Antenna testing - 202 aircrafts simultaneously


#3

the last days my antenna test continued - with wimo and flightaware models.
interim result:
jetvision with n-plug = 100%
flightaware = 100%
jetvision with hardwired antenna cable = 90%
wimo = 80%

https://dl.dropboxusercontent.com/u/39745369/antenna_02.jpg

https://dl.dropboxusercontent.com/u/39745369/antenna_03.jpg


#4

Good effort, definatley worth playing like you are before you get it up on the side of the house and cant.

I think for the sake of being able to with your set-up, use an adaptor to go from N-type to MCX and put the dongle on a short USB lead to the pi and see what difference removing all the coax and extra connections make.


#5

hi theresjam,

yes - this is a good advice - and i already did and replaced the long 15 feet cable with a 20" pigtail :slight_smile:


#6

My goofy little antenna is kicking ass over the coco. I built the coco over the weekend and put it up on the tower. I wasn’t to impressed with its results. I made a different one using 68.5mm lengths of copper wire soldered to an SO-239 connector and wow what a difference. Getting data from the 240-300 ring. Coco wouldn’t even come close to that.

Haven’t figured out how to post a pic to this site from an iPad yet.


#7

the problem with the selfmade cocos is that adding every single element can end in total failure. best way is to check impedance with multimeter when adding each single piece …

upload pictures to dropbox - and then add link with img tag


#8

Coco is very alluring. It is very easy to make. The problem shows up only when it is put to service, and results are far less than expected or claimed. Only a small number of lucky ones endup in a good Coco, majority ends up in a poor coco & associated frustration.

Coco is very easy to make, but hard to get right.
Antennas with a 1/4 wavelength whip (67 to 69 mm for 1090 Mhz) are easy to make and easy to get right, and good for beginners.

It seems you made an antenna similar to “EASY ANTENNA # 1 : SPIDER” of the thread:

Three Easy DIY Antennas for Beginners.

You can see the photos there.

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#9

Agreed - start simple - a coco is hard to get right, and if it’s your first antenna - you won’t even realise if it’s bad.

I’ve just ordered one of these ebay.com/itm/271904826225 - with the intention of replacing the SAW filter with a TA1090EC (which I have).

On it’s own for indoor intallations it should perform like the well regarded HABamp.

I really want it where it will do most good up real close to the antenna outside - so i’m thinking to wire end it and slip it into an upturned aluminium beer can up on the mast after putting a small coil of enamelled wire from the center pin on the ‘RFout’ to the +ve power connector on the board (for bias power) … anyone got any idea of how many turns and what diameter for the coil? (I’m guessing maybe 6 turns at 1/4")


#10

Your guess is good.
7 turns, 1/4" dia, coil length 13 mm -> inductance 0.149 µH -> impedance at 1090 MHz = 1020 Ω -> 6.8% RF signal goes to power adaptor, 93.2% to receiver.

These 2 posts may help …

forum.Planefinder.net, “ADS-B DIY Antenna” Page 169

(1) Post #3369

(2) Post #3374

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#11

when making a coco you need to solder the sections together otherwise they are too inconsistent.


#12

I’m sure glad I didn’t know this when I built my QST coco from junk which I already had in the garage, as described in this article: arrl.org/files/file/QST/This … 013QST.pdf

I did not use the 90 degree F adapter shown and used heat shrink tubing on the joints. I also checked each section while building, as well as the completed assembly, for shorts. Regardless of all the criticism of this design which many have made, concerning the design, wavelength of the tip element, etc. it has performed better than anything else I’ve tried. FlightAware shows I’ve been running for 361 days as of today. All of this was with this “inconsistent” coco except for the first few days with a simple ground plane, and the few weeks that I ran the commercial FlightAware antenna which I purchased from Amazon. I put the coco back up as my results dropped slightly while using the FlightAware antenna, which is really well built and performs acceptably. My range is just a little better with the coco.

Maybe I just got lucky! My site isn’t perfect and I’m really surprised at my reception considering all the tall trees surrounding my home.


