Hello,
Couple of questions regarding inductance - measurement and use.
Identifying the tap positions on an inductance w/ an Autek RF-1 for use in
a Pi-L tank circuit and noticed a marked difference when the unused portion
of the coil is shorted. Example, 12 turn coil has a total inductance of
15.0 uH (@ 4.8 MHz measurement frequency, w/ 517 Ohm impedance). Six turns
inductance is 5.9 uH (@ 9.0 MHz w/ 392 Ohm impedance) w/o short on the
unused portion of the coil; same six turns w/ the unused portion of the
coil shorted is 4.32 uH (@ 9.0 MHz w/ 275 Ohm impedance). Which method,
shorting or non-shorting, should be used for determining where the taps
should be placed on the coil?
Next question is related in that tank circuits in most commercial
amplifiers use a shorting switch to select the inductance values. Where
as, the amp. circuit designs in ARRL Handbook, etc. use a non shorting
switch. Which is the better (electrical) switch method - shorting or
non-shorting?
73,
Mike, K4GMH
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