While browsing on eBay, I came across this sturdy and neat lookig $10 ground plane (Spider) antenna.
It is for 800-940 Mhz, but if its elements are trimmed to 69 mm, it will be resonant at 1090 Mhz.
Has anyone tried it? I would have purchased it if its shippig charges from next door USA to Canada were not 150% of its cost 
Why?? You make better antennas than that for free. 
Also, it looks like it has an N connector. More stuff to buy. I think if you’re curious about the effect of the larger gauge wire you could get a couple of welding rods and make one just like it, but with a F connector.
True. I got carried away by its beatiful & neat looks. You know I am not crafty, so my antennas are ugly, and their elements are made up of wavey wires, sometimes even having kinks. It was love at frst sight
I know what you mean. Those professional looking antennas look great. But as we all know, it doesn’t have to be pretty.
You can buy all the materials from local hardware store. You may not be crafty but all your experiments, calculations and diy performs better…
@blueskyspotter
Thank you. Your remarks are very encouraging.
stumbled over this - and immediately thought that’s something for abcd 
http://ads-b-antenna.blogspot.de
cheers
tom
p.s. you find different filters and amps there too …
@ToMuc:
Interesting. Thanks for sharing.
QUICK DATA:
Item: ADS-B antenna
Frequency range: 1030-1090 MHz
Gain: 1.53dB / 3.67dBi
Polarization: Vertical
Pattern: Omni directional
Impedance: 50 ohms
Size: 140x140x65 mm
Weight: 60 gram
Material: FR-4 laminate
PRICE 20 Euro
SHIPPING 5 Euro
abcd - what was the URL for this antenna? searching on fleabay has been fruitless. Dependent on the cost to get it to Australia, I might give it a go.
Cheers.
Might be this one?
http://www.ebay.com/itm/Maxrad-800-MHz-Omni-Directional-ARDIS-Ground-Plane-Antenna-NEW-/201348635313?hash=item2ee1505ab1:g:AI8AAOSweW5VAzVv
The shipping charges are more than the cost of antenna
YES, you found it right.
Whoa, I see what you mean about shipping?!? That’s insane! $3.99 to ship to me in California, $15 to ship to you in Canada. And you probably are closer to the seller than I am…
This antenna is made by Adam - 9A4QV
It is a folded monopole and excellent for static reduction as it is a direct DC short to ground - be careful with this antenna if you have Bias-t voltage on your coax as it will look like a short circuit to DC voltage and may damage your Bias-t voltage supply.
He also makes the LNA4ALL and the ADSB1090 filter
I have just purchased the amp and filter (but not yet fitted) - parts are well made and delivery was less than 1 week.
Postage cost was combined for all items (he only charged once for postage for both items).
Nigel.
and $23 to ship to me in Australia - but … I reckon thats not too bad for what I want to use it for, which is a portable ADSB setup. Considering I can’t get one of the Flightaware ones from Amazon, this may the next best alternative and taking into account its size, for a portable setup it’d be spot on.
I just ordered one, we’ll see what happens when it’s delivered. Shouldn’t be too hard to Dremel the elements but measuring to get the exact length may be an issue. Hopefully there is enough room to get the digital calipers in there.
Give us update after you tested that $10 antenna…
Measure the 3 slanting radials 69mm from edge of disc to the tip of the radials. Do not measure 69mm from center line of the antenna / whip.
While making the DIY Spider using SO239, the slanting radials are measured from the edge of the flange, not from center of whip. The additional horizontal surface provided by flange improves the performance. In MaxRad antenna a small disc does the job of flange.
TomW of Planefinder forum has tested two Spiders, one with radials measured 69mm from vertical whip, other with radials measured 69mm from the edge of flange, and found that the one in which radials are measured 69mm from edge of disc performed better than the one in which radials are measure 69mm from vertical whip (center line of antenna)
EDIT: Jan 08, 2016 - Corrected last sentence (in red color) above.
Click here: Side by side antenna testing - by TomW
TomW’s two Spiders under comparison test:
Left one has radials measured 69mm from the antenna center line /vertical whip.
Right one has radials measured 69mm from edge of the disc.
Spider measurements with SO239
Note the length of radial is measured 68mm starting from edge of flange.
Thanks for the very helpful information, I’ll have to get the OPi all dialed in with the graphs so I can do a good comparison. (I think this may be the top of the slippery slope down to filter/amp/external mounting, lol…)
(1) Cutting vertical whip to 1/4 wavelength basically most effective in optimizing the antenna to that frequency.
(2) Cutting radials to 1/4 wavelength is not as critical as the whip trimming. Radials even somewhat longer than 1/4 wavelength are ok. Radial shorter than 1/4 wavelength reduce gain.
(3) Angle of bending down the radial affects impedance & swr. Horizontal radials make antenna impedance around 30 ohms, and 45 degree makes something like 60 ohm, a good match for both the 50 ohm & 75 ohm systems.
(4) Some amount of horizontal groundplane at base of whip (like flange of SO239 connector, or copper disc in TomW’s spider) does improve antenna gain. I have tested this by comparing two antennas, one made of F-barrel connector (zero flange) other with SO239 (1" x 1" flange).
