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Automatic Link Establishment - MIL-STD-188-141a (ALE 2G) decoding extension

Hi John,

Lots of utility stations use ALE and plenty of folks on the UDXF forum spend hours monitoring frequencies in the hope of identifying nets which only sound once an hour (or longer).

A Kiwi running in 8ch mode would be ideal for ALE monitoring (Bonnie - HF LINK ?)

Any chance of incorporating an ALE decoder with time and frequency logging to file ?

Here are some links to source code that I found.

The 0.0.1 version of LinuxALE has only minimal features: it can decode ALE bursts from .wav files or sound card, write timestamp and simple text log, but nothing else. And it's still pretty hard to decode ALE without errors

Decoding block for GNU Radio

Maybe Chris has some ideas - I see he offers an iPhone app ?


Martin - G8JNJ


  • 2G ALE is still is use but is being replaced by 3G, 3G+WB (Harris Proprietary), and 4G (not yet totally defined)
  • There are thousands of 2G ALE signals on the air. ALE has become one of the most common signals on HF. It would be wonderful to have an ALE decoder for the kiwiSDR. I certainly would use it every day.
  • I tried to install the LinuxALE using normal compile of tarball at the download site. There are no ReadMeFirst instructions and no option to do a normal three ./configure, make, make install steps.
    The configure step is not there and somewhere in the process a folder does not get created as required and thus the the make and make install fail with multi errors. (OS is ubuntu studio 18.04 LTS). If anybody has had success installing this maybe you could describe the steps you took here. Thanks, 73 & Gud DX
  • I had a quick look and found the following.
    1) gcc -O2 -o main *.c should compile everything.
    2) sound samples are read from the soundcard and it does not seem to be foreseen to read wav files

    You can have a look at the gnuradio OOT gr-ale which is based on this code. However it does not look like it is actively maintained and it does not implement the complete specification.
  • edited January 2019
    WRT the popularity of 2G ALE... 1) US DOD no longer uses much of it 2) even when used it consists of a short period of signalling to set up a link and to terminate one. The actual communications can be plain SSB or many forms of data other than the waveform and protocols used to link/terminate.
  • It is OK by me as detecting links or sounding gives an indication of propagation which is why I am interested in this. PC-ALE or MARS-ALE are both available for more serious hobbyists related activities.
  • edited May 2021

    Just returning to this now 2 year old discussion. Comparing with MultiPSK I noted that the gnuradio OOT gr-ale module works quite well in single (and multi-channel channel) mode. Sensitivity for weak signals and decodes are almost similar.

    The gr-ale module evolved from LinuxALE and has much better symbol detection and shows BER and up to 6 characters of sending station id.

    I am wondering about whether there is a way to to port this ALE grc or its improvements back to Linux, Python or for instance java as a stand alone decoder. The idea of course is not having the need for a GNU radio installation in that case. I tried to contact the author but no response from him.

    The reason of asking this is that having a 2G ALE decoder as an extension might still be a useful addition to KiwiSDR, given the wide use on HF even nowadays. Another possibility is to use such a decoder as a back end of kiwirecorder.

    Best regards,


  • Update:

    4G spec has been out for awhile, and implementations exist.

    3G continues to supplant 2G although I suspect 2G will be around for awhile.

  • jksjks
    edited June 2021

    Can anyone tell me some particularly active HF ALE 2G frequencies?

    I've been using 2784 in the UK, catching XSS ground wave from Forest Moor. But there are only a few transmissions per hour which makes over-the-air debugging very annoying.

    The thousands of frequencies listed online don't particularly help (e.g. I need someone with real world experience.

    Thank you.

  • I can provide test signals to my kiwi if that will help

  • I ask because the following is from the built-in test signal. Over-the-air decoding doesn't work for reasons I don't understand.

  • edited June 2021

    when do you want to test? I can do it now

    obviously I need extension on my box

  • jksjks
    edited June 2021

    I have a few hours now. But after that I get on a plane and things will be disrupted for a day or two. I would need to install a new v1.460 image on your Kiwi (I can do that remotely over the net).

    I assume you have a simulator that would feed a low level sig into the Kiwi RF input?

  • edited June 2021

    No I have an actual ALE station with a 150W radio 100 miles form my kiwi (near Utica NY)

    It'll be a little bit before that is up and running ... want to lock it to a single freq and just run Sounds

    Source s Mil-compliant hardware based ALE system

    My 8075 box would be good to use

  • Should I go ahead and start installing s/w on your 8075 box? It always takes a while to build on a running system.

  • that would be fine

    its a BBAI box so a bit faster

  • Okay, will start that now..

  • Up and running.

  • 4416.9 kHz dial freq

    is my test freq

  • that will run periodlly

    LQA sounds

    I'll check as night goes on

  • Great! Thank you. My bug has to be really simple. I just can't seem to find it.

  • jksjks
    edited June 2021

    Well, that worked!

  • ALE TX via PRC-150C

  • jksjks
    edited June 2021

    I need to restart this Kiwi and check something.

  • And.. now it's not working. I'm beginning to suspect there is some initialization or buffer overrun problem. It's like the original open source code the SSTV extension is based on. I spent forever getting all the overruns out of that code before it would run without problems.

  • jksjks
    edited June 2021

    Worked once after a careful reset to a known state. The signal was also strong compared to the first successful decode which was very weak. So that rules out a level problem I think. So I need to go looking carefully at the code..

  • jksjks
    edited June 2021

    Fixed a bug causing it not to work when multiple channels were using the extension.

  • edited June 2021

    Morning report..... at 1010Z when the band opened on this NVIS path, it decoded a barely discernable Sound just fine

  • Have TX sounding every 5 minutes all morning and been decoding with BER as high as 20 (poor) or as low as 2 (VG) with no issues

  • edited June 2021

    Still running solid and at the same time, I'm learning a bit about my antenna systems and local NVIS condx.

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