Currently in the process of upgrading my ADS-B station what is located in the South West of the UK, need some advice on any changes I should make to the plan - as I’m relatively new to ADS-B tracking. At the moment I’m using:
Pi Zero, planning to upgrade to the newer version (Zero 2)
FA Pro Stick, no additional filter as I live in a rural area with not a lot of noise (although need a second opinion on this)
AirNav 1090 Antenna (Gain 7dBi, Impedance 50Ω±5Ω)
The main change at the moment what I’m planning is to mount all the equipment directly bellow the antenna in a waterproof box, which would be powered using POE. This would reduce the current 30 feet of 3D-FB which the antenna comes with by cutting it down. With a quick bit of research, the estimated loss is about 3-4dB for 1090MHz signals. At the moment I’m considering if this is worth the effort, or would the addition of filters and a preamp would give the best benefits to my setup at the moment.
Hi.
Regarding whether you need a filter or not, here’s how to find out:
Your noise level is rather high in your signal level graph. That could be due to interference in which case a filter would help, or because your gain is set way too high.
If you’re using the piaware 6.0/6.1 image or dump1090-fa 6.0/6.1 on a Raspbian install you can enable it’s adaptive gain features.
For other demodulators you can use this:
Compare yours to mine:
This is with a cheap Chinese PC board antenna in a plastic case (it’s actually a decent antenna, being a 4-element colinear) with an RTL-SDR Blog triple-filtered LNA next to it followed by 10 meters (33 feet) of LMR240 coax, a bias-t injector board powered by USB, and a Nooelec NESDR SMArt dongle. The antenna’s around 9.4 meters above ground. My gain’s currently set to 22.9. Before I added the LNA near the antenna I was using a FlightAware Pro orange dongle like yours and my noise level was typically around 34dB, always 30 or less anyway.
If any issues you’re having are due to high noise moving the Pi closer to the antenna will either do nothing or make it worse.
It certainly wouldn’t hurt to upgrade the Pi Zero to a more powerful model. I have no experience with the new Zero 2s as I have a 3B+ but from what I understand their hardware is so new that Raspbian or PiAware that’s based on Debian Buster won’t run on them, they need Bullseye-based operating systems. PiAware 7 will be coming soon which is Buster-based.
Bad idea IMHO. Lots of complications, adding EM noise next to the antenna itself…
Just use a LNA at the antenna (in a small waterproof box), Bias-T power, and reduce appropriately the gain at the receiver. It will compensate for almost any cable length, certainly for those 30 feet you have.
I have 150 feet of RG6 cable between antenna’s LNB and receiver.
Plus having the Pi in a box on the antenna mast will make it a pain should something in the Pi malfunction such as the SD card going bad. There’s no great advantage of having the Pi up there vs. an LNA and coax, especially with only around 10 meters of coax. 3 to 4dB of attenuation is basically nothing.
Re: SoNic67’s suggestion about adding an LNA near the antenna see It’s not about the gain its about the signal to noise… | Ava High Altitude Balloon Project. I just swapped out my NEDSR SMArt dongle for my FA Pro then ran the autogain1090 script for two hours which brought the gain down to around 10dB. My setup’s working fine with both an LNA near the antenna and one in the dongle. You will need to add a means of supplying 5V DC BIAS voltage and ground to power the LNA over the coax. I’m using this with the red and black wires from a USB cable connected to the screw terminals and the other end plugged into a USB port on the Pi:
I put the board inside of my old plastic Pi case as I’ve replaced my case with a ventilated aluminum one with a fan. I live in the tropics and it gets rather warm sometimes so I wanted more cooling to prevent premature failures. I attached two 30cm. RG316 jumpers to the two SMA connectors on the board which then attach to the dongle and LMR240.
Great to see a Pi Zero being used. Some decry these devices but it all depends on what one wants out of this hobby. Being less than a third the cost of a 3B or 2GB Pi 4 they are a low cost way into ads-b tracking and if one gets bitten by the hobby then same MicroSD can be inserted into the full size Pi.
Your adsb exchange link gives error ‘Problem fetching data from server’.
Be interesting to know how the new Zero 2 deals with heat, my Zero is around 45c in Winter months with ambient temperature of about 18c. Tried same card in a 3B+ which is quad core, mA increased from about 450 mA to 550 mA in the 3B+ but temperature not much different.
