Thank’s to both of you who replied. Excellent article regarding long cables.
I have also read the entire post at:
Whilst I am getting pretty good results for my first try, this has confirmed my concerns that the coax is adding noise to my setup and limiting my results. I am lucky that my location gives me an unobstructed view of the sky with no terrain blocking or buildings in the way.
While I am nervous about installing the Rx in an outdoor cabinet, sometimes simpler is better and the simplest configuration would be to install the receiver right at the antenna. I am going to try doing that temporarily to see how much improvement can be had.
Since the FA Blue Rx contains an RF amp I will install it without an LNA but try it with, and without the FA Mode S filter.
If that does not give me a good improvement, I will try using a AirSpy Mini (with LMA) or maybe a Beast and see if that gives me better results, similar to this: http://www.martellotowergroup.com/ads-b.html
Eric, that’s one of my sites and it’s doing well but this one is performing even better. I don’t particularly like using any length of coax but had no real option here and had to run 5.5m of cable between the aerial and the receiver.
If you are using an LNA mounted at the antenna then the gain provided will more than offset any increased noise from quite a long coax.
Case in point - my receiver has about 10m more coax in line than it needs (~16m in total) at the moment, and (much to the disapproval of @keithma it’s 75 Ohm WF100), yet I get good performance because the gain of the amp is high enough that the reduction in cable loss wasn’t worth the extra expense of replacing it. The 1m patch lead between the antenna and the amp is 50 Ohm low loss however. I’ll probably get round to trimming it to a more sensible length at some point, but I wasn’t sure if I would need to move the receiver.
If the amp were at the other end of the coax (as would be the case using an FA pro stick for example) then having a high quality correctly matched coax would be much more beneficial.
This is by far the most important factor - ADS-B isn’t really a signal strength constrained system. The transmitters on aircraft are quite powerful and should easily reach the radio horizon. If your antenna has an unobstructed view of the horizon, then it makes everything else much easier.
I have the receiver and pi indoors, but with an LNA at the antenna. It’s a good solution for having access to the pi without having to go on the roof, but keeps the advantage of having signal amplification close to the antenna. It also requires a much smaller enclosure to weatherproof the LNA than it would for the pi, amp and dongle together.
Does a Pi 4 make a difference for a busy ADS-B system? Will the FA PiAware build work with Pi 4 without modification? Can I take my SD card from my Pi 3 and install it in a Pi 4 with no problems?
Curious if you have had any interference from your ADS-B setup into your amateur radio equipment?
I have not checked my amateur station in detail yet. I do have a lot of signals that are from all the computers, IP devices, Ethernet switches, etc., but not so bad it is a big problem. Running a Flex 6600 and a new Elecraft KPA 1500 but only have individual dipoles for 40, 30, 20 and 17 meters so far. Used to have a big beam when I was in Connecticut.
Yes and no - the pi 4 makes a difference if using an airspy as it has more cpu available to run the higher sample rate with more aggressive decoder settings. There is no performance advantage if using an rtl dongle, where a pi 3 is sufficiently powerful. The current piaware sd card image doesn’t support the Pi 4, but it’s quite simple to use a raspbian buster image and install the piaware package on it, which works fine. I believe the next version of the piaware image should support the pi 4 directly.
None whatsoever that I can tell - As you saw from the link, my aerial is on top of the hexbeam and I’ve noticed no problems on the bands from the receiver and no problems to the ADS-B signals from transmitting at full squirt through the hexbeam.
@wiedehopf With all the changes that have been made to the Airspy code, I wonder if it’s possible for you now to make a version of your automatic gain script that works with the Airspy? I do appreciate that it’s not quite so critical with regard to strong signal handling but it’s just a thought.
The effect isn’t so obvious as with an rtl dongle, but you definitely lose messages if you have the gain too high on an airspy. I suspect that how much it affects you depends on how busy your area is and how close to you the majority of traffic is.
Well, often there is talk about 75 Ohm cabling without an LNA or before the LNA.
Which as the article linked highlights is a completely different story.
No real difference outside the normal deviation if you’re running any of the DVB-T Sticks or the orange / blue Flightaware Sticks. But there’s a difference if you run more powerful sticks like the airspy.
You can simply use an SD card created for a Pi3 also in a Pi4. I’ve tested this a few days. Then i decided to get a different SD card and built it from scratch on my Pi4
