yagi - do you have experience with directional antennas?


#1

hi all,

wanted to ask whether some of you have personal 1.hand experiences with this type of antenna …

thanks in advance
tom


1090 Mhz beam antenna
Directional antenna for ADS-B?
#2

Tom,
Yes I’ve built a couple of 1090Mhz Yagis and they worked well. I have a line of hills, the Chilterns, between me and Heathrow airport so my CoCo can’t see over them. I thought I’d try a Yagi pointing East to see what I could see. The Yagi allowed me to follow aircraft down to 1200’ as they dropped into Heathrow. My CoCo cut off at 4000’

http://www.vk5dj.com/yagi.html

http://www.modesbeast.com/resources/mea1090-10ele.pdf

The one I built wasn’t a folded dipole as it was too complicated. I also designed my own using 4NEC2 free software with abcd’s help.

Reflector length is 67mm at 0mm from the end
Dipole length is 66mm at 66mm from the end
first director length is 59.5mm at 76mm from the end
second director length is 59mm at 125mm from the end
third director length is 58mm at 184mm from the end

If you want more gain then add more directors of 58mm at 250mm, 330mm and 410mm from the end. Theoretical gain is 12dB and SWR is about 1.1

I built them using 22mm plastic pipe. Drill holes through the pipe to poke the elements through and hold in place with mastic. The dipole connection was challenging. I simply used a pipe connector with a slot cut in it. This slipped over the pipe. If I can find my camera, I’ll take some shots later.

Dave


#3

hi dave that sounds pretty cool!

but i’m afraid that building a yagi on my own - in the end i do not measure what a yagi can amplify by design but just what my personal disability in making one is :slight_smile: so - i searched on the internet and found these - not really low-cost ones:
http://www.amateur-radio-antenna.com/ism-aeronautical-antenna/secondary-radar-1090/antenna-secondary-radar-flu-sr-y13.php
http://www.amateur-radio-antenna.com/ism-aeronautical-antenna/secondary-radar-1090/antenna-secondary-radar-flu-sr-y13-prof.php

how much more planes would you say did you get from heathrow with the yagi compared to a coco?

regards
tom

p.s. my site is 25nm from munich airport with a soso sight and about 150nm from frankfurt airport with a brilliant sight


#4

I didn’t see much of an increase in numbers, just the ability to see them down to a lower level. I may have caught the odd plane at 40,000 feet over Holland heading my way :smiley:


#5

What guage wire do you use for the elements?


#6

Hi Rusty,

1.8mm from the earth core of UK 13 amp mains wire.


#7

Thanks Dave


#8

found another type of high gain antenna: http://www.radioworld.co.uk/radar-beam_external_beam_antenna_for_radarbox_490x200x180mm


#9

1.8 mm is diameter of wire. Its area of crossection is 2.5 square mm.

Standard practice in metric system is to specify electrical wires & cables by area of crossection in mm², and not by wire diameter. Hence if you want to purchase the wire used by Dave, you have to tell the electrical store you want a wire size 2.5 mm².

In North America, the electrical wires are specified by AWG.
12 AWG dia 2.053 mm, crossection 3.31 mm²
13 AWG dia 1.828 mm, crossection 2.62 mm²
14 AWG dia 1.628 mm, crossection 2.08 mm²


#10

Photos as promised

22mm plastic overflow pipe. T connector

CoCo and Yagi


#11

I put up a yagi to try and fill in a weakness to the south east that my 5/8 antenna has. The yagi did improve it but not to the amount I had hoped. Surprisingly the antenna still has good omni directional reception, something I wasn’t expecting.

The plot shows the reception from the two antennae, blue is the 5/8 omni and red the yagi. The yagi doesn’t really perform much less than the omni even though the plot is smaller, it seems to pick up a lot more aircraft within it’s area as compensation.



