Topband: GI-46B Revisited..

[Robert Briggs]

Gidday all..I have built around 25 aVHF amplifiers over the past three 
years using the Russian triodes, GS-35 and 31B tubes as well as GI-6 and 
7B tubes..All of these amplifiers are in daily service on 6 and 2 meters 
and trouble free..

I have looked through all the information on the GI-46B tube and a few 
things don't add up..A company in Europe uses these tubes in their 
amplifier product's...I see many retro fits in UTube clips for TL922 and 
Heathkit amplifiers replacing the 3-500Z and supposed power outputs of 
1600 watts..

Just taking the TL922 conversion to GI-46B tubes as an example the tubes 
are openly mounted with GI-7B coolers in place of the original 46B 
cooler...The film clip shows the TL922 cooling fan retained blowing 
against the tubes...I question how are they getting rid of all the heat 
produced with such a pissy setup..I would have thought the tube should 
be mounted in a box construction with a good blower and chimneys etc...

According to the Russian GI-46B specs the tube is only rated at 350 
watts anode dissipation...Most of these conversions will be running at 
close to 3kv and to produce 1600 watts output even at 50% efficiency a 
pair of tubes will have to be dissipating a lot more than the tube anode 
rating..

Obviously the sketchy information for the GI-46B supplied on the Russian 
spec sheet  must be very conservative...

I am wondering if there are any members on this reflector have used the 
GI-46B triode and what the real results are and also the cooling used..I 
am about to do a 46B 6 and a 2 meter amplifier for a client using these 
tubes..I am confident that with proper attention to the cooling etc that 
the amplifiers will turn out ok..It has been suggested that the GI-46B 
is a substitute for a 3CX800 tube..

Bob..VK3ZL..