6 meter linear amplifier.

[VK3ZL]

Hi all, I have been hard at work building 6 meter amplifiers these past few weeks....I built one in October and offered it on ebay and it sold straight away with 8 separate bidders...I then got requests to build more so I have been fairly busy....This unit pictured is MK2...I started it 2 weeks ago and finished final testing last Sunday....I offered it to one of the hams wanting my work and 2 hours later the money was in my bank..I currently have three more all identical in various stages of completion and hope to have them all finished early in February...

These 6 meter amplifiers are a straight forward no bells and whistles unit producing around 800 watts output which is far beyond the legal power limit in VK....However they have a comfortable headroom and if looked after will last for years on the same tubes..

The tubes are Russian GI-7BT Planar triode's which will operate to 1.5ghz....They only cost $25 each and are by far the best value tube on the market these days...Plate dissipation is 350 watts and they use around 2.4kv on the anodes...A pair of these tubes comfortably will put out 1kw if correctly cooled...I buy the tubes in bulk lots from Europe, 10 tubes $200 posted...

I love using my hands crafting simple metal work....I have a small lathe and drill press...All other work is done by hand from the first aluminum sheet to the last coat of paint....I am my best critic and can always point out my building mistakes which nobody else can see...I am thankful that I have had a worthwhile hobby to keep me busy in my old age having been retired since 1983....

Enjoy and Happy Christmas to all..

Bob..VK3ZL..

[K7SGJ]

You do some really fabulous work. I see a lot of attention to detail. That says "craftsman" or "artist" to me. Keep up the good work. You have a great Christmas and New Year as well.

[PA5COR]

Kudo's to you!

I'm just running 100 watts into a 5 element beam, we can use 120 watts pep....though most use more power here as dx station, i limit myself to the 110 watt the transciever puts out.

If i ever needed such amp you would be the place to ask for....
HF is covered, Heathkit SB-1000 i overhauled, new 3-500ZG so that will last me a long time.

Great job on your amps, it shows the dedication put in, and the excellent thinking behind it.

Cheers,
Cor

[kd8dey]

I was trying to find info on those tubes a while back out of curiosity.
Wondering about the input/output impedance (per tube) and suggested voltages for grounded grid.......

Looks nice.

I have seen posts somewhere of a guy converting Heathkits to 6m
thought it might be interesting to convert them to the russian tubes :)

[PA5COR]

Those Russian tubes can be had here cheap as chips on the local ham fests.
Some use them to make H.F amps cheap, 600 - 800 watts out, we can use 400 watts PEP here, so they always run within specs.
http://www.xs4all.nl/~pa0fri/Lineair...0/FRI750uk.htm

Including one with the GI7B

[N8YX]

What kind of drive power does that amp require for 800w out?

[NQ6U]

Looks great, Bob. Do you have a sheet metal brake for bending all that aluminum?

[VK3ZL]

Hi again.....Input resistance is around 40-50 ohms for a pair of tubes....Drive for 800 watts output is about 50 watts...

With 2000vdc on the anodes output resistance is around 2000ohms...

I have a home made bending brake to do all my own sheet metal work....I cheat these days and order all the sheet metal already cut to my size requirements....Each case costs me around $100 in aluminum and 12mm angle, rivets etc....It takes me around 2 days work to construct a case.....I assemble it all with small bolts then pull it apart and give all the metalwork a good etch in a caustic soda bath then reassemble it all permanently using pop rivets....there are no short cuts if you want to do a professional job but as I have been doing this for many years it is easy for me....

Bob..VK3ZL..