Next Generation PI4 beacons

[Trevor Smithers]

Is there any possibility of adding PI4 beacon monitoring to Spark ?

The ability to continuously monitor PI4 beacons for propagation research would be outstanding. Existing software PI4-RX and MSHV already have this mode but require multiple instances to cover different frequencies.

Information here

OZ2M - Next Generation Beacons - PI4 (rudius.net)

All sorts of source code here

OZ2M - Next Generation Beacons - Software (rudius.net)

The developer OZ2M also seems keen to help with integration into other software.

Trevor  G0KTN

[ahop...@googlemail.com]

Hi Trevor,

that looks very interesting, I shall sift though it over the next few days and see how easy it is.

73 Alan M0NNB 

[Trevor Smithers]

Hi Alan,

Any further thoughts on this ?

73 Trevor G0KTN

[ahop...@googlemail.com]

Hi Trevor,

I read all the links you sent and have started to try and modify my wspr decoder to see if it can decode these signals, early days but I it looks possible.

73 Alan

[PE3ES / F4VTQ]

I just contacted Bo and got this in response, maybe helpful:

Hi Erwin

There may be several ways to skin this cat.

- I send the source code for PI-RX
- do as Christo, LZ2HV, and modify the JT4 decoder from WSJT-X
- swing around the WSPR decoder from WSJT-X with K=40

I cannot say which approach is the easiest and/or best. However, my gut
feeling is in reverse order of the above. WSPR is a K=1 mode and the
decoder in WSJT-X is not very robust compared to the JT4 decoder in
WSJT-X and the PI4 decoder in PI-RX.

One more thing PI4 does not have a 1:1 relationship between timing and
FFT size, this is not a problem when K=40.

Time = 2000/12000 s

FFT BW = 12000/2048 Hz

where as

WSPR: 8192/12000 and 12000/8192

JT4: 2520/11025 and 11025/2520

Bo

Op woensdag 22 juni 2022 om 20:16:28 UTC+2 schreef ahop...@googlemail.com:

[ahop...@googlemail.com]

Hi Erwin, Bo and Trevor,

thanks for that.  I have to be careful with licensing issues as Spark is not GPL code so I can't use code from WSJTX and I don't even look at it.  The source for PI-RX would be interesting if it does not have license issues.

An alternative is to use an external decoder the same way Spark uses the jt9.exe from wsjtx.  Maybe a command line version of PI-RX could be made.

The Internal (level 0) wspr decoder in spark is a 'clean room' implementation optimised for low cpu rather than maximum decode but tweaking it would be fun.

73 Alan M0NNB

[ahop...@googlemail.com]

Hi all,

just wondered if anyone had or could point me to some recorded PI4 signals to help develop a decoder.

73 Alan M0NNB

[ahop...@googlemail.com]

Hi all,

in trying to get some real PI4 signals I've been running an orion board on 6m with spark into PI-RX and been watching on psk reporter and have noticed that PI4 spots are few and far between vs FT8 6m. I can see there is real value in beacons as they are just there 24/7 but the lack of reporting is a problem, the spark view of doing lots at once may be valuable here. So I'm keen to hear ideas as to how best to make good use of the world of beacon transmissions.

73 Alan M0NNB

[Trevor Smithers]

Alan

There is a sample sound file right at the bottom of this page if its of any help

OZ2M - Next Generation Beacons - PI4 (rudius.net)

Trevor  G0KTN

[ahop...@googlemail.com]

Trevor,

thanks for that, I contacted Bo and he kindly sent me a collection of recordings.

73 Alan M0NNB

[ahop...@googlemail.com]

Hi Trevor,

I'm close to having something ready to test, what OS do you run on?

73 Alan M0NNB

On Tuesday, June 28, 2022 at 7:08:44 PM UTC+1 tsmi...@cix.co.uk wrote:

[Trevor Smithers]

Hi Alan

That's good news - I'm on Win 10/64

Trevor  G0KTN

[ahop...@googlemail.com]

Hi Trevor and PI4 fans,

there is a test version here https://www.sparksdr.com/download/SparkSDR.2.0.20.win64.zip that has a PI4 mode, it is receive only and simply lists beacons heard, they are not uploaded anywhere.

To use, tune to 800Hz below the nominal beacon frequency.  Please let me know if it works and if there are any false decodes, once I'm confident in it I'll add spot uploading.

