[Boatanchors] Tube shields CORRECTION

[Francesco Ledda]

One of the main purposes of shields is mechanical stability in vibration
rich environments. 

Frank

KF5RXV

-----Original Message-----
From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of
Jim Wilhite
Sent: Monday, May 26, 2014 11:20 AM
To: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] Tube shields CORRECTION

Correct me if I am wrong, but I don't think the purpose of those shiny
shields was to aid heat transfer.  My recollection is they are to prevent
the tubes from emitting a signal of any sort and came into being because of
WW2.  Moral receivers on shipboard require extraordinary shielding to
prevent submarines from hearing the oscillator and mixer signals so the
shields were developed for miniature tubes following the metal tube of WW2.

Those metal tubes with the octal base are nothing more than miniature tubes
in the can with (usually) pin 1 grounded to prevent radiation.  I would
surmise that following the war manufacturers continued with various shields
should subsequent wars break out like Korea which they thought might flare
up to a world conflict.

Jim
W5JO

-----Original Message----- 

There are a number of people who have tried painting the "shiny" shields 
with flat black paint, both inside and outside, that have found a reduced 
tube temperature.  Over the years, I have tried this a few times and the 
temperature of the tubes did seem to be lower.  However, I never actually 
measured the temperature and, as such, the reduction in temperature is more 
anecdotal than scientific.

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