HF Digital Error correcting? Also, what's up with PSK31?

Discussion in 'General Technical Questions and Answers' started by N0NS, Oct 9, 2008.

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  1. N0NS

    N0NS Ham Member QRZ Page

    Are there any digital HF modes that provide error correcting, can be decoded by a standard piece of software (e.g. DigiPan, DM780, etc.) and are “free”?

    Last night I had a QSO using PSK31 and the band conditions were fairly up and down. I lost some of the information from the other station and thought that it would be great to switch from PSK31 to some mode that had error correction. I then realized that I could not switch to a mode in DM780 that provided any error correction. So, does an error correction mode exist?

    Also, I’m relatively new to the digital modes after taking an extensive leave from amateur radio. Why is everyone so enamored with PSK31? On DM780, there are quite a few other modes and I rarely see anything other then PSK31. What’s the deal?

    Thanks for your input! Joe N0NS
     
  2. KR2D

    KR2D Ham Member QRZ Page

    Switching from BPSK to QPSK might be helpful. I don't think it has real error correction, but it can be more robust.

    Olivia has forward error correction, and it works very well. I've seen Olivia continue to work when the signal fades to humanly undetectable - can't hear it, and can't see it on the waterfall, but it keeps chugging along. However, switching modes mid-QSO can be a problem. PSK31 is the narrowest mode commonly used. The most common bandwidth for Olivia is 500 Hz, if you switch to that in the middle of the PSK31 segment, you will make a lot of people angry.
     
  3. K0RGR

    K0RGR Premium Subscriber QRZ Page

    Yes, there's a new mode out there that uses PSK modulation, but does TOR-like error correction. Unfortunately, I've lost it's name. Perhaps one of our anti-WINLINK brethren can enlighten us as this has been developed as an alternative to WINLINK.
     
  4. N2RJ

    N2RJ Ham Member QRZ Page

    WinMOR???

    The message you have entered is too short. Please lengthen your message to at least 10 characters.
     
  5. W9MAV

    W9MAV Ham Member QRZ Page

    Do not even mention winlink that makes me want to throw up!:mad::mad:

    The lids in amateur radio are on Winlink.
     
  6. AB8ZL

    AB8ZL Ham Member QRZ Page

    AMTOR ( a form of RTTY) is error correcting.

    I don’t think DM780 supports it but TrueTTY does.
     
  7. N4CR

    N4CR Ham Member QRZ Page

    PSK31 is easy to use and tune and it sends about as fast as a good typist can type. You can fit 20 or more signals into a 3khz segment. Olivia is built into DM-780 and provides Forward Error Correction. You can fit 2-4 of them in a 3khz segment and the text comes across much more slowly. But it's really good at getting the information across. Vastly better than PSK-31.
     
  8. W8JI

    W8JI Ham Member QRZ Page


    I'm not.

    I know it for what it is. A slow-speed very poor dynamic range system without error correction.

    I consider it a very poor system used by people who take pride in being weak and who want and often demand everyone else to be weak too.

    73 Tom
     
  9. AG3Y

    AG3Y Guest

    I don't know if that is totally true, Tom. I had a PSK 31 QSO with a friend of mine in Alabama today. His tones were hardly audible, but the copy was easily 95% .

    There are several FEC modes that you can use now days. MFSK, and Olivia come immediately to mind. Several of them have different baud rates by incorporating different numbers of tone streams so they will either crawl or dash, depending of course, on the band conditions you try to use them under.

    Don't forget that Amtor and Packtor have both FEC and ARQ modes, and by using ARQ, copy will either be 100% or nothing!

    There is a program out there called FLARQ that when used with a companion program called VBDigi, will turn PSK 31-250, MSK and standard RTTY ( baudot ) into an ARQ protocol. I haven't experimented very much with it yet, but it does look promising!
     
  10. K2WH

    K2WH Premium Subscriber QRZ Page

    I use PSK from time to time and always use a scope to monitor the output wave form to be sure it is perfect. However, the enamoration of 31 is also a puzzle to me. I have tried in the past to encourage PSK62 and 125 but not much response. I have also used Hell, MFSK16 and all the other numbers RTTY, SSTV, Throb and all the others but the one that won the popularity contest was PSK31 and I find it very boring but it is just about the only one used with RTTY close behind. RTTY is fun.

    Anyway, if you are losing data using PSK31, it simply means THE SIGNAL IS TOO WEAK!

    K2WH
     
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