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Author Topic: 35mhz amplifier  (Read 1655 times)
MUVR2007
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Posts: 56




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« on: March 20, 2010, 08:49:53 PM »

Hello,


I would like to build a 35mhz fm amplifier (PPM modulation).
Input power will be ~200mw and output not less than 7w.
Is there any schematic I can use to do that?
Can you help me?


Thanks
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K6AER
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Posts: 5617




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« Reply #1 on: March 20, 2010, 10:19:03 PM »

There are a lot of amplifier circuits available as application sheets from many of the transistor manufactures that are available on line.

Questions that arise that affect the choices;

•   Will the amplifier terminate into an antenna or is this a close loop system?
•   If it is to be used for antenna radiation it might need to be FCC Certificated.
•   Harmonics out to the tenth place must be down 60 dBc for operation above 25 MHz.
•   The amplifier will need to have case radiation limits as per TIA603C for amplifier used above 25 MHz and be field tested on a range or indoor chamber.
•   How is the amplifier controlled? If you have a switch mode supply or a micro on board it will need part 15 testing and approval.
•   Do you have an IMD specification? This effects the Class of operation you should use.

What is the general application? There might be an off the shelf amplifier already available.
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G3RZP
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Posts: 1090




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« Reply #2 on: March 21, 2010, 12:38:36 AM »

Do you mean mHz or MHz? If the former, the biggest problem will be DC drifts and 1/f noise. There will be drifts, too, with devcie heating and cooling during part of the cycle.

If it's 35MHz, that's another kettle of fish, although whether or not PPM is better than straight FM and a Class C or higher (D,E) is naotehr matter.
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