Tag: pi4

Raspberry Pi4 Remote Mount ADSB Receiver.

I know I am late to the party as ever, but I wanted to try and increase my knowledge of the Raspberry Pi and Linux so decided to try my had at 1090 MHz ADBS reception.

I wrote up some initial thoughts in a previous blog, this was my attempt to improve the reception and remote mount the Pi close to the antenna.

The problem with traditional deployment is the antenna and SDR receiver (FlightAware) are mounted some distance apart. High quality coax is needed, and even then the losses at 1090 MHz are high. I calculated 10 m of RG213 would equate to at least 3 dB loss, my antenna would need 25 m or coax to mount it in a convenient location. Factor in connectors and I was looking at a 9 dB loss, close on 90% or my received signal lost in attenuation.

The Pi has WiFi, and previous tests had shown me the range and reception was very good, so the idea of mounting the Pi in a waterproof box close to the antenna was conceived. Its not new, im not the first but this is my process and lessons I learned.

The rule of thumb in a box, is think of a size then double it, its not the pi that causes the issues, that is small.

85 mm x 56 mm in new money.

Its the routing of power, USB, SDR and the coax socket that need some consideration. Cooling may also be an issue, a sealed box could get very warm in the summer without some fan and ventilation.

Box options, I selected something marked waterproof and 150 x 110 x 70 mm and it cost £6.25 delivered.

Next was some waterproof sealant, I was going to be drilling holes in the box, and some waterproofing would be required. A tube of Silicon bathroom sealant seemed suitable. I would use this to seal around the power and coax cable entry points. I was going to be drilling all my holes on the bottom of the box, but everything needs to be sealed

The next issue was around the USB ports, I wanted the flexibility to mount the Flight Aware USB receive in a location of my choice and not be limited to the position of the USB ports.

Right angled USB extension cable

The short extension cable offered the ability to mount the USB receiver flush to the case, with a hole drilled for the SMA to poke out.

USB C Power cable with break out for wires.

Only suitable for short runs of power cable.

Powering the Pi needed some thought, was I going to connect 5v directly onto the board (this would have been easier) of could I look for some way to wire directly into the USB C connector. In the end this connector cause me a few concerns, it worked exactly as described, but in a tight box it takes up and incredible amount of space. If I could have got a right angled version, this would have made for a much neater installation. They are also quite expensive, but needs must.

For longer power cable runs voltage drop will become significant, and so I used a DC to DC converter from PIMORONI. They have one detailed on their website as Wide Input voltage SHIM, and you can power it with 3 to 16v

Wide input DC to DC converter

The last piece of the puzzle for me was a coax cable, I wanted N type on one end to connect to the antenna, and SMA on the other for the Flight Aware receiver.

If you wondered why I selected the blue Flight Aware receiver, in the tests I completed the band pass filtering and amplification out performed a standard RTL dongle by 10 to 20% range.

You will need a good 1090 MHz antenna, having something with some gain mounted as high as possible will make all the difference. I opted for a commercial made option, but if you have the equipment you could consider making a co-linear.

Have a look at the antenna options on amazon or ebay.

So having gathered all the items together, it was now just a case of positioning them in the box, the flight aware receiver has a long SMA shaft, so the hole can simply be drilled through the box and SMA pushed out. Once the SMA plug with coax is connected you can use a liberal application of silicon sealer to prevent water ingress.

I added a fan into the box, and made sure the Pi had a large heat sink fitted to the processor. The fan isn’t running right now, but this in itself provides a challenge. Not much point adding a fan if it doesn’t extract or force air into the box. I decided to drill 4 x 6 mm holes, and then as it turned out badly align these with the fan. I fitted some foam to the inside of the box, and then bolted the fan down, sandwiching the foam to the inside of the box.

Temperature readings of boxed Pi4

This again was mounted on the bottom of the box, as with every hole, to hopefully prevent water ingress. The other issue is likely to be insect infestation, they like nothing more than a warm dry home high up on a pole!

