My name is Onno de Vries and i'm living in the Netherland and building
big amps is my hobby.
I just bought a 4CX 5000A on a radio market here for a good price (180
Euro) including socket.
Becourse the price was so good i took the challenge to build a 88-108
Mhz final from it.
I allready build many with all diferent kind of tube's but after some
experimenting with this tube i found out that the anode resonator a a
bit of a problem course of the high cappacity of the tube.
I try to do it with a double output coil (together Almost a half wave)
wich you see in manny designs for 144 Mhz amateur amps using for
example the russian tube GU84.
This works but it has a terrible efficiency,about 30%.
I hope that someone have experiance with big transmitters with
4CX5000A or simular in the final wich has about the same anode
cappacity and inpedance.
I hope that somebody can give me some Info about making a good and
high efficiend tank with these kind of tubes.

In article , (Onno de
Vries.) wrote:

My name is Onno de Vries and i'm living in the Netherland and building
big amps is my hobby.
I just bought a 4CX 5000A on a radio market here for a good price (180
Euro) including socket.
Becourse the price was so good i took the challenge to build a 88-108
Mhz final from it.
I allready build many with all diferent kind of tube's but after some
experimenting with this tube i found out that the anode resonator a a
bit of a problem course of the high cappacity of the tube.
I try to do it with a double output coil (together Almost a half wave)
wich you see in manny designs for 144 Mhz amateur amps using for
example the russian tube GU84.
This works but it has a terrible efficiency,about 30%.
I hope that someone have experiance with big transmitters with
4CX5000A or simular in the final wich has about the same anode
cappacity and inpedance.
I hope that somebody can give me some Info about making a good and
high efficiend tank with these kind of tubes.

Hi Onno,

RCA used the 4CX5000A as the final in their model BTF-10D 10kW FM
transmitter. The manual doesn't include any photos that show the complete
anode cavity, or even photos that show all the details. It's been nearly
forty years since I have had hands on one of these, but basically there
are two adjustable lines used as inductors in a pi network connected
between the tube anode and the transmission line to the antenna. The
first inductor is in parallel with the anode capacity. I will review the
manual and see if I can figure out any of the details.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

(Onno de Vries.) writes:

I hope that someone have experiance with big transmitters with
4CX5000A or simular in the final wich has about the same anode
cappacity and inpedance.
I hope that somebody can give me some Info about making a good and
high efficiend tank with these kind of tubes.

The Collins 830F transmitter used this tube -- there's one still in
service as a backup here in the Boston area -- and the tube socket
sits on the deck of a 1/4-wave-length cavity that can be tuned
roughly by raising and lowering a sliding plate that forms the
"ceiling" of the cavity. Fine-tuning is accomplished by moving a
vertical plate inside the cavity connected to the cavity wall;
it acts as a shunt capacitor. Another capacitor in series with
the output RF sample loop acts as a loading control.

The Harris FM-25K power amplifier is similar but is built around
a larger tube (8990/4CX20,000A).


umar
--
rm -rf /luser/bush 270 days, 8 hours, 24 minutes

umarc wrote in message ...
(Onno de Vries.) writes:

I hope that someone have experiance with big transmitters with
4CX5000A or simular in the final wich has about the same anode
cappacity and inpedance.
I hope that somebody can give me some Info about making a good and
high efficiend tank with these kind of tubes.

The Collins 830F transmitter used this tube -- there's one still in
service as a backup here in the Boston area -- and the tube socket
sits on the deck of a 1/4-wave-length cavity that can be tuned
roughly by raising and lowering a sliding plate that forms the
"ceiling" of the cavity. Fine-tuning is accomplished by moving a
vertical plate inside the cavity connected to the cavity wall;
it acts as a shunt capacitor. Another capacitor in series with
the output RF sample loop acts as a loading control.

The Harris FM-25K power amplifier is similar but is built around
a larger tube (8990/4CX20,000A).


umar

Hallo Umar.

Thank's for responding. Atleast i have some transmitter type's wich
uses the 4CX type of tube's.
I did some searching on the net and found the Collins and the Harris
transmitters but no photo's, manuals or schematics wich i realy need
to bild this thing.
When i read Your story i understand a bit how they do it.....but a bit
is not enough.

Umar......thank's again for helping,if You know where i can find some
more info please let me know.

Regards. Onno.

Onno,

http://www.qsl.net/g4ftc/amplifiers/8171/home.htm

http://tinyurl.com/yq6a9

http://www.angelfire.com/darkside/rfbox/

http://www.somis.org/

and when you wish to plug it into the mobile:

http://www.extremecb.com/Engine_3.jpg

Enjoy
--
Philip de Cadenet G4ZOW
Transmitters 'R' Us
http://www.transmittersrus.com

Philip de Cadenet wrote in message ...
Onno,

http://www.qsl.net/g4ftc/amplifiers/8171/home.htm

http://tinyurl.com/yq6a9

http://www.angelfire.com/darkside/rfbox/

http://www.somis.org/

and when you wish to plug it into the mobile:

http://www.extremecb.com/Engine_3.jpg

Enjoy

Well i just wright a big reply........use the backspace button and my
mail was gone. Great....
O.k . Just start over all again. GRRRRRR.

Hallo Philip....first i have to excuse myself for not replyíng Your
mail.
Sombody was and is still so friedly to sent me mail with a virus.
I had to install(ghost)my pc again and thatswy i lost mail and
adresses.

I just take a look at the site's You put on this page. Some i
allready saw bur the www.somis.org/ is verry interesting. I copy'd
much and printed it out.
They other site's has more to do with six meter transmitting.

But....Umar was talking about a Harris FM-25K. Well on the Harris
page(after much digging)i found much. I found two different kind of
schematics and a drawing of a cavity. Verry good.....i'm happy.....
The onely thing i have to do now is measure the socket or tube on the
drawing , compare it to the real size and than i can calculate the
size of the cavity.

THAN BILD THE THING.

If it's finish'd the AMP i will let You know all.

Philip and Umar.......thanks for helping me out.

Greetings from Elburg....the Netherlands. Onno.

P.S. This engine dynamo thing.........is it normal to build those
things?....Crazy?.......awsome.

http://www.extremecb.com/Engine_3.jpg

P.S. This engine dynamo thing.........is it normal to build those
things?....Crazy?.......awsome.

It all happens in the USA!

I flew over to some of these mobile amplifier "shootouts" and took a
bunch of pictures.

That van owner above lives in Florida.

He has another rack of high output alternators on the main engine in the
front.

He has full throttle control of both engines in the front.

I'm afraid your tube amp would not get much of a lookin as the champion
that day ran a pair of 4CX20,000's in the output of his amp:-)

By the way, one of your radio ships just came to the UK for a refit:

http://www.mvcommunicator.com/39400.html

Take care and good luck with your project.
--
Philip de Cadenet G4ZOW
Transmitters 'R' Us
http://www.transmittersrus.com