Thin (0.5 mm dia) Steel Tie Wire used to make collinear whip with V-stub.
Thin wire can easily be wrapped over threaded stud of magnetic base.
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Couple of questions:
Is this just a thought you had or is is based on a proven design?
Why do you measure from the screw thread and not the point where the coax is separated in the base?
This design (V-stub) is my thought. It may have existed, but I have never seen it anywhere.
Simply because when the wire is cut and bend, it is the measurement from the threaded screw which is required & used.
If someone wants to simulate the design, then he has to add to 58mm, the length from screw to the point of separation of coax. This lenght is inside base and is about 15~20 mm depending on individual make of the mag mount whip.
Just to complete the records, I have now measured the lengths in my mag-mount base and marked these on the diagram below.
The dimensions may vary few mm in mag-mounts from different manufacturers/suppliers.
Yep - understand.
Is the 30mm gap a random length or have you played with the dimension to optermise it?
I started with 10mm, increased in steps of 5mm up to 30 mm (did not try other sizes of gap).
Conclusion: Bigger the gap, better the performance.
FA
Tweaked dimensions using simulation software followed by physical trimming. Got improved performance over original design of first post.
Compared V-Stub whip with 52mm optimized whip. Conducted test by swapping the two whips. No changes in any other Hardware/Software. Results below:
CLICK ON IMAGE TO SEE LARGER SIZE
Thin (0.5 mm dia) Steel Tie Wire used to make collinear whip with V-stub.
Thin wire can easily be wrapped over threaded stud of magnetic base.
To tune the antenna to best receptiom/SWR, instead of cutting the wire, use a sliding piece of wire attached at top wire with a sleeve or tape. Once sweet point is found, solder the two wires in position.
CLICK ON IMAGE BELOW TO SEE LARGER SIZE
CLICK ON IMAGE BELOW TO SEE LARGER SIZE
@abcd567 You said in the other thread…
…so I did.
I had to make a modification to the radials though. With 4 horizontal, I couldn’t get a good impedance match so I wound up using the 4-double arrangement and bending the radials UP almost like a co-linear. With that though…
I just started testing it next to my mutant spider so I’ll see how it does over the next day or so. So far it doesn’t look like it needs to be double filtered to reject all the RF crap around me. I’ll also test what effect rotating the “V” has on message rates and gain. It does have a slight effect on impedance as you might expect.
It looks like a dead spider at the hand of Vlad The Impaler.
You guys are too funny!
Here’s a two hour comparison with my mutant spider.
Same RadarBox 1090 SDRs, no additional filter, same coax, etc.
Same dump1090-fa settings… gain 44.
The Mutant Spider:
The V-Lad (previously V-Stub):
They’re very close in terms of performance.
@abcd567 suggested I try with the radials back at horizontal which I just did just after I captured the above graphs. I’ll post the results in about an hour and a half.
Too bad there is no attributable gain between 44.5 and 48 since it appears your setup could use a touch more. Interesting results, keep them coming.
Looks slightly better with the radials the way you had them judging by the averages. That’s my interpretation anyhow. Can try one more side by side using your original radial position and 48 gain on the Mutant? (May be too much gain, but I’m curious…) - keep the watermark the same.
EDIT/ADD: If you have Virtual Radar Server setup, you can drag data from both setups at the same time and compare messages to go along with your graphs. It can help tell a good story. I love side-by-sides 
Oh, let me clarify. I didn’t touch the spider; I only flattened the V-Lad. I wanted to keep the spider stable as a reference.
Current Mutant Spider:
Current V-Lad:
The V-Lad improved with the radials flat vs the radials bent upward. I’ll run the VNA on it after lunch.
Ohh, OK, either way, the first Mutant Spider (very top graph) test appears to be showing the best result the way I see it - but it could have been the V-Lad adjustment flattening the curve since they were much more comparable on the bottom test - so flat radials on the V-Lad helped me thinks. I initially read it that you were adjusting the Mutant - so your watermarks are on the top graphs. I’m in the game now. LOL
Perfect time to toss a little more gain on one of them since they are so close to see how it changes things.
V-Lad appears to be showing ~1-2db more on your signal than the (Mutant) spider as well
