[Amps] Power transformer...

[DAVE WHITE]

Hi Bob

Whatever you're using now certainly puts a decent signal into Europe on 160! (thanks for the QSL, by the way)

Personally I'd put the Yaesu transformer on ebay, get something really big and use a large tetrode with handles......but that's just me.

Have you thought of a GU43B?

Your HT might be a bit on the low side, because the tube's rated to 3.3kv, but it's a 1kw plate dissipation tetrode and is quoted as giving 1.6kW out  with a plate voltate of 3kv, screen at 350v and anode current of 0.9A.

I bought a box of about 6 of these at Weinheim a few years ago along with a few sockets, but so far haven't got around to doing anything with them.  There are usually lots floating around hamfests in Europe.

I guess running it at 2500v on the plate it'd pretty much coast along at about 800w-1kw out

I do have a book of all the older military Russian tube data sheets in English so can scan the relevant pages and email them to you if you need them.

Maybe also you could try a big glass bottle like a GU81M?  These are usually dirt cheap.  At one time I was going to build a 160m amp with some of these - I got them for about DM20 each - but eventually sold them to a local Tesla coil builder.  Those tubes would go like stink on 160m, they're just a bit on the big side physically.  One would certainly do the trick for you.  According to my book, they're quoted as plate voltage up to 3kv at < 6MHz,  specified as giving greater then 700W out at 2kv plate voltage, screen at 600v, grid at -200v, grid drive voltage amplitude 300v, min anode current 450mA, max grid 1 current 20mA, max screen current 220mA.  The lower the frequency, the greater the efficiency with this tube (it's a pentode like a big, fat 813) but the data sheet doesn't specify the frequency of that spec.  There are also sites around with some good designs - they're all in Russian but Babelfish did a decent translation and I can send
 you the translated copies of the webpages offline if you want them.  I also have a full datasheet for the GU81M as tranlsated by a Russian lady I knew at a client's office who allowed herself to be bribed with coffee for a translation! - I can also scan and email this if you're interested.  I need to do this for Hsu in China anyway who subscribes to this list - I've just remembered!

cheers Dave G0OIL

--- On Sun, 25/1/09, robert briggs <vk3zl at bigpond.com> wrote:
From: robert briggs <vk3zl at bigpond.com>
Subject: [Amps] Power transformer...
To: amps at contesting.com
Date: Sunday, 25 January, 2009, 6:41 AM

Hi all....I have just received a power transformer salvaged from a Yaesu 
FL dx2500 linear...I have checked it out and it appears in excellent 
condition....I am about to build another monoband 160 meter CW only 
amplifier and would prefer to use a single tube rather than pairs of 
GI-7BT....I already have two linears with the 7B tubes.....I am 
wondering if this transformer would handle a GS-31B say to 800 watts 
output CW....The primary is 850 volts ac with about 17ohms DC resistance 
through the secondary....According to Yaesu it is rated to 1 
amp...Voltage doubled it would give around 2500volts....I know the 31B 
would only be coasting at this power level and cooling wouldn't be a 
problem..

I do have a second new twin C core transformer which is heavier but it 
was built for running a pair of 813's and has a heavy filament winding, 
useless to me...The secondary also has around 17ohms resistance  and 
produces 2900 voltsdc but running a pair of 4/240A tubes it only 
produces around 800 watts CW....

What would be your pick ?? I will build the case large enough to 
accommodate either transformer....

Regards to all.....Bob VK3ZL....
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