[ARC5] Front panel widows

[Mike Feher]

Brian -

I have about a dozen of these sets with almost as new windows. Then of
course I have also had and still do have some that are all shriveled up. I
agree, in time they will probably all be shriveled up. However, I am sure
before I shrivel up, the good ones will stay good. 73 - Mike 

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
848-245-9115


-----Original Message-----
From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Brian
Sent: Friday, February 03, 2017 8:46 PM
To: arc5 at mailman.qth.net
Subject: Re: [ARC5] Front panel widows

The original window material in the Command transmitters and BC-221 family
was nitro-cellulose acetate - the basis for early cine film. The original
solvent gradually evaporates, leading to physical distortion and coloration.

You could smell the solvent in the early cinema projection rooms. The
degradation is not reversible. The observation that a solution was to buy up
old stock transmitters to scavenge their windows will not beat the natural
chemical and physical degradation.

The better solutions emerging from this discussion are the use of Perspex,
Lexan, other clear cyano-acrylates and polycarbonates, though even these
will change shape over time. Plenty of this material is used for 'gels' over
follow spots for stage shows - and so becomes a cheap source of our raw
material. Think how sexy your transmitters would look with yellow, green,
blue and red windows!

The scales and numbering on the Command transmitters varied between
manufacturers and most definitely with operational frequency range; on the
lower frequency models, the markings were closer spaced. So, the possibility
of making 'one size fits all' is a forlorn hope.

My solution was to photocopy an engineering mm scale onto clear plastic and
cut to fit. Cheap and cheerful. In the old days of Drawing and Design,
scales with all sorts of spacings and numberings were available.

73 de Brian, VK2GCE. 

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