Building up watts of power in an FM transmitter

For best efficiency and amplifier performance: use a resistor as the RF load.

Kevin - if you try to keep things legal you will get a lot better help here. There are folks here who know how to get 200-500 feet range without breaking the law. If this device has a commercial purpose, apply for an experimenter's permit. I's nearly free, and lasts 2 years

- form 442 with the FCC ... assuming you are in the USA.

Frank Raffaeli

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Frank Raffaeli
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Hi all, I have a VCO set to 106Mhz with the VCO feeding into a CC buffer amplifier. The buffer amp then feeds into a CE amplifier the active device here being the BFG97. This then feeds into a class C amplifier again the active device being a BFG97. On the CRO I'm seeing a Vout of 21volts RF the Vcc being 12v.

The antenna is a 50ohm telescopic whip. The thing is I'm not getting much range with this setup maybe 30 meters.

I know the antenna isn't great. I have to get around to designing a hi gain antenna in the comming weeks. The Ptot of the BFG97 is 1 watt so do i chain a couple of class c amps to get a hi power output?

How do I get a good efficiency from the amplifier stages?

Any thoughs welcome. Kevin.

Reply to
Kevin Doyle

It looks like he's in Ireland.

Graham

Reply to
Pooh Bear

And that was even before I noticed his surname - lmao ! A sure give away.

Graham

Reply to
Pooh Bear

And where are you from Pooh Bear?

Reply to
Kevin Doyle

There's this book written by A.A.Milne.....

Graham

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Pooh Bear

Reply to
Kevin Doyle

Did M. Milne also write the one called, "The Tao of Pooh"?

I found that one to be pretty cool. %-}

Cheers! Rich

Reply to
Rich Grise

with 21V RF you should be doing km not meters; something is oscillating on totally different frequency, or output stage is overdriven.

IMHO on 106MHz to reach 30 meters is enough just a VCO & the following amplifieing stage ...

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Spajky

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Kevin Doyle

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