Hi, after making my own spider antenna with an old piece of RG56 coax as advised by this forum, I was impressed by the difference about 800 aircraft per day compared to about 40 with the old antenna bough on Amazon. I catch planes over 100 miles away on a regular basis. Thanks to the great community, Louis
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Edit: Just checked your stats, you have reception out to 160 nautical miles, that’s more than 100 miles 
For looking at the planes flying overhead it’s perfectly sufficient!
You can always try this filter if you have $15 to spare: https://www.amazon.com/ADS-B-Dual-1090-Band-Pass-Filter/dp/B010GBQXK8
Or reduce the whip part a bit in length, if i remember correctly i had to shorten mine to around 61 mm to get best results.
Ok, thanks for the feedback. On the filter I’m all ready using the “Plus” USB dongle, is the filter not included in that dongle? Also, As you maybe noticed on my photo my spider is only one single coax of about 5’ long with an RG56 connector at the end, would the filter work ok after 5 feet of coax and just before entering the dongle? I tend to keep things simple and would not want to add something that doesn’t significantly improve reception.
For shortening the whip, that is a no-brainer, it’s just that I won’t have any going back, I guess I have no way of knowing the impact except trying it? I was very careful in cutting it at the prescribed length of 64 mm. Thanks again, Louis
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I think that if you had left the insulation over the copper center wire, then you would have to change the length, because the velocity of EM field in the insulation is smaller than in air. Velocity factor is usually 0.8…0.9.
In air the wavelength of 1090MHz is 275mm. Divide by 4 (antenna is called lambda/4) and you have the whip length 68.75mm.
There are other factors in play.
Not sure what the effect is called, but it doesn’t matter.
My experimental results were also without isolation.
Cutting the 69 mm whip you have (64 mm + 5mm) by 2 mm will in my opinion give you an improvement.
At the very least it shouldn’t reduce performance.
The filter is located after the LNA, and that can be overloaded by interference as well.
For some people there was a big and for some a little improvement using the FA light blue filter for the ProStick Plus.
For some it doesn’t make a difference, depends on the interference in the location.
It doesn’t matter where the filter is.
Only for external LNAs it’s preferred to have them at the antenna, but even for them it’s not mandatory unless your coax is really long.
(With long coax you can also compensate by using expensive cable)
Did you take any close-up photo of the Spider while it was still on ground?
Sorry, as we always say, I should of, but I did not, will try to take one next time I go on the roof.
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If you download the hi-res photo, you can see a bit more detail, like the weatherproof sealant on the left side.
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