Noise level - ads-b muta setup

Ordered.the rtl-sdr. Have asked them a question though, they like all amp producers, want it as close to the antenna, before the coax, as possible. In powering it from inside via bias t set up or suitable powered dongle for coax work, what the distance limits are before the voltage starts to be affected by distance.

Jeff

The RTLSDR blog dongle has an integrated bias-tee that can put about 5V onto the coax line. A normal RTL dongle doesn’t put 5V on the coax and the prostick doesn’t. There are some systems that will fail with 5V on the coax and there are some antenna that don’t work with 5V on the antenna input.

There is a program you have to run on PiAware to turn on the bias-tee on. And then it will power the coax with 5V and all the way to the mast head amplifier.

The other solution is to use a power injector for coax. These are fairly common with F connectors but harder to find with sma connectors.

The distance limits for power over coax is hundreds of feet. A good coax cable has a DC resistance of a couple of ohms. The 50ohms and 70ohms rating is based on RF signal reactance.

1 Like

Never use a loop antenna with an RTL-SDR Blog with bias T enabled, or you’ll need to purchase a new one (short circuit).

As for power injectors with SMA, they are available for around $7 shipped, on eBay.

https://www.ebay.com/itm/New-10MHz-3000MHz-3GHz-Radio-Frequency-Transformer-Bias-Feeder-Bias-Tee-/222711150051?_trksid=p2349526.m4383.l4275.c10

When you know the dimensions of the cable you can calculate the resistance and using this value the voltage drop.
But before you get into such voltage problems you will have signal problems…
For a voltage drop of about 2.5 V your cable should have about 350 m (considering a center core diameter of 1 mm)

Coax RG6, solid copper conductor 18 AWG (1 sq. mm crossection), Copper Braid:

Nominal Conductor DC Resistance = 6.4 Ohm/1000ft
Nominal Outer Shield DC Resistance = 2.7 Ohm/1000ft

Total DC Loop resistance = 6.4 + 2.7 = 9.1 Ω /1000ft

For any appliance to work properly, DC supply voltage at its terminals should not be less than 90% of its rated dc voltage (unless it has a built-in voltage regulator). Hence the Amp should get not less than 4.5V DC at its terminals.

With Pi sending 5V DC, this allows only 0.5V drop in the coax. Assuming Amp consumes 300mA, the total DC resistance of dc loop should not exceed R = Voltade Drop/Current = 0.5 / 0.300 = 1.67 Ω

Max permissible length of coax = 1000 x max permitted R of DC loop /Coax DC loop resistance per 1000 ft
= 1000 x 1.67/9.1 ft = 184 ft

There are higher voltage bias-T devices available for longer runs.
There are also higher quality types of Coax that should have less loss.

The uputronics devices have an option for ~20V.

This one is 9V and easy to find arounde here.

https://www.walmart.ca/en/ip/digiwave-power-inserter/6000086198941

  1. The preamp draws 40mA, not 300mA
  2. The listed voltage range for those preamps is 3.3-5V. Those are not digital circuits.

Hi abcd567,

I installed rtlpan after seeing your post, and captured the following:

What’s your assessment of it? There is a strange signal around 1.050, and a wide one around 1.090.

Thanks.

I think it is 1030Mhz , secondary radar.
Do you have an airport or tracon nearby?

YOW is about 18 miles from here. YND is closer, at 8 miles, but not as busy. I looked for info on tracon in Ottawa, but did not find anything.

Any idea why 1,090 looks the way it does?

Thanks.

Thanks all for your contributions.My plans,… first some description of my setups. 2 antennas total heights 8.3m off the ground and 6m off the ground. Both next to a flat roof, 1st antenna is about 5m above roof height, 2nd about 2 m above roof height. So to install the amps and PI3’s near the antennas, 1st antenna is a job to drop the mast down to get to the antenna, 2nd one not so bad, a step ladder has you near the antenna.

So to install the PI3’s and amps near the antennas, 1st antenna not easily accessible, 2nd one no problems. So method of working this, using existing coax runs OR putting in network cables (I have about 90 metres of Cat 6 network cable in the shed, so no issue/cost there… lol). So network cable and utilising POE power source, rated to 100 metres, gigabit speed, plug and play with auto determines power requirements. I will be going with the POE option given what that unit can do.

So the 5 metres off the roof problem. Thank heavens for heywhatsthat !!! I have both antennas plotted, with location and heights. I had a look at the lovely dump 1090 maps, showing the theoretical distance of each antenna (which I find very accurate, when observing actual detection’s !!!). The 2 plots, with the difference in heights, in my main detection areas, are virtually the same with heywhatsthat system, so I don’t need to have antenna 1 as high, to get the same results, access to the weatherproof box and Pi3 /amp a lot easier, without have to raise or lower the mast. I am going to get the V3 rtl-sdr dongle and the new pre amp and also the nevis uptronic pre amp filter, and compare the 2. :slight_smile:

Now I will firstly have to drop antenna 1 to remove a masthead amp near the antenna that my current amplifier uses (and as well on antenna 2). But then I will be able to do this upgrade in stages. I can trial the new amp similar to the current set up, with the amp/Pi3 being located at the end of the coax run. and see/compare with current setup. And then, with not too much problems, run the network cable, mount the Pi3/amp in the weather proof enclosure, close to the antenna. :grinning:

@jlb56
If you plan to use PoE, reading this post may help:

https://discussions.flightaware.com/t/rasberry-pi-wifi-dongle/32119/10

this is the unit I am looking at: TL-POE150S | PoE Injector | TP-Link Australia
seems to meet those requiremnets.
#overview

HARDWARE FEATURES

Interface 2 10/100/1000Mbps RJ45 Port
AUTO Negotiation/AUTO MDI/MDIX
1 48VDC POWER INPUT PORT

Network Media 10BASE-T: UTP category 3, 4, 5 cable (Max 100m)
EIA/TIA-568 100Ω STP (Max 100m)
100BASE-TX: UTP category 5, 5e cable (Max 100m)
EIA/TIA-568 100Ω STP (Max 100m)
1000BASE-T: UTP category 5, 5e, 6 cable (Max 100m)

Power Supply 15.4W (Max. 48VDC)

LED Indicator PWR

Dimensions ( W x D x H ) 3.22.10.9 in.(80.85424 mm)
IEEE 802.3af compliant

. Auto-determine the necessary power requirements

.Gigabit speed support

.Plug-and-Play, requires no configuration

The sdr-rtl amp power use is about 170 mA with a 180 mA at startup (checked 3 times just to be sure)
Voltage drop value helps me to chose the input voltage to have at consumer (LNA) the correct voltage.

Uputronics has a 26V option

That is PoE INJECTOR only.

You will also need a PoE SPLITTER near Pi. Please see diagram below.

This splitter makes a matching pair with injector.you have mentioned above: TL-POE10R | PoE Splitter | TP-Link Australia

Po_E_48_V

I was planning to use a Pi PoE Switch HAT, on the PI 3 to overcome that.

@jlb56

Before you purchase Pi PoE hat, make sure it is compatible with your model of Pi.

As far as I know, Pi PoE hat is compatible only with Pi 3 B+ , the latest Pi released yesterday (March 14, 2018).

.

1 Like

Thanks, I have seen in a few places, that it will work on the current pi 3 irrelevant however, you haven’t already got a PI3 B+ yet… :wink:

Thanks for the update. Seems I had incomplete info. I haven’t got any model of Pi3 (Pi3, Pi3 B, Pi3 B+). I have only Pi1 B+ and Pi2.