73 Alan M0NNB

[Ronald Spiering]

Dear Alan,

Is it decoding only one frequency?

On 50MHz all beacons are within 30kHz

https://iaru-r1-c5-beacons.org/index.php/syncronised-beacon-project-sbp/

Regards, Ron 

Op maandag 25 juli 2022 om 18:08:43 UTC+3 schreef ahop...@googlemail.com:

[ahop...@googlemail.com]

Hi,

yep for now it just tries to decode one frequency per virtual receiver.  Once I'm happy that the decoder works I might make it search for more than one in the receiver bandwidth.  For now you just have to open multiple virtual receivers.

73 Alan M0NNB

[Ronald Spiering]

Ok thanks Alan i will open multiple ones but would be nice to receive multiple decodes in one slice.

Op dinsdag 26 juli 2022 om 12:28:54 UTC+3 schreef ahop...@googlemail.com:

[Ronald Spiering]

Alan, isn't it possible in a definitive version to tune 800Hz lower in background so that the beacon frequency is clear in psk reports? 

Regards,

Ron

Op dinsdag 26 juli 2022 om 16:27:04 UTC+3 schreef Ronald Spiering:

[Ronald Spiering]

I made all slices for SBP which have beacons 6 of them after switch of it dissapeared when I opened last session so it doesn't save PI4 receivers.

Op dinsdag 26 juli 2022 om 22:26:33 UTC+3 schreef Ronald Spiering:

[Ronald Spiering]

It seems it started up the older version how can I remove? It is not in the Windows apps list..

Op woensdag 27 juli 2022 om 01:06:20 UTC+3 schreef Ronald Spiering:

[ahop...@googlemail.com]

Hi Ron,

Spark simple runs from where ever you unzip the files to so you must be clicking on the old version or a shortcut to it. You can have many versions installed at once.

73 Alan

[Ronald Spiering]

Hi Alan, thanks i removed the old version.

I have runned for 24 hours on 50MHz on a 4 elements LFA quad from TA4 (KM66).

According PSK reporter:

FT-8 395 transmitters from 47 entities

FT-4 1 transmitter JT6M

WSPR 5 transmitters

Q65 no decodes

PI4 on all used 6 frequencies of SBP (synchronised beacon project) as well as OZ beacon.

Not one single decode while nearly all day there was Es.s

Is anyone receiving beacon with PI4?

Would be nice to have slices of MSK144 for meteor scatter as Perseids are coming and JT6M used for long distance propagation.

Regards,

Ron

Op woensdag 27 juli 2022 om 16:56:47 UTC+3 schreef ahop...@googlemail.com:

[ahop...@googlemail.com]

Hi Ron,

are you seeing any PI4 signals on the waterfall?  I have found testing a bit tricky as finding real on air signals seems rare here.  All my testing has been done by feeding recorded signals through my emulator.

[Trevor Smithers]

Headline: It works !!

RSPDuo, dipole antenna, 8m (40MHz)

I have been monitoring PI4 on 40.669.2 (S55ZMS/B) and 40.070.2 (OZ7IGY/B) using PI-RX, DigU and vac together with Spark 2.0.20.0 so as to compare the two decoders.

There was a big SpE opening to oz7igy/b yesterday (27th) which lasted well over an hour. All told I decoded 80 spots on both systems. In fact PI-RX decoded a few more spots but then it has the advantage of the built in decoder enhancements.

Spark PI4 decoder appears to reach its limit around -15 snr whereas PI-RX continues to decode down to around -20 snr.

Notes:

Time of decode shown as local instead of utc

Spot counter not shown

No snr value

73

Trevor  G0KTN 

[ahop...@googlemail.com]

Hi Trevor,

that is great news.  The decoder is a 'clean room' implementation so that is not a bad start. I can work on improving the sensitivity, I have a number of rather conservative checks in to reduce the chance of false decodes which may well be rejecting weaker signals.

I'll add the other features and pskreporter upload.

73 Alan M0NNB

[Ronald Spiering]

Hi Alan, 

I have not seen any trace myself but it monitors whole day.

Yesterday there was not much Es from here so also no decode.

I will try to add some more PI beacons on 1 hop from here.

PI-RX I have tested in the passed and was from what I remember also a far better decoder than the one in MSHV you should be able to decode -22 to -23 snr.