#12

hi rogjack,

thank you so much - that’s exactly what i was hoping to talk about :slight_smile:
looks really professional your pole with the two antennas mounted and this is what i wanted to install on my attic under the roof where my standard antenna sits at the moment.

what i do not understand is why the directional antenna is so omnidirectional - and does not get more from paris traffic?
did you already made a ‘heywhatsthat’ plot for your antenna-position to see what is theoretically possible?
where are these antennas from and how did you connect them to your raspi?

here are three pictures of my testing as it’s always easier to talk about something you saw:

https://dl.dropboxusercontent.com/u/39745369/antenna_one2one_2.jpg

https://dl.dropboxusercontent.com/u/39745369/antenna_test_01.jpg

-> enlarge here
https://dl.dropboxusercontent.com/u/39745369/map_reach_s.jpg


#13

**@rogjack: **
Your both antennas (5/8 and yagi-uda) do not seem to be DIY. The 5/8’s performance is good. The 5/8 is inherently high impedance and will not match with 50 ohm & 75 ohm systems. Seems it has some impedance matching arrangement inside the pvc tube (may be a coil). Have you ever opened it & seen what is inside the pvc pipe? What is the make/model of the 5/8 ?


#14

hi triggers,

thanks so much for your detailed antenna building howto :slight_smile:
did you make range plots omni vs yagi too?


#15

It is strange to see that the commercial yagi-uda is omnidirectional. All litrature and theory praise yagi-uda as high gain, highly directional antenna.

Yagi Antennas
A Yagi antenna is formed by driving a simple antenna, typically a dipole or dipole-like antenna, and shaping the beam using a well-chosen series of non-driven elements whose length and spacing are tightly controlled. The Yagi shown here in Figure 1 is built with one reflector (the bar behind the driven antenna) and 14 directors (the bars in front of the driven antenna). This configuration yields a gain of about 15 dBi with azimuth and elevation plane beamwidths that are basically the same, around 36 degrees. That is a common feature of Yagi antennas. Many times these antennas are designed so that they can be rotated for either horizontal or vertical polarization, so having the same 3-dB beamwidth in each plane is a nice feature in those instances.

Figure 1. Yagi Antenna Model with 3D Radiation Pattern, Azimuth Plane Patten, and Elevation Plane Pattern

SOURCE: http://www.cisco.com/c/en/us/products/collateral/wireless/aironet-antennas-accessories/prod_white_paper0900aecd806a1a3e.html


#16

Both were purchased from eBay from a guy in Slovakia, they are very reasonably priced. I haven’t opened it up since it has been sealed and is now 30ft in the air. I had to get someone to put it up for me as I am far too old to go up there myself. I will probably not touch it again unless it fails.

There are no makers marks on either so I assume they are constructed by the seller. They are well made and I am pleased with them both.


#17

Hi TomMuc,

I was also surprised that the yagi is so omnidirectional, there are longer ones and they will become less “omni” the longer they get. I have done a heywhatsthat plot and a low range of hills about 10km away seem to be the problem, I don’t think I will be able to improve things in that direction. I have found that the reception varies with the weather, some days I can get well beyond Paris, but not on the day that plot was made.

I see from your plot that you have big mountain problems to the south that you can’t do much about, there does seem to be a weakness to the east that might be improved with a yagi.

I purchased mine from eBay the seller’s name is stanislavpalo130. He doesn’t have any on sale at the moment but it may be worth an email, he will probably have them again.


#18

hello rogjack,

ah - ok - now i understand the ‘paris thing’ :slight_smile:

regarding my site - you are totally right - there is no real chance for me to get better reception over the alps in my back.

what i wanted to improve was munich airport 25nm in the east (as you mentioned) and frankfurt airport 150nm in the north-west.

at the moment my antenna under the roof shows not too bad results and when i did the outdoor testing i had about 20% improvements. as the antenna man asks for 300$ to install the antennas on the roof i wanted to test first what a second (maybe third) antenna is good for.

yesterday i already ordered the cheaper one from this seller: http://www.amateur-radio-antenna.com/ism-aeronautical-antenna/secondary-radar-1090/antenna-secondary-radar-flu-sr-y13.php

how did you connect both antennas and merge the input?


#19

I didn’t attempt to merge outputs, I run each antenna to a separate Pi. I don’t think there is any way to merge ouputs without losses.


#20

because i was curious about the differences in detected positions per distance i looked into your site’s stats and found only one pi reporting.
so - you don’t feed the yagi to fa …