SDR C/Ku Sniffing?

arlo

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Dec 4, 2016
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Wondering if there's any interest in sniffing the IF bandwidth on satellites for signals that can be decoded using an SDR?
How about tappng into the coax to keep from feeding 13/18 V into the radio?
Just wondering because on sat charts I see some channels showing data or data dl which I would think means data download?
What about aero signals?
Ideas?
 
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arlo

Thread Starter
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Dec 4, 2016
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So to screw around what sort of a splitter or tap would I use that would give LNB power but either block dc to the sdr or provide a tap for a dc block to the antenna input? Adapters from F to sma are no problem here. Not even really worried about an impedance mismatch to get my feet wet.
 

Comptech

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I use rg6 solid copper quad shield on everything. DC blocks are cheap for cable type installs. a short pigtail from F to SMA is cheap and takes the strain off the sma connector.
 

Comptech

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I guess a simple CATV slitter with a DC block on it would work. But ou would loode half your signal. I use a 4x8 multi switch here that solves that problem.
 

Comptech

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On a side note, I tie rapped a old NMO mount to the LNB of my 10 foot perferated unimesh, pointed the dish southwest towards Athens georgia and typed in the control frequency and hear them almost perfect a 100 miles away on a 800 system.
 
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delta_charlie

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A while back I had a HTPC with a satellite card mounted in it. Played around with WireShark (packet sniffer) on one of the data transponders. Tons of packets showed up. Seems like a SDR might be a lot of fun to play around with. Not sure what you might find - just a wide data band or maybe some side channels?

Should be interesting in any case.
 

harshness

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May 5, 2007
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Most consumer SDRs can handle only a fraction of the bandwidth of a typical satellite transponder. Digital multiplexing means that you have to take the entire transponder in one bite.
 
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spongella

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So how wide is a typical signal, say an FTA signal? Haven't the slightest idea. I have looked at FTA transponders using an HP spectrum analyzer and I guesstimate around 25 megs. However if you look at a spectrum of a typical FTA satellite there are signals of all different bandwidths. Never been able to figure out what is on the screen.
 

Brct203

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Dec 24, 2016
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I use my SDR to look at details on satellite signals. You can see the beacons, and once calibrated for LO inaccuracies (especially on DRO, but also with PLL) and watch out for LO drift, you can use it to help identify satellites by their beacon frequencies, to some extent. Note that most satellites have some beacons on global beams, so from here in the US we can actually "see" most of the South-American satellites even those that don't cover north America at all. You can also "track" drifting satellites, or check inclined-orbit satellites for when they cross the clarke belt.

You can also use an SDR to tune in to low SR DVB-S(2) signals, but it's not easy.

Last but not least, I use my SDR as a spectrum analyzer with RTLSDR Scanner. Not really usable for real-time display of the spectrum but can give a detailed spectrum when trying to verify if a signal exists or not, or if it's just below locking level

all in all, it's well worth exploring as long as you don't expect miracles
 

N6BY

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Mar 1, 2006
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Are there any analog WBFM radio modes on Ku band satellites anywhere between 100 to 400 KHz bandwidths ranges? :hungry :hatsoff
I think it's all digital (DVB-S2). The problem is demodulating DVB-S2 fast enough in software. It usually requires a dedicated demodulator chip.
 
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lyn

Member
May 20, 2012
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Eastern US
I use my SDR to look at details on satellite signals. You can see the beacons, and once calibrated for LO inaccuracies (especially on DRO, but also with PLL) and watch out for LO drift, you can use it to help identify satellites by their beacon frequencies, to some extent. Note that most satellites have some beacons on global beams, so from here in the US we can actually "see" most of the South-American satellites even those that don't cover north America at all. You can also "track" drifting satellites, or check inclined-orbit satellites for when they cross the clarke belt.

You can also use an SDR to tune in to low SR DVB-S(2) signals, but it's not easy.

Last but not least, I use my SDR as a spectrum analyzer with RTLSDR Scanner. Not really usable for real-time display of the spectrum but can give a detailed spectrum when trying to verify if a signal exists or not, or if it's just below locking level

all in all, it's well worth exploring as long as you don't expect miracles
Can you explain how you connect your SDR to the sat antenna? I have a well functioning 10 foot dish with a Pansat FTA receiver that has a loop out connection. Using a DC block, can I run a feedline from there to the SDR (an Airspy R2) to look at the sat signals?
 
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Brct203

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Dec 24, 2016
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Can you explain how you connect your SDR to the sat antenna? I have a well functioning 10 foot dish with a Pansat FTA receiver that has a loop out connection. Using a DC block, can I run a feedline from there to the SDR (an Airspy R2) to look at the sat signals?
i've done it both ways:
- either with an older receiver (in my case a Fortec Mercury) that has a loopback port. Basically that port has the RF signal from the LNB but "should" not have the DC voltage that would hurt the SDR (check with a voltmeter). Then you can select band and polarity with the receiver and once that's selected, then play with the SDR to see what is there
- or use a DC block splitter. I found one that is sold for DirecTV, it's simply a splitter that passes DC to one port and signal to both ports. I insert it between the receiver and the LNB, with the LNB connected to the input and the receiver to the DC-Passing output. Then connect the SDR to the remaining port of the splitter. This way the receiver can still power the LNB but the SDR gets only the RF signal, not the DC. This allows the use of more recent sat receivers that don't have the loopback port.

as usual, power off the receiver before you disconnect or connect those, and I would also suggest you check the port going to the SDR with a voltmeter before you plug the SDR, to confirm that there's no DC
 

lyn

Member
May 20, 2012
13
1
Eastern US
i've done it both ways:
- either with an older receiver (in my case a Fortec Mercury) that has a loopback port. Basically that port has the RF signal from the LNB but "should" not have the DC voltage that would hurt the SDR (check with a voltmeter). Then you can select band and polarity with the receiver and once that's selected, then play with the SDR to see what is there
- or use a DC block splitter. I found one that is sold for DirecTV, it's simply a splitter that passes DC to one port and signal to both ports. I insert it between the receiver and the LNB, with the LNB connected to the input and the receiver to the DC-Passing output. Then connect the SDR to the remaining port of the splitter. This way the receiver can still power the LNB but the SDR gets only the RF signal, not the DC. This allows the use of more recent sat receivers that don't have the loopback port.

as usual, power off the receiver before you disconnect or connect those, and I would also suggest you check the port going to the SDR with a voltmeter before you plug the SDR, to confirm that there's no DC
What frequencies should I check on the SDR?
 

Brct203

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Dec 24, 2016
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What frequencies should I check on the SDR?
the typical L-Band frequencies, so usually 950 to 2050 MHZ. I'm not sure what the upper limit of the Airspy R2 is. My RTL-SDR cuts at about 1700 MHZ

If you want to check the beacons, many are published here: http://frequencyplansatellites.altervista.org/Beacon-Telemetry_Americas.html and here: http://frequencyplansatellites.altervista.org/Beacon-Telemetry_Atlantic.html

you then have to convert to L-Band. by subtracting the LO frequency (or from the LO frequency if C-Band)
so for example a beacon at 3950 MHz would be seen by the SDR as 5150-3950 = 1200 MHz
Note that it's not uncommon that the beacons be on circular polarization on an otherwise linearly polarized satellite, or vice versa

you should also be able to see narrow transponders on the spectrum in SDR#
 
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