Topband: Non-inductive resistors

[Larry Higgins]

I have to agree with Mauri.  Film resistors have very small inductance.

Back in the early 60s, I was working in the engineering department of a
small company making carbon film and metal film resistors.  All of us in the
department were hams, so naturally the question of inductance arose.  The
senior engineer said the inductance was extremely small.  To resolve our
doubts he suggested we run some tests.  After that many years I can't
remember the exact results, but in general the inductance was negligible
clear through HF and into VHF.  This was true for both carbon film and metal
film. We measured more reactance on some of the carbon composition resistors
we tested. Maybe that's because the leads of a composition resistor have
capacitance to one another, so at some frequency they resonate and above
that they are capacitive.

It's the fact that the current flows through a spiral path which makes us
think they're inductive.  While that is true, if you calculate the
inductance of a two turn single layer solenoid, wound with a thin film
conductor on a very small diameter, it will be very small indeed.  And, as
other responders have pointed out, you can make it even smaller by
parallelling several resistors.

> Folks,
> can anyone recommend a source for relatively inexpensive non-inductive
resistors.  I have exhausted my supply.  I need  ~ 6 or so resistors in the
450-500 ohm range (1 watt or better) for my beverages.  They are hard to
single source and very expensive even in lots.  In addition, many
manufacturers say they are non-inductive but that is not necessarily true at
1.8 MHz.    Carbon composition seem to be the only non-inductive resistors
at 2 MHz