Need 50 to 60 watts VHF / UHF

[kc4umo]

Want to increase my output from 10 watts to 50 or 60 watts.
This is mostly for satellite work. All four of my Yaesu's only put out 10 watts.

Thought about 2 amplifiers and one power supply.
Something in a tube.
Homebrew .

Any suggestions?

[KC8TCQ]

Want to increase my output from 10 watts to 50 or 60 watts.
This is mostly for satellite work. All four of my Yaesu's only put out 10 watts.

Thought about 2 amplifiers and one power supply.
Something in a tube.
Homebrew .

Any suggestions?

http://www.radio-ware.com/old/pa2.htm

http://www.minikits.com.au/kits2.html

[KA5PIU]

Hello.

Look for an external amplifier, what is in the MFJ catalog works fine.
Dual band amps are super common.
To find them cheap, look at the swapfests as well as online.
Also, remember, from 25 watts to 50 watts is a 3 decibel gain, so from 50 to 60 watts is very little indeed.
I do satellite with 5 watts just fine, a good yagi antenna is the answer.

[WV6Z]

Hello.

Look for an external amplifier, what is in the MFJ catalog works fine.
Dual band amps are super common.
To find them cheap, look at the swapfests as well as online.
Also, remember, from 25 watts to 50 watts is a 3 decibel gain, so from 50 to 60 watts is very little indeed.
I do satellite with 5 watts just fine, a good yagi antenna is the answer.

Hey post Lazarus..... Buddy said, 'tube type' VHF/UHF amp. :roll:

[kc4umo]

Hey post Lazarus..... Buddy said, 'tube type' VHF/UHF amp. :roll:

Right you are. I have found some info but not alot. Going to have to build on the fly.

Anyway, I work most sats with less than 5 watts. But this is not always so with AO-7. Sometimes you need a little more and sometimes you dont. The rigs I run are only ten (10) watts.
When they get some high earth orbits sats up you can forget your 5 and 10 watt rigs. Plus you have to think about feed line loss.

I have 24 elements on VHF and 20 elements on UHF.
Plus a little extra power for simplex operation would be great!

[HUGH]

Make sure your amplifier will handle SSB if that's one of your chosen modes. It simply implies some bias on the output transistor (and driver if there is one) to make the the thing linear. Some of the CW/FM amps have no bias at all, I suppose they're operating effectively the same as Class C.

[kc4umo]

Make sure your amplifier will handle SSB if that's one of your chosen modes. It simply implies some bias on the output transistor (and driver if there is one) to make the the thing linear. Some of the CW/FM amps have no bias at all, I suppose they're operating effectively the same as Class C.

Good comment.
Yes ssb operation only. I very seldom and mean "very" operate FM unless it is simplex or the FM birds. But 5 watts works the FM birds fine.

[HUGH]

OK, try this idea. I bought an old 2m amplifier off EPay at a good price, it was optimistically rated at 40W form 13.8V but NOT linear. It had 2 transistors and an RF detector which operated a couple of Rx/Tx relays. I replaced the output transistor with an MRF247, quite an old transistor but very good, and lifted both the base RFCs from the ground-plane. Next, I fitted a scrap of stripboard with a temperature-compensated bias circuit containing a small AF power transistor and a couple of rectifier diodes. There is a pot on it as well to tweak the bias. One diode I glued into a crimp O-ring and this went under the MRF247 securing nut for temperature compensation. The bias circuit is on the internet and if I could find again I'll point to the website on this thread.

The output is still 45-50W but nicely linear and I had the advantage of having the case, heatsink and PCB ready to go!

[KA5PIU]

Hello.

Yes, tube type.
But, I look at all the options.
50 watts on a tube radio is not that hard, the Motorola Motrac is a good place to start.
But, unless you can find someone with old Motrac radios, one VHF and one UHF, and have or can get the tubes, cheap, you may end up spending more than a new transistor unit.
The Motrac I like, as the entire PA section is the bottom end of the radio.
One can unscrew it from the rest of the radio and keep the bottom cover.
A 110 watt Motrac will run 80 watts cool, so 50 watts would be well within the ratings.
There is very little to do to a Motrac final unit, provide filament and plate voltage along with keying and drive.
But, remember, tube type amps are not wideband no tune.
Even a few KC up or down and the amp will drop power.
Tuning is not hard, and one can drill holes into the bottom cover for tuning and use a diddle stick, but tuning is a matter of life.
That is why I like the solid state no tune amps of today, and no HV.
Remember, the power supply in a Motrac can kill.