I know I asked about swapping to an AirSpy R2 a while ago but I’m considering it again. In my situation, I wonder if there would be any improvement switching to a Pi5 with an R2.
I’d run PoE and use an NVME drive to avoid the SD card wearing out again.
/edit - What about the LNA? At the moment, I’m using an RTL-SDR-LNA but I believe they’re no longer available. What’s the best LNA currently available (please don’t suggest Uputronics)?
On a Pi4, an R2 with decent traffic and 12 MHz sample rate gives ADSB usage at 120 to 130%. Using an R2, the 20Mhz sample rate pushes that to 220% on the 4 cpus. 20 might improve counts by a couple of percent, might, no guarantee. Not worth it for the additional power used nor component stress. Night time, cpu usage bumps up as the code searches the noise for a signal. I have one of the Uputronics LNAs and it has less gain, seems like a wider bandwidth and more vulnerable to interference than the two RTLSDR ADSB LNAs I use (one is flaky). Love cavity filters.
Sadly, RTLSDR ADSB LNAs are no longer available. You could use a cavity filter between the antenna feed and a wide band LNA as a possible substitute. I have heard it is a parts problem, and a redesign is contemplated, but depends on the parts situation. Seems like a Pi5 is overkill, though the NVME drive definitely has benefits. Maybe it can run PiHole for you too to remove trackers and ad websites from your internet traffic. It runs well on a Pi3 even with the lower ethernet speed (100 Mbps).
I was running the Airspy Mini as suggested in a different thread at 20 MHz for a while on a Raspberry 4.
The whole system didn’t have a problem over the time and there was enough CPU power available all the time.
I don’t think that moving over to Pi5 with an R2 brings you any significant advantage especially not if you are already if your current range achieves already the max. range at your location without moving the devices
Not sure if there are other sites offering a PGA103+ or if there are other suitable models.
The CPU spikes are weird.
No clue what’s happening. (maybe just do a reboot, that looks like some bug with the data gathering rather than actual CPU spikes)
50% CPU usage isn’t that high really.
The R2 is actually rated for 20 MSPS while for the airspy mini it’s kinda outside the specs.
Doubt that it’s a big upgrade. Also it’s kinda too late now with the black friday sale for it having passed
Really with the newer sd-cards they should have more than enough write cycles.
So it’s just general electronics survival.
And an nvme drive is in no way guaranteed to survive longer than an sd-card.
Difficult to improve a setup that is already getting great results. Still there might be some improvements to make.
A hardware refresh might nevertheless be a good a idea. It has been running for quite a while now, hasn’t it, in a box outside “in thunder lightening or in rain”. Maybe upgrade it properly now before something breaks and you have to fix it in hurry, which is not easy given it lives on a tower.
Mabe add AIS to, close to the sea you might catch a few ships, too. Doesn’t tar also allow to combine these type of feeds?
I quite like the sysmocom cavity filter. In whichever hardware combination I used it with, it lead to better results (more messages).
My gut experience tells me to suggest that you bring the entire equipment box down off the tower and into the air-conditioned home hobby environment. Of course, you leave the antenna behind on the tower and procure an appropriate length of KMR400 coax to make the signal connection to your receiver of choice. Having the electronics inside the comfort of your home is such an advantage when it comes to the care and feeding of the components. I have run with both 75’ of KMR and now 50’ of KMR coax with no issues with signal quality being delivered to the system. Whatever you do, i hope it provides positive effects to your already great results.
I’m running the AirSpy Mini at 20 MHz now on my Pi 4 so if I were to change to a Pi 5 and an R2, I’d push that up to 24 MHz.
I’ve had the Uputronics LNA before and it’s awful for interference. Less than 5 watts on either 2m or 70cms totally kills it, received signals drop to zero instantly. I don’t think I’d want to try one of those again, even with a cavity filter. The box at the top of my mast with everything in is within a foot of the coax to my HF aerial where I regularly run a kilowatt on frequencies from 40m through to 10m.
I know and it’s really frustrating.
I have two Pi-holes running already, a main one and one for redundancy
Aye, it’s all about diminishing returns. Remember I went out of my way when I did the aerial work last year just to get the aerial up another three or four feet!
It does look as though it’s going to be a different LNA with a filter. If I’m going to do this, I just need to find one I know is bombproof to nearby RF.
The R2 will run at 24MHz?
The SD card started failing earlier this year and I hadn’t noticed that my backups had been failing so it was a bit of a flap to get a new card built and swapped over before it went completely tits up. Hopefully I’ll get a good few years out of the replacement if needed.
Air conditioned? In the UK? LOL!
I’ve still got about 70m of Hyperflex 10 on the drum from when I bought some a couple of years ago so the coax wouldn’t be a problem. However, from the top of the mast to my radio shack is around 40m away and that’s just too far for me. I simply wouldn’t be happy with that.
The cost isn’t a huge issue here, yes, it would be an expensive upgrade but realistically, if I do this, it will be built slowly over the winter so I’d have a few months to procure everything and it wouldn’t be one big chunk spent out in one go.
Yes Keith, 40 meters is a long stretch. The Hyperflex 10 is pretty low loss I expect but the length makes one have doubts. I have to wonder what the theoretical signal loss is for 1090 at that distance in the Hyperflex? However, the signal is likely to remain relatively “clean” at the end of the trip and would respond well to amplification. Happy trails.
