Re: Not LF: Opera via QO-100

[Markus Vester <markusvester@aol.com>]

Here's spectrogram of differential Doppler between the two 2.4 GHz uplinks, scaled to cover 16.5 hours (8:30 yesterday to 1 UT this morning). A 0.1 Hz wide diurnal variation is clearly visible, presumably caused by inclination and ellipticity of the orbit, and possibly also tidal effects from the moon.

Best 73,
Markus

-----Ursprüngliche Mitteilung-----
Von: Markus Vester <markusvester@aol.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Sa, 9. Mrz 2019 13:28
Betreff: Re: Not LF: Opera via QO-100

Hi Luis, all,

I made some tests regarding the usability of QO-100 for very narrowband modes. Over the web-sdr, we can normally stay only within a few Hz, and my own receiver using an unstabilized crystal PLL-LNC is drifting over many kHz. However it seems possible to achieve almost perfect stability using a pilot carrier, e.g. the bottom CW beacon as a reference. During the last couple of hours, I sent a Rubidium derived carrier on 2400.0512 MHz, and observed the 1.2 kHz beat frequency using SDRsharp in AM mode and SpecLab at 5.7 mHz resolution:  

http://df6nm.bplaced.net/VHF/QO100/eshail_beacon_AM_190309_1222.png

We find some remaining instability on the order of 10 mHz or so, i.e. only about 4e-12 of 2.4 GHz. This may be due to transmit frequency variations either from my Rubidium (10 MHz LPRO), or perhaps the beacon itself (presumably a GPS-DO). Another source could be differential Doppler from lateral satellite movement between the two uplink sites (Doha, Nuernberg), although I would expect that to occur predominantly over 12 h and 24 h periods. 

Note that when trying to use the BATC web-sdr in AM mode for this purpose, I noticed much larger variations, which are caused by automatic samplerate adaptations following buffer fill states.

So as a bottom line, it looks like Es'hail 2 is indeed usable for narrowband visual and digital modes, although coherent PSK (EbNaut) would probably still be limited to relatively fast transmissions. 

BTW the browsable folder http://df6nm.bplaced.net/VHF/QO100/ also contains some more pictures from my lash-up GHz hardware.

Best 73,
Markus

-----Ursprüngliche Mitteilung-----
Von: VIGILANT Luis Fernández <luis@vigilant.es>
An: rsgb_lf_group@blacksheep.org <rsgb_lf_group@blacksheep.org>
Verschickt: Do, 7. Mrz 2019 12:59
Betreff: RE: Not LF: Opera via QO-100

Keeping off topic  ;-)

 

I’m also making QRP tests over QO-100

Currently using 150mW to a biquad linearly polarized antenna. Apparently Hpol works better than Vpol for unknow reasons

I’m getting decodes in Opera but the WebSDR is not good enough for weak signals

 

There is still room for decreasing power. And using an omnidirectial RHCP antenna like cuadrifiliar helix would be also much better

 

I’m thinking about EbNaut over QO-100. An ADF4351 PLL can be used to generate the signal directly from GPSDO reference

The Rx chain may be a problem. The downconverters in the chain may introduce phase changes. But there are I/Q downconverters

to get the signal directly at baseband using just one LO

 

Any ideas ?

This may be little bit more focused on topic. Would be amazing to transfer a message trought the sat using minimal power and

small omni antennas

 

 

73 de Luis

EA5DOM

 

De: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] En nombre de mal hamilton
Enviado el: jueves, 07 de marzo de 2019 12:22
Para: rsgb_lf_group@blacksheep.org
Asunto: Re: Not LF: Opera via QO-100

 

Hi David

That is what I am doing the PLL LNB is manageable without modification for cw and ssb and most of my equipment is left on 24/7 so no warm up problems.

I do have a high spec  satellite RX with selectable digital or analogue reception plus various outputs, IF, BASEBAND etc. also manual frequency and parameter settings. This could be an alternative method of reception and maybe more stable than the more common LNB/DONGLE method and avoids a T bias module

73 de mal/g3kev

 

 

 

 

From: David Bowman

Sent: Wednesday, March 06, 2019 5:18 PM

To: rsgb_lf_group@blacksheep.org

Subject: Re: Not LF: Opera via QO-10

 

Hi Mal

 

Most of the LNBs designed for HD TV have a PLL for low phase noise. These have 'acceptable' drift for CW and SSB QSOs......Just let them warm up for 10mins before you use them.  (or fit a TCXO instead of the 27 / 25MHz crystal)

No set top box required.  Just small dish + LNB into a dongle.   Trying to get an output directly at 70cms is a bit hit and miss as you are well below the lower 750MHz limit of the LNB.

