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Author Topic: Sunnyvale/Saint Petersburg Amp on AM  (Read 11451 times)
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Tom KC2DTQ
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« on: April 27, 2007, 09:32:30 AM »

Folks I am conidering a homebrew project. The Sunnyvale(ARRL Handbook) Amplifier.
What power levels could I expect to get out of this amp on AM and can it be modified for a low drive input (30 Watts). Your comments would be appreciated.
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WA1HZK
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« Reply #1 on: April 27, 2007, 10:17:04 AM »

I'm not familiar.
What Tubes? What Voltage?
Keith
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Tom KC2DTQ
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« Reply #2 on: April 27, 2007, 12:52:40 PM »

Single Sevtlana tube 4CX1600B, B+=3000V, 2003 ARRL handbook.


 
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WQ9E
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« Reply #3 on: April 27, 2007, 02:02:36 PM »

I remember at one point the 4CX1600B from Svetlana became very difficult to acquire, not sure it that is still an issue.

I built a homebrew amp in 2002 using 3 of the Svetlana  4CX800 tubes grid driven with resistive loading.  Definite overkill but it was with the idea of building an amplifier that would stand up to contesting, AM linear, RTTY, etc.  I used Peter Dahl iron with 56 uf of oil capacitor filtering, a 5 KW rated roller inductor and a vacuum tune capacitor.  In retrospect, 2 of the 4CX800 tubes would have been plenty but with careful layout and the vacuum variable cap it tunes up fine on 10 meters.  I bought a set of the tetrode boards from G3SEK and they provide a very nice control and protection setup.

I like the 4CX800 tubes a lot, they are fairly inexpensive still (even cheaper at $30 apiece when I bought two sets for building the amplifier); have a pretty rugged screen structure, and using swamping resistors on the grid they are completely stable without neutralizing.

It takes around 20 watts from my Yaesu FT-1000MP to generate 375 watts of carrier output.  It works fine for AM linear but with the Viking 500 and Desk KW about the only time I use it for AM is on 160 meters.   As soon as I get the Gates BC-250GY finalized it probably won't get much AM use at all.

There used to be a U.S. site with all of the Svetlana technical bulletins but I don't think it is in operation anymore.  The Russian site with tube data is at:  http://www.svetlana-tubes.com/

73, Rodger WQ9E
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Rodger WQ9E
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« Reply #4 on: April 27, 2007, 04:58:35 PM »

The 1600B may still be hard to get.  RF Parts shows it as "not available"

There's some hinky arrangement where all Svetlana (SED "Flying C") tubes are marketed in the US and Canada by SED in Memphis, TN.  They list "stocking distributors", but I checked several of them and no one lists this tube as available.  It's either not listed, not available or "call".  The main Svetlana website indicates no services for US/CAN.

Grant/NQ5T
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« Reply #5 on: April 28, 2007, 07:58:37 AM »

George Daughters, W6?? (A mind is a terrible thing when its wasted) did the article on the Sunnyvale Kilowatt. At that time, the 4CX1600 was a nice cheaper altenative to the 3CX1500/8877. Even to the point Emcon(?) and I think Ten-Tec made commercial amps based on the same design. However something happened that production was curtailed at Sevetlana's St. Petersburg plant. This was also about the same time they cleared out their offices here in the US. I remember something about them letting Sovtek market their audio tubes but don't quite remember what the deal was with their RF tubes. George would post quite often on the AMPS list. Check out the archives for his call sign or it should be listed in the ARRgghhL article. I'm pretty sure he has his email address on qrz.com. He'll answer your questions because he seems to be a pretty square fellow.
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Mike(y)/W3SLK
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Tom W2ILA
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« Reply #6 on: April 28, 2007, 09:02:05 AM »

within the past year or two I was seeing 4CX1500B tubes available in tested used or NIB American Eimacs for very reasonable prices.
If you have a 20th edition 1978 era copy of the W6SAI handbook there is a Linear with this tube.
Make some comparisons with the Sunnyvale rig and you may be able to build around a more available, less expensive tube.
   
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WBear2GCR
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« Reply #7 on: April 28, 2007, 09:14:20 AM »

Sitting out here in left field...