#13

My first coco was 6 seg out of spare RG6 built in almost total ignorance. Worked about as well as an 8-legged spider (which in turn works almost as well as the FA one). Beginners luck- second one was Carp. First one traveled 14 K miles, 33 States last year propped atop the RV when wifi available. Gave up the ghost (rattled apart) early this summer. Replaced with 2nd FA ant. Might still be going had it been soldered, but I don’t solder well. My spiders are done with pop-rivets or screws. YMMV


#14

The Dark Art of DIY Coco Making! :frowning:

In last 2½ years, I have made about a dozen Cocos, all were poor.

To the last one, I added a 2 pf capacitor in feed line at 0.85 of ½λ (0.85 x ½ x 275 x VF) from the point feed line connects the coco. Impedance matchig by this method improved it from “poor” to “average”, but still inferior to my default antenna, the Cantenna.
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#15

… aside the self-built antennas - i think the flightaware antenna is a real bargain - at least for us customers.


#16

You are right. I will love to purchase & try it inspite that my home-made Cantenna gives me 200 nm in most directions and 250nm+ in one (east) direction.

Have you ever built and tried any ¼ wavelength antenna such as Spider or Cantenna?


#17

no - not until now - but i will the coming months. i thought i first use professional made components to minimize sources of error at newbie stage. now i know a little about what amount of positions an antenna at my site should receive. in my antenna testing up to now the jetvision with n-plug was the winner followed by the jetvision with about 97% - but this difference is smaller than my measuring precision or series dispersion. so at 40$ it is a great deal and looks better than the white ones.

p.s. but i cut my tiny antenna to 67mm along your howto - and found it very cool that the before small and now tiny antenna improved about 20-30% at no cost and 2minutes for the cut :slight_smile:


#18

The improvement to whip is 3 stepped:

(1) Most important is cutting it to ¼ wavelength (67mm for 1090 Mhz) and provides the largest chunk of improvement. The % improvement depends on how much the original whip was deviating from 67mm. Larger the deviation, larger will be improvement.

(2) Placing whip over a metallic can, box or sheet to enlarge it’s insufficient groundplane provided by it’s tiny magnetic base.

(3) Although enlarging groundplane by above method improves reception by another 10% to 20%, but since the shield of coax is not solidly connected to ground plane, and groundplane is not optimally dimensioned, the real benefit is not achieved. When you make a regular, properly dimensioned Spider or Cantenna, you get the full optimization.

For me the main problem is surrounding high rise buildings in various directions, including my own building. Also in direction of Ottawa & Montreal, down town Toronto exists at about 20kms from my place, and high rise buildings restrict my range to 150 nm in that direction. Under this condition, even a good high gain antenna like Flightaware’s cannot overcome this problem.

See my coverage with Cantenna. In most of un-obstructed directions I get 200+ nautical miles, and in the best direction (south east) upto 250+ nautical miles., but in the direction of surrounding high rise buildings, my range drops to 50 nm or completely blocked :frowning:


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#19

… took 20 minutes to find the website again - where the antenna was shown i thought it could be interesting for you - bi quad arrays:
https://keptenkurk.wordpress.com/2015/08/29/ads-b-receiving-station-description/


#20

Thanks. The bi-quad in pdf downloaded from link given on Keptenkurk (Captain Kirk?) web page looks interesting and worth trying.


#21

i thought it maybe could perfect fit to your indoor-site-concept with the big widows to different directions :slight_smile: and instead of me you already have great experience with antenna self-building …


#22

Thanks. Will give it a try on a weekend.
As I said earlier, even the best antenna cannot overcome a physical obstruction to line-of-sight like a high rise building or Alps :slight_smile:. My main problem is high rise buildings obstructing line of sight. There are only two ways I can think of to overcome this problem:
(1) Tie my antenna to a helium filled baloon floating several hundred feet above ground, tied to ground with ropes and a coaxial cable (or powerful wifi dongle).
(2) Our City Council decides to acquire and demolish all high rise buildings in our area and uses the land to make a soccer field, park, community center, scool, public library etc etc…seems while typing this post I dosed off and started dreaming…