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[AMPS] Nichrome wire and tube chimneys!

To: <amps@contesting.com>
Subject: [AMPS] Nichrome wire and tube chimneys!
From: RMcGraw@InfoAve.Net (Bob & Linda McGraw K4TAX)
Date: Mon, 14 May 2001 08:06:50 -0700
Just an observation, the design of a chimney is such that the vertical
flow of air is directed evenly around the tube envelope and as it exits,
also against the anode seal & heat sink at the top.  I really don't
think a Coleman lantern globe or a pickle jar does the job.

Bottom cooling is also required on many tubes due to the heat produced
by the heater/filament.  Socket contacts last a lot longer when they are
kept cool.  I've seen solder melted out of the tube pins due to
inadequate cooling.

As to blowers, a centrifugal blower is the only way to go.  Muffin fans
just won't produce the required air flow with typical back pressures
presented by air system sockets.  My experience says big diameter wheels
that are 2" wide are better than small wheels that are 4" to 6" wide.
Even though the two fans may spec that same CFM, this has to do with
radial velocity.

73
Bob K4TAX


Jon Ogden wrote:
> 
> on 5/13/01 9:52 AM, measures at 2@vc.net wrote:
> 
> > ?  You don't seem to get it, Jon.  A high-speed centrifugal blower is
> > required to overcome  the back-pressure in the SK-510 air system socket.
> 
> Perhaps I don't, Rich.
> 
> And perhaps I am full of BS.  But I prefer cooling systems that work in the
> direction of natural convection of heat.  Heat flows up.  So something that
> blows cool air over something in an upward direction is in my mind better
> than something that blows air across it.
> 
> Your comments about the blower and the reduction of air flow are quite
> correct, I am sure.  Yet, the guys at Eimac that designed the cooling system
> and chimneys and tubes way back when weren't a bunch of boobs either.  I am
> sure they had good reason to do it that way.
> 
> Jon
> 
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
> 
> Member:  ARRL, AMSAT, DXCC, NRA
> 
> http://www.qsl.net/ke9na
> 
> "A life lived in fear is a life half lived."
> 
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