Just cut a 2-minute explainer video for SOTAmat since all my other instructional videos are far too long for those who don’t know why they should care. I had a lot of fun playing with video effects, can you tell?
73 de AB6D
so I need some guitar music to play into my radio on 14074. how does that work again?
just kidding about the music but seriously, I don’t know which receiving stations will get anything I send there, are they everywhere, who are these mysterious people or robots?
73 Andrew vk1da/2da
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@VK1DA SOTAmat was designed to use the already existing network of PSK Reporter monitoring skimmers. Any receiving station skimmer that forwards Callsigns + Suffixes to PSKreporter will work.
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For FT8, only monitoring stations that extract callsigns+suffixes from an FT8 Free Text message work. Currently that is:
- SparkSDR based skimmers (about 90 worldwide).
- CWSL_DIGI skimmers can also do it, but the code has a bug so SOTAmat ignores those spots (the author is working on a fix) (about 28 worldwide).
- There is a developer’s build for OpenWebRX that also does it, but that community has not granted his pull request yet (so 1 out of 353 skimmers worldwide).
- Joe Taylor considered adding it to WSJT-X skimmers but has given it a low priority compared to other feature requests (25,247 skimmers).
In practice FT8 travels 2000 to 4000KM from QRP. Most users who repeat the transmission 4 times are heard by at least 2 SparkSDR skimmers, and often many more (I was heard by 10 skimmers in my last activation).
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For PSK31 most skimmers report callsigns+suffixs to PSKreporter and work. There just aren’t many of these skimmers left. The USA West Coast only has 1 regular PSK31 skimmer on some bands.
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CW skimmers do NOT work since the author of the most popular CW skimmer software did not understand the difference between callsign suffix “locators” vs. “indicators”. His code only allows “locators” and changes/eats “indicators”.
If you want to understand the technical and legal foundations, there is a long 1 hour video that covers those topics and is listed on the web site.
73 de AB6D
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Thanks, yes I read your earlier post about using the free text message of the FT8 protocol. I don’t know of anyone using this in VK, but I wondered whether there are sufficient PSK reporter nodes in this part of the world.
I’m fortunate to almost never find myself really out of reach of the standard methods (cellphone, satphone, RBN for CW), but I do see the inherent power of your system. Well thought out and I hope it works well for those that need it.
73 Andrew VK1DA/VK2DA
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Hi Andrew,
It would be really interesting to know how well it works in your area!
I successfully spotted from 15 summits in Europe (Switzerland, Germany, France and Spain) using just my smartphone and the microphone of my HF SSB transceiver. It’s my ongoing experiment to test the reliability of the system. Sometimes, even a DX-skimmer receives my FT8 message.
Using a satphone with a valid subscription or CW (or APRS texting) can be another reliable way to spot off-grid, but not everybody has these tools available.
73 Stephan
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Works just fine here in VE6 where we have a fair number of places that are not only cell phone dead zones but also lack digipeater coverage to self-spot the APRS way. Did a self-spot the other day using the 20m FT8 frequency, on an antenna that was resonant on 17 and it worked the first time anyway, even though I was running limited power and there are a relatively few skimmers that digest the SOTAMat tx in the right way. I also tested the one-way email and one-way text functions from home (still using the portable rig) at 5W and both worked first time. I’m impressed so far …
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The app is brilliant! Just what the doctor ordered for remote summits where there is no option to self spot. Works flawlessly and the video tutorials are very well done.
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I’ve used sotamat a few times now from summits, and have found it really useful. I find the best results are to be had on the 20 meter band, 14074 kHz, and setting the smartphone speaker loud enough, but not too loud, and close enough to the TRX mic - it’s important to shield the mic from any wind noise.
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I’ve just set SOTAmat up and tried it from my home QTH and managed to post a POTA spot - which I quickly edited to say it was a test and to be ignored. It took a few minutes to appear on the POTA page after transmission but I will certainly give it a try from a SOTA summit soon. I used 20m and after trying 14.074 without success I switched to 14.0735 which I think was the one which got through. I suspect like when using WSJT-X you have to choose a free frequency for best results which will be trial and error when you can’t see a waterfall.
