Range problems, direction sensitivity on collinear antenna?


#1

Since a couple of days i’m running with the following setup:

FA Pro stick on RPI 2+
Dump1090-mutability running at -10 gain right now
FA Filter

29ft of Aircell 5 coax
static1.nevadaradio.co.uk/downlo … rcell5.pdf

Antenna:
ebay.com/itm/Antenna-ads-b-c … 1742466173?

The antenna is mounted on a mast at the rooftop, with a clear 360 degrees view of the sky. No buildings or trees in the immediate surroundings.

I’m not really satisfied with the results i get in range. I had hoped to reach down to Arlanda/ESSA which is about 173 miles/150nm from my location.

As one can see on this map i do’nt have these bad issues with the range in other directions so it got me wondering if it can be because of the direction my antenna is mounted.

http://forumbilder.se/F9I3U/skarmklipp.JPG

Arlanda/ESSA lies southeast of me, and is rather “dead” on the map as you can see.

According to Fr24, right now there’s a helicopter in the air about 50 km southeast from my site, and i can’t even catch that one with my setup.

A thing that crossed my mind, can this be because i have another 1090Mhz antenna mounted on the same mast? The spacing between the two is around 50cm.

This is a view from above, how the two antennas is mounted, one pointing W and one pointing N.
http://forumbilder.se/F9I3U/namnlos.jpg

My stats page:

flightaware.com/adsb/stats/user/tottoman

http://forumbilder.se/F9I3U/skarmklipgp.JPG

Any help and thoughts much appreciated!


#2

Isn’t there a bunch of 500 metre high hills and dells in the SE direction?

Normally you are only going to see aircraft above the angle to the hills. Radar can’t see through mountains.


#3

The signals are vertically polarized, so your antennas should vertical for best performance.


#4

They are vertically mounted.

The lines are the distance between them, not the actual antennas.

The red dots are the antennas, and the black line is the boom they are mounted on. Still viewed from above.

http://forumbilder.se/F9I43/namnlos.jpg


#5

Oh, sorry, just making sure :slight_smile: Since you said they were pointing W & N I was confused.


#6

The antenna separation should be OK. You just need more than a wavelength, which I think is 10 inches at 1090 MHz.

For best separation, most commercial towers will use vertical distance, rather than horizontal. But there you have some blockage from the tower.

I don’t think that’s the cause of your null.


#7

Have you run http://discussions.flightaware.com/ads-b-flight-tracking-f21/what-is-the-maximum-range-i-can-get-t35912.html from your location? It will work out where any blind spots are.

[Edit] Ooops, just tried your Latitude and Longitude in Heywhatsthat but you are just a bit too far North for it to plot :unamused:


#8

Yup, unfortunately im too far north to use that… :angry: