2m Amp which Tube is best

[EI2GLB]

HI All

I want to get a Amp for 2m and i have 2 models in mind.

Both are 1kw output and made by same company.

First uses a GU74b and as we all know the are a bit on the hard to come by side these days. I have a Acom 1000 and it uses the same Valve and i have a spare one here.

2nd uses 2 x GI7BT's which i know nothing about only i have seen them on Ebay for about $50.

here is a link to the manufacture of the Amps

http://ha1ya.config.hu/hipwrampl.htm

What is my best option there is only 50$ in the difference price wise so Im looking to see which tube will give better service. I will only be using it at 400w.

thanks

Trevor
EI2GLB

[W9GB]

Trevor -

I have no knowledge of this Hungarian company -- although I am aware that there are
a number of surplus Russian designs in Denmark, Eastern Europe and the Balkan region.

You might want to look at the excellent webpage for a 144 MHz (2 meter) amplifier
using a pair of GI-7b tubes by Paul G4DCV.
His largest expense was the HV transformer (torroid design)!
http://www.g4dcv.co.uk/amp.htm

There are a large number of surplus Russian tubes on the market -
many more in Europe than are imported here in North America.

ND2X/5 QRO designs and Russian tubes
http://www.nd2x.net/

QRO Parts (EU and NA) is one of the large Internet sellers of these surplus Russian tubes.
Seattle, USA +1 (206)426-6094
EU: Stockholm, Sweden +46 8519 71373
http://qro-parts.com/

I have not seen as many GI-74b tetrode tubes sold on the surplus market.

The GI-7b is a microwave triode that has been quite popular for sweep tube
amplifier conversions (~ 400 watt class) here in USA.

Ron Wilson. K4POZ and W4ZT(sk) developed a nice socket for the GI-7b tube
http://k4poz.com/gi7b/

IF you desire to build your own one day, I would highly recommend
using the G3SEK, Triode Control Board for the operation, control and protection of the RF tube.
http://www.ifwtech.co.uk/g3sek/board...e/triode-1.htm

w9gb

[WB2WIK]

For 400W on 2m I use the ubiquitous 4CX250B which has been around since about 1960 and runs exactly that much power with low drive and an easy-to-find socket -- without having to homebrew any part of the socket.

They cost about $25 each as "pulls," but are still manufactured brand new. I must have 20 of them or so, and they're all "good."

Easy to use, easy to drive, easy to cool.

My main 2m amp uses a pair of them in P-P at 2200Vdc and runs exactly 1.0 kW output power with 7W drive. I built that in 1981 and it still has the same pair of tubes in it after 28 years, having been used constantly.

I'm old fashioned...

[EI2GLB]

Thanks for the replys. I would love to be in the position to save myself a load of money and build one but I have to say that dealing with HV is not for me.

there is a real lack of 2m tube amps on the market.

I have a TE brick that does 160w and i dont fancy the 400w model. The tokyo high power stuff is crazy money.

I have not seen any bad reviews of HA1YA's amp and the ones i am intrested in are a keen price.

What i really need to know is which valve will give me the longest service if i look after it and keep the power at about 40-50% of max.

i know there can be bad one of any type of Valve but thats the chance you take.

Thanks
Trevor
EI2GLB

[WB2WIK]

Originally Posted by EI2GLB

Thanks for the replys. I would love to be in the position to save myself a load of money and build one but I have to say that dealing with HV is not for me.

there is a real lack of 2m tube amps on the market.

I have a TE brick that does 160w and i dont fancy the 400w model. The tokyo high power stuff is crazy money.

I have not seen any bad reviews of HA1YA's amp and the ones i am intrested in are a keen price.

What i really need to know is which valve will give me the longest service if i look after it and keep the power at about 40-50% of max.

i know there can be bad one of any type of Valve but thats the chance you take.

Thanks
Trevor
EI2GLB

4CX250B. It's cheap, very available, and has inexpensive and available sockets. You can't run 400W output using a tube without dealing with high voltage, no matter what tube you use.

[EI2GLB]

The 2 options open to me are either GU74b (4cx800) or GI7BT I do not have the Skills to build my own amp It will be a store bought AMP.

while the 4cx250's are popular with homebrewers the are not an option for me.

Thanks

Trevor

Originally Posted by WB2WIK

4CX250B. It's cheap, very available, and has inexpensive and available sockets. You can't run 400W output using a tube without dealing with high voltage, no matter what tube you use.

[W2VW]

K 1 F O .

[W9GB]

K 1 F O
K2vw

K1FO is Steve Powlishen, who founded Lunar Link Systems
http://home.cshore.com/lunarlink/info.html
and they make a 2-meter amplfier that uses the popular triode tube, 3CX800A7
http://home.cshore.com/lunarlink/la-x2A_data1.pdf

Steve, K1FO (then WA1FFO) first 2 meter kW amplifier was built in 1971 and
he used the classic push pull 4CX250 tube design. Steve, WIK is grinning about now.

The 2 options open to me are either GU-74b (4CX800) or GI-7BT

Trevor -

OK, here are some of the pros and cons (hopefully Steve, WIK and Randy, W2VW will add to list!)

The GU74b is a Tetrode and the GT-7BT is a Triode tube
Tetrodes, IMHO, require a bit more TLC from the amplfier's power supply and control circuits -- hopefully that is addressed in the amplifier's microcontroller.

The Svetlana 4CX800A is manufactured in the "Svetlana Electron Devices" (SED) factory in St. Petersburg, Russia. The tubes current being sold by QRO tubes for $199 rach (Soviet marked as GU74B) were made in the USSR from 1980-92 at the Svetlana factory.
As you have commented, there have been many conversions lately about availability of many ceramic RF tubes. Some manufacturers even delayed or canceled production of amplifier models due to sources for RF tubes.

The GI-7BT is a surplus Triode tube used by the Soviet military.
While there is a LARGE surplus of these tubes currently, I have not seen anyone currently producing this tube.

I noted that the amplifier that used 2 - GI-7b tubes, listed an alternative tube.

w9gb

[K9KJM]

I had a CommanderII VHF amplifier that uses the 3CX800A7 tube and had really good luck with it. (The 3CX800A7 tubes were available cheap as "pulls" a few years ago)
I also have a large TE systems solid state "brick" that I really do not think all that much of.
No question in my mind that unless for a special application like going mobil, The tube amplifier is the way to go.

[EI2GLB]

Thanks to everyone for the replys.

the alternative is the GI39B I cant seem to find much info on it does anyone know is it still in production. I see QRO-Parts have it for about $110 which seems a ok price.


Thanks
Trevor

Originally Posted by W9GB

I noted that the amplifier that used 2 - GI-7b tubes, listed an alternative tube.

w9gb