Variometers were very common in shipboard transmitters. HF Shipboard transmitters, in the age of wire antennas had to match up on several harmonically related bands to one or two wire antennas. One or two because, wire antennas, interfere with all the other stuff on the masts, cargo gear, radar and on an on. Not to mention, the constant maintenance required, just to keep them up and working, in a salt water environment.You always had to have two antennas on 500 KHZ to comply with regulation. The ship I was on for a long time had a 1/8 wave on 500, anything else, would have been longer than the ship. The TX had a variometer built into the load side of the tank circuit.

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!