best antenna

[abcd567]

1. For someone who's new to antenna design and theory, how important is it that I seal/weatherproof the connection between the center wire and the SO-239 core element? I've seen mention of sealing, weatherproofing, and enclosing these antennas, but how important is it really?

It is not very essential. Lot of people use it without any sealing, weatherproofing, and enclosing.

It works ok without sealing / water proofing. However after some period (say 1 to 3 years, depending on local weather conditions), rust & moisture set-in, and performance drops, or fails altogether.

Applying water sealing increases the span of trouble free service.

2. Would a more accurate measurement and completely straight wires help the antenna perform much better, or is that a nominal difference?

Depends how inaccurate it is initially. These antennas are very tolerant to dimensional errors, and will work OK even when built with an average skill. Making wire length, straightness of wires, and angle of bend more accurate may give an improvement of say 5% ~ 10% if it was originally build with an average skill.

3. Would soldering more wires on (say, 4 more to make it an 8-legged spider) make a big enough difference?

It does make an appreciable difference, say 10% to 20%, but not a BIG difference.

4. Compared to those options above (improvements), would the better choice be to add an in-line amp?

First you should try improving the antenna.
After antenna improvement is done, then add an amplifier.

[aesoprrp]

Delved into this thread a few weeks ago, and started out with a cantenna for my first DIY antenna build. Surprisingly good results! Got about 160nm range from my south-facing apartment window.

So, naturally I want to see how far I can take this project, so I tracked down some SO-239 connectors, and this past week I soldered together a 4-legged spider antenna (see attached photo - no idea how to rotate it, sorry!). Measured roughly, bent the wires haphazardly, and mounted it in PVC piping with tape on the brick outside the window. Seeing about a 10% increase in data from this antenna over the cantenna. Pretty cool! I have a few questions for anyone who cares to chime in:


1. For someone who's new to antenna design and theory, how important is it that I seal/weatherproof the connection between the center wire and the SO-239 core element? I've seen mention of sealing, weatherproofing, and enclosing these antennas, but how important is it really?

2. Would a more accurate measurement and completely straight wires help the antenna perform much better, or is that a nominal difference?

3. Would soldering more wires on (say, 4 more to make it an 8-legged spider) make a big enough difference?

4. Compared to those options above (improvements), would the better choice be to add an in-line amp?

My apartment is up pretty high, but the antenna can only see South, East, and West. Almost zero north coverage due to the building and the mountains directly to my north.

Thanks for the help!

[abcd567]

IMPEDANCE MATCHING STUB ADDED TO HORSESHOE ANTENNA

Untested proposal. Expected to bring down SWR from 3.5 down to < 1.5

[abcd567]

SIMULATION OF HORSESHOE ANTENNA


Gain = 3.2
SWR = 3.5

[abcd567]

Horseshoe Antenna

Found a very interesting horseshoe antenna made by galenthurber.
Please see this thread

[petercr]

Got up on the roof today and relocated the FR24 antenna from its previous location on the side fence to above the TV antenna... now sitting about 1.2m above the highest point of the roof-line...
(also solved a TV reception issue)
FR24 antenna on roof.jpg

(shot of previous location in this post https://forum.flightradar24.com/thre...l=1#post105113)

[mem0tap]

Screenshot from 2018-07-20 23-06-53.png - results of my 'new' waterpipe antenna. fitted around midday Tuesday, it's mounted 7 feet below Jetvision antenna (which yields around 2400 a day, Since it looks promising I've upped the anti a touch and building an 8 section 22mm outer, 8.5mm inner air spaced.

[Rooster]

Rooster:
[ATTACH=CONFIG]9675[/ATTACH] [ATTACH=CONFIG]9675[/ATTACH] [ATTACH=CONFIG]9675[/ATTACH]
Fully agree with you.

Glad to see you after a long gap. Welcome back.

Thanks mate - keep lurking, but not a lot has happened on here :-(

[abcd567]

Below are the simulation results for a CoCo (8-Elements, made of coax VF=0.86).
These results show how a 1 or 2 mm error in element length can grossly affect SWR and Radiation pattern.
Gain is relatively less affected by 1 or 2 mm error.

The error in element length can either due to using wrong VF, or wrong cutting or a combination of both.

In this simulation the a VF of 0.86 was used, giving element length 118 mm.


SWR vs Element Length




Gain vs Element Length




Radiation Pattern vs Element Length

[abcd567]

Despite designing my own antennas I'm not an antenna expert, nobody is, it's a black art, guided by experience and a few rule of thumb calculations. I reckon for every successful antenna there's a few dozen in the bin!

Fully agree

[abcd567]

Rooster:
thumb-single.jpg thumb-single.jpg thumb-single.jpg
Fully agree with you.

Glad to see you after a long gap. Welcome back.

[Rooster]

A couple of questions being no expert in this subjects.
-Can be two different type antennas be plugged at the same time (A spider and a Coco for example)?
-Using a Coaxial antenna can bring much improvement compare to a spider antenna? If so, what type of improvement? An increase in the distance of the planes registered or an increase in the hits/position catched within the same distance?

You cannot connect two at the same time (technically you can, but theres no advantage +its VERY difficult to do correctly)

The spider is a simple "half wave dipole" and as simple as antennae get - the coco (colinear) adds more elements , and so more "gain" ie you can receive further away signals.

The crux of the matter is accuracy... and we are talking fractions of a millimetre at these frequencies - the spider is only critical at the centre element, so you have a good chance of getting "near" - and near enough is usually good enough !!!!

When making multi element antennae, the errors in cutting mount up... and its easy to create an antenna that is far worse than a simple dipole.

[mem0tap]

A couple of questions being no expert in this subjects.
-Can be two different type antennas be plugged at the same time (A spider and a Coco for example)?
-Using a Coaxial antenna can bring much improvement compare to a spider antenna? If so, what type of improvement? An increase in the distance of the planes registered or an increase in the hits/position catched within the same distance?

There are multiple antenna installations (Yagis e.g) - but different types of antenna? - if you did manage to couple them so that all impedances lived well with each other, you would find 'phasing errors' which means the signal would mostly arrive at each antenna at different times sometimes adding sometimes cancelling. I would suggest you either use an antenna switching unit (but there will be losses this way) or have separate receivers. - Despite designing my own antennas I'm not an antenna expert, nobody is, it's a black art, guided by experience and a few rule of thumb calculations. I reckon for every successful antenna there's a few dozen in the bin!

[goku1976]

A couple of questions being no expert in this subjects.
-Can be two different type antennas be plugged at the same time (A spider and a Coco for example)?
-Using a Coaxial antenna can bring much improvement compare to a spider antenna? If so, what type of improvement? An increase in the distance of the planes registered or an increase in the hits/position catched within the same distance?

[mem0tap]

Makes an interesting alternative to electrical conduit that I had my previous CoCo installed in...

So pleased with it, I've designed a prototype using 8.5mm water pipe as a core and 22mm as a shield, 51.3 ohm 66pf/metre 175 nH/Metre, I'll be using 100% air dielectric so propagation will be a shade under 100% with 137mm sections - working on the jigs to build it (as you can see below BUT the soldering Iron is not up to it) and there are other problems I foresee, - no more pipe for one thing!!! and i can only buy it 3m lengths The original prototype seems to be happy to receive echoes from 160nm against the original Jetvision 109nm based only on 24 hours of data. CIMG3761.jpg IF anyone is interested I'll keep posting pictures and progress otherwise I'll save myself some time.