best antenna

[rederikus]

My LNA + filter http://www.ebay.com/itm/1090MHz-ADSB-Filter-LNA-band-pass-filter-with-SMA-connectors-Mode-S-SAW-aviation-/122360480859?hash=item1c7d40c45b:g~AAAOSw44BYZl4~ arrived this morning so I tested it with my Franklin antenna. The range improved quite a bit but not as much as I had hoped.

I then decided to put an extra element on the end of the Franklin. 20170224_135528.jpg20170224_135545.jpg Once more range increased but it is still not to the limit defined by the HeyWhatsThat 30,000 ft Up In The Air ring.

I think I am done building antennas. I shall wait a couple of weeks and then buy a DPD Productions model.

[MrMac]

I agree with you that the extra heat is not needed. I would not mind getting rid of the switch entirely. I may ultimately drop back to one station once I have finished playing with antennas and got the absolute maximum range that I can squeeze out of all this.

I would just add a kit like this and remove the switch. I had a switch completely destroy my AIS reception on one site, you never know which ones are good or bad...

https://www.amazon.co.uk/Ethernet-Ca.../dp/B000Q6EC0C

I think I am done building antennas.

Building low-gain antennas like GPs or dipoles is easy, but most people will never be able to build anything above 3dBi gain without instruments, and even then it's hard to get it right. I used to work for a company that had one of the worlds best antenna measuring ranges, so I know...

/M

[rederikus]

I would just add a kit like this and remove the switch. I had a switch completely destroy my AIS reception on one site, you never know which ones are good or bad...

The switch will not be staying. It is there because I am currently running two stations. Main, T-KCLT3 only gets known good upgrades once they are tested and proven working on my Test station T-KCLT19. Once I have the setup as good as I can get it then I will drop back to a single system with a single CAT5 cable going into one single Raspberry Pi3. The switch will then go away. My LAN is nearly all gigabit and I am fairly good with IT type stuff.

Building low-gain antennas like GPs or dipoles is easy, but most people will never be able to build anything above 3dBi gain without instruments, and even then it's hard to get it right. I used to work for a company that had one of the worlds best antenna measuring ranges, so I know...

Making antennas is fun and I got lucky with the first collinear type I built. It is still the best antenna I have. The lack of high quality measuring equipment is a major stumbling block. My oscilloscope only works up to 30Mhz so it is useless for ADS-B. I know that I must be doing sort of OK since my station T-KCLT3 is currently #2 in Charlotte NC, where I live. However I am not sure if that means I am doing really super well or, just OK-ish if you see what I mean. Many stations here have better range that me but less uptime so it is really hard to find a level.

I am an electronics engineer turned IT manager and now retired. I understand the theory pretty well and have worked in professional satellite ground stations as well as working up masts and aligning Yagis and point to point microwave dishes - A looong time ago. The problem with home built antennas is benchmarking them. I do not fully know what results a "perfect" (no such beast...) antenna would deliver at my home station. I have looked at HeyWhatsThat's, Up in the Air rings on maps and find that I seem to be getting more range than I should in some places but far less in others.

The only way to be sure I'm getting the best from my system is to buy a really good (and expensive) professionally built and tested 1090Mhz antenna. Of course, once I have this as my benchmark standard, I can check it against my home built devices but, then there is no point in doing so as I will now have a very good antenna in place.

[Rooster]

There is really little need for building (or buying) antennae with "gain"
Aircraft fly in essentially a hemisphere over your head... so a 1/4 ground plane is the best for overall coverage IMHO - antennae with "gain" dont actually have ANY gain whatsoever... they simply redirect the radiation pattern, ALWAYS at the cost of coverage elsewhere... Imagine it as a torch bulb, visible from all angles - now add some "gain" in the form of a reflector... yes it LOOKS brighter - but only in the one direction.

[rederikus]

What you say is true for a ground plane antenna. If you used a simple dipole then it would be as you say, gain in one place would result in a loss in others. The classic cardioid pattern. The length of the antenna is critical because it resonates and the required frequency. In this case at 1090Mhz. This amplifies the signal just as a guitar string makes a noise of (mainly) one note as it is plucked on a particular fret. The amplification is not caused by an amplifier. It is only caused by resonance. It also rejects other frequencies (I am ignoring harmonics here) and so also acts as a filter. This is what you describe I think.

Consider a collinear antenna where there are multiple antennas all independently resonating and producing signal. The antenna is vertical so there is no loss of signal anywhere in the hemisphere. There is an effect wheregenerally the more elements you introduce, the larger your hemisphere becomes at somewhat the expense of nearer signals. Thus an antenna of this type can pick up signals from further away than a simple ground plane antenna with just one receiving element. This is expressed as dBi (decibels relative to isotropic radiator). An isotropic radiator is (I think) considered here as a point source and I assume carries a value of 1. The multiple element signals are additive and, naturally since bigger numbers are easier to sell the marketing people tend toward using dB instead of dBi as a "gain" figure.

I have built various 1090Mhz antennas and have had varying positive results when compared to the original non-ground plane. I first used a tomato can underneath the stick antenna. This worked much better when I connected the feeder shield to the can and formed a real ground plane - duh. I then made a spider. Better still. Better here is defined (by me) to mean increased range in all azimuths. I built an 8 element collinear and this first try increased my range by nearly double. It is still my best antenna. Encouraged I moved on to a 16 element collinear. Not so good as the original 8 element. Since then I have built several more collinears and none have given the range of my initial effort.