My main thought is/was something like this: if you have to ask, you probably shouldn't be thinking about building around this sort of design?

Dunno if this is going to be your first homebrew project or not - or perhaps your first attempt at something with big power/high voltage? If so, I'd suggest starting out with something that is a bit less at the hairy edge of voltage ratings and that has less chance of zorching. Maybe some 813s? Even 4 x 813 if you gotta have more zest in the fire wire...

Otoh, go for it! ;_)   Shocked

I've seen some other Ruskie ceramic power tubes coming in that have similar power ratings... AB2EZ just posted about one, and Ken W2DTC runs one, soon to be a pair, I believe.

               _-_-WBear2GCR

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« Reply #8 on: April 28, 2007, 01:50:37 PM »

GU-78 and GU-84 would be better choices. Tetrode ham-plifiers can be difficult. The screen supply is difficult and the main advantage of ceramic tube use will be lost without a low inductance screen bypass type tube socket. Triodes are easier to build around and there are really good values out there in the surplus market right now. If you do stick with a tetrode and have too much available drive then adding inverse feedback to the amplifier via cathode resistance is a good way to go. This will also clean up the amplifier's output if done correctly.
Drive power needs to be specified in the same terms as it would in ssb. Your 30 watts carrier of AM will be around 120 watts P.E.P. when 100
% modulated. If the amplifier is supposed to be driven with 100 watts of single slimeband then it might only need 20 watts carrier of AM.
Output power of a linear amplifier will be slightly less than 1/2 plate dissipation of the final tube. A 4CX1600 could deliver 750 watts carrier IF the supply and cooling were good enough. Most hammy amps  are designed for ssb and the supplies and cooling are the limiting factor. 
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WQ9E
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« Reply #9 on: April 28, 2007, 04:26:15 PM »

If you do decide to go with tetrode amplifiers (and I do like the fact that you can use resistor loading for stability and still drive the amplifier with fairly low power) then I strongly suggest you look into the tetrode board by G3SEK: 

http://www.ifwtech.co.uk/g3sek/boards/tetrode/tetrode-1.htm

It takes care of providing a nicely regulated screen supply plus protection for the screen.  It also provides relay sequencing for HV and antenna switching, a "warm up" timer for indirectly heated tubes, and additional protective circuitry inputs for excessive cathode current, high temp or swr, or whatever other protection you would like to incorporate into your amplifier.  You could duplicate the functions of this board (the needed information is on his website) but re-inventing such a nice wheel would be false economy for most of us.

The tetrode board has been in use in my amp for a number of years and has worked flawlessly. As suggested by W2VW and the Svetlana application note for the 4CX800 I am using a small amount of cathode resistance in my amplifier.  I used the recommended Svetlana sockets which provide the proper built-in screen bypass.

I would stay away from the 4CX1600 since there definitely seems to be availability issues.  The 4CX800 (or GU-74B) is readily available.  As I recall, Ten Tec ran into problems getting the 4CX1600 also.  About the time I was building my amplifier I had considered buying the Ten Tec amp to save time (contest season was near) but an uncertain delivery time coupled with reports of drifting tuning on 160 (due to output network capacitor heating) made up my mind for me.  I am glad I took the path that I did, it was a fun project and it works well.  My daughter was born shortly after I completed this amp but now that she is getting older (and I am getting to sleep normally!) I plan to put it back to its intended use as a contesting amp.

Rodger WQ9E

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Rodger WQ9E
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« Reply #10 on: April 28, 2007, 04:44:06 PM »

I certainly remember a fine HB Tx using a 4CX1500B. A handful of watts and it would put out 2500 watts without sweating. The P.S was 3500 VDC@5 amps. It was the famous "Big Rig" K1KW, Chuck. A pair of 3CX1200A7's modultating the final with a 5KW mod transformer and its 50Hy Heising choke.
The new owner has yet to put it on the air! Why did I get rid of that master piece of electronics?Huh
Not all there Fred............MOPRADIO
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Fred KC4MOP
Tom KC2DTQ
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« Reply #11 on: April 30, 2007, 09:35:24 AM »

Thanks for the input. I will consider the options that you folks have stated.
 I am an experienced home brew builder just this is my first amp project.   

Thanks for the help
Tom
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