Posts by SQ6QV

    Happy to see any discussion in this topic.
    I've got one of these for testing - this is DVB-S2 IP router. Only problem it works with 900Mhz IF minimum.
    It has linux onboard. Hacking into was needed because it doesn't have "factory reset" button.
    https://www.ebay.com/itm/Inter…-DVB-S2-DV3-/254219286566

    Our main problem is that now DATV is very complicated for "normal" hams. And with IP we will complicate this even further.
    What we need IP for ?
    We will build normal IP network and what ?
    I thought about sending internet in emergency situations. We could easily build 2Mb link...

    No "experimenting wednesdays" :(
    Experimenters were meeting on wednesdays evenings...

    And those guidelines just get weird and weirder.

    Transmission Power All uplink transmissions should use the minimum power possible. QPSK transmissions should have a downlink signal with at least 1 dB lower power density than the Beacon – the web-based spectrum monitor enables users to set their uplink power to achieve this. Transmissions with symbol rates of less than 333 kS using 8PSK, 16 APSK or 32 APSK should use the minimum power density required to achieve successful reception.

    So sending 1MS 8PSK 3db higher than beacon it's perfectly OK now!
    Not QPSK, not 333k or less.


    Transmission Modes
    Transmissions should use DVB-S2 where possible. For normal standard definition transmissions, 1500 kS is the maximum symbol rate that should routinely be used.

    OK, so now there are no restrictions...we all use HIGH definition or even ULTRA high definition.
    https://en.wikipedia.org/wiki/High-definition_video..
    Oh....and there is no 1.5MS slot in the bandplan!

    ------
    When I look on a transponder now (after 2 years) I see narrow spikes all over the transponder transmitting test screens. It was WIDEband transponder before...personally I would prohibit anything less than <250kS (except wednesdays :) )

    Bandplan that prohibited narrow modes in 2M slot was much better. When there was many 333kS signals they used it in a right way - from right to left..and collegues with wider switched to narrow...and now You see one transmitting shitty 5W 16APSK signal undecodable with 90cm...just in center of transponder...and that's OK?

    Now it's friday evening and there are only 3 signals...where's everybody?

    "Due to the very large number of potential users, "

    Like 215 users now...last year 1 march was 160.
    Nothing changed...we've got bored.


    You could always use any SSB channel in NB and ask to receive You with NB websdr (If You just like to talk) almost all of us have internet all the time, and can do this without any problem.
    But if You like to do standard QSO, low SR only-audio channel is best option.
    Many of us do not have mixed setups that can do WB and NB simultaneously.

    Our standard receiver is Minitiouner.

    On Wednesdays (UTC time), experimenters are encouraged to try other modes – perhaps 6 MS using the whole transponder for brief (less than 10 minute) periods. It is essential that users announce their plans on the chat room page, and always monitor it.

    That's almost like You would mention me. Thank You :)


    My only comment, there should be an easily editable page (like wiki) on WB monitor (<div> periodic grabbing from wiki?) where we can announce our next activities. Many like to see 6M test for example, but it requires that for this 5 minutes everybody stop TX. There is no problem doing that at 2 a.m. but also there is no point to do that in that time.
    It would be better to just inform others, that everyone can enjoy this 5 minutes without delays for contacting "that last one not reading chat frequently".


    Also really valuable content like Renny PE1ASH videos should be aired within schedule.


    I understand a liitle "how it's made" because of my many failed attemts to build something.
    I've got spectrum analyzer from the begining...and seeing DIY hamradio on spectrum analyzer is like seeing cheap fast food :D
    There is dirty everywhere, awfully dirty :D

    Still there is common that somone says "my switching power supply does not make noise at all"...
    He just didn't measured it...
    And those switching power supplies are powering our PAs and LNAs, gain blocks...and LDOs are not better.
    In my BladeRF I had oscillating (xtra low noise :D) LDO! It added +-250khz harmonics to signal output.
    And there comes phase noise..,Just count how many generators our signal "pass" from modulator to demodulator...

    But dirty signals on WB seems to be no problem to anyone...this is just "esthetics" problem I think.
    Some are more "pointy" and "eyes hurt" on them...but whats wrong if they are there just for our fun.

    Everything as Mike said....but...
    I've done a lot of experiments to have cleanest output possible and it is a problem more (&more) complicated than You might think.

    1st...Web monitor shows spectrum of your signal in Goonhilly, not power, not MER.
    To measure how good your MiniTiouner decodes your signal compared to power You need something to compare to.

    Only way (I think) is to transmit 1M or 2M signal and control its power to be exactly at same level as beacon and using same rolloff.
    then You have beacon MER for example 7.0db and Your signal MER 6.2 in my case.
    So my signal decodes 0.8db worse than beacon.

    I could write pages what I've tried to fix that gap and I still didn't discovered it yet. But I've made a progress.
    Mike's list is not complete.

    What I see on transponder most have problem with non linear amplifiers.

    Bitrate on QO-100 puts power over quality.
    QPSK and 8PSK works good with horribly overdriven amplifiers, and we (almost) all like to use more bitrate.
    Would You use Your amplifier at 20% of its maximum power capabilities?
    Or just solve 1db "signal quality problem" with that 6db more power available :D

    Second problem is modulator quality (SDR software & hardware). It is also not easy to make clean signal in digital domain, and as Mike said SDR hardware is not perfect (I think right words are "it is barely usable").


    Nice to hear any news in that matter!

    There is one feature that is easy to make, and we would be very happy about it - turning beacon off at 18:00 to 24:00 every day.

    Today I've sucessfully transmited 333K 32APSK signal which was received (only) by Renny PE1ASH with his 3m dish.

    I've done this test just to smile at:


    Users are encouraged to experiment with higher-order DVB-S2 modes at lower symbol rates (for example 333 KS 32APSK) to conserve bandwidth for other users.
    from: https://amsat-dl.org/en/p4-a-w…and-operating-guidelines/

    Power required for that signal was quite sick :) and reception on 0.9m dish was still impossible (mer 14 of mer 14.1 required).

    I think I'm the only one who achieved this "333K 32APSK" goal :)

    So please change guideliness: 32 APSK to 8PSK

    (as 333K 16APSK needs power comparable with 2M beacon)


    8PSK FEC 2/3 is really a maximum when there are so many stations that we care of bandwidth.
    -----
    Also It is worth to reconsider "overpower" message over 1M signals - making it absolute in scale (<7db) rather than relative to the beacon.

    I'm perhaps the only one who was decoded with 8PSK with this software (and it's no mystery why :D ).

    I've played with it some time and it works. I've used cheapest rtl-sdr.


    The problems are:

    1. With 2.4M sdr sample rate, only 1M or narrower signals are possible to decode.
    2. Locking is slow. We are used to MiniTiouners, and not patient.
    3. It needs much stronger signal.


    I've done some tests today and locking 8PSK needed D3 signal on MiniTiouner, and after lock it could go down to D1.

    It was 333K FEC 3/4 mer 12db+ signal


    It does not decode 16APSK, but I think technically it is possible, as two circles in constellation were visible.


    Screenshot by Rob PE1CME