Long Range ADS-B Report

Hi Guys. Thought this might be of interest to some of us newbies. To avoid this happening, :unamused: , you old hands may want to look the other way :stuck_out_tongue:

I installed a PiAware setup with DVB-T Dongle and stock aerial a little over a week ago. Was pleased with the results but thought I could do better so I built an 8 element collinear and stuck it to the window with duct tape. Quadrupled the reports but thought I could do better so I put the collinear in a PVC pipe on top of a two meter mast outside on the roof with 360 degree views and 600 feet up on a ridge with a 5 metre 75ohm coax lead. That was a mistake. Reports dropped to a couple of thousand. So I brought the aerial back inside and stuck it to the window again. Reports are now back up to where they were. I must have screwed something up with the outside install but anyway the main purpose of this post was to point out a pretty extraordinary range (for me anyway) that I got tonight with the reinstalled (to the window) aerial.

251NM !!! 8)

My usual hits are in the 210 -230nm range on this particular airway but I have recieved a few 240-242nm reports on nearby airways.

Radio horizon from my site to FL390 is approx 236nm though reports on this airway usually begin or end in the 210-230nm range. So 251nm is pretty extraordinary and had to reflect some kind of OTH ducting or tunneling.

This long range hit was on a WSSS-NZAA flight inbound on the A464 at FL390 at 2100 on 21 May 2015. Rain radar showed a belt of moderate to heavy rain between my site and the reporting aircraft lying parallel to the airway.

According to ‘The Basics of Radio Wave Propagation’ by Edwin C. Jones, MD, PhD (AE4TM) Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200):

“Inversions that occur along frontal systems support propagation along a line parallel to the weather front, and radio amateurs using frontal inversion often point their antennas parallel to the frontal system to take advantage of this form of propagation.”

I have noted that other 240nm+ reports on the R599 and B333 airways which have also occurred during bad wx and wondered if wx had anything to do with it.

Here’s a picture of the report (the yellow circle) and my ADS-B site. That’s New Zealand in case you were wondering. The airway is the A464.


And here’s an image of the Auckland rain radar at that time. You’ll not how the front lies parallel to the airway.


So I thought that was pretty neat. To get a 251nm hit made me fell like this;


I told my wife I can now see around corners but a vacant stare was all I got. She’s a bit bewildered by all the aerials going up and down, things getting taped to the window, me running outside and reeling off data about passing aircraft and multiple computer screens that look like something out of the Matrix!!



Good stuff! I periodically see some pretty impressive distances to the east and south from my location. Usually when they are up > 40000 feet.


Test the type of pipe that you inserted your DIY antenna into, some actually attenuate signal. Take a small piece and place it into a microwave oven and run the oven for 30 seconds. If the piece gets warm then it’s affecting your signal.

Read that here on this forum, but don’t know who to credit.

…and don’t forget to also have a small cup of water in there with it. :wink:

A quick search of the forums found the post you’re referring to:



lets think on this

  • make the joints on the coco watertight - heat shrink sleeve on the joints?
  • use cable ties to attach the coco to nylon cord - so it can be hung without pulling apart
  • suspend nylon cord from a bowed fireglass rod - a bit like a kids home mad bow (bow and arrow)

… No PVC tube - less attenuation

250nm is good, not exceptional over water especially if you have no trees etc in the way

go to heywhatsthat.com/ do a new plot, accurately put in your antenna position & height. choose ‘in the air’ and put 38000 ft, then zoom out - you will see the range you should achieve.

Hi Guys,

Sorry about the late response. Real life matters got in the way but I’m back now.

Thanks for the responses. I was pretty chuffed with 251nm but I see some others on the forum are talking about 270nm range which is pretty awesome.

Thanks for the ideas regarding the external aerial setup. I guess I just screwed something up but I took your advice and cut off a piece of the plastic pipe and, when the wife wasn’t watching, put it in the microwave (with cup of water!). It stayed as cool as ice so I am assuming it is not the problem. I will approach the problem in increments maybe using your ‘fibreglass bow’ idea Peter. The existing aerial and lead combo which seems to be working so well, I will just extend out of the window and plant on a stick in the lawn at the same height it is in the window. I’ll see how that performs and I’ll take it from the there.

Peter, I tried ‘Heywhatsthat.com’ but the choices for setting up a new panorama don’t allow you to choose ‘in the air’ and put in 38000 ft. Am I screwing that up too? :confused:


Create the panorama and the “up in the air” option is on the page it generates.

251nm is quite awesome and I certainly wouldn’t put any effort in to chasing down an extra 19 miles. Depending on RF conditions at the time and the altitude of the aircraft, you may very well see more than 251nm given enough time.

If the pipe didn’t warm up in the microwave, it isn’t causing an attenuation problem for you. No reason to change that setup - especially if you’ve seen 251nm at some point.

You found your way to the ‘New panorama’ page…now you just have to click the ‘Submit request’ button at the bottom there… :wink:


In perfect conditions, around 276 miles for aircraft at FL410 is probably about as good as it’s going to get for your location with an antenna 20ft above the ground. Other than making sure the antenna has a clear view of the sky (no buildings in the way) - I wouldn’t change a thing.


Thanks guys for help with ‘Heywhatsthat’. It all makes much more sense now. Yeah, I agree it is not really worth chasing more range especially in those quadrants where the coverage is good. However, in the NE where I have negligable coverage, I need to get above the house to get a better line of sight in that sector. So, I’ll keep trying to find out why the setup doesnt seem to work outside.



For the non-locals, what makes this even more impressive is the location, the country out there is like corrugated iron so you’d have lots of terrain blocking line-of-sight signals. I’ve had a very few 200+NM hits, but then I’m surrounded by ridges and hills on almost all sides, so all the long-range stuff is in a 45-degree wedge in a SW direction.

Fortunately, I’m sited on top of one the corrugations which does help for sure. Hey 186Mhz, are you somewhere near Whenuapai? I see you getting some good hits usually just as the flights start going over me inbound to NZAA and my antenna loses sight above the horizontal.


I’m on the upper harbour with line-of-sight to Whenuapai (not sure why my location isn’t shown in the sidebar). Unfortunately I’ve also got the Greenhithe ridge, the Waitakeres, and behind me the Glenfield ridge, around me, so most of my stuff is coming from the SW. I’ve just set up a collinear on the roof after lots of hassles with the RPi and USB power so I’m getting a lot more data as of yesterday afternoon.

Ah I see where your approximate position is from the map locater. I left the RNZAF about 10 years ago. From all the approaches we did in C-130’s and B727’s at NZWP, I know the valley you are in quite well and yep, you have a lot of signal shadow in there. Still, your Rasp PI set up and collinear on the roof seems to have done wonders to your reporting stats and has made you one of the higher ones in the country along with mabnz in Wellington (and I bet he’s surrounded by lot’s of hills as well!! :laughing:). How many elements in your collinear?

I am still limited in reports from the NE to SE primarily because the house is in the way so I need to get my collinear on the roof but I had some connection problems last time I tried. Yesterday, I moved the aerial outside and away from the house to get a better view of NZAA and although I missed eight hours of reports stuffing around with this, I still ended up a pretty credible collection rate. I am hopeful that the next 24 hours will better show the extent of that improvement. Then, I’ll try the roof again.

In the meantime keep up the good work 186Mhz.



PS I envy your oversight of NZWP watching all the herks taking off :mrgreen: