Suppose a ham was building a balanced matching network, consisting of
variable inductors and vacuum caps. It would be designed for full legal
limit on any mode (AM, SSB, CW), from 160M-10M.
To keep it balanced and safe, it would be enclosed in an acrylic or
polycarbonate case (say, 1/2" stock), and might measure approx. 18"x12"x6".
If ceramic insulators were not available to "float" the components above the
(plastic) chassis, nylon standoffs or polycarbonate/acrylic stock would be
used as standoffs.
Depending on its tuning condition, this device could have rather large RF
currents or voltages. Are you saying the standoffs, and plastic case itself,
would be unsuitable? And what would be the result? HV breakdown and arc
over? RF coupling and "unbalancing" of the network? Meltdown of the
standoffs?
What would be the "best" materials to use in this scenario?
73
Dan
K0DAN
----- Original Message -----
From: "Karl-Arne Markström" <sm0aom@telia.com>
To: <amps@contesting.com>
Sent: Tuesday, March 15, 2005 3:31 PM
Subject: Re: [Amps] nylons
> Nylon should probably be avoided entirely in strong RF fields.
>
> The dielectric material property list in ITT Reference Data for Radio
Engineers
> lists the dissipation factor of nylon as about 0.022 at 1 MHz , 0.02 at
100 MHz and 0.012 at 3 GHz
> (actually decreasing with frequency).
> This is about two orders of magnitude worse than the best plastics and
ceramics.
>
> Coupled with its low softening point and dielectric strength, it seems
that nylon is a
> low-priority choice as an RF dielectric.
> Much of the same also goes for acrylic plastics (Plexiglas and Lucite).
>
> 73/
>
> Karl-Arne
> SM0AOM
>
> ----- Original Message -----
> From: "David Kirkby" <david.kirkby@onetel.net>
> To: "John Irwin" <crazytvjohn@yahoo.com>
> Cc: <amps@contesting.com>
> Sent: Tuesday, March 15, 2005 9:06 PM
> Subject: Re: [Amps] nylons
>
>
> > John Irwin wrote:
> >
> > >dudes
> > >
> > >a large ace hardware store opened here last week , One block away. I
have noticed a lot of nylon items that look a lot like the ceramic standoff
insulators, they come with a hole in the center,and some are taped for 6-32
or other simular sizes. lenght every 1/8 inch or so,diameter 1/4 to 1/2
inch
> > >
> > >How does nylon act in rf? Like in a amplifier as used to support
variable capacitors or inductors? Next to the plate choke.
> > >
> > >Anyone put some in the pi coil and see if it holds up. or does it go up
in smoke?
> > >
> > >thanks
> > >john kb9tc
> > >
> >
> > One other thing I forgot to add is that I have here some Ross HyperSPARC
> > CPUs, which were from a Sun workstation. (Sun did not make this CPU,
> > but a 3rd party did). I know this particular machine had been run 24/7
> > for many years, and never broke down.
> >
> > The heat sinks were attached using some sort of black plastic screws.
> > When I moved the computer, several snapped. The material (probably a
> > nylon) had become very brittle indeed. But these HyperSPARC processors
> > were known to run very hot and were subjected to this for many years
> > indeed. So a short-term test does not give the whole story.
> >
> >
> > --
> > Dr. David Kirkby,
> > G8WRB
> >
> > Please check out http://www.g8wrb.org/
> > of if you live in Essex http://www.southminster-branch-line.org.uk/
> >
> >
> >
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> > --
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> >
> >
>
>
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