Grab bag of transmitters?

Somebody buy these and tell me if they work...

Ebay

FM Transmitters? When I was young, I built an FM transmitter to put in the payload bay of my Omega rocket. It had a microphone hooked up to relay the sound from in the rocket. Optionally, I could hook up a sensor to measure something like temperature. When the sensor hooked up, the circuit transmitted an audio tone with a frequency based on the sensed value.

I think the circuit design was from a magazine article. I'm sure it wasn't something I designed.

I built a lot of things from Popular Electronics and other magazines at that time. It was around the time that I lost interest in rockets for a while. I don't think I every actually flew the transmitter in a rocket.

-- Roger

They look a lot like Ramsey Electronics FM band transmitters.

John

McKailas Dad said:

Somebody buy these and tell me if they work...

Ebay

Click to expand...

I wouldn't count on them at all. I built a bunch of these sharpening my chops with soldering. Major problem is they aren't crystal controlled and as the battery voltage drops, one has to continually retune their receiver to hear them. One really needs a crystal controlled unit for frequency stability. I've built several types, one, two and three transistor and for playing around with they're fun and sensitive. The required antenna length for an optimal tuned system is pretty long for a rocket since they are in the FM broadcast band. They're only 15mW if you're lucky.

For a modroc, this transmitter is fun: https://www.dealextreme.com/p/m-80-walkie-talkie-monitor-module-1-x-cr1220-80924.

It's low power but one will need a scanner in the 70cm ham band to hear it. One can optimize the antenna length for it.

If you take the time to get a Ham technician license, there are more options out there that are economical for you like this:

https://www.west.net/~marvin/microhnt.htm

There are other Fox Hunting trackers out there for Ham operators that are a bit cheaper.

Another site is this one: https://www.byonics.com/mf

The MicroFox can be flashed with a Byonics BIOS and just add a $40.00 GPS receiver and one can have a GPS tracker for about $125.00. Not near as featured as a Beeline GPS tracker but O.K. for run-of-the-mill HPR flying.

Remember one thing: You go for higher power, battery weight goes up or the transmission time goes done with a smaller, lower capacity battery. Low power transmitters do fine in the air but not as far on the ground after landing. A sensitive Yagi antenna helps with receiving a low powered transmitter signal.

Kurt

And, of course, don't forget these:

https://bigredbee.com/BeeLine.htm

Cheaper and/or more powerful than the other options, and includes the necessary battery and charger already integrated into the unit!

16 milliwatt and 100 milliwatt versions available on the 70cm ham band.

-- Greg

ksaves2 said:

For a modroc, this transmitter is fun: https://www.dealextreme.com/p/m-80-walkie-talkie-monitor-module-1-x-cr1220-80924.

It's low power but one will need a scanner in the 70cm ham band to hear it. One can optimize the antenna length for it.

If you take the time to get a Ham technician license, there are more options out there that are economical for you like this:
Kurt

Click to expand...

I would be interested in more info on this one (ie: what it modulates, etc). By the way though, given its listed frequency in the 70cm band, you would need a license for it as well.