Lost Model Locator - with long range capability

srnet

Senior Member
#1
This is my take on a lost model locator (LML).

Documents and plans will be found here;

https://www.dropbox.com/sh/ompujkefda543w6/NXgepgXrmW

There are two documents there; MK3 28X2 Lost Model Locator Information Draft V1_0 (explains how it works, is put together etc) MK3 28X2 Lost Model Locator Information Draft V1_0 (explains the range testing I have done)

It uses an RFM22B radio transceiver and in its basic form the LML acts as a simple UHF RF locator beacon. Gets power from the main RC supply and\or a backup Lipo battery. The Lipo charges from the main RC supply.

It will go into beacon (lost) mode on expiry of a timer, or when a RC servo pulses fail, go into fail-safe or hold mode.

Hear the tones on a radio, a cheap hand-held UHF FM one will do, and go search for your model.

Add a GPS, and the LML will transmit its location as RFM22 data packets on a regular basis. There are a range of other options for receiving the location, some with very long range reception.

There are two versions of the LML, one small one using SMT components, and a larger on using easier to assemble wired components. Both the small and large LML can be used as a transmitter or receiver for the data packets. The large LML can be fitted with an Openlog logger which will log the data packets to a micro SD card for reading on a PC.

One of the pictures is of the large LML being used with an attached LCD display to receive data packets, showing you where the model is. The display has the location, altitude, speed, track, how far away and in what direction the model is. For a model in flight and at altitude, expect a range of tens of km using simple antennas.

There is the option of sending the location information as fast (120WPM) Morse, just hook the audio from the UHF radio up to a PC and decode with free PC software designed for Hams. Should have a range of about 3 times that of the data packets.

The distance and direction information can be also be transmitted as a few digits of slow FM Morse which you can listen for on the UHF radio. If you cant read Morse numbers yourself, record the audio and send it to someone who can, or give them a ring on the phone and let them listen.

The slow FM Morse will give you the information to locate the lost model, and will be heard at a distance that is more than 10 times greater than the RFM22 data packets will manage.

If you have the necessary receiving equipment the LML can transmit the GPS co-ordinates as FSK RTTY data at 200 baud. That should get you about 20 times further than the data packets and give a position read out on a PC display. Expected line of sight range should be more than 1000kM for this mode.

As a last resort the LML can be set-up to transmit the distance and direction as slow FSK Morse, that should have a range of around 45 times that of the data packets, say in excess of 2000kM LOS, satellite to ground for instance.

The LML uses a PICAXE 28X2 and PICAXE basic, so the software can easily be customised.

I had considered selling them, but fear the certification costs to manufacture and sell such a radio device would be considerable.

Maybe a kit ?

Parts cost, around £22, plus LCD, plus GPS.

Anyway I have a few PCBs available, which can be supplied to PICAXE forum members for the cost of the postage.
 

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srnet

Senior Member
#2
Packet Relay

As you may realise height makes a big difference to UHF reception, the higher you can get the RX the better, but there may not be a handy hill overlooking the search area where the lost model is.

One of the LMLs can be used as a relay, put it in a model fly it to altitude, it will listen for the data packets from the lost model and re-transmit to a receiver where your flying from.

To test this, I put the 'lost' model in stuck in tree mode (up a pole in my garden) and went 6km away to the other side of a hill. I could hear the data packets but only at S0 on my UHF HT, you need about S4 for packet reception.

So I attached an LML to a kite, and flew it up a couple of hundred feet. The LML on the kite easily picked up the packets form the lost model and relayed them down to a receiver, so I could see the GPS location of the model.

The Kite was from SOTAbeams in the UK, was stable in flight and lifted the large LML and 4 x AA batteries with ease.
 

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#3
Need Hepl

Hello...could you please forward me your e-mail address..I urgently would like to talk to you about a GPS/UHF module I need for wildlife monitoring. TKS My e_mail is
edited
 
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srnet

Senior Member
#4
Hello...could you please forward me your e-mail address..I urgently would like to talk to you about a GPS/UHF module I need for wildlife monitoring. TKS My e_mail is
edited

Sorry, I am cautious about giving out my email address.

Feel free to ask questions in here, or send a PM.
 
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#5
Sorry, I am cautious about giving out my email address.

Feel free to ask questions in here, or send a PM.

Hello...I have tried to send you a mail but it says your box is full...I have a Wildlife Sanctuay in South Africa and my Sanctuary web is www.ishonalanga.co.za
Please have a look and you can verify who I am . I really would like to talk to you ...about my work in conservation and saving Rhinos..but I believe this is not the forum to do that in.Other than that I do not know how to contact you. Kind Regards Victor Hugo
 

srnet

Senior Member
#8
LED1 has its anode near the edge of the PCB, LED2 is the other way around.

However, its easy enough to check; from the circuit diagram, the anode pad (for both LEDs) will be the one connected to one end of the respective current limit resistor, you can check this with a continuity tester.

I usually just hold them in place temporaily, to see if they light up when the board is powered up.

Then solder in place when I have confirmed its the right way around and also is actually working.
 
#9
As I thought Thanks
LED1 has its anode near the edge of the PCB, LED2 is the other way around.

However, its easy enough to check; from the circuit diagram, the anode pad (for both LEDs) will be the one connected to one end of the respective current limit resistor, you can check this with a continuity tester.

I usually just hold them in place temporaily, to see if they light up when the board is powered up.

Then solder in place when I have confirmed its the right way around and also is actually working.
 
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