Power Amp 11 Meter Band

I know one made by Yaseu thats simple, I can give you the schematic, but it is a small hard to read one, it can use 2 or four tubes.

I believe you will need two or four 6jsc6 tubes...

T23

Amplifiers are very tough to build, and VERY dangerous.

Transformers are also hard / expensive to come by.

-Richard-

office888 said:

Amplifiers are very tough to build, and VERY dangerous.

Transformers are also hard / expensive to come by.

-Richard-

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I agree..
The 2 problems you will face are:
1. Getting the transformer
2. Working with high voltage if you are inexperienced.

I'm all for anyone building and learning....but just realise that you are dealing with high voltage.
That being said...... go to the CBTricks website and look under the "amplifiers" section. There will be alot of schematics available... alot of them are older tube stuff.
Check under Wawasee or Black Cat for some small amps....but check all the sections, I seem to recall seeing a few small tube schematics.

Personally...you might find it easier to buy a old non working tube amp with some good parts and repair it rather than build from scratch. If you buy an old amp that needs repair, at least you will have the transformer and most of the other parts you need....and most of the wiring should be intact ( but maybey in need of replacemnt).

bejo said:

Dear all Member ....

Do you have information for 11 meter band amp with Tube, i want learning step by step with easy and simple schematic... any body can teach me...

Thanks for your kind attention

Bejo....

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Building a tube amp is not for beginners....period, unless of course if you have a death wish.

It can be done.... Yes it can be dangerous, at the very least you can uncurl your hair and the extreme is death! With that said....

I have built a small audio amp, I know it is not an RF amp! I used two 120 volt to 12.5 volt center tapped transformers like so.... 120 volts AC in, the output to the output of the second transformer and it gave 120 volts AC out. The point where both transformers are joined, the 12.5 volt is where the filament voltage is tapped. (A dropping resistor can knock it down to 6 volts)
At the output of the second transformer I made a voltage steering diode (two) with salvaged caps from a computer power supply. These were 470µf @ 200WV. (working volts) The net output after the diode and caps was 230 volts AC. And it does power up a small amp.
You could order a suitable transformer from Hammond out of Chicago. but homebrew is always fun!
Now for a tube amplifier with more that 25 watts RF out you are going to need more voltage and current and the translates to transformers the use 220 volts @ 200 amps and the output could be as high as 4000 volts @ 25 to 50 amps! Can we say electric chair?

You 'stepped down', then 'stepped up' to the original voltage, rectified it, filtered it a bit(?), and came out with 220 vac? Really??
- 'Doc

W5LZ said:

You 'stepped down', then 'stepped up' to the original voltage, rectified it, filtered it a bit(?), and came out with 220 vac? Really??
- 'Doc

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Yes, the step down then up offers a bit of isolation and a good place to tap the 12.5 volts for the filament. The rectification is more of a steering of the wave cycle and the filters fill in the cycle "void" to smooth out the wave a bit like a time lag. Close to a full wave rectifier but the diodes follow each other with the filters acting as the reservoir "pump" and a third cap @ 300 volts as a pool of electrons. You could say it is "ripple DC but I did not DVM it as it is too high of a voltage for my Fluke. A bleeder resistor is included to drain the caps when off along with an LED pilot light. I believe this is called a voltage doubler.
I found this on the WEB someplace and I'll upload a drawing as soon as I find it!

73 mechanic

mechanic said:

Yes, the step down then up offers a bit of isolation and a good place to tap the 12.5 volts for the filament. The rectification is more of a steering of the wave cycle and the filters fill in the cycle "void" to smooth out the wave a bit like a time lag. Close to a full wave rectifier but the diodes follow each other with the filters acting as the reservoir "pump" and a third cap @ 300 volts as a pool of electrons. You could say it is "ripple DC but I did not DVM it as it is too high of a voltage for my Fluke. A bleeder resistor is included to drain the caps when off along with an LED pilot light. I believe this is called a voltage doubler.
I found this on the WEB someplace and I'll upload a drawing as soon as I find it!

73 mechanic

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It sounds like the gentleman hooked up the secondaries of two 12.6 volt transformers. If they are both 120 volt primaries and you feed one with that voltage, the other primary will of course have 120 volts. I think he is describing a full wave voltage doubler as the rectifier and that would produce 2.828 times the AC voltage across the DC filter caps under no load conditions. The transformer losses are also double in this case. Under load this could easily drop well below 300 volts. It's an easy way to make the voltage his amplifier needed using the parts he had while providing isolation from the line.

I really do know what a 'voltage doubler' circuit is. But using two transformers just isn't the typical way it's done. I can see where it would provide some isolation, but is it really needed?
I would think that using one of those transformers for a filament supply, and the other as a high(er) voltage source would be a 'better' way of doing it, more efficient, less 'hysteresis' etc.
If you don't have access to a transformer more suited for that situation, it is a viable solution. But while you do have twice the voltage with that voltage doubler, you are still limited by the transformer's current limits. 12 volt transformers just don't have that much current 'ability', or at least the ones I've had my hands on. Larger transformers are not going to be cheap, or as common, true, but...
- 'Doc

The voltage doubler uses a pair of filter caps in series. It also uses two diodes. One to isolate the negative AC peaks and charges the first cap with them. The second diode isolates the positive AC peaks and charges the second cap with them. Since both caps charge to the peak of the applied voltage and are wired in series, you get twice the DC voltage at half the current.

In his case one transformer could not make the high voltage because each transformer only had a 120 and a 12 volt winding. Wiring the secondarys together gave him the 120 volts with isolation. Since the amp was only 25 watts these transformers probably worked well. If the transformers were 10 amps at 12 volts that would be 120 watts available continuous.

You are both correct and this application is for a light duty audio power amp using a double tube. It contains a small pentode preamp and a triode in the same envelope. Most likely the output would be less than 20 watts.
This power supply uses off the shelf components done cheaply and is more for a learning project and made use of an otherwise useless tube. The 13EM7 tube was used in old television sets. and we all know where these are nowadays!
The design can be scaled up for use as an amp for a small linear but it would be best done with the proper components. Like Shockwave said there is loss with this setup. For me it was a learning process and yes I did learn to work with one hand in my pocket!