Thanks for your reply, regarding the high noise levels - its probably due to a Wi-Fi dongle what is directly next to the SDR as the zero doesn’t have a Wi-Fi chip. I’ve just ordered a USB extension cable to create a distance between the dongle and the SDR, what should reduce the noise level. I’ve just ordered a Pi 4 which should bump up the performance for my setup, as most of the time the CPU is running at 98% utilization what doesn’t help overall. I’m currently running readsb with the automatic gain optimization enabled, so that should sort out the gain.
The antenna what I’m using has the coax fixed annoyingly, only option would be to cut it down and then connect the LNA then run a high quality coax to the SDR what would be located inside. At the moment I’m thinking of keeping the coax connected to the antenna, which would then terminate at the LNA with a pigtail SMA cable connecting it to the SDR. As my station is located with clear view of the north Atlantic, it seems the most logical idea to install some sort of LNA - what would increase my range and allow for more messages to be received with positions.
At the moment I’m thinking of getting one of these LNA’s: RTL SDR ADS-B LNA Triple Filter Low NF Amplifier, or a uputronics 1090MHz filtered preamp. Any further ideas would be helpful, thanks.
I’ve always enjoyed using Pi Zero’s, mainly due to the price. I’ve taken down my aerial mainly due to the upgrades what I’m doing, and the weather what was another factor. I’ve purchased a Pi4, but I’m still thinking to get a Pi Zero 2 what I could do some tests on and see its performance capabilities compared to a Pi4. If I get the Zero, I’ll make sure to let you know with the results with the heat question and overall how it works.
I am using that one, with slight mods. It’s not weather proof, so I added a small enclosure box (from Home Depot) with the sealed openings pointing down.
My cable was so long that I decided to add a voltage stabilizer inside the LNA and feed the other end with something like 7.0V.
The’s plenty of signal after the LNA, that is able to compensate for very long cables.
PS: I also used a no-name LNA from eBay, with two SAW filters. I de-soldered and re-soldered another chip, more performant in regard to noise factor, in the first stage. That one is slightly better than the one from above!
That would be an interesting comparison, I know the Pi 4 generally needs cooling, I haven’t got one so cannot comment byt my Pi 3B+ doesn’t have any overheating issues, having said that I don’t really stress it out.
Just wondering if anyone has any experience with the RTL-SDR LNA’s, in specific the Triple Filter Low NF Amplifier and the ADS-B Triple Filter Low NF Amplifier. As I’m not a expert in LNA’s, could anyone give me the specific benefits of spending £17.50 more (for some added benefits?). I’m also having a look at the Uputronics preamp which seems to be the most commonly used, as I’ve read before it outperforms the RTL LNA’s by 5%. Any advice would be helpful, thanks.
Thanks Keith, that is the plan at the moment. I’m still deciding if I would prefer just to mount the LNA at the top of the mast, then use high quality coax to run it into the inside. Would you recommend any good coax for this use, had a quick look at it seems jetvision sell this: https://shop.jetvision.de/epages/64807909.sf/en_GB/?ObjectPath=/Shops/64807909/Products/70100
I have both. The uputronics seems to be susceptible to RF overload a little more than the rtl-sdr. It is easier to power the uputronics with a USB cable.
My location requires a cavity filter for both.
Thanks for the reply - at the moment I’m thinking if I would go ahead with the RTL version I would use a bias tee (external) as recommended by @jaymot earlier. This would be powered via USB, so it seems easy enough just to strip a USB cable and gather the relevant cables inside to power it. But the uputronics seems to be the easier option.
The 1090MHz band looks pretty poor as the antenna is inside at the moment as I’m currently doing work on the new setup and should be up and running soon.
Sorry, but NO.
RF simply isn’t that straight forward.
It’s a beginners mistake to treat RF as DC
You need to take into account the mathematical relationship between two (or more) frequencies.
For example, a strong 364MHz signal could easily resonate a 1090MHz antenna and de-sence a receiver.
There is an old RF adage that says: " Every mixer can be an amplifier, every amplifier can be a mixer"
As we all know, the output of a mixer is four frequencies: the two fundamentals plus F1 +F2 and F1-F2
Using a simplified example: a high powered, FM station on 110MHz plus a local transmitter on 980MHz could produce 1090MHz inside your LNA and you’d never know why your system performed poorly.
Not to mention possible splatter and bleed-over from strong signals on nearby frequencies and harmonics from transmitters on completely different frequencies and bands.
