best antenna

[abcd567]

i think he should make one of yours antennas(co-co...etc). single coax is not antenna. i cant find those images you uploaded in this topic

Here are the images you are looking for:
Post #257:
http://forum.flightradar24.com/threa...ll=1#post41619
Post #258:
http://forum.flightradar24.com/threa...ll=1#post41620

[abcd567]

Hit the proverble gold at work today, i spotted a signal analyser at work (hadn't noticed it before) that has a tracking generator in it, work are using it for EMC work. So with the addition of a directional coupler i could be tuning aerials that alone made me pretty happy.

Then to top it off i was chatting to another person about it (the only engineer i know to do any antenna work) and it turns out we have a vector network anayliser that goes upto 3GHz.

I'm quite happy with my current aerial but i'm looking forward to making some just for the learning.

Waiting for your exleriment/test results eagerly. Your results/findings sure will be a great asset for this forum.

[abcd567]

A NEW EXPERIMENT - THE COILED WHIP
I have run a computer simulation of a coiled whip antenna based on design on following webpages:

1. http://martybugs.net/wireless/collinear.cgi

2. http://cheatthezone.tripod.com/wireless/colinear.html

Thanks to Dave of Plane Finder forum who built the antenna in above webpage.
The dimensions in mm in above pages were based on 2.4 GHz (Wireless LAN).
Dave changed dimensions according to 1090 MHz.
http://forum.planefinder.net/threads...age-6#post-464)


Later Dave made a trial run of new antenna & advised me the results: much inferior to his Franklin.
http://forum.planefinder.net/threads...age-7#post-476


I then ran computer simulation on software 4nec2.exe. The computer simulation results tallied with the trial run - poor: extremely high SWR (2,000). Gain is ok (4 dB) but nullified by very high SWR.
daves-coil-type-whip-wire-data.png

daves-coil-type-whip.png


I then changed the coil diameter to 22mm to make it's circumference 22 x pi = 22 x 3.14 = 68 mm = 1/4 wavelength at 1090 MHz. It did improve the SWR from 2,000 to 170.
coil+whip-sweep-varying coil dia.png



I then added a ground plane, consisting of 3 wires equally spaced (120 degrees) and connected to each other & to braid of coaxial cable. This brought down the SWR from a whooping 170 to mere 2.8, and increased Gain from 5 dB to 9.5 dB

Output of computer simulation on software 4nec2.exe are shown in screenshot below (SWR=2.8, Gain= 9.5 dB)

Whip+Coil+Ground Wires-R1.png

.

[SpaxmoidJAm]

i have one of those half built at the minute, i was intending to go through all the DIY one's and see what they come out like by default. Unfortunately its going to be a week or two before i get to play.

[peterhr]

Has anyone tried these, four of them should give 360 degree cover (just curious)

http://www.ebay.co.uk/itm/Outdoor-di...item2ed021e268

[abcd567]

Has anyone tried these, four of them should give 360 degree cover (just curious)

http://www.ebay.co.uk/itm/Outdoor-di...item2ed021e268

4 x US $89.70 (£53.99) = US $358.80 (£215.96) = TOO COSTLY!

Sent from my N762 using Tapatalk 2

[abcd567]

T-EGBB19 : RTL2832U / R820T+ Raspberry Pi + Dump1090 with Bulgarian collinear 8m above ground level
Stats for: 2014-03-17, Uptime (as % of available time): 100%, Aircraft seen: 1,003, Positions reported: 1,107,731, Maximum distance: 268nm (496km)

Wow great coverage ... almost 500 km ...Congratulations.

Are you using an in-Line Amplifier? RTL2832U / R820T USB Dongle normally does not give such a great range without an in-Line Amplifier, as its built-in pre-Amplifier is not as good as that of SBS, Radarbox, etc.

Your Bulgarian antenna seems good. Checked its specs, found as follows:

Omnidirectional antenna 1090 MHz ADS-B 6 dBi for SBS, Radarbox, microADSB-IP
Up to 250 NM range with straight view (attached to microADSB IP BULLION receiver)
N female type directly mounted connector
Perfect for use with SBS, Radarbox, microADSB

Frequency: 1090 MHz
Gain: 6dBi
Azimuth: 360 deg
Impedance: 50 Ohm
Max Power: 50 W
VSWR 1,5:1
Vertical polarization
Wind Survival: 125 km/h
Temperature range: -45 to 60 deg C
Length: 70cm
Weight: 540g
Conektor: N(f)

[peterhr]

No amp, the distance is what fr24 reported in the stats on day

The antenna hahs an N to F adaptor, then the downfeed is RG6. At the other ens the rg6 has a tv aerial plug to suit the mcx adaptor for the mini dongle.

There are no cable joins / pigtails so no cable reflections

Sent from my GT-P5110 using Tapatalk

[abcd567]

........the distance is what fr24 reported in the stats on day.......

How do you get the report from FR24?
I am also feeding data to FR24 (T-CYYZ-9), but never got any report.

[abcd567]

.......There are no cable joins / pigtails so no cable reflections.......

Adaptors cause reflections like joints. You have two adaptors, one at antenna side of RG6, other at the Dongle side of RG6.
Furthermore you have impedance mismatch (Antenna 50 Ohms, RG6 & RTL2832U/R820T USB Receiver 75 Ohms).

Reflection at N-Connector.png

[peterhr]

I have just one mismatch - at the antenna end, there is no cable between the adaptors and the antenna / dongle. The adapter at the antenna end means I could pop an amplifier in there really easily.

Sent from my Nexus 4 using Tapatalk

[abcd567]

I have just one mismatch - at the antenna end, there is no cable between the adaptors and the antenna / dongle. The adapter at the antenna end means I could pop an amplifier in there really easily.

Sent from my Nexus 4 using Tapatalk

With one mismatch (50 Ohm connected to 75 Ohm):

Reflection Coefficient Γ = (Z₁ - Z₂) / (Z₁ + Z₂) = (75-50)/(75+50) = 0.2
VSWR = (1+Γ)/(1-Γ) = (1+0.2)/(1-0.2) = 1.5 : 1

Later Addition:
Don't get terrified by 1.5:1 VSWR ...
The Mismatch Loss in dB = -10 log(1 - Γ²) = -10 log (1-0.2 ²) = -10 x -0.01773 = 0.1773 dB .... peanuts

[peterhr]

But I was going to get that mismatch somewhere ... Unavoidable since the antenna is 50 ohms and the dongle 75.

Sent from my Nexus 4 using Tapatalk

[YSWG]

How do you get the report from FR24?
I am also feeding data to FR24 (T-CYYZ-9), but never got any report.

Click on More. You need to be feeding with FR24 Linux uploader or FR24 FlightFeeder.

IMG_20140330_195454.jpgScreenshot_2014-03-30-19-49-30.jpg

[Amper]

Click on More. You need to be feeding with FR24 Linux uploader or FR24 FlightFeeder.

[ATTACH=CONFIG]3758[/ATTACH][ATTACH=CONFIG]3759[/ATTACH]

not all T feeders have status page