Where can I buy a 12V bias-T for satellite usage?

[KE7IZL]

I would like to use a simple SDR (such as RTL-SDR) to receive satellite signals. The problem is the upper frequency of these is only 1.7GHz, while satellites for which there are commercially available LNBs are either 5GHz (C-band) or 12GHz (Ku-band). Now of course there's the issue of powering the LNB. Inside every commercially available satellite TV receiver is a DC injector or bias-T that injects 12 or 18 volts into the coax to power the satellite dish's LNB, and then separates the DC from the received signal to send to the rest of the receiver's circuits. The exact voltage used configures the LNB to receive either horizontal or vertical polarized signals (or for a circularly polarized LNB it configures it for either right-hand or left-hand circular polarization).

Unfortunately there's no way to actually divert the received RF out of commercially available satellite TV receivers (so that I could put the RF into an SDR), so if I want to use such an LNB for satellite reception with an SDR, I will need some kind of external bias-T. The problem with that is that the bias-T devices I've seen being sold for use with the SDR hobby community (including some SDRs like the hack-RF which has a built-in one) seem to only output 5 volts (for powering either an external RF amp, or powering the Ham-it-up up converter for receiving HF signals with a VHF/UHF SDR). This won't allow me to send 12 or 18 volts down the coax, and 5 volts is simply not enough to power an LNB.

I looked around and found nothing commercially available that would let me do what I need to power an LNB. While I did find this MFJ-4119N,BIAS TEE, HF/VHF/UHF, 1-50VDC, 1A,PWR INJECTOR, N from MFJ, it has 2 problems. First, it's a discontinued product. Second, the manual https://cdn.shopify.com/s/files/1/0289/7782/3843/files/MFJ-4119.pdf?v=1586534125 says it can only go up to 450MHz but the output of a satellite LNB is between 950MHz and 1750MHz, so even if it was still for sale, this bias-T's builtin lowpass filter would block the required 950MHz to 1750MHz signal from the LNB from ever reaching my SDR.

So this leaves me in a troubling situation. There seems to be no commercially available external bias-T that allows injecting 12 to 18V while not blocking the LNB's signal between 950MHz and 1750MHz. So I'm stuck without the ability to actually explore satellite signals with my SDR.

If anybody knows of a company that actually makes bias-Ts that would meet the specs I need, please let me know.

 

[Ubbe]

It's just a choke coil to stop RF from being short circuit from the DC supply. Its one capacitor in series to the receiver to stop the DC voltage to it. In many cases a receiver have protection diodes at its input that conduct at +/-0,7 volt. Ebay are full of bias-T that claims to go up to 6GHz. I would think that it is that DC blocking capacitors highest frequency that sets the frequency limit, and perhaps the stray capacitance between the windings in the choke coil. Its the choke coil that set the limit of how much current it can supply, but there's no voltage limit.

/Ubbe

 

[thebaldgeek]

@KE7IZL I'm wondering what satellite you want to receive? You talk a lot about how you cant get any parts, but don't actually tell us what you want to pick up.
@Ubbe is correct, just use a bias-t injector.
Also this is a solved problem, I have been building satellite LNB systems around the world for the past decade.
My past few systems have even gone so far as to use a 4 port mixer for GPSDO LO injection along with DC voltage to run the LNB.
Ebay has a lot of Norsat LNBs that might work for you.

Please take a look at the 'C-Band' page on my site as it breaks down the exact parts you mention that you need (and cant find).

Decoding ADSC, ADSB, ACARS, VDL2, Iridium, HF-DL and other aircraft type messages.

Rough notes on how to go about setting up the hardware and software for ACARS decoding.

thebaldgeek.github.io

 

[ArloG]

The problem with working with microwave frequencies that high is that very careful designs are required before the mixer in lna/lnb circuits.
If you look at teardown photos and circuit descriptions. Every part of the pc board is very accurate.
Now. If you want to use your SDR with frequencies that high you could use a lnbf that performs in the bands you wish to work. And use the downconverted LO frequency output directly to your SDR. 950-2400 MHz is easier to work with and you won't go broke buying cable and connectors that work at the fundamental frequency.

