I only really just got into ADS-B receiving/ tracking and have been inspired by many of the numerous posts here about reception, filters, antenna construction and testing, etc. There are a lot of very knowledgeable folks who have written very detailed instructions that anyone can follow.
Like many new users, I was in a hurry to get going and so built two antennas; one 1/4 wave spider and one 8 element collinear. I experimented with un-amplified Rg6 coax runs of varying lengths feeding into the FA Pro + dongle into a Raspberry Pi. While I was receiving 30-40 flights with each design ( yay, sparky it works ) and ranges of maybe 90nm, I was thinking my antennas were probably not spot on and I probably simply wasted my time with those efforts and should have just bought the FA antenna and better coax.
I built a second Pi and moved the same collinear to a different location. HUGE and I mean HUGE difference ! Same un-amped coax and using no filter other than the Pro + dongle internal filter I’m seeing 150+ planes out to ~250nm - nearly the same as the HeyWhatsThat website depicts for this low (12ft above sea level) elevation.
The antenna was built from junk Rg6 coax of unknown heritage that was just lying around and may not even be tri-shield. I also apparently watched the wrong how-to video as I used 111mm element lengths and it’s not terminated. I did artistically add a 1/4 wave element to the last element and mount it inside a sealed 3/4" PVC pipe … In other words, this thing probably should not be working at all I was totally ready to pitch it into the trash.
The reason for my post ? For anyone who is starting out and not getting the results you expect, for heavens sake, move your gear and try it at another location as a sanity check. Location, location, location.
What I hoped to be my main FA site is location-challenged and while I’m going to work on improving it, there’s no miracle fix for it.
Yes, you are right.
Both the location and height of antenna greatly influence reception, but location has more influence than height, specially if you move from indoors to outdoors.
Did you also try your Spider at the better location? The Spider is a good bench-mark antenna to judge the coaxial collinear by comparing performance of the two, while keeping everything else same (location, height, length of coax, dongle etc).
Unfortunately I had left that spider running at home in case I couldn’t get this location up and running. I’ll have to cobble up another spider or cantenna while I’m here to test and then bring it back to do a comparison at my other location for a benchmark.
Sorry, just got distracted by an unknown plane at 58,500 ft, I presume military as there is a lot of it around this location. I didn’t expect to pick up anything like that…an hour later one at 118,700 ft. Really ? What the heck would that be ?
Hi Skip, great news about the extra hits, can you let us know where you moved it from - to, so we have an idea if a move of location would work for others.
So here’s the scoop. Location one is heavily treed, perhaps 6 or 7 nm from KRDU airport. Land is at 350-400 ft above sea level , sloped upwards toward the West, and there are numerous nearby residences and associated competing wifi, cell and other RF clutter. Suburbs. Best sky view is towards the NNE in terms of obstacles. I’m not done with my setup there but it is not at all ideal.
Location two is near Beaufort NC, wide open at nearly sea level, with only a couple of tall condo complexes to the SSE and SSW to block line of sight, Great open sky but compromised some by low elevation- I cannot get an antenna above 12 feet or so above ground level, and that’s only about 7-9 ft above mean sea level. I’d probably have to elevate the antenna 150 ft to overcome the condo blocking, so its a moot point.
As good as location two is in terms of reception, part of that great reception/ range is maybe hindered by the fact that a great percentage of the surrounding air traffic goes on over land on a NE/SW track, leaving the East quadrant with relatively sparse traffic that flies over water ( transatlantics, Caribbean, etc.)
Inland, a similar situation might capture heavier traffic on all points of the compass - so that’s learning point number Two for me: you can have great ADS-B reception and not have planes that fly where you are able to see them. 80+ percent of the traffic at that location is in the Western half of the map. ( from about 200 degrees clockwise towards 20 degrees) As I type this, the Eastern half of the map is nearly empty of planes.
So just to follow up I built a 4 wire spider - had no SO239 here so used a 1/2" copper pipe cap as the base, center drilled for the coax bulkhead connector. Drilled 4 holes 90 degrees apart just below the flat end, inserted 18 ga copper ( actually ran two pieces straight through and bent them to clear the coax connector) and soldered the ground plane, bent to 45 deg down. Trimmed to 69mm free length.
Results at the same location and height were not as good as the collinear but I may take that one and continue tuning it at my other location.
Weather proofed my install as best I can as this is a really tough environment: heat, salt, humidity and at times high winds. Fully expect that it will brick within the year.
I have tried to build a few spiders using s0239, just cant get enough heat into it to solder. I ended up drilling holes then bolted the radials on. My other spider was the one commonly shown here using just the rg6 and placing the radials into the coax. I find both perform the same and give me good range. The copper rust quickly and i replaced one yesterday. The rusted radials drop conductivity, and quick sand paper and its back to normal. I built another and sprayed with silicone spray, so i hope that will slow down the corrosion. A Cantenna is great too, i just found it had slightly less range.
8-Leg Spider performs better than 4-Leg version.
Try Quick Spider, does not require soldering and does not require SO239 or any other connector what so ever.
For outdoor use, apply sealant at its hub to prevent ingress of moisture inside the coax. You can also spray it with some sort of paint or silicone to retard corrossion of whip and radials.
Nature’s selection: 8 legs for all species of Spiders
Do not bother with SO-239, or any other type for now. Use an RG-6 cable TV patch cord already terminated with F plugs on both ends. Depending on the length, you’ll have material for 2 QuickSpiders terminated with F plugs.
Then go to eBay, and buy adapters from F to any other type you have/use. Yes, you are adding some losses, but so what? They are easily compensated for if using the FA dongles, or any other ADS-B preamps.
I guess the good part is that for folks that like to build stuff, there’s always the next one.
My first spider has bolted ground plane elements. After only a few days they started to corrode around the 8-32 bolts.
One aspect of the collinear I built is that it is much more weatherproof in use than any of the spiders or antennas with exposed elements, so perhaps that is a good thing in the long run.
An indoor antenna is probably more durable in designs like that.
It may not be pretty but my antennas do work pretty good. I can see out from Lawton Ok, to the Mexican border. Takes time to experiment and have success.
Cantenna is tolerant.The food-can need not be precisely the dimension of soft-drink can (66 mm dia, cut to 69 mm height). A 5~10 mm fatter and 5~10mm taller food can will perform almost equally good.
I was totally ready to pitch it into the trash.
