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Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
Reaching:
Because of construction techniques, temprature and currents involved inside the envelope, Tungsten was a necessity so the designers had to find some way of matching the thermal expansion coefficients between the Tungsten and the glass. One way to do this is to make the whole envelope a glass that matches the temp-co. of the Tungsten, but this is very expensive and wasteful. Insted the manufacturer uses a graded seal, which means its a transition from one glass to another. Here the temp-co. of Tungsten closely matches that of Uranium Oxide glass.
The UO glass is still very expensive today, that 5 inch piece is $1 per inch! Now if you're good, you could melt down some vaseline glass and gaff some rods out of it, but I'm not that good. (making rods is called gaffing, and the person who does it is called a gaffer)
Anyways, I have some Tungsten that I will practice making seals sometime, and hopefully a Crooke's tube out of Pyrex. That is if I can get a good constant flame out of my avitar.
Other materials that match Pyrex well are Titanium, Kovar, and Platinum. With the intense heat involved, Titanium would make a good electrode in Pyrex, with the exception that it might catch fire. I dunno yet because I haven't had any responses from a Ti supplier yet.
I am a serious glowbug myself. I had a MUCH larger tube collection than I do now but plan on adding to it again.
Needing to find a tube that can handle MOT X 2 voltage with a small footprint for my newest project.
I am also a Ham (KG4WTL) and get a warm fuzzy feeling when I click the switch on one of my old boat anchors. I work all CW.
seeing all of your great old gear makes me miss my shack from a few years back, had to get rid of allot of it when my wife joined the ARMY. Building it back up slow but sure!
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