 

73

 

David

 

On Wed, Mar 6, 2019 at 1:56 PM mal hamilton <g3kevmal@talktalk.net> wrote:

Marku

There must be a way to modify a satellite RX to receive the AO 100. The SAT BOX would have AFC built in to avoid LNB drift in normal use.

One method would be to set up the RX box to analogue reception and tune across the base band, another to tap off the IF 480 Mhz and tune across the IF with a 70cms amateur RX or SDR dongle and computer

Maybe someone has tried a similar method

73 de mal/g3kevr

 

Fn rom: Markus Vester

Sent: Sunday, March 03, 2019 4:51 PM

To: rsgb_lf_group@blacksheep.org

Subject: Re: Not LF: Opera via QO-100

 

Hi Mal,

my 2.4 GHz TX is fairly improvised and may not be easy to reproduce... I've extracted the LO from an old Sat-TV receiver, followed by a small Minicircuit amplifier and a 60 cm dish indoors. The PLL consists of the 1/64 prescaler output fed to a CD4030 XOR phase comparator, along with a 18.75082 MHz Rubidium-controlled reference.

There are surely much better ways to generate a decent 13 cm signal. PA1SDB mentioned that he uses an Adalm-Pluto SDR from Analog Devices.

You might be able to pick us up on the web-sdr, using 10489603.5 kHz USB dial, and Opera SW set to Op-05 speed by selecting e.g. the 1296 MHz band. Yes we could try a crossband contact, but not today. To count as a valid QSO, we'd probably also need to set up our own receivers, both for 10.5 GHz and 472 kHz.

Best 73,
Markus
 


-----Ursprüngliche Mitteilung-----
Von: mal hamilton <g3kevmal@talktalk.net>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: So, 3. Mrz 2019 16:24
Betreff: Re: Not LF: Opera via QO-100

Markus

How about a XBAND qso AO100/MF on CW

You TX via satellite to me and I tx on 472.5 Khz CW

73 de mal/g3kev

 

 

From: Markus Vester

Sent: Sunday, March 03, 2019 1:44 PM

To: rsgb_lf_group@blacksheep.org

Cc: pa1sdb@amsat.org

Subject: Not LF: Opera via QO-100

 

Listening to the below-mentioned Goonhilly web-sdr, I noticed an interrupted carrier on 10489.605 MHz, which turned out to be 10 mW Opera-2 and Opera-05 transmissions from PA1SDB. Peter has been well known in the LF group for running a VLF-Grabber in Appingedam.

During the last week, I had managed to built a rudimentary but stable 2.4 GHz CW transmitter, allowing me to add in another Opera signal on Es'hail-2. Anyone else to join in?

Best 73,
Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: VIGILANT Luis Fernández <luis@vigilant.es>
An: rsgb_lf_group@blacksheep.org <rsgb_lf_group@blacksheep.org>
Verschickt: So, 17. Feb. 2019 22:21
Betreff: LF: MF/LF chat over QA-100 Geostationary Satellite ?

Hi All

 

May be someone has the equipment and is in the footprint of Es'Hail-2, formely AMSAT QA-100 satellite?

Nice place for chats working as an HF band permanently open and with outstanding sensibility

 

Anybody (appart from David, G0MRF) interested in joining an MF/LF/VLF chat ?

 

You need just an SSB rig at 144 or 432, an upconverter to 2.4GHz and a WiFi PA and antenna and you are in

For Rx you can even use the WebSDR at Goonhilly

https://eshail.batc.org.uk/nb/

 

Unfortunately the footprint of the satellite do not cover America (only the extreme East of Brazil)

nor Australia (reaching up to thailand). But sites like Reunion are in the footprint

 

73 de Luis

EA5DOM

eshail_beacon_AM_190309_0830-190310_0100_small.png
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