[AMPS] Non-Inductive Carbon Resistors

[Lamb]

Non Inductive seems to be a relative term.  In the late 30's, advertisements
touted non-inductive resistors that could be safely used in power supplies
with no problems.  The clear implication is that earlier resistors were so
inductive that they caused problems in power supplies.  Some resistors from
the WW II vintage are marked N.I., but they are clearly inductive at amateur
frequencies and refer to the earlier use of non-inductive.

The Autek or MFJ "antenna" bridge can tell you quite well what is
non-inductive.  A carbon film resistor, for example, will gradually creep up
in resistance from 7 to 14 to 28 megahertz.  Although some "antenna" meters
quit there, we can infer that the resistance will have a somewhat linear
increase in indicated resistance because it has inductance.  These resistors
could probably be combined with series and parallel combinations to be a
suitable load for input resistors on a hf amplifier or as a dummy load, but
they could be very poor when used in a parasitic suppression circuit
resonating at 120 mhz.  In that case, you would want a known resistance with
very little inductance.

73,  Colin  K7FM




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