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Old 17th November 2012, 01:29 AM   #11
sco1t is offline sco1t  United Kingdom
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thanks for the tips. I thought LPAM (low power AM) as in super low power did not need a license in the USA as long as it meets part 15 of the fcc??????????
Look here Part15.us | THE FREE Resource For Part15 Community Radio! or google it any way I was only going to transmit 1 or 2 meter so how would any one ever find out..... unless I lived next door to the police station lol

I'll open up an old fm valve radio to see how they have there I.F valves connected for tips

Thanks
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Old 17th November 2012, 01:37 AM   #12
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For such power you need 1 transistor and 1.5V battery.
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Old 17th November 2012, 01:41 AM   #13
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Quote:
Originally Posted by sco1t View Post
I'll open up an old fm valve radio to see how they have there I.F valves connected for tips
Look for heterodyne, not IF. It should have appropriate for the frequency coils.
If you want to transmit FM on 88 mHz it is a different story. The easiest way is to modulate it by a varactor diode,
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Old 17th November 2012, 01:51 AM   #14
sco1t is offline sco1t  United Kingdom
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Hi wavebourn, thanks for the tips
So vales are to powerful?? That's normally a good thing but not in this case.
I have a 8Mhz quartz crystals oscillator which I was trying to get a valve to amplify but it would not do it. (mean valve)
I'll stick to AM, FM,s is a bit harder and i'm not as smart as you lol :'(
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Old 17th November 2012, 02:01 AM   #15
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Here is an example: use your crystal from base to ground instead of a resonant tank.
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Old 17th November 2012, 02:04 AM   #16
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Quote:
Originally Posted by sco1t View Post
thanks for the tips. I thought LPAM (low power AM) as in super low power did not need a license in the USA as long as it meets part 15 of the fcc??????????
Look here Part15.us | THE FREE Resource For Part15 Community Radio! or google it any way I was only going to transmit 1 or 2 meter so how would any one ever find out..... unless I lived next door to the police station lol

I'll open up an old fm valve radio to see how they have there I.F valves connected for tips

Thanks
Well the other issue is that you don't live in the United States and the laws here don't apply in the UK.. You need to check your local laws, and having a ham radio license may be necessary.. There are some unlicensed experimenter bands here in the US but the power levels are extremely low.
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Old 17th November 2012, 02:07 AM   #17
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You might want to look around this site for some tips,circuits,etc. Antique Radio Forums • View forum - Homebrew Radios

Just do be careful of the power output.
In fact,for a short distance,you could probably use a dummy-load,and still have enough signal leakage to pick it up across the room.
I've done a similar thing for attenuating the 1W output of an FM transmitter. A long,~50ft piece of 'cheap' coax,with a dummy load at the far end. The cheap coax had poor shielding,so it would leak some signal out -just enough to cover about 1 square block.
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Old 17th November 2012, 02:09 AM   #18
sco1t is offline sco1t  United Kingdom
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hi, that's similar to how I connected my valve . I'll get a transistor like that one and make that circuit. Thanks for helping
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Old 17th November 2012, 02:19 AM   #19
sco1t is offline sco1t  United Kingdom
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I know, the laws are even tighter in the UK but a few meters is still ok . I guess I will ask my friend. He's a manager at a (rubbish) radio station lol
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Old 17th November 2012, 02:23 AM   #20
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Quote:
I thought LPAM (low power AM) as in super low power did not need a license in the USA as long as it meets part 15 of the fcc?
We can't fire up on any frequency we choose. Part 15 is restricted to allocated broadcast bands.

8mc is fixed and mobile radio service in your ITU region. Your crystal might be on a government or military frequency. I doubt you are going to be loud with a simple rig with a lousy or no antenna but you might be hearable. I worked hams in Asia with 3 watts.

That being said, I assume you want to modulate the signal with audio rather than just producing an empty carrier. I'd recommend getting a triode/pentode and screen modulating the pentode with the triode section as modulator amp.

Have a look at this, for example: A One-Tube Controlled Carrier AM Transmitter

That is quite a simple circuit for what it does.

Maybe pick a frequency with some forethought. There might be some legal frequencies for this sort of project in the UK, but I wouldn't know about that.
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