[Amps] GU-81M

Hsu hsu4qro at gmail.com
Wed Feb 29 18:22:33 PST 2012

Some picture about
Chinese GU-81M:

China made many GU-81Ms in end of 1950s to 1970s.It was called
FU-81 .
Here are some  pictures:
New socket:
and http://www.zmdz.com/bbs/incomefiles/20123/19551084489.JPG
  I purchase this socket in our local FU-81 manufacturer
New old  in stock. $35 ,foundry  aluminium and  ceramic,very  rugged.
Old socket:
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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