SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Aug 21, 2012, 09:32 AM
Stuart
srnet's Avatar
UK, Cardiff
Joined Dec 2008
3,289 Posts
Discussion
Improved GPS Locator with remote Morse and Data Telemetry reception

I have been working on the GPS locator to add the ability to receive, by data telemetry the GPS data from the remote transmitter.

The locator still acts in radio location mode transmitting a series of tones that descend in power and increase in frequency. Thus you can tell with a simple UHF transceiver if you are getting closer or further away from the model (or balloon).

SMA sockets for the antennas have been added and this has improved the range, cheap SMA UHF antennas easily found on eBay can be used as well as simple bits of wire.

The smaller PCB is intended for use in a model aircraft (or balloon) and will (using the attached GPS module) establish a home fix and from then on transmit data telemetry for the Latitude and Longtitude, Distance and Direction from home, home altitude and AGL, as well as battery volts and temperature. An AXE132 Serial LCD driver PCB and 20x4 display can be attached and will give a running picture of GPS location and distance and direction from home.

The larger PCB is deigned as a 'Groundstation' and uses mostly pin in hole components to make it easy to assemble. Too big for most models, but OK for a balloon. There is a header to take a OPENLOG logger (the small red PCB) and an expansion connector for connecting a GPS, AXE132 Serial LCD for display and other stuff. The logger records all the received telemetry to a micro SD card such that there is a PC readable log or track of where and how high the transmitter has been.

An optional add on for the groundstation PCB allows display on a Nokia 5110 LCD display.

Both PCBs use a PICAXE 28X2 with a common pin use such that the programs for either PCB are interchangeable.

Line of sight range, such as between a groundstation to an in flight model aircraft or balloon, is difficult to predict without actual testing on a balloon. I did some line of sight tests with the earlier modules between distant hilltops, where a range of 8kM was achieved with 12mW, with some packets received with as low as 3mW. The better antenna arrangement of these newer modules already shows a reasonable improvement on this, such that the line of sight range should be in excess of 40kM using the modules full 100mW and simple vertical antennas. There is still scope for further improvements by tweaking the settings of the RFM22 transmitter.

The modules can still transmit the GPS 'telemetry' as 15WPM or 60WPM morse, all you need to receive that is a UHF transceiver and a PC with soundcard to decode the morse. This has about twice the range of the data telemetry.

Details here;

http://www.picaxeforum.co.uk/showthr...etry-reception

and here;

http://www.picaxeforum.co.uk/showthr...0-graphics-LCD
srnet is online now Find More Posts by srnet
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 26, 2012, 07:45 AM
AMA# 1004189
conbones's Avatar
United States, FL, Panama City
Joined Jun 2012
342 Posts
That is awesome. i want one. So cool, have you retrieved a lost plane equipped with your device yet?
conbones is offline Find More Posts by conbones
Reply With Quote
Old Aug 27, 2012, 03:26 AM
Stuart
srnet's Avatar
UK, Cardiff
Joined Dec 2008
3,289 Posts
I have been fortunate, not needed to use for real yet.

I generally just use it in radio beacon mode, all you then need to find a model is a simple UHF transceiver.

The GPS info is a nice feature to have of course.
srnet is online now Find More Posts by srnet
Reply With Quote
Old Aug 28, 2012, 05:11 PM
Registered User
Joined Jul 2012
5 Posts
About how much would it cost to build both?
sknnyftn is offline Find More Posts by sknnyftn
Reply With Quote
Old Aug 29, 2012, 01:35 AM
Stuart
srnet's Avatar
UK, Cardiff
Joined Dec 2008
3,289 Posts
The small locator and the larger 'groundstation' PCB use about 25 in parts each.

Plus a serial LCD, plus a GPS module.