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Looks good! For anyone wanting to explore, the website is here: https://sotamat.com
One question from me - Do you need an account for each call sign you use, or can one account be linked to multiple call signs? I am thinking in particular of the regional designators used in UK call signs.
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Finally set myself down to work out why I was going wrong. As expected my fault and now all sorted. Text rx’d and I put a spot on for a local hill. Apologies for any confusion with it I couldn’t delete or edit it. Good job, I now have one hill in particular that I’m going to use it on.
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@MW7PAJ You do not need a separate account for all the different UK callsigns you use. When you define your SOTA Regions and/or POTA Locations, there is a field called “Posting Call (optional)”. If you leave that field blank then your Callsign (your SOTAmat username) will be used to post the spot. If you supply a non-empty “Posting Call (optional)” value for a given SOTA Region then that callsign will be used when posting from any summit within that particular region. A similar concept exists for POTA too.
73 de AB6D
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@2M0OSB Note that the UK has new anti-spam regulations on SMS text messages such that I think they will stop allowing SOTAmat to send SMS replies to the UK. The USA also has new regulations. Most of these new regulations are aimed at companies using SMS for marketing. They don’t handle hobbyist situations well. Sigh.
AB6D
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@M0WIV Normally you should use 14.074 for FT8 / SOTAmat. That’s where most skimmers are listening. It takes about 5 minutes from sending until it will get spotted because of the way the PSK Reporter monitoring stations queue reception reports for 5 minutes until they relay to the central server where SOTAmat gets them. You should transmit multiple times (3 or 4) as interference or QSB, etc. may prevent some of them from getting through. SOTAmat will automatically shift the transmit audio frequency by 51 Hz with each transmission, so even if one of them was interfered with, the next one will be on a different frequency (FT8 uses a 50 Hz bandwidth).
73 de AB6D
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Up until using SOTAMAT I’ve never used any digital mode. Last night was my first success. When sat on one of the FT8 freqs do you have to wait on a gap and tx or will the skimmer extract your data from multi transmissions? Last night I waited for a few seconds gap and went for it.
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FT8 works in 15 second slots and the device sending needs to have a clock synchronised to within a second or so of the correct time. By convention, in Europe we transmit on the second time slot, starting at 15 seconds past the minute then again at 45 seconds. Listening is done at the 00 and 30 time slots. From my short trial of SOTAmat it transmits on all the slots so it doesn’t matter when you start you should cover at least two slots where skimmers might be listening if you let it transmit four times. You might have noticed when you set it to send it didn’t start immediately but waits until the start of the next time slot.
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Ahhhh that’s why it did that. Thank you
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Brian, thank you, I didn’t realise it was clever enough to shift the frequency - that’s very neat. Thank you also for the explanation about the delay in reporting. I suppose there can also be a delay in reporting when PSK Reporter gets overloaded. This used to be quite bad, I’ve seen a message saying reports were delayed 15 minutes due to the volume of traffic. However, it seems much better recently, perhaps they have upgraded the site?
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This might explain the problem I have.
I’ve just set up SOTAmat and was giving it a test. Email spotting worked fine but SMS is not - on the EE network the message seems to send but no spot appears, on Vodafone I get an “error 28” saying it’s not able to send the message.
I’ll test it out over FT8 when I can get up on a summit, but looks really useful so thanks for the effort.
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I placed my very first SOTA spot with SOTAmat today. I have used FT8 on 20 meters, audio coupling (= no cable between mobile fone and radio), KX2, worked on first try in the field!
I did have cell coverage as a back-up, but good to know that there is an alternative! I wish I had known on my 3-week section hike of the AT earlier this year. SOTAmat would have given me a few more successfull activations when I had no cell service.
Thanks Brian!
73 Heinz
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