DVB-S signals via UC-SDR dongles ?

[mr.sneezy]

A two part question for the experts.

I have an old pay TV dish, matching LNB, and mounting laying around. Is it possible to use a UC-SDR dongle and SDR# or HDSDR to detect DVB-S satellite signals (if I feed the LNB power via a DC blocker) ?

The idea would be to see if the dongle can be used like a 'satellite finder' box for pointing it, using the spectrum display amplitude.

Part two.

If it is possible to use a DVB-T UC-SDR dongle (an R820T chip type in my case) to receive free-to-air DVB-S signals like above, is there any technical reason that the signals could not be decoded to video by something like SDR# or HDSDR in the distant future ?

Martin

[Paul Warren]

In my part of the world, most satellites are on either the Ku,
12-20GHz or Ka, 24.5-40GHz bands, well outside the range these dongles
can tune. Wikipedia says that there are some DVB-S transmissions on
the 1.2GHz amateur band, which could potentially be tuned, but in
addition, the bandwidth for DVB-S is 6MHz, while the dongles can only
do ~3MHz in IQ mode. So, you could use it as a satellite locater if
your satellite is transmitting low enough!

So, unlikely

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Paul Warren
p dot a dot warren at gmail dot com
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[Adam Nielsen]

> In my part of the world, most satellites are on either the Ku,
> 12-20GHz or Ka, 24.5-40GHz bands, well outside the range these dongles
> can tune.

The purpose of the LNB is to downconvert these frequency blocks into a
much lower range, but I'm not sure what the standard range is. Can you
find out from your LNB's datasheet? If it will downconvert below 2GHz
then you may be able to use the DVB dongle as a satellite finder.

I don't know whether DVB-S is close enough to DVB-T, but in theory if
your LNB downconverted the signals to the same frequency range used by
DVB-T, you might be able to use the non-SDR part of the USB dongle to
receive and decode the signal.

Cheers,
Adam.

[Paulino Kenji Sato]

Hi,

On Tue, Oct 16, 2012 at 8:34 AM, mr.sneezy <mr.s...@bigpond.com> wrote:
> A two part question for the experts.
> I have an old pay TV dish, matching LNB, and mounting laying around. Is it
> possible to use a UC-SDR dongle and SDR# or HDSDR to detect DVB-S satellite
> signals (if I feed the LNB power via a DC blocker) ?
> The idea would be to see if the dongle can be used like a 'satellite finder'
> box for pointing it, using the spectrum display amplitude.

One way to figure out, is it trying.
With some precautions to don't blow up the dongle. Like extra ESD diode.
If I remember, LNB down converter the down link frequency (ku band) to
L Band (1GHz to 2GHz).
However, R820T officially can tune only to 1GHz. I don't know upper
side practical limit. Lower limit is around 25MHz.
E4000 can tune above 2GHz.

> Part two.
> If it is possible to use a DVB-T UC-SDR dongle (an R820T chip type in my
> case) to receive free-to-air DVB-S signals like above, is there any
> technical reason that the signals could not be decoded to video by something
> like SDR# or HDSDR in the distant future ?
>

This dongle is designed to receive digital TV broadcast, modulated in
COFDM. And use a internal demodulator to recover digital stream.
Documentation of RTL2832U don't mention DVB-S.
Some Linux driver support DVB-T and DVB-C,
And RTL can decode ISDB-T 1seg to.


--
Paulino

[mr.sneezy]

The LNB's I have receive in the range (roughly) 11Ghz to 13Ghz. The down conversion frequency I think ranges from 1000MHz to 2000Mhz depending on which satellite your pointing at and which of the two LNB's I use. 

If DVB-S is 6Mhz wide then it may be hard to see it on the spectrum display. 

Yes, I guess I'll know if it works when I try it eventually :)

Martin

[Doug Reed]

Hi Martin.

Most modern satellite LNBs (Low Noise Block converters) have outputs in
the 950-1450MHz range. It varies a bit, but in that range is where you'd
look. If you do a bit of research you can probably find out what voltage
range your LNB requires and its output frequency based on the equipment
it was originally used with. Most LNBs use input voltage to select
antenna polarization and this control is provided by the original receiver.

As was mentioned, the DVB-S signal is 6MHz wide. I doubt you could
decode it with the bandwidth you can get from the DVB-T dongle. But I
seem to recall seeing DVB-S decoder boards for PC's starting around $30
on Ebay. You also would have trouble because in order to receive DVB-T
video, the dongle does some of the decoding in hardware. When we use
RTL-SDR drivers, we are bypassing the hardware inside the chip and
getting the raw data. My guess is that may be one reason that we seem to
be unable to achieve the full specified 3Mhz digitizing rate from the
chip's spec sheet.

An additional problem you haven't mentioned is the LNB itself. The Dish
Network and Direct TV satellites over the US use circular polarization,
the other services, including FTA (Free-To-Air) satellite signals, use
linear polarization. There are not many LNBs available that will receive
both types of signals.

If all you want to do is use the dongle to replace a $20 Sat-Finder,
then yes, you should be able to do it by simply looking at the waterfall
signal levels around 1000MHz as you adjust the antenna.

If you are thinking of decoding the actual satellite TV signals, you
haven't mentioned that most satellite video is from Pay-TV services and
is encrypted. So even if you have the correct LNB and have a DVB-S
receiver, the video is still digitally encrypted and you will not be
able to watch it. The exception is the FTA services which are broadcast
"in the clear" and some uplink remote video feeds.

For much more detail on the subject, you should search "FTA free to air
satellite" and all the associated web sites and wikis.

Good luck with your project.

Doug Reed, N0NAS.

"mr.sneezy" <mr.s...@bigpond.com> Oct 16 04:34AM -0700 wrote:
> DVB-S signals via UC-SDR dongles ?

[mr.sneezy]

Thanks Doug a most excellent reply. I understand the technical issues much better for it. 

I'll certainly research the satellites that I may be able to get here in Australia. I understand there are some FTA sat's covering us and Asia as well. I think both LNB's I have are linear polarised. 

It will be a week or so before I get time to cobble together a setup to try, I'll report back when I know the result. 

Thanks,

Martin

[Paul Warren]

On Wed, Oct 17, 2012 at 9:47 AM, Adam Nielsen <a.ni...@shikadi.net> wrote:
>> In my part of the world, most satellites are on either the Ku,
>> 12-20GHz or Ka, 24.5-40GHz bands, well outside the range these dongles
>> can tune.
>
>
> The purpose of the LNB is to downconvert these frequency blocks into a much
> lower range, but I'm not sure what the standard range is. Can you find out
> from your LNB's datasheet? If it will downconvert below 2GHz then you may
> be able to use the DVB dongle as a satellite finder.

Ah right, I didin't know that! Learn something new every day :) I'll
have to see what the one on my foxtel dish does, It's apparently a
10.7 LNB, I'm imagining that's 10.7GHz LO?

Cheers