Sat meter with API (realtime serial comms)..??

P

profqwerty1

Member
My Satellite Setup
Tooway viasat, 75cm dish.
My Location
Bristol, UK
Hi Guys,

I'm new to the forums, but been playing with satellite systems for a while - used to have a D2MAC, and 36VDC motorised dish.

We're working on a project to build an automatic dish positioning system, for rapid deployment of our Tooway satellite internet system. Everything's going swimmingly, but currently the satellite strength + S/N ratio is determined by query-ing the viasat modem's setup pages - ie it's a bit hacky. If the box were to have its firmware changed, or we change the system, then our current approach is invalid.

So I put it to the forums, is there a satellite meter out there, in the <£400 range (preferably lower!) that can output current signal strength, S/N ratio, and a positive satellite ID, all via a serial connection (USB or RS232)?? All of them have a nice screen and USB for updating, but there's no real information about serial communication capabilities...

Ideally LNB loop through would be used to power it, and so it can be left connected permanently.

Many thanks!
 
Hi,

On the lower price segment, the Dr. HD900S will, depending on which firmware is used, output on the RS232 the signal strength (only) continually.

On the higher price range, meters like the Spaun Sparos 609 (OEM model of Sefram), can output the data you want through ethernet, but the protocol is proprietary (I couldn't figure it out).

If Signal Quality is enough, you might want to consider the KWS AMA 214S (second hand on ebay, ranges vary from 150 to 250 Euro). Check my website and blog as I did implement something similar (see my signature for links or search "vma satellite" on Google). This is an analogue meter!

Another option would be grabbing the screen of the meter. The Dr. HD900S will output the screen on the composite video port and you can grab it with a cheap frame grabber. Search Google for an article of mine on TELE-satellite, regarding waterfall diagrams.

Please note that meter's are not build to be permanently turned on. Expect problems with battery, continuous charging, heat (specially low spec meters like the Dr.HD900S get really hot), burning the screen on meters with CRT, etc.

If you know how to program, take a look at modern DVB-S2 cards. Tools like CrazyScan show what is possible (even real time constellation diagrams). I think that this would be your best bet. Solid programming capabilities are needed, though, as you won't find that much documentation.

Hope this helped.

Cheers,
vma
 
vma said:
Hi,If you know how to program, take a look at modern DVB-S2 cards. Tools like CrazyScan show what is possible (even real time constellation diagrams). I think that this would be your best bet. Solid programming capabilities are needed, though, as you won't find that much documentation.

Hope this helped.

Cheers,
vma
Click to expand...

Yes, Crazyscan results display in a constellation monitor , but it's building a continuous dot sequence over time, not real time as in a standalone analyser, so it's difficult to see the actual spot sequence in the display at any given moment. However, it can invoke the stream to, say, TSReader, where you can view the signal quality/strength, PID bit rates etc. on one of several charts in real time.
 
Hi,

The constellation diagram is by nature displayed over time!

It shows the demodulation of bits in respect to their quadrants. It must be measured over a period, otherwise you would miss erroneous bits.

Regards,
Vitor
 
Hmm this is trickier than I thought. We can program but not immense at it; we're actually trying to load the whole thing onto an Arduino so ideally it needs to be as simple as possible, just sending some serial commands and getting a nice value back - like AT commands! The DVB-S2 option is not something I thought of before - it looks possible but unknown whether we could API into one.

I was looking at something like the Horizon Nanosat, but from what you've said that seems totally not suited.

I'm wondering if there's a hacky way to do this - like monitoring a cheap meter's audio out tone, or reading LED outputs - but this won't get the NIT positive ID function.

Is there a meter, do people know, where one can tell it what satellite you want and it only bleeps/lights up when you've hit that particular satellite? Or a different way to differentiate between satellites? The only ones we really care about are the current high capacity internet sats in Europe, and any that might come online in the future.

Many thanks for responses so far!
 
Or am I completely missing how these work?

Am I right in thinking that there's an ID signal in the sat beam which I assume the NIT picks up; the cheaper ones look at the signal parameters I have loaded into the device (freq, etc) and 'match' these to a prestored satellite ID.

