Tony, your point is well taken and the explanation on your site is very
probable. I usually space PA tubes at least three inches from walls in my
amplifiers so this is probably why I have never had problems with hot
spots,etc..It`s very understandable for a plastic based chimney to be burnt
if spaced closely between an rf generating device and a fairly large piece
of metal...Of course the design Q of the tank as well as other factors such
as circulating current may produce similar effects...Perhaps some of the RF
engineers on the list may care to comment..73,Jim K7RDX..
----- Original Message -----
From: "Tony King - W4ZT" <amps080605@w4zt.com>
To: <amps@contesting.com>
Sent: Thursday, April 13, 2006 2:41 PM
Subject: Re: [Amps] Sources of CPVC for GS35b Chimney
> Kevin,
>
> I have experienced failure of PVC used as a chimney. This failure was
> NOT due to temperature. See <http://gs35b.com/pvc/>. Though this may be
> a rare occurence it is certainly worth considering. Although CPVC is
> rated for use with hot water, it typically has more additives,
> particularly those pigments which change the color of the pipe. It is
> impurities in the plastic that may be the cause of the failure in RF
fields.
>
> I have NOT seen any reason to not use PVC because of temperature. The
> cause of the impurity problem appears to be in the manufacturing process.
>
> 73, Tony W4ZT
>
> Kevin LaHaie wrote:
> > Hello group
> >
> > Among the many amp projects I have in the works, one is based on the
GS-35b.
> >
> > Per Jim, K7RDX, 'Hot Water Rated' PCV in the 4" size is the perfect
> > size and a durable material for a chimney. This is known as CPVC to
> > the pipe world, and apparently is good to several hundred degrees F.
> >
> > So, run to the local pipe or plumbing shop and get some, right? WRONG!
> > All the places I tried only stock it sizes up to 2".
> >
> > You can imagine their delight in my asking for 1 FOOT of the 4" size
> > (still way more than I need!). I was told that it comes in 10 foot
> > lengths, and to special order it I may need to buy a pallet full. This
> > may be different depending on the relationship one has with the shop,
> > but a 'walk in off the street ham' won't get any special favors!
> >
> > So, here perhaps is an opportunity for someone to buy a stock of 10
> > footers, cut it into 1 foot lengths and provide us GS35b amp builders
> > what we need? Maybe offer to silkscreen the tube number on it? Your
> > callsign? Your Amp's Name? (Ampzilla, for example)
> >
> > Just kidding. hihi
> >
> > Does anyone know of a source of this in small quantities?
> >
> > Thanks!
> >
> > Kevin K7ZS
> >
> >
> >
> >
> >
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