What it has done is to convince me that I can see aircraft further away with certain antennas than I can with other. My conclusion is that the better the antenna, the further I can see given the same antenna height and the same receiver.

I therefore think that an antenna that produces signals from further away may be defined as gain withing the hemisphere relative to either an isotropic point or a (however bad) reference antenna.

[F-EGLF1]

There is really little need for building (or buying) antennae with "gain"
Aircraft fly in essentially a hemisphere over your head...

Actually they don't fly in anything like a hemisphere, I can detect aircraft out to 300+nm in all directions other than straight up! I suspect that if they flew at that height the ISS would be considered a collision risk��
Antenna don't require much gain straight up as the distance to an aircraft overhead is much less than one on the horizon, that is where you need the gain.

[MrMac]

There is really little need for building (or buying) antennae with "gain" Aircraft fly in essentially a hemisphere over your head... so a 1/4 ground plane is the best for overall coverage IMHO - antennae with "gain" dont actually have ANY gain whatsoever...

Completely untrue, all of it.

The definition of antenna gain is passive re-distribution of radiation pattern. Every dB that can be won from a direction where you don't need it, is added link margin for detection of weak signals, or overcoming feeder loss.

A 5dBi antenna is often optimal. It will outperform your 2dBi GP every time, and still have enough gain straight up not to lose a/c above your head.

Gain is not amplification, but it's most definitely real, and beneficial.

/M

[MrMac]

The antenna is vertical so there is no loss of signal anywhere in the hemisphere. There is an effect wheregenerally the more elements you introduce, the larger your hemisphere becomes at somewhat the expense of nearer signals. Thus an antenna of this type can pick up signals from further away than a simple ground plane antenna with just one receiving element. This is expressed as dBi (decibels relative to isotropic radiator). An isotropic radiator is (I think) considered here as a point source and I assume carries a value of 1. The multiple element signals are additive and, naturally since bigger numbers are easier to sell the marketing people tend toward using dB instead of dBi as a "gain" figure.

It's not at the expense of nearer signals, it's compressing of the radiation that would otherwise go upwards and downwards. The more elements you add (if done optimally), the smaller opening angle towards the horizon you will get.

An isotropic antenna is a theoretical point from where radiation goes exactly equal in a sphere. This is referenced as 0dBi.

A 1/4-wave GP has 2dBi gain in it's sweet spot (normally towards horizon and slightly upwards), most of that is "taken" from what would have been the lower half of the spehere.
A 1/2-wave dipole has 2.15 dBi gain, taken equally from top and bottom of the sphere.

Collinears vary in gain depending on how they are built, but they all just compress the "sphere" further and further into a horizontal "disc".

/M

[Rooster]

It's not at the expense of nearer signals, it's compressing of the radiation that would otherwise go upwards and downwards. The more elements you add (if done optimally), the smaller opening angle towards the horizon you will get.

Exactly... at the expense of vertical signals !!!! Adding elements magnifies this effect...
Point taken over the hemisphere - wasn't meant as an English experiment, I only used it as an example - 360 degrees around and some up ! lol

[abcd567]

It's not at the expense of nearer signals, it's compressing of the radiation that would otherwise go upwards and downwards. The more elements you add (if done optimally), the smaller opening angle towards the horizon you will get.

An isotropic antenna is a theoretical point from where radiation goes exactly equal in a sphere. This is referenced as 0dBi.

A 1/4-wave GP has 2dBi gain in it's sweet spot (normally towards horizon and slightly upwards), most of that is "taken" from what would have been the lower half of the spehere.
A 1/2-wave dipole has 2.15 dBi gain, taken equally from top and bottom of the sphere.

Collinears vary in gain depending on how they are built, but they all just compress the "sphere" further and further into a horizontal "disc".

/M

Exactly... at the expense of vertical signals !!!! Adding elements magnifies this effect...
Point taken over the hemisphere - wasn't meant as an English experiment, I only used it as an example - 360 degrees around and some up ! lol

[Anmer]

Quick 1090 antenna question.

Why not buy them and test for yourself? They're low cost and ship from the USA.

[Anmer]

That wasn't the question and your answer wasn't very helpful to others.

I thought it was a helpful suggestion. That's what I'd do for a small outlay of under $20. What they call a no brainer.

[F-EGLF1]

Having looked at the postings, I personally wouldn't waste my money, they would probably be no better than the rubbish supplied with the dongle after it has been trimmed to the correct length.
Save your money and build one of the ground plane antenna that abcd567 promotes all the time, it would save money and perform better.

[SoCalBrian]

Hi F-EGL1,
Thank you very much for the on point answer.
Yes abcd567 does great antenna testing. That's why I was asking

[abcd567]

Why not buy them and test for yourself? They're low cost and ship from the USA.

Having looked at the postings, I personally wouldn't waste my money, they would probably be no better than the rubbish supplied with the dongle after it has been trimmed to the correct length.
Save your money and build one of the ground plane antenna that abcd567 promotes all the time, it would save money and perform better.

Hi F-EGL1,
Thank you very much for the on point answer.
Yes abcd567 does great antenna testing. That's why I was asking

2016-05-22
Trial Run Results for Three Types of Whip Antennas

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