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Post by 2e0ily on Mar 21, 2017 9:56:42 GMT -5
With my AIM4170, when creating a custom cal, to measure the induction of an air cored coil for use in a Wilkinson combiner on 137kHz, and that should be around 87uH, should I make the cal with a 50 Ohm impedance, or something different? Thanks
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Post by Bob on Mar 21, 2017 17:43:21 GMT -5
The impedance used for calibration isn't critical as long as the resistor is a good RF type with very low reactance. In real life, resistors have some shunt capacitance around a pf and some lead inductance of a few nanohenries. At 137KHz, these reactances will be negligible.
50 ohms will be fine. You could also use 75 ohms or 100 ohms. If you have any doubt about the resistance, measure it with a good ohmmeter and enter that value during the cal procedure at the prompt.
--73/Bob
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Post by 2e0ily on Mar 27, 2017 8:20:44 GMT -5
Thanks for the reply Bob, will use the 50 Ohm cal resistor in the kit, appreciate the help, all the best.
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Post by smokchsr on Apr 6, 2017 5:05:14 GMT -5
I would just add, that you want to be sure to place the calibration loads at the end of your test cable.
I use a custom made "Clip Cable" it's about 6' of RG400 that breaks out into 2 18" pieces of flat braid (in clear heat shrink) which each terminate into a 40 Amp gator clamp.
using that it's easy to do work on AM broadcast equipment. But to get accurate results all calibration has to be done at the gator clamps, if not the readings can be totally erroneous. I also have to be aware that that cable has a maximum usable frequency of around 10Mhz.
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