Facts are facts though and this keeps getting worst and worst.
It will be a few weeks before I can get back home again. But I will be changing back to the Spider, hell might even make a new one.
I made three antenna’s originally years ago
A coke can antenna. Actually worked really well
A 6’ long Coaxial Co-linear antenna antenna, results were not as good
A spider antenna
Wow, i am always jealous about such manufacturing skills…
Don’t be jealous until I post some real testing results. 
I’ve created a few antennas in the past that looked great in a simulation, great on the VNA but horrible in real life performance. I’ve also created a few that were marginal in the simulation and the VNA but performed really well in real life.
I’ll try the V-Stub in the next few days.
This is exactly my experience also.
Interesting, but with respect, why cut the radials where you did?
If your radials were twice as long, you’d have two radials per bolt.
Either you could have twice as many radials or half as many bolts.
The answer is quite simple… I didn’t think of that.
However, at this wavelength, twice as many radials isn’t going to help. The rule of thumb I’ve always used is to have as many radials as needed to keep the tips of the radials a little less than λ/4 apart. That gives the electrical appearance of a solid surface. The other concern I’d have is mechanical. As stiff as the steel wire is, adjusting 1 radial would probably cause the other to move or cause the wire itself to pop out from under the screw. Those are only M3 screws.
I might try it though if I’ve got time this weekend. I’ve got plenty of wire and a 10-pack of the N bulkhead connectors.
Maybe you can try to put a metallic cone around that? Cut a sector from a thin disc/plate and then join together? You can calculate the resulting cone angle:
http://jwilson.coe.uga.edu/EMT725/CarlCone/Solution.htmlhttp://jwilson.coe.uga.edu/EMT725/CarlCone/Solution.html
I actually have exactly that (a whip-cone) for other purposes but while cones are really good for wide/multi band use, they’re not so good for narrow band use. No to mention, they’re hard to tune and they can collect snow. Here’s some preliminary info to demonstrate why I’m concerned about bandwidth…
This is what I have to deal with:
The FA antenna connected to an unfiltered SDR will find absolutely NO aircraft at any gain setting. Right now I have the amp gain set to 20 as a test. Still no aircraft. The SDR is just completely overloaded. My antenna, with an amp gain of 20 sees 35 aircraft with NO filter. This is a simultaneous test, 2 radios of the same model with the same settings, two cables, made and swept by me, etc. if I add a filter to the FA antenna, I’ll get about 5 less aircraft than my antenna. Granted I could increase the gain on the FA’s SDR to compensate for the filter insertion loss but that wouldn’t be fair. This is one of the advantages of constructing and tuning your own antennas. You can fit it to your own specific environment. Now, would I actually run without filters? Probably not but I’ll have to do more tests. My “production” system is capturing about 215 aircraft but that’s with filters, antennas on the roof and a gain of about 40.
Again, this isn’t a knock on the FA antenna. You simply can’t mass produce antennas that work “the best” in every environment.
Oh, here’s what my plot looks like. The range rings are at 50mn intervals. The pesky Rocky Mountains get into the way in the west.
I don’t think that the ground plane has to be tuned that precisely like the active element you are describing.
Based on those high power antennas that I see in the picture, I would guess you need filters there. I have a LNA filter after my antenna.
The gain of the RTL-SDR Blog ADS-B LNA is 27 dB’s at 1090 MHz, and out of band signals are reduced by at least 60 - 80 dB’s. Attenuation in the broadcast FM band and below 800 MHz is actually closer to over 100 dB’s. In the LNA signal path there is first a low insertion loss high pass filter that reduces the strength of any broadcast FM, TV, pager or other similar signals that are usually extremely strong.
Exactly my situation, except that you have cell phone/communication antennas at hill top, and I have these on roof tops of my building and adjuscent buildings.
EXPAND TO SEE THE GRAPHS
You’re right, it doesn’t have to be but 5 mm of movement up or down on the tips of the radials can alter the impedance by a few ohms or more and that in turn can have a big effect on the “notch” in S11/VSWR. The deeper the notch the more you’ll reject outside your chosen target. It might be a moot point since I’ll probably use filters anyway but saving the insertion loss could mean reducing the gain on the LNA which in turn will result in less heat being generated.
I’m going to do a test without filters and see what levels I get from the TV/FM stations up on Lookout Mountain.
I’m kinda “lucky” in the cell phone respect. I get crap reception at my house from all the carriers.
You can do a scan and see the levels:
The LNA that I linked has FM and TV traps besides the usual SAW filters.
Results of tests I conducted in November 2016:
Please note the drop in performance of ProStick Plus (which you call “Blue Flightaware Dongle”) when External Filter was removed.
Yeah I’ve done that but it’s too much trouble. Easier to just use gqrx at one frequency and eyeball it.
I’ll take a look at that LNA, thanks!
Yeah no filter = no good. The price we pay for living in a modern world.
But it is a try and error. I am using the blue Pro Plus Stick with a Jetvision Antenna.
Adding the dark blue filter from Flightaware does not improve my site. Seem to be that i am far enough away from electronic obstacles
Absolutely! There are a ton of variables involved and only actual/individual testing can tell the real story.
Ok, it seems that I might get a chance to get back to home this weekend.
I changed the gain to 42.1 as advised and the reporting has actually dropped. Unfortunately, I have not been able to see the graphs that I installed as I am not on the same network, but this weekend I will.
If the error’s are greater than the 5% that was advised, do I go up with the gain or down with the gain?
Is the default gain set to 30 or?
Will I be tuning the gain to 42.1, 42.2, 42.3 etc.? or lager steps like 43, 44, or downwards even?
Thanks!!
