[BC] FW: [Tech-Assist] Harris SX-1 Spur Problem -- Brass vsfrequency

[Milton R. Holladay Jr.]

Steve,  Whoever told you that about brass was full of mud.
You've obviously never been inside a CCA or many other FMs. If you took out
all the brass, what few parts were left would have fallen apart, with or
without silverplating.
Even most grades of stainless steel are fine for holding things together,
though it's not such a good conductor (remember the SS hose clamp around the
tube in the FM-20, &c. ?)  It's the magnetic steel that's a big problem,
even at MW freqs. (I really should take pictures of the burned places in a
wooden stud around where a steel wood screw was located near a coil in a
50kw phasor.)
Silver is the best conducting metal; copper is a close second. Brass ( an
alloy of copper and zinc, is not far down the list.) IIRC,  SS and
bronze(copper and tin) are a bit too far down the list to be considered a
really good conductor, especially for RF.
Silver oxide is about like copper; silver sulphide or copper oxide are
another story altogether (VU meters have copper oxide rectifiers, you will
recall).
A majority of hardware used in RF fields is brass, though SS is used more
and more these days.Any metal that has a lot of magnetic hysteresis --or,
for that matter,  any insulator that has a lot of dielectric
hysteresis--will heat up and be a problem.........
M
----- Original Message ----- 
From: "Lewis Munn" <looey323 at yahoo.com>
To: "Broadcast Radio Mailing List" <broadcast at radiolists.net>
Sent: Wednesday, November 30, 2005 11:45 AM
Subject: Re: [BC] FW: [Tech-Assist] Harris SX-1 Spur Problem -- Brass
vsfrequency


> Steve,
>
>   Brass is used for the slightly higher conductivity for the RF currents,
over steel.  I use it in AM (MW) when I am able...also use brass, copper, or
bronze washers and lockwashers.
>
>   I have never heard about not using brass at VHF, but the good VHF gear
is always silver plate.
>
>   Only possible thing I can think of is that the surface effect at VHF is
such as to put the current flow into the tarnish area on brass, if is is
tarnished, and causing high losses in the tarnish.  May be why so much is
silver plated, tho I have seen a lot of tarnished silver running along just
fine.
>
>   Tuning lines in Harris FM transmitters, for one.
>
>   Or just maybe poorly tightened brass works its way loose from steel
threads with thermal cycling and loosens until it burns.
>
>   I tend to think that this is more an urban legend tham factual.  But
that is just my thinking.
>
>   Looey Munn
>   Roundup, MT
>
> radioranger <radioranger at comcast.net> wrote:
>
> I remember reading or hearing somewhere that brass screws are the fastener