ATV co-ordination on Es'hail-2

Latest News and Discussion about the use of the DATV transponder on Es'hail-2
Post Reply
g8gtz
Posts: 1105
Joined: Wed Apr 07, 2010 6:26 pm

ATV co-ordination on Es'hail-2

Post by g8gtz » Wed Feb 27, 2019 6:03 pm

AMSAT-DL has agreed to a proposal by BATC for the use of the bottom 100KHz of the wideband transponder (10491 - 10491.1 MHz) for ATV co-ordination purposes. This is on an experimental only basis and stations must keep their power levels to a minimum and certainly not exceed power levels greater than 15dB above the noise floor as shown on the Goonhilly spectrum monitor.

This is sanctioned on an experimental only basis and AMSAT-DL reserve the right to move the WB beacon towards the band edge or implement DVB-S with a wider rolloff which would render the frequencies unsuitable for this purpose.

So another challenge but should be manageable and prove a useful facility although we do see the chat being the major tool for reports and contacts.

73
Noel - G8GTZ

G4GUO
Posts: 609
Joined: Tue Feb 16, 2010 12:51 pm

Re: ATV co-ordination on Es'hail-2

Post by G4GUO » Wed Feb 27, 2019 9:45 pm

Just tried it, 15 dB above the noise floor is fairly noisey on NBFM but readable.

- Charles

User avatar
G4IUG
Posts: 25
Joined: Fri Nov 23, 2018 6:28 pm

Re: ATV co-ordination on Es'hail-2

Post by G4IUG » Wed Feb 27, 2019 10:57 pm

I thought FM was explicitly forbidden whatever ? Who makes the rules ? Who owns the transponder ? AM ? (more efficient than FM ?)

Personally 12.5Khz FM might be a good idea generally in the NB section, but I understand the issues here.

Dave
Ex G6ANG/T and G8EAO

g8gtz
Posts: 1105
Joined: Wed Apr 07, 2010 6:26 pm

Re: ATV co-ordination on Es'hail-2

Post by g8gtz » Thu Feb 28, 2019 8:55 am

Hi Dave,

Answers to your questions as follows:

If you read the statement it does not mention permitted or forbidden modes but we should use common sense.

AMSAT-DL

Es'hailsat.

This agreement applies to the WB transponder only and to ATV co-ordination only - it does not apply to the NB transponder or general communications.

Sometimes it is better to accept things (gifthorses) at face value and not ask too many questions - and perhaps not make too much noise about it, incase others spoil it for us....

73
Noel - G8GTZ

g0mjw
Posts: 765
Joined: Sat Sep 20, 2014 9:15 am

Re: ATV co-ordination on Es'hail-2

Post by g0mjw » Thu Feb 28, 2019 10:44 am

There is a case for SSB though as we could get more channels in. 15 dB above the transponder noise floor implies we can see it. That depends on the dish.

Meanwhile, as the sun passes behind the satellite and all line up, it's raining and the sun is nowhere to be seen.

Mike

G8GKQ
Site Admin
Posts: 1174
Joined: Sun Mar 22, 2009 1:21 pm

Re: ATV co-ordination on Es'hail-2

Post by G8GKQ » Thu Feb 28, 2019 10:56 am

Mike

The text is carefully agreed: "15dB above the noise floor as shown on the Goonhilly spectrum monitor".

Various modes were considered, but the aim is to make this a minimum equipment, minimum impact, usable talkback facility alongside DATV taking into account the effect of frequency drift etc. It will should enable more reactive experimentation and testing with DATV modes, as has already been happening using the text talkback.

Dave

YL3AKC
Posts: 16
Joined: Wed Aug 08, 2018 8:42 am

Re: ATV co-ordination on Es'hail-2

Post by YL3AKC » Thu Feb 28, 2019 1:25 pm

Hello!

Topic title set to: "ATV co-ordination on Es'hail-2"

Let's talk about coordination in general.

There should be system where TXers send TX parameters:
Requred parameters:
*) callsing
*) frequency
*) symbol rate
*) format: DVB-S; DVB-S2, DVB-T etc
*) encoding: MPEG2;MPEG4(H.264);H265 etc
Optional parametrs:
*) Locator
*) TX power in Wats
*) TX antenna size/gain
*) Scheduled start and end of TX

An RXers (listeners) Report following to system:
Required parameters:
*) Callsign
*) MER
Optional parameters:
*) Locator
*) Signal level (absolute or relative to beacon?)
*) RX antenna size

I see this "system" digital and internet based (something like chat).
But this chat is special and build with functionality what can be used for automatic or semiautomatic use by software. For example every user have program or web page who can assist in process. Program automatically can set Minitiouner parametrs, write into logbook etc.

And now regarding voice channel.
This is good idea. Thanks to AMSAT-DL to allow more experiments including voice on WB transponder. But it doesn't mean we need to setup and use it immediately. Better to think and use efficiency than just simply use something.

For voice channel there is no "history". You can not "scroll back" and see what happened if you missed something in voice channel.
Many RXers start to asp for parameters and TXer need to replay parameters many times.

Regarding modulation.
SSB:
Pros:
*) narrow band
*) low power
Cons:
*) voice quality
FM:
Pros:
*)voice quality
Cons:
*) higher power
*) wider band

You really need to set goals and only then make decision regarding modulation. I vote for FM, because we need reliable voice contacts (in broadcast it is called "back channel") and not experiments with SSB or low power.

My Conclusions:
*) TX and RX information (including parameters) can be in chat.
*) Chat should be upgraded with one more "window"
*) When patrician send "Nickname StationTechInfo: some data" then data goes to second window and automation software can parse it to setup minitiouner software, log QSO etc.
*) When patrician send "Nickname whatever text goes there" then data goes to regular chat window.
*) System (server) keeps all TX and RX evens in some kind of online logbook database.

g0mjw
Posts: 765
Joined: Sat Sep 20, 2014 9:15 am

Re: ATV co-ordination on Es'hail-2

Post by g0mjw » Thu Feb 28, 2019 2:32 pm

A problem - Portsdown does not do FM. Express I think can. I don't want to be swapping transmitters back and forth. Can the Portsdown be made to do FM, e.g with the Lime or creative modulation of the LO?

Mike

YL3AKC
Posts: 16
Joined: Wed Aug 08, 2018 8:42 am

Re: ATV co-ordination on Es'hail-2

Post by YL3AKC » Thu Feb 28, 2019 3:42 pm

It is hard but possible with LimeSDR, Pluto or hackRF. Most complex part is to program more advanced libdvbmod library or something like this. Maybe some kind of mix between libdvbmod and rpitx libraries. When library will be modified that it is not important on what modulation to add for tx voice channel, because it is software and could be added both modulations.

Post Reply

Return to “Es’hail-2 - DATV Transponder”