Interesting discussion. You have already debugged your installation and seem quite happy with it all mounted in a box near the antenna. If you have no reason to change that arrangement then why would you consider mounting it anywhere else and then have to worry about long coax and associated problems.
I have no experience with the Airspy kit so offer no opinion but since the discussion seems to be centred on CPU load I would just go the Pi5 and be done with it. I cant see any reason not to and the addition cost in AU is only a bit over $10AU.
I use RTL-SDR blog V3.
Good luck and stay safe on the tower.
S.
I replaced a Pi3B running up in the roof space with a Pi5 just so I can run Raspberry Pi Connect now that VNC is no longer free.
It is running on the same PoE which is probably 2.5 amps and so far has shown no heat stress whatsoever. It is coming into summer so it may get a bit warmer when it is over 40C.
The R2 definitely runs at 24MHz and that sample rate doesn’t add significantly to the processor load on a pi5. Here are some screenshots from a test I did in August - going from 24 to 20 and back to 24:
24 MSPS adds about 20% CPU on a single processor or 5% overall.
My main reason for getting a pi5 was to allow running adsb and ais on the same machine. As I couldn’t see any significant improvement at the higher sample rate (admittedly from a short test period of 48 hours), I ended up swapping my Airspy Mini to the pi5 and adding RTL-SDR Blog v4 for AIS-catcher when I upgraded.
The pi5 is quite happy running the two dongles, with plenty of headroom. These charts show load and temperature on my main station which swapped from a pi4 1GB (Airspy Mini) to a pi5 4GB (Airspy Mini + RTL-SDR V4):
My setup uses POE to an enclosure at the base of the mast - both the pi4 and pi5 use Waveshare POE hats which have constant speed fans. My POE Switch tells me the pi5 HAT is drawing 11 Watts / 200mA
There are PoE hats available for the PI5. The PoE hat I have was the first to hit the market, but I don’t recall who the seller was. I had a PI5 w/8 GB and a PoE hat running a home automation trial and a print server app serving for 10 months.
In August 2024 I added FA and an Airspy to the PI5 and uninstalled the expired home automation trial. Currently CPU utilization is about 50% feeding FA and print serving.
Tall Tower mounted antenna, significant interference sources also on the same tower makes for a tough comprise between systems. As an old ham started in the mid '60’s through around 2000, NOT going to reduce your ham system to bandaid any other systems on the same tower.
Given the above, and playing the “I want the best of everything” kind of attitude, perhaps keep the ADSB antenna above the Ham feeds/antennas by as much as you can, then feed the ADSB antenna into a shielded enclosure (think isolation box) with only bottom entry cables (rain avoidance) with an internal cavity filter feeding a BiasT powered LNA, with the output feeding down the tower to a base system in a box at the bottom of the tower in another shielded enclosure. Yup, fancy shamchy kind of setup. Power via POE from your shack. This way, you can try whatever SDR receivers you can find, or scrounge. LNAs could be swapped if you must, though the thought of climbing a 35+ meter tower is not my idea of a simple trip at my 75 years.
I agree, the R2 is the best receiver I have used and found over the years. I have two R2’s and one Mini, all with heatsinks appropriately glued/attached to cover most of the surface. Yes, the Mini can run at 20 MHz, and the heat sinks are an absolute requirement. R2’s appreciate the extra cooling too. I use sun shades over external boxes here in Florida where temps can get very interesting. Mostly Attic based here now.
For the Pi5 itself, most any memory option should work well, 8gb is overkill, though much easier to find than a 2 gb model. For what you are planning, the Pi5 should be more than adequate. It does have the power supply tradeoff of watts vs cpu capability.
Would love to have a nice tall tower, but my years and the hurricane seasons in Florida kind of lessen the desirability quite a bit. No falls from antenna towers yet, and I intend to keep it that way.
Have fun there, and hope they trash the “Other” aircraft counting in the rankings.
If you were going to replace the pi 4, then a pi 5 is a reasonable choice simply due to the ease of adding a cheap nvme drive. That will be far more reliable than an SD card - the only problems I’ve had with my system over the past 5 years have been SD cards going bad. One advantage other than the extra cpu headroom is that the USB implementation is far better on the pi 5 than the 4. The ports aren’t all forced to share the same bandwidth, so plugging something else in alongside an airspy won’t cause dropped frames. That gives the option to have a second dongle for other purposes (running spy server, ais, acars/vhdl or whatever).
It seems rtl-sdr.com have given up on replacing their lna and are now working on a combined lna and antenna instead. That probably means it will be a compromise and unlikely as good as their old lna combined with a decent antenna. I’m not looking forward to the day mine dies as I don’t know what I’d replace it with. None of the other options I’ve seen appear to be as good or as cost effective.
I’m not sure it’s worth the extra expense to go to the R2 to run at 24MHz. Last time I tried it the difference between 12Mhz and 20MHz was far less noticeable than before the decoder upgrades, so I imagine the difference between 20Mhz and 24MHz would be smaller still. Given your location though and frequent lifts from ducting, if anyone is going to see an advantage you will.
I am running an RPI4 since two years with an external SSD instead of the SD card. Works perfectly.
Of course it’s not an integrated solution and will use an USB port. But it works.
24 MHz is not recommended at all, even if it manages to catch some very weak frames the other modes cannot. The main reason is the reliability (or lack thereof) of the USB pipe.