You may want to consider the application of some grease on the pole, its amazing how earwigs can find these warm homes.

Power was the final thing to do, I did try and power it direct from home, but the voltage drop was just too much. I decided to use a DC to DC converter, this allowed me to feed with anything from 3 to 16v.

PoE was considered, but i couldn’t really see the advantage over WiFi and separate power cable.

Under voltage messages would indicate I still have some issues to resolve, but its working.

The box on a pole, cable ties used as a temporary fix

Pi 4 with DC to DC converter fitted
Typical text display

PI4 next generation VHF/UHF beacons?

Beacons have like other digital modes moved with the times, making use of the latest digital modulation techniques to improve detectability far beyond the human ear and CW.

The name PI4- PharusIgnis4 comes from the ancient words for a beacon, lighthouse and fire and is a digital modulation that is compliant with the IARU Region 1 VHF Committee accepted 1 minute mixed mode beacon sequence.

The sequence of events is illustrated below, and always starts on a full 1-minute cycle.0 to 24 seconds PI callsign

pause

25 sends CW ident callsign and locator

pause

carrier until 59.5 seconds

pause

To decode the PI4 beacons you can download software PI-RX by Poul-Erik OZ1CKG or MSHV by Christo LZ2HV, they both report being compatible with Linux and Windows.

OZ7IGY beacons date back to 1957, and they are now QRV from 28 MHz to 24 GHz. You can review the dial frequencies and check the operational status online.

Frequency [MHz] USB dial* ERP [W] ASL [m] 99% accuracy [mHz] Year QRV
28,271 28.270.200 10 95 1 2009
40,071 40.070.200 10 97 1 2007
50,471 50.470.200 25 98 1 1990
70,021 70.020.200 25 100 1 2003
144,471 144.470.200 50 102 3 1957
432,471 432.470.200 75 103 9 1958
1 296,930 1.296.929.200 90 95 26 1978
2 320,930 2.320.929.200 30 98 46 1985
3 400,930 3.400.929.200 50 96 68 2006
5 760,930 5.760.929.200 50 98 115 1992
10 368,930 10.368.929.200 80 97 237 1999
24 048,930 24.048.929.200 20 97 481 2012

To support the PI4 beacon project, or to see a technical description of the modulation technique read more on their website.

Other becons to look out for.

PI4 + CW + carrier/Next Generation Beacons platforms
4O0BCG in JP92PK – 70,048 MHz
DB0HRF in JO40FF – 144,475 MHz
DB0IH in JN39HJ – 432,447 MHz
DB0JG in JO31HS – 432,412 MHz
DB0LTG in JO31TB – 1296,7435 MHz
DB0MMO in JN49RV – 144,455 MHz and 432,425 MHz
EI0SIX in IO63VE – 50,005 MHz, SBP 5/0
GB3CFG in IO74CR – 70,027 MHz and 1296,905 MHz
GB3MCB in IO70OJ – 50,443 MHz and 50,005 MHz SBP 5/1 and 3
GB3MHZ in JO02PB – 10 368,830 MHz
GB3UHF in JO01EH – 432,430 MHz
IW9GDC/B in JM78SD – 50,006 MHz (Later SBP 6/4)
KG4BYN in EM75RV – 28,2368 MHz
ON0EME in JO21JG – 10 368,875 MHz and 24 048,875 MHz
ON0SNW in JO21BE – 10 368,965 MHz
OX4M and OX6M in HQ90AL – 70,047 MHz and 50,047 MHz
OZ4BHM in JO75KB – 50,005 MHz, SBP 5/4, later also 50,466 MHz
OZ7IGY in JO55WM – 28 MHz to 24 GHz
PA0AG in JO32GH – 70,095 MHz (personal beacon, 07-21 UTC)
SK4MPI in JP70NJ – 144,412 MHz
TF1VHF in HP94AC – 50,457 MHz
UA1ZFG/B in KP69AK – 144,425 MHz
VA2NQ in FN35NL – 50,295 MHz, 144,491 MHz, 222,295 MHz and 432,302 MHz