Hi All, noob with questions I can't find answers to


#1

Hi Everyone,

I only just got my Pi3 up n running today so I’m new to this and have quite a few logistics to sort out for a permanent piaware installation as well as a few questions.

  1. Why does my skyview sometimes show ACFT that don’t appear in the flightaware live? Dare I mention it but, Flightradar24 agrees with my skyview feed so I’m pretty sure they’re not phantoms or anything. I refresh the live view a number of times but it doesn’t show these ACFT, but then another will take off and it will appear straight away.

  2. Aerials and antenna height. I live in suburbia quite close to a capital city AD. With the stock $11 el-cheapo DVB-T aerial I bought, I got almost 70Nm range. Following advise from this forum I cut it down to exactly 67mm (almost half) and basically halved my range. I then mounted a large tin lid underneath and have ended up with about the same that I started with, so I’m wondering what the benefit of all of that was.

  3. I’m am looking for ideas on a budget 3-5m antenna pole to get the antenna up a bit higher. I really don’t want to spend much on this atm and am a bit limited as I’m living in the afore-mentioned suburbia and also in a rental atm. I do have an air conditioner mounted to the roof that I’m sure I could bolt something to and am toying with the idea of using 2.5-3m length of pvc pressure pipe but I am thinking it might be too flexible.

  4. Finally, If I was to build a simple spider antenna, is there any benefit for mounting 2 or 3 antenna in the same spot?

Sorry if these questions have been asked before but I have searched and not found anything.

Thanks.


#2

You didn’t say what you are using for the SDR part of the system – hopefully it’s one of the FLightAware SDRs which has a built-in amplifier and filter.

Depending on your environment (in terms of local transmitters such as cell sites and commercial TV stations) you’ll probably need a filter between whatever antenna you use and your SDE. A good place to start is the FLightAware filter.

A simple spider antenna is a great start. Putting a spider on the end of a piece of grey schedule 40 pvc pipe (its heavier and stiffer than the white stuff) should be a good start. Follow the recipes in this forum on spiders, and use a good quality RG-6 cable down to your SDR.

The exercise in cutting down the DVB-T antenna was to bring it closer to the proper length for ADS-B signals (a quarter wavelength of 1090 MHz to get technical). Putting it on the metal tin provided a ground plane which improves the antenna performance. The “legs” on the spider do the same thing, getting the antenna to do its work.

Have fun, keep track of what you try, and what the results are – things that don’t work out often teach you more than the things that do!

And keep asking questions – we’re here to help.

cheers

bob k6rtm


#3

Hi Bob,

Thanks for the reply. I just bought a cheap DVB-T aerial and dongle off ebay to get started as a proof of concept and see if it worked, so I imagine it is not great quality although I was getting up to about 70Nm range which wasn’t bad. I did try adding a mast head amp but it didn’t make any difference.

I decided yesterday to go ahead and build a collinear antenna which worked out great. I more than doubled my range and have seen targets out as far as 190Nm. I’m pretty happy with that given I live in suburbia and the antenna is only mounted on top of my ladder.

Now that I know it works quite well, I think I will go ahead and mount things properly. I’d like to get my Pi inside the house rather than have it outside. I also have to decide whether to mount the aerial on an existing structure on the roof or just go with a dedicated pole from the ground. Do people worry about any form of lightning protection? I imagine my final fixture will only be a maximum of 2 metres above my roof line and neighbours houses are taller than that.

cheers

Ant


#4

FlightAware doesn’t automatically show all MLAT’d aircraft on flightaware.com; we have various requirements such as some sanity checks to filter out bad data/noise. Also you need to have “position only flights” enabled in your account settings to see all flights.