LimeSDR / OsmoTRX for SAR application

It is end of summer so time for some more serious work, regarding the LimeSDR :blush:

Some community members already knows that my main goal in Lime
use is not HAM hobby, but project related with SAR Search And Rescue,
in case of people who needs assistance on wide forest or country side with
poor GSM coverage. Trick is to cheat lost GSM unit to start with some TX - after that,
principle of TDOA & FDOA & Multilateration (MLAT), should be used.
Time Difference of Arrival (TDOA) and Frequency Difference of Arrival (FDOA)
measurement combination for stationary “targets” obtained by sensors
mounted on mobile platforms, for example on a pair of helicopters or even ultralight planes
and in future possible UAV-s.

Starting from info here:
And here:

Reading that, cooperation level between Lime and OsmoTRX must be fair.
The only possible source of trouble may be Lime on-board clock source.
Therefore expecting external add on clock generator.

Like to hear members experience and estimation of feasibility of Lime / OsmoTRX
use with necessary SW & HW add on-s, like LNA, PA, external clock, 5 GHz high speed links
between two sensors and some missing measurement modules within OsmoTRX.
All comments and suggestions are more than welcome :wink:


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I am the only one crazy enough to try that with Lime :smiley:

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That would be a really great application. We (Fiarwaves) have built a PeopleFinder device specifically for SAR customers. We’ve discussed direction finding for it many times but we’ve never got to implement it.

PeopleFinder uses our industrial grade SDRs ( or instead of LimeSDR but the chips of those SDRs are Lime, so porting from one to another should not be hard.

A short intro and source code for the PeopleFinder:

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Thank you Alex,
Yesterday have filled up your survey (within crowd update) proposing similar SAR application.
Can be nice to cover SAR on all devices operating from 110 MHz up to 2 GHz
For example:
Aviation AM 121,5 beacon
HAM 145.500
Marine 156,8
Aviation AM 243 beacon
Crospas/SARsat 406 beacon
PMR 430
PMR 800-900
GSM 900
GSM 1800
So end product can be more than “peoplefinder”, it can be useful tool for
all in accordance ICAO Annex 12 SAR for aviation, marine and land use.


Yes, thank you for filing the survey - that’s exactly how I found this topic :slight_smile:
Once the direction finding part of the system is developed in general, I don’t see any issues with making it work with as many systems as needed.


Right, it is nice to know that you are prompt on survey :wink:
BTW at the moment I am using two sets consisting out of LimeSDR plus SDRPlay RSP1
plus some LNA, PA, antennas and BPFilters.

I am quite sure that you are more than able to do that alone, but on my side I have
some fix wing planes and helicopters with regulatory environment / ready to support
testing and possible use :slight_smile:

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Things like this raise the hope level in the world. Thanks.

Hello there,

I am also interested in direction finding.

I found an open-source device to measure DOA of sound waves using microphone array. Its algorithm is cross-correlation function, and its code is open source. So I am now trying to modify its code to use with LimeSDR.

But my current problem is I don’t know how to receive 2 channel data from LimeSDR in Octave (I have cross-correlation code in Octave already but only for simulation). Right now, I have found the example octave code to receive 1 channel data in Lime’s workshop.

By the way, I have ordered the 4x4 MIMO QPCIe, so once achieved to measure DOA with LimeSDR, I can try to use it with QPCIe for higher resolution.

have you achieved the goal???

If you asking me, been busy upgrading one plane glass cockpit
and waiting happy end here →

Great news, congrats to Lime team, thumb up. / must be for SAR too :wink: