Some picture about
China made many GU-81Ms in end of 1950s to 1970s.It was called
Here are some pictures:
I purchase this socket in our local FU-81 manufacturer
New old in stock. $35 ，foundry aluminium and ceramic，very rugged.
This socket pick up in our local flea market , just only $5!
This tube made by our lacal tube manufacurer in 1978.
you can see the different base ( ceramic), Russian is glass.
Chinese GU-81M still in high price level in China , quote $100 orso,
but few people want them.
But Chinese GU-80 is very inexpensive, This tube can replace GU-81 direct?
As far as I know, GU-80/80 have very good IMD performance but low output in
band and difficult to match
, even can not work in 21MHz or higher.But I have no experience.
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