strange high powered push-pull variometer. There are no markings.

Would it be right to think that there's no reason this arrangement would be any different, from a results standpoint, than a regular moving link coupling coil? It's just wierd because of the VHF appearance of that when I am thinking about the old stuff. I know I should be posting pictures of it, just have not had time to take any. No markings at all on it.

It's a variable inductor, not a coupling unit. Was used in the PA tank circuit of the ART-13.

The GO-9 transmitter i have uses one in the oscillator instead of a cap for frequency tuning. The outer coil is tapped for different frequency ranges.

Many hams have lost sight of the advantages of varying the L, rather than the C of a resonant circuit.

One of those advantages is when rotated, a vario can represent in- or out- of phase coils, therefore can subtract or add L over the median point, unlike a variable cap.

Variometers were an answer before roller inductors were widespread.

73DG

Looking at the different 'Eastern European' parts site, it seems the Russians used variometers more so than those on this side of the world!