FlightAware Discussions

A couple of questions


#1

Hi,
I’ve been playing with Piaware for a few weeks, and having done some research I have a few questions.

I have been using the latest Piaware 3.6.3? running on a couple of new Pi 3 units. I was very pleased with the results and purchased the FA antenna and a Prostick as well as a Prostick Plus…

My antenna placement is not perfect by any means, whilst it is external at the top of the house, it does not yet clear the roof, and can only see about a 150 degree angle of sky. On the plus side, we are reasonably high on the side of a hill, and although it won’t “see” central London it has a good view North & East.

I decided to try playing with the gain setting to improve things, and with a bit of analysis settled on 38 as a good figure. The range increased slightly as you can see from the two screen shots below.

However, whilst the number of Messages almost doubled to 1500/sec I didn’t see much improvement in the number of total aircraft / With Positions etc.

I noticed that the Prostick works significantly better with a FA filter, but the Prostick+ does not seem to make much change, although that was before I played with the gain settings.

Any ideas what I could try next?


#2

This is after I set the gain to 38

This is with the gain set to -10

The rings are set at 50nm, the lower image only has four rings for some reason.

Flights are now typically seen to 220nm at -28db RSSI


#3

I would say that’s typically the max range is around 240NM. Once you have cleared the obstacles, the line of sight to a plane at 38-45000 feet goes only so far…

http://www.calculatoredge.com/electronics/lineofsight.htm


#4

The Prostick+ already has a filter built in.


#5

@MDSBattery
Your maximum range curve is plotted below, using your aproximate latitude & longitude.

You can get a more accurate curve by using accurate latitude and longitude.

Blue curve is for planes at 40,000 feet height, yellow curve is for planes at 10,000 feet height.

This is assuming that your antenna is outdoors, above height of surrounding buildings and tall trees.

Please see this thread:

What is the Maximum Range I can Get?


#6

My range map is like this, based on the actual location. So we are not too far off that in terms of performance.


#7

The Prostick+ already has a filter built in.

Yes it does, but it seems here in the UK there are mobile frequencies that the Prostick + or FA filter do not block, and I am in a very busy (noisy) area…
I was going to try to do some more research on that subject.


#8

Sorry, didn’t mean to imply the filters are equivalent (they are not).

The PS+ has a SAW band-pass filter, whereas the the FA in-line filter is made using two filters: a High-Pass followed by a Low-Pass to create a wide band-pass filter.

With no evidence at all, my assumption is that the FA In-Line filter was designed to pass both the 1090MHz ADS-B as well as UAT on 978MHz.


#9

Thanks for the reply, and the good info about the 2 FA filter designs.

I had been reading this thread which was suggesting that the FA filters do not work so well in the UK.

One thing I have found is that with some fine tuning I have increased the number of messages / second but no gain of aircraft seen or positions reported?


#10

One explanation is that you did not increase the range (you can’t go past the line of sight horizon). You did improve the signal quality to the point that more messages can be decoded, but you still “reach” to the same distance as before. So your number of planes remained probably similar.

Also, you might not had a good baseline of “before”. For example, here in US we had last week the Thanksgiving holiday when the number of planes increased due to number of travelers that are expected to be on those days.
If you would live in US, measured a “baseline” last week, and this week you try to see the “improved” sitiation, you will be disappointed, thinking that something went wrong.

Airplane traffic is not a constant. You need to integrate multiple days, sometimes weeks, to make a better assessment.
Now, the numbers dropped a lot.


#11

Thankyou Sonic67 and all who commented.

I did increase range, but only slightly, so it may be that I am not able to see any further, hence only a slight improvement on the number of planes seen. I have been using a number of local sites to get a reference score, to help compare my tweaks and I think that has helped compare well. As you mention, different days give hugely different scores, a change of wind direction completely changes the flight paths to three major airports in my range, which is also very significant.

If I can get the antenna where I want it, I am sure there are some much bigger gains to make.

Thanks again for all the comments.