DStar - how strong of a signal needed for decode?

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I have had quite a few DStar QSO's on 2 semi local Dayton,OH DStar repeaters that are about 18 miles away.  It seems to work real well.  I can also see a 3rd DStar repeater in Dayton on the Panadapter but it does not decode well.  It's signal strength is just below an S-8.  The two other DStar repeaters I can copy well and get into are S-9+10db.  I use a 10 element yagi.  My transverter is an Elecraft XV-144 that works very well on CW, SSB, and FM.

I can rotate my yagi away from the 2 DStar repeaters I decode real well AND when their signals drop under S-9 they start cutting in and out.

I also tried a simplex QSO on 2 meters DStar and while I could see the other stations signal (S-7) I did NOT get any decode at all.  He, however was able to decode me with his DStar rig 100% solid even though he said the signal was only S-5 or so.  We also simultaneously talked on 220 FM repeater between us.

Of course, S units on one radio and another are not a great indicator of much depending on the radio calibration, etc.  There was NOT a huge power differential between us though.

So ... my Question for you other folks who are using DStar via the 6300 (and especially anyone who has a dedicated DStar rig also) is - How strong of a signal does it require to decode it?  Is the DStar waveform + Dongle perform as well on RX as a dedicated DStar transceiver?

---Gary WB8ROL
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Gary L. Robinson

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Posted 2 years ago

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Kent Hufford

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I have been on DSTAR since 2009. I have ICOM 51, 5100, 2820. And DSTAR HF 7100 and 9100.

I have a FLEX6500. I have been on DSTAR HF for about 4 years. On DSTAR HF with the FLEX since it came out. IMOHO, at least on DSTAR HF, the ICOMs decode a little bit better. But, I know FLEX is working hard on improvements to the software to make decode the best.

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Gary L. Robinson

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Thanks Kent.  I am not too worried.  I have been a "Flexer" for over 5 years now and know they will do their best.  I also just wondered just how strong a signal has to be for a decent decode.  I know the FreeDV takes a respectable signal to get a good decode on HF.

Thanks again!

---Gary WB8ROL
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Michael Coslo

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DStar, being digital, tends to be an all or nothing signal. So S-8 sounds about right. Noise becomes extra bits. I do know on our local repeater net (W3YA) which covers a big swath of Pennylvania and iwoth polling repeaters set up in various places - probably half of the checkins would disappear if we went D-Star just from the signal levels. 

And there's the rub. I'm all about commercial high power digital. But for Amateurs who are often trying to dig signals out of the mud, digital isn't quite all that. Maybe some day we can figure out a way to bridge the digital cliff, I hope. Just not at the moment.
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EA4GLI - 8P9EH - Salvador

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I had my first HF DSTAR contact 2 days ago and the s8 is the right threshold at the moment. Anything below s8 will not get decoded.

I totally agree with your comment Michael. When I first installed FreeDV I was excited to be able to get to talk to people far away, with low signals and still be able to copy them. Then the reality of the technology became patent to me... only high signals will get through, everything below a 6 or 5 signal is impossible to hear. DStar seems about the same.
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Lawrence Gray

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I have a 6500 and the dongle.  On D-Star HF, I find that the ICOM radios decode at lower signal strengths than the Flex with the dongle.   Similarly, on FreeDV, I find that the FreeDV software decodes weaker signals than the Flex.  There have been similar comments from other Flex users.

Also, the newer FreeDV modes that the Flex doesn't currently support allow better decoding of weak signals.