So it would be nice if you can improve the sensitivity.

FT-8 decodes here -26 very well but PI4 is a more robust system with doppler and fading etc. so better with Au, FAI and eTEP etc. 

Trevor can you add MSHV in your tests as well? 

I am interested in the results as I plan to place YM4SIX (50Mhz) and YM4VHF (144MHz) as a TEP beacon.

Regards,

Ron

Op donderdag 28 juli 2022 om 15:20:45 UTC+3 schreef ahop...@googlemail.com:

[Ronald Spiering]

Hi Alan,

I have entered now 16 virtual receivers for all PI4 beacons on 50MHz I could find on the internet.

I was surpriced that I didn't have decodes from IW9GDC/B beacon as we have open band to Sicily most of the days quite regurarely.

I checked the receiver and found many decodes the reason I thought it was no decoding is that the counter is not working it still gives 6 decodes.

What surprissed me is that IW9GDC/B who is transmitting on 50.006 was also decoded the same time on 50.005 probably your filter is to wide or maybe shifted 800Hz? Narowing the bandwidth is also giving better snr according docs it is 709,124Hz please solve this problem before activating the PSK reporter.

Regards

Op vrijdag 29 juli 2022 om 10:17:54 UTC+3 schreef Ronald Spiering:

[Ronald Spiering]

I had to remove virtual receivers as they only showed black screens probably more then my laptop can handle.

So i reduced to the active frequencies from the SBP and additonal SV and OZ beacons. 

Op vrijdag 29 juli 2022 om 14:02:15 UTC+3 schreef Ronald Spiering:

[Ronald Spiering]

Trevor how did you connect both PI-RX and Spark SDR at the same time via VAC?

Op vrijdag 29 juli 2022 om 15:16:59 UTC+3 schreef Ronald Spiering:

[Trevor Smithers]

Assuming you already have VAC (Virtual Audio Cable) installed and you are using a SDRPlay receiver then this is how I did it...

(1) Create a new virtual receiver with the mode set to DigiU

(2) In "Virtual Tranceiver Settings" look for Audio Output and Audio Input tabs and assign the same VAC cable in both boxes

(3) Look at the new virtual receiver you created in (1) above and set the same VAC cable in the Audio Output box.

(4) Open PI-RX and set the audio input to the same VAC cable. Use the volume control to adjust the input level

(5) Create a new virtual receiver with the mode set to PI4.

At this stage PI-RX and Spark should should both be operating on the same frequency looking for PI4 decodes

Hope this helps - it works for me

73 Trevor  G0KTN  

[Ronald Spiering]

Trevor,

Thanks for answer.

No i don't use SDRplay but use sparksdr directly without any VAC.

This consumes much less CPU power.

I will run it in another but it will be not real parallel then.

But I checked on FT-8 and get the same decodes when I use the same decoder.

Regards, Ron

Op vrijdag 29 juli 2022 om 19:44:47 UTC+3 schreef tsmi...@cix.co.uk:

[Ronald Spiering]

Alan,

I had 3 decodes from IW9GDC/B last night and they showed both up on 50.005 and 50.006 so it must be a bandwidth problem of the filtering.

As the SBP frequencies are 1KHz from each other it will cause the problem at any frequency when two or more frequncies are monitored.

see: https://iaru-r1-c5-beacons.org/index.php/syncronised-beacon-project-sbp/

Regards, Ron

Op zaterdag 30 juli 2022 om 08:09:29 UTC+3 schreef Ronald Spiering:

[Ronald Spiering]

Trevor btw I use a Red Pitaya...

Op zaterdag 30 juli 2022 om 08:16:53 UTC+3 schreef Ronald Spiering:

[Ronald Spiering]

I have intensively tested PI-RX and MSHV against Spark at the IW9 beacon today.

At the start when conditions where instable with a lot of fading Spark was even not able to decode at any values below +0.

No probs for MSHV as long as the signals where strong enough en all decoded with PI-RX every period.

When it got stronger and more stable sometimes up to +26 I turned my antenna sidewards to the beacon.

I did get many signals -19 to -20 and both PI-RX and Spark where decoding every period while MSHV received but only get ? as not fully decoded.

I will try to test again when signals have much fading.

The thing is that PI4 mode is especially designed to work with fading and doppler (Aurora) so I don't understand why Spark cannot handle.