If the latter is correct, then could I make do with a cheaper one and hack it into searching for the signal I want, then it will only bleep/light up when it hits that particular satellite, ignoring others? We're happy to do a couple of weeks of pulling it apart and fiddling with it (I mean, it may get to the point of using transistors to 'push' buttons).
 
Hi,

Basic stuff:

1) To know what satellite you are pointing at: this is normally called the NIT function. Once the signal locks into a transponder, it will read out the NIT (Network Information Table), which normaly contains the Satellite name, also. The NIT is broadcasted with most transponders, but requires a locked signal.

You could tell what satellite you are locked on, by the frequency of the transponders. Many satellites have one or another unique frequency, which allows a good guess at what the satellite is.

2) Signal: on analog transponders you typically measure the signal voltage, while the signal power is measured on digital transponders. The cheap meters do not give you adequate MER or C/N readings.

If I remember it correctly, the Dr.HD900S has one firmware (guess it was one of the 2.xx) that will output BER continously on the RS-232 port. You *could* get an idea of the alignment based on this value. BER is the Bit Error Rate. It does require a locked signal, otherwise you get basically an infinite value.

The meter's I know cannot be controlled remotely. Such functionality is only available in broadcast-style equipment and is even more expensive.

Also, bear in mind that solutions with satellite meters will fail after a power failure: someone will have to turn them on again and set the required measuring mode.

As I said, the best implementation would be using a PC with a DVB-S2 card, but I just remembered that you could easily use a Linux satellite receiver like the Dreambox, VU+, Clarktech or AZBox. Enigma and Enigma2 are fairly documented for developers and you do get access to all you need. Major advantage: you could even use the receiver to control the motorized dish. Because you aparently don't need accurate readings (otherwise you wouldn't be considering low spec meters), you might as well get such a receiver and with it you probably won't need an arduino at all - just do everything on the receiver!

Cheers,
vma
 
Hi VMA,

Many thanks for your knowledge, it's being very much appreciated! I don't want to jump into this without doing work myself also, good knowledge is key!

The dish is actually controllable on Azimuth and Elevation axes, mechanically accurate to <0.05deg each. Currently, we look at the numerical values returned from the viasat modem on its setup pages and these are accurate enough to get a signal strength reading when getting close to the satellite (KA SAT 9deg east), then use the S/N value to find peak signal. Initial finding of the beam is by manual adjustment or (hopefully) electronic GPS / compass (under development). I don't think that sat broadcasts any video feeds, but the transponders would still be readable for ID? Argh this is confusing!

Those linux boxes do look useful though, but will they work with Ka band? I can't find info on that?

I'm going to try out the 'fastsatfinder' software (although just seen this only supports Ku band), we could run it on a mini pc with a USB DVB-S2 adapter.

How do things like the Nanosat work??

The remote control is another issue - the system will by its design be powered on and off many times, so it needs to be autonomously controlled - at present we just send web commands similar that a browser would when under user control.

Many thanks for your help!
 
profqwerty1 said:
The dish is actually controllable on Azimuth and Elevation axes, mechanically accurate to <0.05deg each. Currently, we look at the numerical values returned from the viasat modem on its setup pages and these are accurate enough to get a signal strength reading when getting close to the satellite (KA SAT 9deg east), then use the S/N value to find peak signal. Initial finding of the beam is by manual adjustment or (hopefully) electronic GPS / compass (under development). I don't think that sat broadcasts any video feeds, but the transponders would still be readable for ID? Argh this is confusing!
Click to expand...

Now transmitting Saorsat in MPEG-4 _http://www.lyngsat.com/eka.html
 
profqwerty1 said:
Is there a meter, do people know, where one can tell it what satellite you want and it only bleeps/lights up when you've hit that particular satellite? Or a different way to differentiate between satellites? The only ones we really care about are the current high capacity internet sats in Europe, and any that might come online in the future.
Click to expand...

Whilst it is not a meter, the Dutch manufactured Astra2Connect kit for Internet over satellite comes with an audible tone meter, powered by the LNB power supply, for setting up of the dish. I would assume it is tuned to the fixed frequency on Astra 1 used by the incoming datastream.

_http://www.hertzinger.nl/upload/Astra2Connect/downloads/Sat3Play_P&P_R1.6_v1.0_English.pdf - Page 33 onwards

You could adapt it to your service, or construct something similar.
 
