alternate frequencies?

[Tristar500]

Anybody have any info on a good alternative frequency range other then 72 mHz for controlling a RC pane or small UAV?

I'd like to do some testing with a new airplane that may eventually become an autonomous UAV and I don't want to deal with haphazard interference.

Radio modem, 2.4 gHx? What do you think?

[kd7ost]

Radio modem, 2.4 gHx? What do you think?

It's likely that or 900 MHz Radio Modem. Your talking about the Spread spectrum units from souces such as Maxstream I presume? If you plan on a Video link in the future, you should decide on one band for video, and the other for RC control.

Dan

[JettPilot]

50 MHZ ham band, with an amplifier on the transmitter :D . FMA sells the new copilot that has computer recognition of the transmitter. It says it will ignore anything that is not your radio. I dont have one YET :) but it looks very promising.

[kd7ost]

50 MHZ ham band, with an amplifier on the transmitter :D . FMA sells the new copilot that has computer recognition of the transmitter. It says it will ignore anything that is not your radio. I dont have one YET :) but it looks very promising.


The stock transmitter puts out ~750 mw. The Ham band 50 MHz allows you only up to 1 watt. You do get to use a Yagi antenna though if you want.

Dan

[Tristar500]

How difficult is it to convert a standard RC tX to ham band? Or does one start from scratch? :eek:

Lawrence

[fhhuber506771]

You buy a new TX that is already on HAM band. Futaba, JR and others sell them. They usually ship with 750 mw output. Technical knowledge of electronics is needed to properly modify for more power.
However... you would rarely need more power... the radios can interfere with each other at over 3 miles. If no other radio is being used on a NEAR frequency within 10 miles.. you can control your plane at over 3 miles if you can see it. (further than you can see... you need a GPS type autopilot for the UAV.)

Note.. you might want to check your purpose for the UAV vs the commercial/noncommercial use limits for the RC frequencies.. you may need to get an industrial frequency operation permit and an industrial frequency radio.

[JettPilot]

I always wondered how much power a standard RC transmitter put out. I forgot about that one watt thing :( But I had no idea a stock transmitter would go over 3 miles :eek: thats cool, I just never tried it that far ! All ham band stuff must be non commercial, but thats ok because I do this because I like to. I just dont have enough of a business mind to find a way to make money with my hobbies :mad:

[kd7ost]

I always wondered how much power a standard RC transmitter put out. I forgot about that one watt thing :( But I had no idea a stock transmitter would go over 3 miles :eek: thats cool, I just never tried it that far ! All ham band stuff must be non commercial, but thats ok because I do this because I like to. I just dont have enough of a business mind to find a way to make money with my hobbies :mad:


I don't think it's even close to a reliable three miles near the ground though. RF propogation, antenna orientation all play factors. These standard setups we use go up high over you, but not far away from you near ground. The receiver antenna is horizontal and every time you're flying away, or towards you, your off the rx antenna null. On the ground you typically hold your transmitter antenna vertical. The thing to do would be to get your airplane antenna to stand straight up so it's oriented to get vertical signals from any angle. Thats a 39 inch antenna if your staying with stock 1/4 wave antenna at 72 MHz. Thats a long piece of wire sticking straight up.

I wonder what kind of antenna's out there would allow vertical polarization on the plane, yet still be shorter, and designed to operate at 72 MHz. IMO this is the first biggest reason why we don't get all the range possible. (2nd is ground shape, buildings, trees, etc.) You get better range when your plane is sideways to you while we have our antenna's running along the fuselage and horizontal.

This is another good reason to consider 900 MHZ or 2.4 GHz radio modems. A 900 MHz antenna at 1/4 wave is only 3.12 inches. That won't be a problem sticking straight up.

Has anyone played around with different antenna's and have tangible range results to pass along?

Dan

[fhhuber506771]

I haven't done much playing with antenna length.. however i have mesaured the visual range distance whee I could keep control of the model at in excess of 1.5 mile with a standard AM transmitter in the 1980's. FM would inherantly have at least the same if not better range. The limit to my ability to keep the model under control was as far as I could see the model and "fly the dot."

The first method of measuring was to have anther person go out n a car, staying under the model an measure the distance before I turned it around and brought it back (so it was as far as I was willing to go.. not really the maximum range of the radio.. thats why I said if you can see it..)

Further testing of radio response was done in a simlilar manner.. with the friend just taking the plane for a ride n the back of a pickup and stipping when the controls quit following the cycling of the TX sticks. 3 miles.

I have read reports of radio interference being detected, and tracked down using a directional scanner... and the interference source being other RC flyers on the same frequency at 2 to 3.5 miles.

I intend to "play with" seeing how far I can detect the flyers at the local field with my Polk's Tracker-III when it arrives. The Tracker-II has been reported to detect other radios at over 2.5 miles, with indicated signals stronger than that of a TX with antenna collapsed at 50 feet. (minimal range check distance...)

[Katanadon]

You may find that 900 mhz to be your best bet......
1 watt max power
ism band.. no liscense required
smaller antenna than 72mhz
frequency-hopping spread spectrum
data keys
data encryption... no one take your uav away:)
data radios at 900 mhz are smaller and lighter than lower frequencies
and the kicker....
225 bucks for a pair from mouser electronics(server/client)
make sure you study and know the datasheets before purchasing
http://www.aerocomm.com/Docs/User_Manual_ConnexLink_900.pdf
this radio does a wonderful job at 57600bps
for the price it's the best thing i could find :)

[Mr.RC-CAM]

1 watt max power, ism band.. no liscense requiredFWIW, the allowed radiated RF power for license-free ISM is under 1mW. On Part-15 approved FHSS systems, effective radiated RF power of a 1W system is essentially 0 watts or so. That is the beauty of FHSS implementations. I also agree that the 900Mhz band would be a better choice for model control over the 2.4Ghz band. Less multipathing and longer effective range. And 900Mhz consumer appliances have fallen out of favor, so perhaps the external interference sources would be less.

RC-CAM

[Tristar500]

Thanks for all the info guys, I'm ordering a ham band module and RX for my JR 8103.

L