Not sure how much the small 5110 serial display module would be, about 12 in parts maybe.
srnet is online now Find More Posts by srnet
Last edited by srnet; Aug 29, 2012 at 02:05 AM.
Reply With Quote
Old Aug 29, 2012, 09:46 PM
Registered User
Joined Jul 2012
5 Posts
Thank you. I am still waiting on approval at the PICAXE forums to be able to open the files in your linked posts. So far it looks like a have a new project to start working on.
sknnyftn is offline Find More Posts by sknnyftn
Reply With Quote
Old Sep 20, 2012, 08:14 AM
Stuart
srnet's Avatar
UK, Cardiff
Joined Dec 2008
3,289 Posts
I have just done some hilltop testing of the locator, mainly to evaluate the receiver performance of the RFM22B radio.

Tested with simple 1/4 wire antennas only.

The Hilltops were 40kM apart and reception of data packets was reliable at full power from the locator,100mW. At 50mW 50% of packets were received.

If the locator was operated at the 10mW limit for license exempt devices, the equivalent LOS range would be 12.5kM

And whilst the use of Morse to transmit the calculated distance and direction might seem odd, the Morse audio was decodable by ear at 40kM with only 1.2mW power from the locator. That equates to a full power,100mW, line of sight range of 365kM.
srnet is online now Find More Posts by srnet
Reply With Quote
Old Sep 20, 2012, 09:55 AM
FPV in Hawaii
iskess's Avatar
United States, HI, Kailua
Joined Feb 2012
2,338 Posts
That's a huge success. Morse code is the way to go. I wish my FMKit could send Morse code, perhaps once every few minutes between normal beacon tones.
If you ever decide to make up a batch for sale, put me on the list.
iskess is offline Find More Posts by iskess
Reply With Quote
Old Sep 20, 2012, 11:30 AM
Stuart
srnet's Avatar
UK, Cardiff
Joined Dec 2008
3,289 Posts
Its unlikely I will make units for sale, there are really to many regulatory issues here in the EU, and the thought of having to use lead free solder - yuk.

To charge a reasonable rate for the hand assembly would make them too expensive, or at least more than most people are prepared to pay.

A kit is a possibility.

Or just sell the PCBs.
srnet is online now Find More Posts by srnet
Reply With Quote
Old Sep 20, 2012, 11:17 PM
FPV in Hawaii
iskess's Avatar
United States, HI, Kailua
Joined Feb 2012
2,338 Posts
Quote:
Originally Posted by srnet View Post
Its unlikely I will make units for sale, there are really to many regulatory issues here in the EU, and the thought of having to use lead free solder - yuk.

To charge a reasonable rate for the hand assembly would make them too expensive, or at least more than most people are prepared to pay.

A kit is a possibility.

Or just sell the PCBs.
I kit with video instructions would be great!
At least you could upload the board to A website like https://www.batchpcb.com/ and others can buy it right off the website.
I think you will sell many of them with the minimal effort of stuffing parts in baggies and mailing them out. There is a lot of demand beyond RC models.
Keep me posted, it sounds like a fun project.
iskess is offline Find More Posts by iskess
Reply With Quote
Old Sep 21, 2012, 10:20 AM
Stuart
srnet's Avatar
UK, Cardiff
Joined Dec 2008
3,289 Posts
Quote:
Originally Posted by iskess View Post
Morse code is the way to go. I wish my FMKit could send Morse code, perhaps once every few minutes between normal beacon tones
Does the FMkit have a GPS function then ?
srnet is online now Find More Posts by srnet
Reply With Quote
Old Sep 21, 2012, 12:46 PM
FPV in Hawaii
iskess's Avatar
United States, HI, Kailua
Joined Feb 2012
2,338 Posts
Yes, it has a place to connect a gps, and the software to support data transmission, but there aren't any instructions on how to hook it up. I believe you need a screen to decode and display the data. Look at FMKits thread where he shows photos of the set up, and discusses its function.
iskess is offline Find More Posts by iskess
Reply With Quote
Old Sep 21, 2012, 02:02 PM
Stuart
srnet's Avatar
UK, Cardiff
Joined Dec 2008
3,289 Posts
I had a look, but did not find the GPS instructions.