@rolfw: I believe that this transmission is only available in Ireland due to the very small spot beams used. The exact same frequencies are used for different transmissions in other regions. Spot beams in Ka-band can be as narrow as 300km! The satellite has a wide array of transmitters.

@profqwerty1: All common LNB's (Ka-LNB's included) down convert signals to 950-2150 MHz (or 950-1450 MHz). Receivers can thus handle all kinds of LNB's. This is not 100% true, as DirecTV in the US uses some custom LNB's with integrated switches/unicable functions that require compatible receiver or additional converters like the BBC - "B-band converter.

If the receiver's software doesn't directly support Ka-LNB's, you will have to do some maths to calculate the correct frequencies when tuning transponders manually.

Cheap meters like the Nanosat basically consist of a tuner and a microcontroller. Most work is done by the tuner anyway: it receives commands from the microcontroller to tune the desired transponder and provide basic information about the reception quality. Naturally the tuner also provides the demodulated transponder stream, but most very cheap meters don't use that, or just filter out the NIT information.

In fact there is even a DIY satellite spectrum analyzer based on an analog tuner and a Siemens mobile phone display: _http://www.juras-projects.org/eng/satfinder.php

Perhaps you just hire Juras... lol

The truth is that the tuner he used is almost impossible to find - I considered building the device myself but gave up due to not being able to find the tuner. And for what you want to do, it is CHEAPER and EASIER to just build your solution on top of an Enigma2 Linux receiver.

Cheers,
vma
 
Wow this is definitely something of a black art! If the box loops through the RX from LNB, will the modem have any issues? This means I can leave the dreambox on/connected permanently.

Back on topic: I'm looking at something like a Dream or VU+ box, then I can access its linux image via telnet through its ethernet port. I had a look but can't find any patches that might let me read out the required data ... unless it's already supported by the basic firmware? Is there an accessible list of valid serial commands for these boxes? Most of the patching literature seems to revolve around getting free tv.
 
You would have to program somthing on your own. You can as it is fully remote control the box through its webinterface (just open the IP of the box in Mozilla Firefox). You can access all functions by this means, as a virtual remote can be popped up and you can update the OSD and even the image on the webpage. As far as I know, there is however no direct way of just getting tuning information as numeric values.

There is a plugin called "satfinder" (or somthing similar). I guess you could look at the source code and modify it to send the values through RS232, RJ45 or even as a simple textfile, which you access by FTP. Naturally you do need some programming experience, but that applies to arduino development as well.

I am very fond of my new AZBox ME and guess what: a quick search on the Google revealed this: _http://code.google.com/p/azbox-enigma2-project/source/browse/trunk/lib/python/Plugins/SystemPlugins/Satfinder?r=11

Here is part of the code:

Code: 
def retune(self, configElement):
returnvalue = (0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
satpos = int(self.tuning_sat.value)
if self.tuning_type.value == "manual_transponder":
if self.scan_sat.system.value == eDVBFrontendParametersSatellite.System_DVB_S2:
fec = self.scan_sat.fec_s2.value
else:
fec = self.scan_sat.fec.value
returnvalue = (
self.scan_sat.frequency.value,
self.scan_sat.symbolrate.value,
self.scan_sat.polarization.value,
fec,
self.scan_sat.inversion.value,
satpos,
self.scan_sat.system.value,
self.scan_sat.modulation.value,
self.scan_sat.rolloff.value,
self.scan_sat.pilot.value)
self.tune(returnvalue)
elif self.tuning_type.value == "predefined_transponder":
tps = nimmanager.getTransponders(satpos)
l = len(tps)
if l > self.tuning_transponder.index:
transponder = tps[self.tuning_transponder.index]
returnvalue = (transponder[1] / 1000, transponder[2] / 1000,
transponder[3], transponder[4], 2, satpos, transponder[5], transponder[6], transponder[8], transponder[9])
self.tune(returnvalue)

Seems doable...

Cheers,
vma
 
Nice! OK this is starting to look plausible yeah. I think that level of programming is fine, I will check with the group experts! Thanks very much VMA :-worship

We will be getting onto it this week / early next week, so I will try and keep this thread updated about how it goes!

Muchos Gracias :)
 
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