One simple solution is to buy a cheap DirecTV power inserter that provides 19 VDC output.
Then any voltage polarity controlled lnb/lnbf could be used. If you don't seriously mind that the impedance is 75 ohms.
18 volts would put the lnb into horizontal polarity for linear frequencies or LHCP for circular polarized frequencies.

In the case of a circular polarized lnbf. You would need to conjure up a variable or switched voltage power supply to supply 13 volts for RHCP and 18 volts for horizontal polarization. Because the smps in the DirecTV inserters are fixed voltage and the circuitry does not easily allow you to add variable voltage control like you would find in a TL431 smps.
So snip the bias tee from the supply and hook up your own variable dc voltage power source du jour.

Norsat lnb's with flange waveguides are physically rotated and work on a wide dc voltage range. So a single lnb simply is rotated to align with the satellite skew angle.

I called and spoke with a guy at satellitedish.com in Florida. I found out the different methods commercial people use power inserting to power equipment. I ordered a few DC block F connectors. A simple injection of DC by tapping into coax and soldering in a DC+ to the "stinger" and DC- to the braid seems to work for many. But in reality an LC network is needed to stop RF from feeding back into the power source.
The DirecTV power inserter bias tee has that. Then use the DC block to supply RF only to the SDR.

There are receivers that have RF (lnbf) pass thru at the rear port. Several FTA satellite receivers have that. I have a Zgemma H7 with the provision.

If you go that route. Stay away from low/high band lnbf's that require 22 kHz to switch bands. Unless you can find a solution to inject the tone of adequate amplitude to do the switching.

What else? 5G interference is rampant on C band. A good thread in on legitfta.com where the admin. used his Tiny SA to 'sniff' C Band with his satellite dish and showed graphs plotting the sources from cell towers.
Another simply used a C Band lnbf powered up and hooked to his Tiny and hand-held it to sniff near field interference with no dish.

In my photo. The Tru-Spec power inserter receives 24 VAC over coax to power 2 Norsat lnb's on my dish.
I had a close lightning strike last summer. It cooked my lnb and all the way back to my dish mover.
Some say it's "too much". But I just got everything back up and working.
I've 100% isolated the "new" Norsat lnb pair from the power inserter, back. I hope!
Too much for me is buy once, cry once. A year without satellite sucked.
And the current load on the receiver to power the lnb's is greatly reduced.
FYI. The power inserter, receiving 24 VAC and regulated with an LM317 made the case of the inserter very warm. I've cut the voltage back to 19 VDC which puts the LM317 at it's regulation minimum voltage and heat is greatly reduced. But the pc power supply mosfet heat sink added was really needed.

Ask me more. Maybe I can help.

 

[KE7IZL]

I found a Sonicview SV-4000 satellite box on eBay just last evening after I made this post.

What is most interesting about this particular satellite box is that it has an IF output port on the back. The IF input port outputs power to the LNB and takes in the 950MHz to 1750HMz IF signal from the LNB. The IF output port then outputs this IF signal to an external device. This is where I could connect my SDR capable of receiving this IF signal. Interestingly, from some stuff I've looked at online about this satellite box, its onscreen menu allows you to manually override the settings for any particular satellite. This includes manually enabling or disabling the 22khz tone, that is used on dual-frquency LNBs to select between the upper and lower parts of a band. Even within a particular band, (like C-band or Ku-band) some satellites transmit in the upper part of the band, and some in the lower part of the band. And the IF bandwidth of the LNB isn't wide enough to capture the entire band, so some LNBs are dual-frequency LNBs. These can have their LO set to the higher part of the band by injecting a 22khz tone into the coax, along with the DC for power.

Suffice to say that designing a bias-T to allow not only DC injection but also 22khz injection, would be a very complicated matter. So a satellite box like this would be even better. And with manual override of satellite settings it means I can take any satellite and reconfigure it as needed to have the specs needed for any satellite that I might want to receive, including ones not on the internal list of satellites. This means I could use this box in place of a bias-T for even non-TV satellites, and then enable or disable the 22khz tone as needed (for upper or lower part of the band), as long as I could find an LNB for the band the satellite is transmitting in (C-band and Ku-band seem to be the most common ones). This way I could use an SDR to even maybe receive signals from any of various commercial satellites like land mapping satellites, weather satellites, satellites conducting scientific experiments, or any number of other types of satellites that might be out there.