For those that want auto (machine) decode of the Morse, connect the audio output from the UHF transceiver to the soundcard of a PC\laptop and use FLDIGI software (free) to decode the Morse. Alternatively build a standalone tone decoder which will output the decoded Morse to a serial LCD display, I published plans for this on the PICAXE forum.

Machine decode is not as good as decoding by ear, you 'only' get about twice the distance as the data telemetry.
srnet is online now Find More Posts by srnet
Reply With Quote
Old Oct 09, 2012, 08:40 AM
Registered User
seojeff's Avatar
United States, GA, Atlanta
Joined Aug 2011
562 Posts
Scratch that, my account is active - I was waiting for them to email me, I guess you're just supposed to keep trying....

srnet: I'd really like to build this but picaxe hasn't approved my membership and I signed up days ago. Any chance you could also post the files here?

Thanks!

Quote:
Originally Posted by srnet View Post
I had a look, but did not find the GPS instructions.

For those that want auto (machine) decode of the Morse, connect the audio output from the UHF transceiver to the soundcard of a PC\laptop and use FLDIGI software (free) to decode the Morse. Alternatively build a standalone tone decoder which will output the decoded Morse to a serial LCD display, I published plans for this on the PICAXE forum.

Machine decode is not as good as decoding by ear, you 'only' get about twice the distance as the data telemetry.
seojeff is online now Find More Posts by seojeff
RCG Plus Member
Last edited by seojeff; Oct 09, 2012 at 08:44 AM. Reason: facts changed
Reply With Quote
Old Oct 12, 2012, 03:40 AM
Stuart
srnet's Avatar
UK, Cardiff
Joined Dec 2008
3,289 Posts
Some info for Morse skeptics;

As part of the project for the satellite version of this beacon I had tested the line of sight range of the data telemetry between distant hilltops, the 100mW that the RFM22 can transmit was enough for reliable reception of packets at 40km.

At the time I made some recordings of the Morse audio also produced by the beacon, and have just been evaluating the results.

The recording of the beacon transmission, 40kM away was made with a FT60 with a 1/4 whip, with at each successive loop of the beacon software the power reducing. This made it easy to work out the limits of reception. The attached ZIP file contains a MP3 recording of the distant beacon at 12.5mW, 6.25mW, 3.2mW and 1.6mW. The last is very feint.

The FLDIGI software (free) running on a low spec PC Netbook will decode the 15WPM Morse down to 3.2mW, and 60WPM down to 6.25mW, which in approximate terms gives the faster Morse data a distance advantage of 4 times that of the RFM22 data telemetry, if Morse and data were running at the same power.

This should equate to a LOS distance for the fast Morse of circa 160kM at the full 100mW.

I have since been experimenting with running the Morse at 120WPM for the satellite version, and it seems to perform much the same as 60WPM, a slight degradation is noticed at 150WPM.

At 120WPM, the distance and direction is sent in 1.5sec, Latitude and Longtitude in 3.5secs.
srnet is online now Find More Posts by srnet
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Spektrum RSSI and improved data log Mikael Pedersen DIY Electronics 34 Oct 03, 2014 04:36 PM
New Product FY91Q with GPS Position Hold-Telemetry,Firmware and Configuration Software feiyudz Multirotor Talk 2029 Jul 14, 2014 04:45 PM
Sold L/new DX 8 tx with 8000 rx/remote/telemetry ronwc Aircraft - General - Radio Equipment (FS/W) 0 Jun 26, 2012 10:20 AM
Sold Hitec Basic Telemetry System with GPS burtgree Aircraft - General - Radio Equipment (FS/W) 1 Jun 25, 2012 05:12 PM
Discussion Any tricks to improve GPS satillite reception? rc_ron FPV Talk 0 Nov 14, 2009 03:35 AM