Eleventeen
New Member
I recently replaced my venerable Mk.3 spider antenna with a Flightaware pole, and was dismayed to see very little improvement in range. Just for kicks, I decided to try bringing a dongle up to my office with the original spider to see the difference.
The original install was an attic install of the spider, mounted on a pole at the peak of the attic:
I had originally mounted it to a telescoping pole to find the best position in the house where I'd get the best range and coverage. I found that a point along the southern wall peak surprisingly got the best northern coverage (or at least, the most complete radius.) Even with tweaks though, the maximum distance was still a disappointing 70-80 miles on average (with spikes near 80 miles to the northeast.)
For a while I was concerned that something in my antenna build was just messed up. Maybe the coax cable was bad? I briefly had the antenna directly connected to the dongle via only an adapter and was getting similar results. Maybe the BNC connector I used to build the spider was bad, or wasn't the right impedance:
I know 75 ohm BNC connectors exist, and have slightly difference mechanical specs, I looked and that wasn't it. I have dozens of these laying around, and adding a washer to mount the radials made this a quick build, so I built two more for testing to ensure something wasn't wrong. I used the second one to fine tune the radials and whip lengths, finding little difference until they were just too short and was getting very few hits past 20 miles.
I bought the Flightaware antenna on Amazon, and was excited until I saw that I had very little increase in range. My packets received increased greatly, as did the total aircraft detected in the range...but I had the same general limit as I'd had before.
For kicks and to experiment, I brought my Mk.3 spider up to my office with an older dongle, just to see what results I could get. I wasn't optimistic about it. I knew that the antenna would have a limited horizontal field of vision, my office has narrow windows, and the columns in between I believe are structural columns that probably contain steel beams, at the very least they'd contain dense concrete. As if that wasn't bad enough, there's a set of metal shutters along the windows that are permanently affixed to the building. The antenna would also have a fairly narrow vertical field to look through...like looking through a slit. The one good thing was my office is on the 7th floor, I'd estimate that with the mechanical level below me, I'm at least 75-85 feet above street level. Knowing that the couple of extra inches to mount along the top of my window wouldn't make that much of a difference, I built a small shelf for the spider to sit in that would sit at desk level. I work in a graphics shop where we produce posters, so I built out of a material I have plenty of: foam core board.
I suspect that the foam core is rf-transparent, at least at these frequencies, but I'm unwilling to try the microwave test with this stuff, so it's a complete guess. The antenna goes to about 4 feet of RG-6, then into the dongle adapter which is connected to my work laptop. Again, this was just to experiment.
I fired up the Windows build of dump1090 (not mutability, as I don't see a Win32 build for that branch.) I was almost immediately surprised by what I found. Not only was I getting a flood of packets, but I was seeing at least 175 miles of range, almost immediately. Throughout the the day I watched as that range filled in a bit more and I started seeing a much better footprint than I was at my house, with the same antenna.
Over four days of mapping, the best range I've seen was 275 miles, although I wasn't watching that flight at the time and I'm not logging on this machine like I do on my pi.
The strong directional reception I was anticipating...my office window faces directly north and I didn't expect much from northwest and northeast. What surprised me was the southern spikes. I believe I'm getting significant bounce from the building across the street. It's a tall brick building so it might be acting as a reflector, bouncing the signal 'over the shoulder' so to speak.
So far, my work antenna continues to receive more packets and more aircraft than my pi at home, albeit with a sharply focused receive pattern. I'm seriously considering moving my pi up to the office, or at the very least trying with the FA antenna to see if it receives even further!
The original install was an attic install of the spider, mounted on a pole at the peak of the attic:
I had originally mounted it to a telescoping pole to find the best position in the house where I'd get the best range and coverage. I found that a point along the southern wall peak surprisingly got the best northern coverage (or at least, the most complete radius.) Even with tweaks though, the maximum distance was still a disappointing 70-80 miles on average (with spikes near 80 miles to the northeast.)
For a while I was concerned that something in my antenna build was just messed up. Maybe the coax cable was bad? I briefly had the antenna directly connected to the dongle via only an adapter and was getting similar results. Maybe the BNC connector I used to build the spider was bad, or wasn't the right impedance:
I know 75 ohm BNC connectors exist, and have slightly difference mechanical specs, I looked and that wasn't it. I have dozens of these laying around, and adding a washer to mount the radials made this a quick build, so I built two more for testing to ensure something wasn't wrong. I used the second one to fine tune the radials and whip lengths, finding little difference until they were just too short and was getting very few hits past 20 miles.
I bought the Flightaware antenna on Amazon, and was excited until I saw that I had very little increase in range. My packets received increased greatly, as did the total aircraft detected in the range...but I had the same general limit as I'd had before.
For kicks and to experiment, I brought my Mk.3 spider up to my office with an older dongle, just to see what results I could get. I wasn't optimistic about it. I knew that the antenna would have a limited horizontal field of vision, my office has narrow windows, and the columns in between I believe are structural columns that probably contain steel beams, at the very least they'd contain dense concrete. As if that wasn't bad enough, there's a set of metal shutters along the windows that are permanently affixed to the building. The antenna would also have a fairly narrow vertical field to look through...like looking through a slit. The one good thing was my office is on the 7th floor, I'd estimate that with the mechanical level below me, I'm at least 75-85 feet above street level. Knowing that the couple of extra inches to mount along the top of my window wouldn't make that much of a difference, I built a small shelf for the spider to sit in that would sit at desk level. I work in a graphics shop where we produce posters, so I built out of a material I have plenty of: foam core board.
I suspect that the foam core is rf-transparent, at least at these frequencies, but I'm unwilling to try the microwave test with this stuff, so it's a complete guess. The antenna goes to about 4 feet of RG-6, then into the dongle adapter which is connected to my work laptop. Again, this was just to experiment.
I fired up the Windows build of dump1090 (not mutability, as I don't see a Win32 build for that branch.) I was almost immediately surprised by what I found. Not only was I getting a flood of packets, but I was seeing at least 175 miles of range, almost immediately. Throughout the the day I watched as that range filled in a bit more and I started seeing a much better footprint than I was at my house, with the same antenna.
Over four days of mapping, the best range I've seen was 275 miles, although I wasn't watching that flight at the time and I'm not logging on this machine like I do on my pi.
The strong directional reception I was anticipating...my office window faces directly north and I didn't expect much from northwest and northeast. What surprised me was the southern spikes. I believe I'm getting significant bounce from the building across the street. It's a tall brick building so it might be acting as a reflector, bouncing the signal 'over the shoulder' so to speak.
So far, my work antenna continues to receive more packets and more aircraft than my pi at home, albeit with a sharply focused receive pattern. I'm seriously considering moving my pi up to the office, or at the very least trying with the FA antenna to see if it receives even further!
