[Milsurplus] Re metal tubes
jcoward5452 at aol.com
jcoward5452 at aol.com
Wed Feb 17 20:34:39 EST 2010
As you all know,inside that metal tube is a glass tube.The metal is for RF and Noise shielding.You really don't want the local oscillator getting into your high gain IF after the mixer and in RX/TX sets you don't want Tx RF getting into your audio section.And in aircraft there is plenty of other sources of noise and other sources of RF especially when you have all sorts or radar and IFF and who knows what all with multiple down and up converting schemes all in the same flying metal tube with engines and wings generating all sorts of static.
Isn't it pretty amazing how well the stuff was designed and the fact that it was over designed allowed cheaper glass only tubes to be used in this harsh RF environment?
Although glass tubes have that romantic glow when you don't have a fireplace...(yea,convince the wife...!)
Jay
-----Original Message-----
From: PHIL <signetics at netzero.com>
To: Milsurplus at mailman.qth.net
Sent: Wed, Feb 17, 2010 2:21 pm
Subject: [Milsurplus] Re metal tubes
I was under the impression that metal tubes came out in 1935, with
he single ended type, 12SK7 etc about 1938
The GT tubes were low cost equavalents. I think they came out about
940 or so
hil
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