Tomas,

Wow, that is a big variometer. I like the way the rotor is partially spherical so it can be a closer fit with the stator coil, that likely improves the mutual inductance giving it more range. The stepped inner support is a good way of achieving that mechanically - thanks for the picture.

I've never seen a variometer at the local junk rallies. :(

Regards,

Alan

There are many variometers on flea markets here in Czech republic, but I like those photos how You construct it on Your own !

Here is photo of "QRO variometer" to You from my dad, for inspiration, he said.. :)

http://web.bxhome.org/image/variometer

Arv,

Yes, in fact I have plans to build a shortwave broadcast regenerative receiver using a variometer for both tuning and regeneration coupling control. I recently wrote some PostScript to generate radial vernier scales - might work well with a simple friction reduction drive, like the CD+grommet trick.

One thing I've been meaning to do is plot inductance as a function of angle. I expect it to be S-shaped 'cosiney' and rather non-ideal for nice linear tuning, but that shouldn't matter in practice.

I took the variometer to the recent Homebrew Group meeting and John VK2ASU mentioned the idea of using a similar arrangement as the "swinging link" in a link-coupled tuner. While mechanically somewhat more complicated than the usual swinging link scheme it could be built physically smaller.

Variable interstage coupling sounds very 1920s TRF receiver technology :) Simple way to control the coupling to a tuned circuit though, much more variable than fixed taps and perhaps easier to intuit than tapped-capacitance matching. There is no question that a few moments with the calculator or twiddling a trimmer cap is much more expedient than building the mechanics of the variometer, but for something that needed to be continously variable it might be a good solution.

Regards,

Alan

Have you considered a VFO which tunes by variometer?

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Variometer based Antenna Tuner?

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Variometer tuning for transmitter & receiver interstage elements?

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Separate the two coils and use this mechanism for variable link-coupling arrangements?

HiHi :)

Veri-good!