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Old 30th June 2017, 11:26 AM   #1
Shhh its me is offline Shhh its me
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Default No RF gear here?

Ok, distracted today... came to sit in lounge to ask why no diy RF stuff here?

yeahhhh, diyaudio

But seriously interested in making a FM transmitter.... something in the 88 to 109 Mhz band. Around 10 - 50W up the stick.

Any ideas where to find?
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Old 30th June 2017, 11:30 AM   #2
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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RF transmitters are not really DIY projects as even a CB radio can deliver dangerous RF burns to those who tinker.
I would join the RSGB or some recognised amateur radio group.
Any power like that is illegal in most countries.
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Old 30th June 2017, 11:42 AM   #3
Bigun is offline Bigun  Canada
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No RF gear here?
I've wondered the same thing - I mean wondered whether there was a good forum like this for rf electronics. Once you get addicted to the audio stuff there's only so many amplifiers you can build ! but playing with analogue electronics is fun and there are lots of interesting things to build at the radio end of the spectrum - receivers are a ver rich topic all to themselves. I suspect that the Ham enthusiasts have a good forum or two somewhere.


Edit: you'll recognize my avatar here: http://theradioboard.com/rb/viewtopi...&hilit=william
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Last edited by Bigun; 30th June 2017 at 11:45 AM.
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Old 30th June 2017, 11:58 AM   #4
DF96 is offline DF96  England
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There are RF forums. They get the same sort of mix of people as here, with the same mix of truth and error and magic. Antennas and transmission lines are what confuse many DIY RF people, but as here some of them are so confused they don't realise they are confused.

DIY transmitters are fine, but to do it properly you need rather more knowledge than for audio DIY. Safety and interference are bigger issues.

I expect there are pirate radio forums too, where there may be even more error - certainly about legal matters!
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Old 30th June 2017, 01:29 PM   #5
TheGimp is online now TheGimp  United States
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In the USA, the FCC allows operation of low power FM transmitters, but anything over 100mW must be licensed.

I'm sure most countries have similar restrictions, whether or not they offer licenses would be up to the individual to check with the appropriate ruling body.
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Old 30th June 2017, 01:43 PM   #6
Bigun is offline Bigun  Canada
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No RF gear here?
I've always found Antennas to be a very complex topic and a big enough topic to be dealt with separately from that of the Tx/Rx electronics. Rather like we have a bit of a divide between amplifiers and speakers (transmission lines anyone !). As I think about it, it's an interesting parallel. In audio we try to treat speakers and amplifiers as independent and once in awhile we have to recognize their interdependence. Something similar happens with Ham stuff, where the standard antenna impedances are an attempt to make it easier to design antennas and transmitters separately but in reality there are inter dependencies. Current drive vs voltage drive has it's parallels too. I guess it's all the same in the end!
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Last edited by Bigun; 30th June 2017 at 01:46 PM.
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Old 1st July 2017, 07:03 PM   #7
Tubelab_com is offline Tubelab_com  United States
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Quote:
But seriously interested in making a FM transmitter.... something in the 88 to 109 Mhz band. Around 10 - 50W up the stick.......In the USA, the FCC allows operation of low power FM transmitters, but anything over 100mW must be licensed.
The OP is in Australia. I'm sure that firing up a 50 watt radio station is illegal there too, but I don't know how well such things are enforced.

Pirate radio seemed to come and go several times while I lived in South Florida. While setting up a radio station off shore in a boat would evade prosecution, all the pirates were land based. In fact there was a pirate radio station about a block from my house.

The operator was on the air for over 10 years. He started out with a 17 watt transmitter that covered about a 3 mile circle around his house. He had a 100 watt amplifier for about two years which gave him about 7 miles. Lightning took out the amp, and he never got it fixed. He got his equipment from a mail order outfit in Israel. There was a card that plugged into a PC, a box that sat on top of the PC, and the amplifier when he had it. The box had left and right line level audio inputs which were fed from a small mixing console. The entire setup could be automated in the PC. Radio "shows" could be recorded, or played back from the PC, and a schedule of totally automated operation could be set up. He has a phone number on his web site, and often took live call-ins on the air. He also had live guitar lessons on the air, which I played along with.

One day about 10 years ago, the station was gone. I assumed that the FCC had finally got him, but later I saw his wife in the grocery store and found out that Jack had had a heart attack and died while having Thanksgiving dinner with his parents......Despite what the web site says. The "radio station" is still alive, but now internet only and run by his Miami firefighter friends (his former occupation.

Jack And Jill Radio

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DIY transmitters are fine, but to do it properly you need rather more knowledge than for audio DIY. Safety and interference are bigger issues.
ANY transmitter operated on any frequency other that valid amateur radio frequencies in the USA must be "type accepted" by the FCC. Amateur radio transmitters COMMERCIALLY SOLD in the USA must also be "type accepted." This means that a licensed ham radio operator in the USA can build his own radio equipment, and it must meet some spurious and harmonic radiation criteria. Making a bunch of complete radio transceivers and selling them would also require type acceptance, which is a process generally not possible for most DIYers. Radio kits, bare PC boards and accessories fall into a grey zone.

My 41 year career as an RF engineer and transmitter designer at Motorola ended 3 years ago, and the employment agreement preventing me from making RF stuff ended 2 years ago. Will I design and build a "Tubelab style" ham radio? It's on my list. I had a rather complete RF setup on my workbench at Motorola. I have been slowly buying dead RF test equipment cheap on Ebay and fixing it. My plan is to duplicate the setup that I had at work.

I haven't seen an RF forum dealing with advanced RF design, but I haven't really looked either.
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Old 1st July 2017, 07:58 PM   #8
DF96 is offline DF96  England
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Yes, I was not condoning illegal operation but answering the point made that RF transmitters are not really DIY items. They are, but only for those who know what they are doing - which includes staying within the law. For almost everyone that means either fairly low power (almost zero power in the UK) or legitimate amateur radio. It is unlikely that a DIY transmitter for the FM broadcast band with significant power would be legal in almost any country.
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Old 1st July 2017, 08:20 PM   #9
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by Shhh its me View Post
Ok, distracted today... came to sit in lounge to ask why no diy RF stuff here?

yeahhhh, diyaudio

But seriously interested in making a FM transmitter.... something in the 88 to 109 Mhz band. Around 10 - 50W up the stick.

Any ideas where to find?
Ask some of the guy's transmitting on those frequencies from the upper floors of tower blocks in Birmingham, I've missed them since I moved..........
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Old 2nd July 2017, 03:11 AM   #10
TheGimp is online now TheGimp  United States
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Quote:
Originally Posted by DF96 View Post
Yes, I was not condoning illegal operation but answering the point made that RF transmitters are not really DIY items. They are, but only for those who know what they are doing - which includes staying within the law. For almost everyone that means either fairly low power (almost zero power in the UK) or legitimate amateur radio. It is unlikely that a DIY transmitter for the FM broadcast band with significant power would be legal in almost any country.
I disagree on the difficulty. I completely agree on the legality.

Look at an old ARRL handbook and it isn't difficult to build a tube based transmitter any where from 750KHz to 220MHz. Above that, get a newer copy and you can go all the way to 1GHz with SS based amps.
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