Topband: GI-46B Revisited..

[Thomas Hoeppe]

Hello Bob!

I have made a small linear with GI46 for HF (See www.hoeppe.name) . 500-550W 
out are possible, but ONLY with proper cooling. I fully agree with you: A 
weak airstream from the side is a bad advice! Those russian tubes have a 
max. seal temperature of only 120 deg. C! I know there are many descriptions 
in the internet showing that....but I would never do it!

Tom, DJ5RE


----- Original Message ----- 
From: "Robert Briggs" <vk3zl at bigpond.com>
To: <topband at contesting.com>
Sent: Tuesday, January 15, 2013 12:55 AM
Subject: Topband: GI-46B Revisited..


> 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..
> _________________
> Topband Reflector
>