Rick Frazier wrote:
: In theory, there is no reason the silicon chimney won't work,
: as most of the surface area is actually in the fins inside
: the circumference, and not the outside diameter at all. The
: minimal additional area you get by having a looser fit
: chimney is likely marginal.

The Silicon Chimney is considered the current technology and
is just fine for the application.

: However, at a hundred bucks, I can certainly see a dozen
: other ways to get a chimney in place for a LOT less money,
: and nearly as neatly as well.

You could make it yourself and save quite a bit of money,
McMaster sells the material.

: Hell, even an aluminum sleeve closed with a couple of pop
: rivets, though far from aesthetically optimum, will keep
: the tube nice and cool (given the same blower capacity)
: and for only a couple of bucks, tops...

An aluminum chimney would be very bad news and a potential
source of serious trouble.

: There are times to spend outrageous sums of money and this
: isn't necessarily one of them (at least for my budget, anyway).

You burn one serious tube up over being cheap on the chimney
or blower, you'll only do it once. It's an expensive mistake
to be a cheapskate.

: Of course, if I were actually building a 5 kW capable linear, I
: probably would have far more money than sense,

The 4cx5000 will do an easy 9kw with the proper power supply.

: particularly if you expect it would be used on the CB Band,

regardless of where it's used.

: and even on the Ham Bands (at least in the US) it is so far
: into illegal territory that you'd probably not give a damn in
: the first place. Therefore, the cost of the silicon chimney
: is probably a mere pittance, compared to eventual costs of
: defending the eventual litigation from running such a linear...
: [sigh]

It not a problem to own and operate such a linear in the proper
application. It is a problem when you run it over the max legal
power allowed. For 100% RTTY Duty Cycle, the mentioned amplifier
would be a legal limit cruiser in amateur service.

: Oh, wouldn't it be nice to have so much disposable cash as
: to not really care the consequences....
: --Rick

Get off the decafe Rick, there are more than a few tetrode
with handles amplifiers found on the amateur bands every day...
running legal power...

cheers,
skipp

ps: Time for a cheap plug for the yahoo rf amplifiers group:

http://groups.yahoo.com/group/rfamplifiers/