Most important thing in CoCo is to know the correct Velocity Factor of coax.
Thank you for your guide.
In my setup:My location (VVCI)
It’s crazy! a $45 vs $470 
Thank you for conducting side-by-side comparison of V-Stub antenna with commercial antennas.
You are using V-Stub with radials slanting down.
Simulation results show HORIZONTAL radials give a better SWR than the slanting-down radials.
Plase conduct the side-by-side comparision with radials of V-Stub bend up to become HORIZONTAL. Hopefully you will get somewhat better performance.
I don’t expected a magic happening to it.
I will try and report back. Thanks.
You are right.
Making radials horizontal wont do magic, it will improve SWR just a little bit. That is why I have said “somewhat better”.
As the V-Stub antenna is already mounted on roof and performing good, please do NOT bother to make radials horizontal.
Sorry to bump this 2016 thread again, but I read it from the beginning and may have a general suggestion. It seems that using a higher gain antenna consistently gave worse performance, and changing dongles made a big difference. I wonder if the dongle AGC gain might be set at the software defaults, which can overload some receivers.
A gain antenna will not only pull in a stronger signal, but also near band noise will be stronger too. A filter may improve performance, but only if there is something that needs filtering.
As always, your equipment needs to suit the location.
Setting the SDR’s gain is SOP for any feeder setup or whenever something has changed that affects gain (different coax, adding or removing an LNA, or changing antennas.)
Only if the location of the noise source falls within the radiation lobe pattern of the antenna. It’s possible that a higher-gain antenna will pick up stronger interference from cell towers that weren’t in the range of your old antenna in which case a filter would help.
Isn’t that what I said?
That’s the case at my location. I was starting with a 3dB Antenna, went over a Jetvision 5dB and currently operate a 7.5dB Vinnant.
Before moving to Airspy and later Airsquitter i was using the blue FA stick together with the dark blue filter for 1090 MHz
By removing the filter there was not much difference from reception.
I was only able to increase gain to almost max without having an increased messages > 3dbFS
Number of positions and number of aircraft was pretty much the same, independent from which antenna was attached.
But it seem i do not have that much interference from other signals here.
And using AGC is never a good idea, at least not for the FA stick:
AGC works very well for broadcast TV or radio stations as well as portable/mobile receivers where the signal strength varies relatively slowly.
Where it fails to cope is the very short ‘bursts’ typical of TDMA where no two stations can be expected to have the same signal strength.
The very short duration of an ADS-B transmission just looks like noise to an AGC.
