2 mile range transmitter - RC Groups
Shop our Airplanes Products Drone Products Sales
Thread Tools
Apr 29, 2013, 06:02 PM
Registered User
Discussion

2 mile range transmitter


I am interested in building my own inflight data system with an onboard transmitter. Rather than re-invent the wheel I am looking for a small (tiny) xmitter with a short antenna for use on a sailplane. Should be license free and not directional. Anyone know of schematics or a unit I can buy. It will ne data only though there might be a way using transmitted audio.

Thanks
Sign up now
to remove ads between posts
Apr 30, 2013, 03:42 AM
Stuart
srnet's Avatar
The range is not a problem, 10mW is enough for about 10kM on 434Mhz or 868Mhz and normally license free, assuming decent RF modules.

The rest rather depends on what you want to do, use a micro controller and RF module you will program yourself, or put together some form of pre-asssembled and pre-programmed module.

And then what sort of 'data' are you wanting to transmit ?
Apr 30, 2013, 07:33 AM
Registered User
xbees 2.4G Pro Series 2 go up to 1km. Then there are the 3DR telemetry radios on either 915MHz or 434MHz. Stated range there is 1 mile, but I reckon this may be a little bit understated. Anyway, you could change the antenna on the receiver to be directional and an extra 6dB should double your range there.

https://store.diydrones.com/3DR_Radi...try-3dr915.htm
Apr 30, 2013, 10:49 AM
Registered User

thanks


Actually I have designed a yaw indicator (like a yaw string on a sailplane to aid in turn coordination. ) I will be converting A/D and sending the data stream back to the pilot.
Apr 30, 2013, 11:03 AM
AndyKunz's Avatar
Just use a Spektrum radio system and add a custom sensor. There are several threads in this forum from people who have done just that.

Andy
Apr 30, 2013, 09:59 PM
Registered User
Be sure to check out the FrSky 2.4 Ghz with full down link telemetry. Saves your data on a micro SD card

Less that half the cost of any other system and twice as reliable.
May 01, 2013, 06:27 PM
RC beginner
Quote:
Originally Posted by srnet
The range is not a problem, 10mW is enough for about 10kM on 434Mhz or 868Mhz
ahhhhh... snet... snet... snet....
May 02, 2013, 03:37 AM
Stuart
srnet's Avatar
Yes me again.

The FSK RTTY 'telemetry' from RFM22 is looking very promising indeed, the FSK Slow Morse has even more potential.

Its difficult to carry out practical full power line of sight tests at ground level due to the curvature of the Earth. However, there is a FSK Slow Morse beacon in orbit (Swisscube) that transmits with the same power as the RFM22, 100mW.

Swisscube can be heard at 2500km, using just an omni antenna and a standard Funcube Dongle.

Coming soon ......... the Lost Model Locator that will receive GPS co-ordinates with Line of sight range greater than 1000km.
May 02, 2013, 04:59 AM
Registered User
A satellite isn't a very good comparison. Swisscube transmits at 120mW at only 10 bits/sec, and doesn't have to deal with much atmosphere.

Typical ranges for 100mW seem to be around a mile or two, LOS.
May 02, 2013, 01:18 PM
Stuart
srnet's Avatar
Quote:
Originally Posted by jakestew
Typical ranges for 100mW seem to be around a mile or two, LOS.
The calculations around the RFM22 achieving 40km (25Miles) at 100mW LOS, suggest the receive sensitivity was about 7dB below the stated -121dB, so I am convinced there is more range to be had by some further experimenting.
May 03, 2013, 02:21 PM
Stuart
srnet's Avatar
Quote:
Originally Posted by jakestew
Swisscube transmits at 120mW at only 10 bits/sec, and doesn't have to deal with much atmosphere.
Atmospheric absorption at the frequency concerned, 437Mhz, is not really significant, although it is at much higher frequencies.
May 04, 2013, 01:10 AM
Registered User
Free space propagation losses are certainly significant, and are affected by all sorts of atmospheric factors.

The fact that they don't have to transmit through hardly any atmosphere certainly boost the range.

In any case, you're talking about 2500km ranges when most people are getting 5km if they're lucky. You just don't seem to be grounded to reality in any practical sense.
May 04, 2013, 04:30 AM
Registered User
Numbers are numbers, reality check is worse, using RFM22 in OpenLRS system I am not aware about someone to reach 10km to date, without using special antennas...
May 04, 2013, 04:47 AM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
I see "Old chool" DIY was different than the way it is done these days.
Pre-internet plumber period of clean air and mind, a solder iron and a grid-dipper.
See the photograph. A well tuned oscillator (about 40 years old), free running, was enough to transmit the audiosignal of the variometer over an out of sight range.
Consumption, 9 VDC 10 mA frequency, ++108 MHz.
What was the out of sight range? More than the distance over which I, with a very good sight, could control my glider with a span of 15 ft .

Taurus Flyer
Last edited by Taurus Flyer; May 04, 2013 at 06:00 AM.
May 04, 2013, 06:35 AM
Stuart
srnet's Avatar
Quote:
Originally Posted by renatoa
Numbers are numbers, reality check is worse, using RFM22 in OpenLRS system I am not aware about someone to reach 10km to date, without using special antennas...
As I implied above, I got 40km out of a pair of RFM22s, 100mW, hilltop to hilltop, but I am convinced there is more to come. The telemetry was two way, I was testing the ability to be able to remotely command from one device to another.

The 'special antennas', were 1/4 wave vertical antennas.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Data 2.5 miles (4KM) range with stock Futaba FASST 2.4GHz!! twinturbostang FPV Talk 104 Dec 03, 2016 09:28 AM
Question How to set up a really, really long range fpv (6 miles)? David97 FPV Talk 35 Jun 08, 2013 11:52 PM
For Sale NEW Lawmate 2.4 Transmitter and Receiver 3 mile Range!! Flying Brian FPV Equipment (FS/W) 0 Dec 02, 2012 01:19 PM