[Amps] nylons

[R.Measures]

On Mar 15, 2005, at 6:09 PM, k0dan wrote:

> 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?

Acrylics do not have a low D-factor.  I use ABS around RF.  It's 
commonly available, costs little,  easy to cut with a sharp saw - 
provided one goes slowly, and it's fairly strong.
>
> 73
>
> Dan
> K0DAN
>
>
> ----- Original Message -----
> From: "Karl-Arne Markström" <sm0aom at telia.com>
> To: <amps at 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 at onetel.net>
>> To: "John Irwin" <crazytvjohn at yahoo.com>
>> Cc: <amps at 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/
>>>
>>>
>>>
>>> _______________________________________________
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>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
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>>>
>>
>>
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>
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>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org