 

[ArloG]

It is a very dated receiver.Basically obsolete if you ever wish to get a FTA picture on a TV.
I know the subject is not sat. receivers. But being a firmware vs Linux OS receiver. Buy it if you think you really need it. I wouldn't.

5G has killed most if not all USA C band transmissions below ~3.8 GHz. But sites like Lyngsat and TVROsat have charts with frequencies and channels on them.
There are projects out there to supply voltage and inject definite tone without having to haul a receiver and monitor around.
BTW. Linux receivers have a web interface that allows you to control the receiver over IP and even stream content to any device with a web browser. Unlike most newer firmware (chinabox) receivers.
You don;t need to design a bias tee. Nine bucks for a DTV power inserter or even your local second hand store with a box of wall warts might have a few. That's where I got mine. Two bucks and change.
A C Band lnb will consume around 200-300 mA. A ku band designed for FTA will consume probably the same. But a Direc or Dish single lnb will use a lot more.

I see you have your mind set on instant gratification. For your project switching polarities is not needed. You simply rotate the lnb for polarity.
A circular polarized lnb would need voltage switching.
Before expecting too awful much perhaps checking out UHF Satcom would be a good thing.
On lnb does not fit all.
Also to clarify your statement. The tuner IC in satellite receivers has the job of tuning and providing proper voltage, tone, and diseqc datastream for thing like multiswitches. All on one chip.

A 3 port splitter with adequate frequency specs with DC pass thru from receiver 1 > lnb and capacitor decoupling on the 3rd port definitely could work. As your SDR won't control the lnb. So any old receiver could work. In essence it's a bias tee.

 

[prcguy]

A C Band lnb will consume around 200-300 mA. A ku band designed for FTA will consume probably the same. But a Direc or Dish single lnb will use a lot more.

A single DirecTV LNB doesn’t draw any more than about 300ma. A SWIM will draw more, maybe 450ma and a Slimline multi-LNB with built in multi switch will draw a little more, maybe 350ma. Not much to see on a DirecTV downlink with an SDR, besides big digital carriers maybe a tracking beacon with encrypted TT&C info but that’s about it.

 

[ArloG]

Data satellites are interesting. Noaaport on 121W is interesting using just wireshark.
Of course Othernet using just a single universal ku lnbf without a dish is cool. Although you need the Dreamcatcher board to make any use of it.
I do know that running a Dish twin lnbf on an fta receiver is pushing it and triple is certain disaster without a power inserter on port 1.
I've been using a 12' dish for long enough to be familiar and just added a twin c band OMT with Norsat lnb's plus a sidecar ku lnb.

The first sentence of the OP's post may lead him to think there is usable content on satellite that can be received with an SDR radio.
Not really so. And buying an ancient Sonicview, chinabox receiver will not fare well with the modulation and formats on satellite.

Receivers such as Novra and TBS pcie cards with specific data applications are fun. Building a NOAAPort station is quite a job. But ll software is readily available.

A list of his specific expectations of using an SDR radio with satellite reception in the Clarke Belt would be nice to know.

 

[prcguy]

Data satellites are interesting. Noaaport on 121W is interesting using just wireshark.
Of course Othernet using just a single universal ku lnbf without a dish is cool. Although you need the Dreamcatcher board to make any use of it.
I do know that running a Dish twin lnbf on an fta receiver is pushing it and triple is certain disaster without a power inserter on port 1.
I've been using a 12' dish for long enough to be familiar and just added a twin c band OMT with Norsat lnb's plus a sidecar ku lnb.

The first sentence of the OP's post may lead him to think there is usable content on satellite that can be received with an SDR radio.
Not really so. And buying an ancient Sonicview, chinabox receiver will not fare well with the modulation and formats on satellite.

Receivers such as Novra and TBS pcie cards with specific data applications are fun. Building a NOAAPort station is quite a job. But ll software is readily available.

