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Author Topic: 10 W power amp  (Read 1505 times)
HEADSHOT119
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Posts: 10




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« on: July 17, 2009, 11:53:58 AM »

Is it easy and possible to build an amplifier that will take my handheld rig from 5 watts of power to ten watts of power.

The handheld is an FDC 160/460, Prefrably an externally mounted amp.

Thanks.
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KM3F
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Posts: 910




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« Reply #1 on: July 17, 2009, 10:17:55 PM »

Yes it's posible but 5watts to 10watts is not a standard amplification gain. Not worth the investment at that output power as it's only 3db gain.
If you keep a check on the clasified ads you can get a low cost amplifier in the 5in to 20 or more out class for less that about $50 for one band not two unless you have a stroke of luck finding such an animal..
Be awhere of what you get and only drive it with enough input power to get rated output or less.
Also expect the amp to draw 4 to 8 amps depending on what power level you get and how hard you drive it.
Good luck.
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KB1LKR
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Posts: 1897




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« Reply #2 on: July 18, 2009, 09:44:15 AM »

Month or two back there was an article (two part?) in QST on building solid state amplifiers in the few watt range as an experimental exercise - easily scaled up in power, the only hitch was they were geared to HF vs VHF if I recall, but again they should scale in freq w/ VHF-UHF transistors ,smaller inductors, and shorter, more careful lead dress.

For a VHF HT/amplifier application you'd want to shoot for maybe 25-50W out for a significant difference in performance. Practically speaking (size, weight, total power consumption, etc.), a 50-75W mobile would be more effective, but if you're looking to build/experiment then and blow up a few inexpensive VHF transistors till you get it right, then scale it up in power.
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WB2WIK
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Posts: 21837




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« Reply #3 on: July 18, 2009, 05:08:05 PM »

Headshot, do you have an amateur radio callsign?

Home built amplifiers are only lawful in the amateur radio service, at least in the U.S.  For any other use, amplifiers and all other equipment must be certificated.

WB2WIK/6
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HEADSHOT119
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Posts: 10




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« Reply #4 on: July 19, 2009, 10:56:32 AM »

Yes I do have a callsign, but I signed up to the site before I received it.
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KB1LKR
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Posts: 1897




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« Reply #5 on: July 20, 2009, 09:51:52 AM »

"Designing and Building Transistor Linear Power Amplifiers, Part 1" & "... Part 2" by KK7B in QST, Feb, 2009 & Mar, 2009 respectively.

Covers HF & VHF experimental amp design at about 5W out -- but same basic methods/knowledge could be applied to a 25W 2m amp. Look it up at a local library.

You might get by w/ the 5W you have too if you used a full sized ground plane antenna (19" +/- vertical w/ four drooping 19" +/- radials) and elevated it some -- anything from a couple feet over your head to say 20-30 feet off the ground. Short antennas on HT's are not as effective as a full size antenna, though often good enough and certainly more portable -- all depends who you want to talk to, how far they are and how high their antenna is.

You can get 15-17" long HT antennas too (Comet, Diamond, Pryme) that will help boost performance a little, then add a 19" dangling wire "rat-tail" to the ground side at the antenna connector for a little more of a performance boost.

Experiment!

BTW you can change your user name to your call -- though I forget the details, the question comes up regularly enough here, so if you look you should find the details. Steve's question arose as it wasn't clear if your application was for amateur or other service.

Hams get a lot more leeway than the other radio services for building & modifying gear for amateur service
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VE5RB
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Posts: 12




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« Reply #6 on: July 21, 2009, 09:39:48 AM »

See the eHam Help (FAQ) link on the left side of the screen. There is a thread ther that will walk you through changing your username.
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