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Old 18th October 2012, 10:18 PM   #1
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Default Tx FM with 6bq5

I looking the project below and thinking about to assemble this. But I have seen other tx, that uses a EL34, but I believe that can work with EL84 too. If I'm right and the el34 tx works with a EL84, the question is: What project give more irradiaton power? And stability?

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note: I know that el34 circuit may have more hum, but I can use a transformer too, right?

Thank you.
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Old 19th October 2012, 10:24 AM   #2
DF96 is offline DF96  England
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Both circuits will probably give more AM than FM. Lots of distortion, poor frequency stability, lots of harmonics. Likely to annoy your neighbours by interfering with their radio and TV reception. In most countries they will be illegal. I do not intend to help a radio pirate.

The second circuit is directly connected to the mains and therefore dangerous, although as you say you could use a transformer.
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Old 14th December 2012, 08:34 PM   #3
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Originally Posted by DF96 View Post
Both circuits will probably give more AM than FM. Lots of distortion, poor frequency stability, lots of harmonics. Likely to annoy your neighbours by interfering with their radio and TV reception. In most countries they will be illegal. I do not intend to help a radio pirate.

The second circuit is directly connected to the mains and therefore dangerous, although as you say you could use a transformer.
I builded the first tx and I installed on my backyard, connected with a homemade antenna too.

But while I'm testing, the stability was very good, all the night I let it turned on and still tuned on exact frequency. At 10 feet it gets the only signal that i tune the frequency. I dont get any kind of interference on analog TV, and of course not in DTV. My house is low in relation to the geography of my neighborhood. My neighborhood is kind of hilly, and other houses higher than mine. With these conditions, I reached 500 meters in certain directions. Hey. it's fun, I dont wanna make any kind of radio, is just for fun.

But until now, I dont know how I can calibrate the trimmers on the output. On the text says that they are filters, but I don't understand what they had to do.

Other problem is the coxial cable. I just have 75ohms cable..
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Old 15th December 2012, 04:46 AM   #4
freax is offline freax  Australia
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that is an antenna matching circuit, and if you dont want the Polícia to come and take it off of you i suggest that you enclose that tube amplifier part of it inside of a metal project box and also buy a dummy load for ham radio use and transmit into that instead of that antenna.

5 Watts is a LOT of power and it will travel for many many miles.

You might also want to make the project safer too by screwing it down onto a bit of wood.
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Old 15th December 2012, 05:38 AM   #5
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felipe it would be wise to listen to freax. Any mains powered circuit is potentially lethal and should be properly housed with attention to proper earthing etc. If not for your own sake, for the sake of others who may come into contact with the circuit.
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Old 15th December 2012, 06:11 AM   #6
freax is offline freax  Australia
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Quote:
Originally Posted by felipemuniz View Post
I builded the first tx and I installed on my backyard, connected with a homemade antenna too.

But while I'm testing, the stability was very good, all the night I let it turned on and still tuned on exact frequency. At 10 feet it gets the only signal that i tune the frequency.
Thats great!
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Old 22nd December 2012, 01:32 AM   #7
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I'm trying now make it on PP, but something is going wrong... Anyone know how make a PP with this project?
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Old 22nd December 2012, 05:16 AM   #8
JMFahey is offline JMFahey  Argentina
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Amigo Felipe, você é doidão mesmo KKKKKKKKKKKK.
Só no "Brazíu"
The transmitter is a screen modulated ***AM*** transmitter, and if you get a little FM modulation it's because the circuit is unstable.
It must also drift a lot.
Leave it as is , you can't mod a bicycle into a Formula 1 car.
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