A list of his specific expectations of using an SDR radio with satellite reception in the Clarke Belt would be nice to know.

You could hunt for satellite pirates doing narrow band voice over commercial satellites and with narrow 10KHz wide signals they just disappear into the noise floor with typical spectrum analyzer settings used in the satellite industry. I once fired up a VHF lo band handheld in the 70MHz range attenuated into a 70MHz satellite upconverter/downconverter on a Ku satellite and talked to a similar distant setup and it worked great. This was on a satellite transponder I had complete control and authority over, so no pirating in this case. Even with a good 20dB SNR it would have been very unlikely anyone would have noticed the tiny carrier.

I’ve heard the U.S. mil makes use of commercial satellites in a similar way but they don’t ask permission.

 

[KE7IZL]

It is a very dated receiver.Basically obsolete if you ever wish to get a FTA picture on a TV.
I know the subject is not sat. receivers. But being a firmware vs Linux OS receiver. Buy it if you think you really need it. I wouldn't.

5G has killed most if not all USA C band transmissions below ~3.8 GHz. But sites like Lyngsat and TVROsat have charts with frequencies and channels on them.
There are projects out there to supply voltage and inject definite tone without having to haul a receiver and monitor around.
BTW. Linux receivers have a web interface that allows you to control the receiver over IP and even stream content to any device with a web browser. Unlike most newer firmware (chinabox) receivers.
You don;t need to design a bias tee. Nine bucks for a DTV power inserter or even your local second hand store with a box of wall warts might have a few. That's where I got mine. Two bucks and change.
A C Band lnb will consume around 200-300 mA. A ku band designed for FTA will consume probably the same. But a Direc or Dish single lnb will use a lot more.

I see you have your mind set on instant gratification. For your project switching polarities is not needed. You simply rotate the lnb for polarity.
A circular polarized lnb would need voltage switching.
Before expecting too awful much perhaps checking out UHF Satcom would be a good thing.
On lnb does not fit all.
Also to clarify your statement. The tuner IC in satellite receivers has the job of tuning and providing proper voltage, tone, and diseqc datastream for thing like multiswitches. All on one chip.

A 3 port splitter with adequate frequency specs with DC pass thru from receiver 1 > lnb and capacitor decoupling on the 3rd port definitely could work. As your SDR won't control the lnb. So any old receiver could work. In essence it's a bias tee.

I wasn't talking about using it for satellite TV. I was talking about just using it as a way to inject the DC for power, and the 22khz tone for changing the LO frequency to receive the upper or lower part of the band. I'm mostly interested in just seeing "what's out there". I'm sure there's tons of general satellites that have specific uses for various industries (things like communication, land mapping, weather, experimental, etc). The box has an onscreen menu as well as ethernet cable for configuring on your computer via a web browser (the main thing I'd need to configure being turning on or off the 22kHz tone to switch the LNB's LO between the upper and lower parts of the band, if the LNB I buy supports such). The same frequency bands (C and KU in this case, as these are the easiest to get LNBs for) used for satellite TV, I'm sure also have uses for other types of satellites. So if I can output the IF from the satellite TV box (as the one I was talking about is capable of), then I can connect the IF output from the satellite TV box to an SDR for checking out all kinds of different satellites. Even if this particular box is outdated and can no longer decode modern TV satellite digital video protocols, it would still work fine as a way of powering the LNB, and if needed sending the 22kHz tone to the LNB, and then outputting the IF signal to an SDR (as this the only satellite TV box I've ever seen with an IF output connector on it, which is an essential feature for using it with an SDR).

 

[Ubbe]

as this the only satellite TV box I've ever seen with an IF output connector on it, which is an essential feature for using it with an SDR).

Most, if not all, LNB's have a mixer in them that have a IF out of something like 750-2400MHz as trying to send a 12GHz signal in a coax will die before it reaches a receiver.

The IF out of a satellite box, it's just the cheapest ones that don't have that, are just a loop and a copy of its input signal so you can attach another sat box. But it is the first main box that sends the voltage and 22KHz tone control signals that then dictate what polarization and band the LNB operates on and that the other box then also have to use.

