matt wilson wrote:

"James Bond" wrote in message
...
are metal film resistors wirewound or not? I've been trying to find this one
out. Someone who I know says they're not so are suitable for RF but Maplin
catalog seems to say they are.

Metal film or metal oxide? There is a big difference. High ohmic values are
almost always Oxide types and these are usually the continuous layer type with
the occasional 'trim'. Really low value metal film are also a continuous tube
or nearly so. It is the upper half of the metal film rage (100R-100k) that is
spiral cut & consequently of appreciable inductance. Unfortunately, these are
the values that are most needed.

I think metal film resistors are made by depositing metal vapor onto
ceramic rods in a vacuum. Then they are attached to metal end caps
with leads and either laser or abrasive engraved to set the final
resistance. Some have only a turn or two, some have more. They are a
lot less inductive than wire wound devices, and the best low
inductance versions have a serpentine pattern engraved in the film, to
keep the inductance very low.
e.g.
http://www.caddock.com/Online_catalog/power/power.html
--
John Popelish