narrow band receiver transmitter

[delija30]

i nedd schematic for simple narrow band transmitter and receiver . Supply voltage 9v , range about a mile, 88-108Mhz operation range.<p>[email protected]<p>thanks

[Dave Dixon]

Argh,
What do you want to transmit? Voice, Stereo Audio, Pulses/Text, streaming video?
Big as a breadbox, or a matchbox?
Reciever needs to flash LEDs, drive a speaker, flip a relay, interface to computer?
It's not possible to give proper advice without a proper question. I don't mean to be rude, but the forum gets a lot of vague questions. Please try to give more details.
Most of us here would not just assume that you want an FM mono audio Xmitter just because of the frequency range you specified - as tempted as I was at first glance!
Spend a little time checking out other threads here, and I'm sure you will understand my point.
With all due respect,
Dave
Please provide more details if you would like our help. (Guys and Gals, let me know if I'm out of line here!)<p>[ March 29, 2005: Message edited by: Dave Dixon ]</p>

[delija30]

Range about 1 mile
power supply 9 v
88-108Mhz
it suppose to transmit voice so NB up to 3kHZ<p>receiver
Battery 9 v
88-108 mhz
NB for voice

[sofaspud]

I'm not sure, but I think transmitting with that kind of power in the FM band might be illegal. Surely someone here knows.
And it might be why you get a limited response to your request.<p>[ March 29, 2005: Message edited by: sofaspud ]</p>

[dr_when]

Ramsey has lots of nice FM transmitter kits in all power ranges unless of course you wanted someone to build it for you too.

[rshayes]

You should look up Part 15 of Title 47 of the Code of Federal Regulations. A google search on "code of federal regulations" will get you several sites where they are located. Some are easier to use than others.<p>The limits on radiation are usually that the transmitted field strength be below a certain value at a specified distance.<p>The receiver can be as sensitive as you can make it and use a directive antenna. One mile range might be possible even with the limit on the transmitted signal.

[jwax]

All depends on your allowable antennas. A wimpy whip at the transmitter may be compensated by a dish at the receiver. Yagis at both ends are cumbersome, but even 100 milliwatts would be an easy link with them. How much room is available, and how much $$ can you spend?

[Bernius1]

Are you REALLY in the USA ? If you are, you can buy any FM radio as a receiver , and buy a wireless FM-band microphone at most toy stores for under $20.00. All you will lack is range. Why? Because power out put AND transmitting antenna design are fixed by design, and spec's are sent to the FCC for filing. You can either modify the antenna, or modify the output stage of the power amplifier, both of which are illegal. Not to mention that over driving the output stage may cause distortion in the signal, and fry the circuit. Motorola makes jobsite walkie-talkies, UHF, that go for miles.
If you design your own, AND it doesn't cause unwanted interference, AND you use 'proper design techniques', and you can prove that it's NOT being develpoed for commercial distribution, then IF you get caught, they MIGHT only confiscate the prototype with a warning.
I was going to piggy back an AM signal on the FM frequencies. Theoretically, even at the power you suggest, interference should be minimal. But the X-mit has to be PLL accurate, and the FCC limit of 1mW @ 1-meter (or 1mV @ 1-meter ? ) still applies.

[terri]

Now I'm waiting for a question on linear amps for this band, and advice on a good J-pole antenna cut for 98 MHz....<p>Hmmmm.... <p>Privateers off the starboard bow, Cap'n!<p>Dave Dixon:<p>"...but the forum gets a lot of vague questions. Please try to give more details."
(snip)
"Please provide more details if you would like our help. (Guys and Gals, let me know if I'm out of line here!)"<p>Not at all. I've been railing and ranting and frothing at the mouth about this since I first found the board. But I'm undoubtedly crabbier than you about it.<p>Actually, I've found it helpful to try to read into the intent of the query, then post a numbered series of questions back to the original poster. This seems to work fairly well, but sometimes I look like a fool doing it, since some of my back-questions don't necessarily relate to the original poster's intent. That's just the way things are. <p>One the one hand, you can't prescribe a rigid question format and inhibit questions in the first place, but on the other hand, this back-question technique usually gives the original poster a chance to formulate hir thinking about it a little better.<p>Your "Argh!" is not out of line at all, in my opinion.<p>My own "Argh!" relates to why this party wants to transmit in the FM BC band in the first place.<p>Argh.<p>[ April 01, 2005: Message edited by: terri ]</p>

[sofaspud]

I found this at Ramsey's site http://www.ramseyelectronics.com/resour ... p?page=fcc
"The most specific FCC regulation of 88-108 MHz FM Broadcast band unlicensed operation is that the "field strength" of the signal must not exceed 250 microvolts/meter at a distance of 3 meters from the transmitter (FCC rule 15.239)."<p>FRS seems like it would be vastly more suitable, even as a homebuilt project. Well within the range spec, no looking over your shoulder for FCC enforcers, no interrupting the neighbors' King Biscuit hour.