[HBR] Dissipation factor of materials

[Brian Burns]

Hello James,

~ I'm sure that most of you know this but if not, lowe's and other big box
stores sell 1-1/2" od polystyrene extension pieces that are 16" long and
have small flanges on both ends.  They are also available in 1-1/4" OD but
not as commonly.  They also sell 3" polystyrene couplings that fit over 3"
nominal sewer pipe. The couplings are about 3-5/8" OD from memory and make
great forms if you need a large coil.
JamesF

If these are plumbing parts they are probably PVC, polyvinylchloride.
Polystyrene has great RF properties, but its thermal and mechanical
properties are not very good.

Cheers,

Brian 







> On Nov 28, 2014, at 2:42 PM, "Brian Burns" <brian at lessonsinlutherie.com>
wrote:
> 
> Hello All,
> 
> 
> 
> Here are some numbers I found for dissipation factor:
> 
> 
> 
> Polystyrene-------------------------------------------.0002 to .00007
> 
> 
> 
> PVC------------------------------------------------------.016
> 
> 
> 
> Steatite--------------------------------------------------.0035 to 
> .0008
> 
> 
> 
> It would appear from these that polystyrene is quite a bit better than 
> even steatite ceramic, probably what was used in old-timey coil forms. 
> No wonder it was so well liked for UHF stuff at Hansen Labs, where I 
> used to work back in the day. Not only does it melt easily, it crazes 
> over time. The base that I have in mind is available from National, 
> and shouldn't have the melting problem, as it's ceramic.
> 
> 
> 
> Next question: Does using the lowest loss coil form "make enough 
> difference to make a difference"? Walt's experience, as well as other 
> builders', using PVC seems to say "no it doesn't".
> 
> 
> 
> Cheers,
> 
> 
> 
> Brian
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
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