The LNB doesn't have any kind of channel bandwidth or modulation type, that's demodulated in the sat box, so a SDR receiver used at the IF out can be set to any narrow 25KHz channel width.

There's few, if at all any, analog channels left for TV type of transmissions so there are old analog only sat boxes you can probably have for free to experiment with as LNB and IF out, as well as polarization control and band switching and also rotor control if needed, isn't related to if sat signals are analog or digital.

/Ubbe

 

[ArloG]

I wasn't talking about using it for satellite TV. I was talking about just using it as a way to inject the DC for power, and the 22khz tone for changing the LO frequency to receive the upper or lower part of the band. I'm mostly interested in just seeing "what's out there". I'm sure there's tons of general satellites that have specific uses for various industries (things like communication, land mapping, weather, experimental, etc). The box has an onscreen menu as well as ethernet cable for configuring on your computer via a web browser (the main thing I'd need to configure being turning on or off the 22kHz tone to switch the LNB's LO between the upper and lower parts of the band, if the LNB I buy supports such). The same frequency bands (C and KU in this case, as these are the easiest to get LNBs for) used for satellite TV, I'm sure also have uses for other types of satellites. So if I can output the IF from the satellite TV box (as the one I was talking about is capable of), then I can connect the IF output from the satellite TV box to an SDR for checking out all kinds of different satellites. Even if this particular box is outdated and can no longer decode modern TV satellite digital video protocols, it would still work fine as a way of powering the LNB, and if needed sending the 22kHz tone to the LNB, and then outputting the IF signal to an SDR (as this the only satellite TV box I've ever seen with an IF output connector on it, which is an essential feature for using it with an SDR).

Since this is your very first rodeo. And before you get your expectations too high and buy a pile of crap that will end up letting you down.
Check out the links.

Okay. So you get your stuff setup. With a dish of adequate size. DBS satellites are a ton stronger than FTA satellites. For ku sats. 1meter diameter minimum.
C-band considerably bigger. Europeans are getting by with 2 meter dishes for TV. Bare minimum.
Then there's the mount. Go polar. Az-El will frustrate you trying to snag a signal. Dish Pointer will assist in finding them.
Just grabbing the rim of my 12' dish and pulling/pushing it 1" will diminish signal greatly. Move it 2" and you lose signal lock.
Although an SDR or TinySA or a man's spectrum analyzer will show signal.
Modulation schemes. Look at all of them. Have you ever decoded a Meteor weather satellite and NOAA APT satellite?
NOAA is easy. Meteor requires a string of software components to decode a single picture.
And with Meteor, all you hear is a hiss.
Fine. PSK, QPSK, 8..16..32QPSK, etc. are decoded in the SOIC in a sat. receiver.

For your first rodeo. I'm not one-iota trying to discourage you at all. Just trying to to teach you how to not get kicked off the horse.

The Novra type of data receivers are going to be way more useful to you than the Sonicview. Pretty inexpensive on eBay.
Decomissioned from different uses. Including NOAA, who have upgraded the systems.
Sockets, UDP, TCP/IP. Multistream, ports. The data you're thinking you can receive and get intelligible information with your SDR? Forget about it.

I saw 0 on the Sonicview providing a web interface. Sifting through the clutter to even find a user guide. Not surprising since chinaboxes of that era didn't even expect a person would ever stream content over Ethernet. Enigma2 Linux receivers? Yup.
They are TV demodulator receivers with web interfaces.
The Novra receivers do it all. Over Ethernet. As well as TBS DVB-S PCIe cards.
Satellite signal will not be like you tuning a radio and hitting a station. And wa-la it's in your face to listen to.
Milsat hacked sat's. Yeah.
Hissssssssss.

LNB pass-thru is common on chinaboxes. Heck. Modern sat receivers with pluggable tuners, you can have your choice.
As the master to control lnb requirements. Even if you did not have a pass thru. Tapping off of the coax into the receiver should be a breeze.
That aint rocket science. Just like probing a circuit with an oscilloscope. Use the correct probes, apparatus.
Slice open the coax. Add a capacitor to the stinger and wire the shield. Slap in your SDR. Bang. No JPL involved.
I'll leave you be and close out my rant. Have fun dude.

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