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View Full Version : New..6 meter GI-46B prototype amplifier.



VK3ZL
03-29-2013, 01:20 AM
Hi all...Back again as promised with my new prototype 6 meter amplifier..I built this amplifier with a single GI-46B Russian triode to see if performance is as good or better than my standard 2 x GI-6B units...The GI-46B tube has a bulkier body than the 6B tubes, with an excellent removable cooling manifold..Although the tube specs rate the 46B plate dissipation as 350 watts, being a pulse triode it can probably be pushed beyond that providing one has adequate cooling..The tube also has a 20 watt dissipation grid, a real plus...The GI-6B tube has a 350 watt plate dissipation but only a 7 watt grid dissipation so although pairs of these tubes give a nice 700 watts anode dissipation the grids at 14 watts are marginal over 800 watts output..

The rest of this prototype is my standard construction with a couple of variations, inbuilt Papst fan pressurising the sealed Anode compartment and the case an inch higher to accommodate the internal fan....The cathode compartment is sealed also and is cooled with a small 3 inch muffin fan...The cooling air in the anode compartment evacuates through the tube cooler and a Teflon chimney on the top cover..I used a T input drive circuit and a Pi-L output circuit.

I had an old transformer I had custom made 20 years ago to run a pair of 813 tubes...This is a twin C core unit rated 1kvac @ 1 amp...Voltage doubled it gives 2800vdc just right for the GI-46B tube..

I switched this unit on this morning first time and as usual all functions worked properly..Initial RF tests look good...40 watts of drive carrier gives 900 watts output..I have to do some refining to the T input network which has a 1.3 drive vswr at present...If using one of the new age solid state rigs a 1-1 vswr is preferred..I will run proper tests over the next few days and this amplifier should be a real worker..I built it out of curiosity to see how the GI-46B tube shapes up...When I complete the testing this will make a nice intermediate power amplifier for the 800 watts range and should run 500 watts JT65 all day..

Enjoy the pics...

Bob..VK3ZL..

VK3ZL
03-29-2013, 01:34 AM
A few more pics to finish this project...The GI-46B tube and the old twin C core HT transformer...I have included a picture of the cooling fan to give you some idea how I get the best from the air flow..Many hams who build with the Russian tubes just install a muffin fan blowing against the tubes with no thought of properly directing the air through the tube cooler...Like all transmitting tubes proper care should be taken to get the most efficient air flow where it is needed..Pic of the amplifier on the workbench after switching it on for the first time, No Smoke!!!! Marvelous..

Anyhow enjoy this project like I have...This amplifier is for my own use but if I am completely happy with it I will build a few more the same..

Coming up next is a new high power 160 meter monoband amplifier for my own shack..It will be a few weeks but I am already itching to get started...

Bob..VK3ZL..

K7SGJ
03-29-2013, 08:39 AM
As usual, another awesome project, Bob. I never tire of looking at your work. What are you planning to use in the 160 rig for the RF amp?

VK3ZL
03-29-2013, 02:53 PM
As usual, another awesome project, Bob. I never tire of looking at your work. What are you planning to use in the 160 rig for the RF amp?


I am going to use a GS-35B triode..I already have two 160 meter GS-35B amps one is water cooled...The new one will be air cooled along with a big 54 pound Harbach Hypersil transformer for the HT..I am retiring the water cooled amplifier...It has given great service but time to move on...


Bob..VK3ZL..

N1LAF
03-29-2013, 03:17 PM
Great amplifiers should have great schematics...

NQ6U
03-29-2013, 04:12 PM
Great amplifiers should have great schematics...

I second this.

N8YX
03-30-2013, 08:48 AM
Nice work - keep 'em coming.

For those wishing to play around with 24V devices (MRF422, etc) a coworker has a big honking supply which will be offered for sale in the near future. A little costly to ship overseas but it may be of use to our stateside homebrew contingent.

mw0uzo
04-04-2013, 04:56 PM
Nice work - keep 'em coming.

For those wishing to play around with 24V devices (MRF422, etc) a coworker has a big honking supply which will be offered for sale in the near future. A little costly to ship overseas but it may be of use to our stateside homebrew contingent.

24V is good for QRO portable operation with a small unit running off LiPo cells. I'd probably be interested in some - any MOSFETs?