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Old 9th Nov 2019, 1:52 pm   #11
Martin G7MRV
Join Date: May 2008
Location: Selby, North Yorkshire, UK.
Posts: 802
Default Re: Building a Radio-Goniometer - inductance values?

Originally Posted by Radio Wrangler View Post
Any value will do as far as getting directional sensing goes.

If you don't have enough inductance, it will be a difficult load on whatever is driving it. If you go for too much inductance you'll run into problems with self resonant frequency due to capacitance between the turns. These are exactly the same issues as with designing a simple transformer.

40uH is going to have a reactance of 452 Ohms at 1.8MHz. If you have amplifiers between the two antennae and the goniometer primary coils, this is almost ten times 50 Ohms. In transformer terms it sets the magnetising current and this factor at the LF end is plenty. So the next question is whether you can make a 40uH winding of the physical size required by your mechanism and get the self resonant frequency to be well above your upper frequency goal of 30MHz?

So 40uH is a reasonable figure if the goniometer is driven from 50 Ohm-ish amplifiers or directly from 50 Ohm-ish antennae.

Cheers David,

That does sound a reasonable value to aim for then. The actual frequency range isnt at all important, so longs as it works well enough to play about with! Its just an experiement for general interest,

when (and if!) I get a working model built, i'll post it up (many of my projects are on the slow boat!)

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