"O. Alvarez" wrote in message
.. .
I am looking to replace a sylvania 12sq7GT that I dropped (!*#%$!) on
the floor when cleaning my Hallicrafters Continental Shortwave Radio.


The diagram on the bottom of the radio shows the tube that should be
in
there to be a 12SQ7 with no mention of GT (that means glass tube
right?)

It probably originally came with a metal 12SQ7. GT as glass tube is
close enough. There's a whole bunch of tube suffixes.


The tube I broke was working without flaw and I would like to replace
but I see there are the metal enclosed military type tubes as well.

The metal tubes were designed by GE and RCA in the mid 30s as a way to
make more compact and rugged tubes. The metal tubes were also the first
series of tubes with octal bases. They aren't specifically military,
although the military bought millions of them in the WW2 and Korean war
eras. Threre's a good chance your replacement tube will come from this
surplus hoard.


Without getting too technical can anybody let me know which types or
brands are best for a am/shortwave radio?

The GTs were designed to interchange with the metal tubes. They are
slightly larger, which is hardly ever a problem. It won't be a problem
in your radio. Either series of tube is much smaller than the older,
light bulb sized S/ST types. Don't worry about the tube's brand. They
are all pretty much the same. There's no guarantee that any tube was
made by the labeled company, anyway. Tube manufacturers specialized in
certain tubes, and they sold them to other companies.

Please post advice.

Regards,
malomarski

Buying new tubes is mostly a mail order/internet business now. I've had
good results with Antique Electronics Supply, Fair Radio Sales, ESRC,
Brent Jessee and others. I also like to stock up on used tubes at
hamfests. Used tubes are usually a very good deal.

One easy way to find tube vendors is to enter the tube's number into a
search engine such as google. The vendor's price list's are easy to
pick out.

Frank Dresser