Instructables

Diy radio transmitter for medium range, 1 mile

Iv'e done a quick search and not come up with anything yet.

Im a scout leader and for some of our events we need to be able to do announcements over the radio but as most of our sites don't have loud speakers set up all the time we have to rent them, and the people to set them up. Even with a discount this can go into the thousands and that goes back to the kids costs and well i hate that. 

Anyway after playing around with my partners short distance radio transmitter that plugs into her iPhone i wondered if its possible to modify, or build a transmitter like this for longer range.
Anyone got any links?

It needs to be fairly clear, doing music and announcements that people can hear over about one km to one mile. 



Belkin Tunecast FM transmitters for iPods have severely limited output, but can usually be modified for more power. Reaching a mile may be possible with a larger and directional antenna. See the negative reviews on Amazon, then google Tunecast hacks. Belkin Tunecasts are fairly common at thrift stores.

Apart from that, the equivalent of FRS/GMRS would be more legal. Although if any prankster figures out the channel (and there's no security code to limit access), expect some unwanted announcements and rude noises at all hours. Music quality will likely be more like telephone quality, but maybe that's part of the charm of outdoor events.
jjefferson1 (author) 2 years ago
Sorry should of helped, im in Australia and from some of my reading its legal to use a radio system that doesn't go more than 10km, is not used permanently (guessing that means 1 weekend at a time, rather than covering the signal with music)

Ive looked at some out of china that may suit, already built and the limit is the size of the antenna but diy is still more fun.
Thanks guys
If you are really interested in this endeavor, I suggest going to Ramsey Electronics and taking a look at their AM1C or FM10C low power AM or FM (respectively) transmitters. These are high quality kits that you can put together and you can have the kids build their own AM receivers - crystal with a solar powered low power amp. LM386 comes to mind. Just read through the manuals before you decide to go this road. You can find them at the bottom of the page under Product Support.

Good luck on whatever you decide to do.

Qa
Get some 22 channel FRS/GMRS 2 way radios. Every scout troop should have a set if they do any kind of traveling. Since the radios only cost about $50 a pair you can easily have several sets on site to lend to troops who don't have 2 way radios. With there 2 to 5 mile ranges they should be perfect. It wouldn't be too hard to hack a set to add a mic jack to them if needed.

These boast a 23 mile range.
http://www.amazon.com/Motorola-MH230R-23-Mile-22-Channel-Two-Way/dp/B001UE6MIO
rickharris2 years ago
1. Radio transmission is strictly controlled.

2. You will be best served by getting a decent radio mike - this is what they are for.

3. Where in the world are you so you can be directed at the best options.
FRS radios might be a solution, although I don't know if there are any legal reasons why they couldn't be used for the music part. They aren't for high fidelity audio anyway, so music wouldn't sound real great, but they should be just fine for announcements. Many of the participants may own them already, and at any rate they are cheap, at $15 - $30 per pair.
Re-design2 years ago
I'll assume you're in the US. Any transmitter that has the power to reliably transmit one mile without getting interference from other transmitters is likely to need a license from the FCC.

Wireless mikes have a limited range. 

A article 15 transmitter (legal to build) is limited in antenna length and power output and most have less than 300-500 ft. range depending on what else is in the area.

You could buy a pair of fm walkie talkies that have a range of several miles for less than $100 but you'd have to accept that anyone else on the frequency would be interrupting your speech.

Check out this companies web site for FR broadcasters.  I use one at home but it only has a range of about 400'.