I have a rather unique situation in that I am essentially along the line between two busy airports: KMKC and KMCI. I’m a little off-center and not quite at the midpoint, but Great Circle Mapper says that it’s like 7 degrees off from one and 9 degrees off from the other. I have the FlightAware antenna for omni-directional pickup and it’s working fine in its current position, picking up aircraft at up to 160nm easily to the southwest with no issues and up to 220nm when atmospheric conditions are just right (I plan to raise it about 10 feet to get more in other directions as well as clear some nearby obstructions).
What I want to do is set up a second ADS-B receiver with directional antennas set to low gain to pick up the ground traffic at KMKC (which I am 200 feet above and, were it not for trees, would have a clear line of sight), as well as try to get more of the traffic flying in and out of KMCI (which is about 100 feet above my antenna position). Since I’m so close the the line between the two airports, and because I try to be thrifty whenever possible, I thought that maybe I could use a single antenna with high back-lobe gain:
Does anybody know if there’s an antenna that would be ideal for this situation? It seems like a Yagi would be a good option, but I’m sure I wouldn’t want a corner reflector in this case since I want the back-lobe pickup. I’m also not certain what the back-lobe reception of a yagi looks like (there doesn’t seem to be much information about antenna gain parameters like the diagram above that I can find). It also seems that the traditional yagi antenna has a rear-reflector element even if I don’t add a corner reflector.
Is anyone here in a similar situation? What solution did you come up with? For those of you who are antenna hounds, could I get a yagi and cut-down the rear reflector element to make it a director element and at least get some decent back-lobe gain?
Any advice, links, diagrams, etc., are appreciated.
Might be easier to change houses than build an antenna with your desired characteristics.
Maybe install three systems, one with a decent gain vertical to cover the whole area, and two with separate yagi antennas aimed at each airport. My guess, the first one will get better results than the other two combined. If you install some method (tower or tilt up pole) to get your first system as high as you can reasonably, you will get all the signals you desire. Have fun!
Change houses? At 7-plus percent mortgage interest? Are you shrooming? Besides, there’s no way my wife lets me leave this school district, and I’m not 100% sure I could afford a different house here after what the market’s been doing lately!
The purpose for the directional antennas is to pick up specific locations that should be visible to me but for which an omni-directional antenna optimized for long-range pickup isn’t suited.
If it has to be two antennas, that’s fine, I can deal with it I’d just rather not. So I’m trying to find out if there’s an antenna style that has both high front-lobe and back-lobe gain. I suppose that I could put up a low-gain omni-directional antenna for the same purpose, but since the high gain antenna picks up traffic at KMKC while it’s in the air, why wouldn’t I pick it up on the ground? Except for some local interference or ground clutter, I don’t see a reason that the omni-directional wouldn’t pick it up. My thinking (hoping) is that a directional antenna could cut through that, depending on what’s obscuring the signal.
Jetvision offers a Yagi-Antenna. Just get two of them, point them in the two opposite directions, use two ADS-B sticks on your device and join them using an appropriate script (e.g. combine1090 )
Still expensive, but cheaper than buying a new house.
Have you confirmed that higher gain on the omni is the reason that you aren’t seeing nearby ground traffic?
If reducing the gain with the current antenna improves nearby reception, another option might be to get a receiver with a wider dynamic range. I use an Airspy mini which runs at close to maximum gain (18+ where max gain is 21) and has no problem receiving very close aircraft.
I’d also be inclined to see what happens when you raise your current antenna, before trying other approaches.
@JRG1956 Raising the antenna is the first project. That might even happen next week if the weather cooperates. This post was “looking ahead” at the possible next project. I’m not certain that high gain is causing the problem, but I’m also not just not convinced that an omni-directional antenna is a good choice in this instance. I’ll also look at the Airspy, but I have zero experience with SDRs other than the FlightAware dongles.
@abcd567 I’m afraid I’m not terribly knowledgeable with antenna theory or design, so while I get the general concept in the post from your reply (and I’ll read through it again when I have more time), I don’t think I could replicate what the author was presenting. It’s good to know that something like what I’m seeking exists. I just don’t think I could build it from scratch.
@foxhunter Maybe I should have said “I’m cheap” instead of “I try to be thrifty!” But I had considered your idea. Didn’t know about Combine 1090 and will look at that as a possibility.
My parents have told me about those nightmare days. I remember seeing 5-8% back in the late eighties and through nineties, but I only ever had to deal with student loan rates in that range.
Use a receiver with high dynamic range (more bits resolved in the analog to digital converter if you want) and you can pick up both string and weak signals, with just one omni antenna.
Besides, there’s no way my wife lets me leave this school district, and I’m not 100% sure I could afford a different house here after what the market’s been doing lately!
But I had considered your idea. Didn’t know about Combine 1090 and will look at that as a possibility.