I got all decodes both on the 50.005 and 50.006 slice so there is defintely a filtering problem.

As my intensiojn is to monitor eTEP then Spark is useless as it is now for me as it has both deep fading and doppler.  

Hopefully there is a sollution to get it working under these condition thanks for making it available anyway.

Maybe you can ask Bo about how it get more resistance against fading, doppler I didn't check as not available here.

Regards, Ron

Op zaterdag 30 juli 2022 om 08:18:34 UTC+3 schreef Ronald Spiering:

[Ronald Spiering]

I spend a lot of time on tests but it looks like "pooling on a death horse" we say in the Netherlands...

Op woensdag 3 augustus 2022 om 13:52:42 UTC+3 schreef Ronald Spiering:

[ahop...@googlemail.com]

Hi,

as I mentioned when releasing this, the decoder is a first cut prototype, the fact it detects anything is good!.  It has very conservative thresholds in to avoid misreporting and many opportunities for improvement.   I'm currently working on coping better with doppler shift, this is not something the mode is magically immune to, it requires effort in the decoder.  All this takes time.

73 Alan M0NNB 

[Ronald Spiering]

Hi Alan, great that you are working on the decoder.

And of course it is not a paid job...

I understand from Bo that the robustness against doppler and fading comes from the tone spacing.

There is a presentation of PI4 from Bo on Youtube https://www.youtube.com/watch?v=jFcCncceSN4

I look forward to test a new version however Es season is ending soon and I will have less possibility to test.

Regards,

Ron TA/PE2M

Op woensdag 10 augustus 2022 om 09:23:01 UTC+3 schreef ahop...@googlemail.com:

[Trevor Smithers]

Hi Alan
I'm still using 2.0.20.0 with the basic PI4 decoder - does the latest version contain any PI4 enhancements ?

The reason for asking is that the GB3SEV beacon on 144.4612 in IO82UI is now running PI4 and being around 110km from me is producing a strong PI4 signal.

I'm seeing strong tones in Spark but no decode. PI-RX is also running from Spark (Digi-u/VAC etc) and decodes every sequence.

It worked well earlier in the year so no idea why its decided to pack up now.

Trevor  G0KTN

[ahop...@googlemail.com]

Hi Trevor,

there was a very small tweek to the pi4 decoder between 2.0.20 and 2.0.33 but I doubt it will make much difference.  I have done some work to make it better but it is not ready to release yet.

73 Alan M0NNB

[Trevor Smithers]

Alan

You are about the same distance from GB3SEV (120km) as me so should get a hopefully reliable PI4 "on air" signal when you resume testing

73 Trevor G0KTN

[ahop...@googlemail.com]

Hi Trevor,

thanks for that, the reason you won't see decodes of GB3SEV is there is an internal list of known stations to reduce the odds of miss reporting and that call is not in it. I shall make the list editable.  Great to have a real signal to test on.

73 Alan M0NNB

[Trevor Smithers]

Hi Alan

Any progress on the PI4 front ?

73 Trevor G0KTN

[ahop...@googlemail.com]

Hi Trevor,

the version I just posted on the airspy hf thread has some small tweaks and the missing beacon added, it is very un tested though.

73 Alan M0NNB

[Ronald Spiering]

Hi Alan, how is this progressing?

1.) Is the filter adjusted to one channel already?

2.) I don't understand why statuions should be in a list to decode, so every new station will not be recognized, for example I want to test two new beacons how can I add, is there some config file where In can add?

PI4-RX doesn't need any call to decode, I understand that it is usefull when signals are low but now even with S9+ there is no decode for a new or testing station.

73 Ron

Op dinsdag 27 september 2022 om 16:48:24 UTC+3 schreef ahop...@googlemail.com:

[ahop...@googlemail.com]

Hi Ron,

the recent releases no longer use the list of known stations, this was an experiment that allowed very efficient (low cpu) decoding but I swapped it for a more conventional method with no list.

I'm pretty certain the filter was changed.

73 Alan M0NNB

[Ronald Spiering]

Hi Alan, that's great! I will test it as soon as the Es season at 6m starts.

At the moment only TEP AS, AF and SA have to see if any beacons there are using PI4.

Op zondag 19 maart 2023 om 11:50:31 UTC+3 schreef ahop...@googlemail.com: