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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Sun Nov 06, 2016 8:37 am 
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jcinnb - FlightAware user avatar

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You may well find the "store bought" antenna does not perform much better than spider. You did a good, neat job on the spider.


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Nov 07, 2016 3:28 am 
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abcd567 - FlightAware user avatar

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Location: Toronto CYYZ
.
Thanks for measuring and plotting the VSWR vs Frequency sweep.

I always wanted to have a spectrum Analyzer/Signal Generator/VNA and other necessary equipment to test the antennas, but these are too costly.


brianroyal wrote:
abcd567 wrote:
EASY ANTENNA #2 : CANTENNA


Completed Cantenna

Designed & Built by Author of this post (abcd567)


Image

.


The best part about this antenna is it's deafness to frequencies that are out of band for ADSB. It's easy to make so that it's got a good SWR (about 1.5) at 1090 band and it all but completely attenuates anything below about 900. MUCH easier to build right than a Colinear Coaxial with better bandpass characteristics.

This helps to keep the receiver from dropping it's AGC when it gets bombarded with extraneous noise.
Image


EDIT: Can't recommend this design enough for a simple and reliable antenna that you WILL probably make correctly on the first try. If you're trying for maximum gain - Yeah, build a COCO. Just be prepared for a "learning experience" or two.
Build one of these FIRST so you have a decent antenna to fall back on while you troubleshoot your quad or eight element coco.


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Sat Nov 12, 2016 12:50 pm 
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jcinnb - FlightAware user avatar

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I came across a very EZ, accurate and SAFE way to cut the can for a cantenna.

Cut a small piece of wood the height desired.
Place a razor knife across the top of the wood
Grasp the can by the top, away from knife and hold agains the knife blade
Turn can until it first is scored, then cut.

Very crude drawing:

Image


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Fri Nov 18, 2016 10:40 pm 
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zeek70706 - FlightAware user avatar

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jcinnb wrote:
I came across a very EZ, accurate and SAFE way to cut the can for a cantenna.

Cut a small piece of wood the height desired.
Place a razor knife across the top of the wood
Grasp the can by the top, away from knife and hold agains the knife blade
Turn can until it first is scored, then cut.

Very crude drawing:

Image


I just used a pair of scissors.


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Wed Nov 30, 2016 4:21 pm 
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I am wondering where to position my antenna in the attic.

I just moved it there from a windows facing westwards, it now it sits in the middle of the attic, ca 1,50 from the top of the roof, pretty much in the center of the whole building, which is rectangular. The reason for this is that on either side is a relatively small windows. This way, I thought, it can "look out" of both of the windows.

Now get a lot more positions and planes from the East, but I am wondering if it might make more sense to

a) put it as close as possible to the top of the roof, even if that means that there is no line of sight out of the windows

b) put it away from the windows, closer to the gable, so it is close to the outer walls/roof on three sides?

I could try this out and maybe I will, but I also would like to have a better theoretical understanding why one of the locations is better than the other.

Any ideas?


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Wed Nov 30, 2016 8:09 pm 
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RickBoatright - FlightAware user avatar

Joined: Thu Nov 24, 2016 8:56 pm
Posts: 32
Open the window. use a hot-glue-gun, or a clamp, or whatever to position it OUTSIDE the window.

Then, get a hunk of foam rubber, and close the window on that to keep the rain out, etc. (this is assuming you're unwilling or unable to drill a hole in the window frame...)

Then, if you want to get REALLY fancy, get another pi, and another rtl-sdr, and put another antenna on the outside of the window on the OTHER side of the house... :-) I know, I know, shear insanity.


biekerc wrote:
I am wondering where to position my antenna in the attic.

I just moved it there from a windows facing westwards, it now it sits in the middle of the attic, ca 1,50 from the top of the roof, pretty much in the center of the whole building, which is rectangular. The reason for this is that on either side is a relatively small windows. This way, I thought, it can "look out" of both of the windows.

Now get a lot more positions and planes from the East, but I am wondering if it might make more sense to

a) put it as close as possible to the top of the roof, even if that means that there is no line of sight out of the windows

b) put it away from the windows, closer to the gable, so it is close to the outer walls/roof on three sides?

I could try this out and maybe I will, but I also would like to have a better theoretical understanding why one of the locations is better than the other.

Any ideas?


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Thu Dec 01, 2016 12:14 pm 
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abcd567 - FlightAware user avatar

Joined: Sat Feb 15, 2014 3:08 am
Posts: 2033
Location: Toronto CYYZ
biekerc wrote:
I am wondering where to position my antenna in the attic.
...........
...........
Any ideas?

You will get lot of ideas about indoor installations from this thread:

Post your PiAware setup


Selected posts from above thread, pertaining to "installation in attic":

1) post182995.html#p182995

Image




2) post183692.html#p183692

Image




3) post197639.html#p197639

Image




4) post197656.html#p197656

Image


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Thu Dec 01, 2016 2:09 pm 
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brianroyal - FlightAware user avatar

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Ok, so after two weeks of testing with both the pro-stick with filter and without and the pro-stick plus, I can conclude that, with gain settings at auto, the cantenna does not appear to need a filter, at least not in my relatively rural area.


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Fri Dec 02, 2016 5:17 pm 
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biekerc - FlightAware user avatar

Joined: Sat Jul 16, 2016 2:17 am
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Thanks for the suggestions, it seems people are opting to mounting the antenna as high as possible and as close to walls.

My assumption was that the signal travels more easily through glas than wood and clay, so a position closer to a window is better.

However, being closer to the windows to the east increases the distance to the window and roof to the west, so fewer signals are picked up from this direction.

I'll try to move closer to the top, closer to the walls, but at a greater distance to the windows that are basically on the same level as the floor and see what happens.

Outside is no option at the moment, I haven't got the right antenna for that. Several Pi would be, a have a small collection of them...


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Sun Dec 04, 2016 8:53 am 
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biekerc - FlightAware user avatar

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So I did some quick and dirty tests.

I achieved by far the best results in terms of number of planes by putting the antennal as high up and close as possible to the outside walls.


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 05, 2016 4:17 am 
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myalias - FlightAware user avatar

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biekerc wrote:
The reason for this is that on either side is a relatively small windows. This way, I thought, it can "look out" of both of the windows.


Glass attenuates the 1090 MHz signal. Wood blocks it less.


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 05, 2016 10:25 am 
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abcd567 - FlightAware user avatar

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myalias wrote:
Glass attenuates the 1090 MHz signal. Wood blocks it less.

For details of attenuation, please see this post:
RF Signal Loss in Penetrating a Building


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 05, 2016 3:40 pm 
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biekerc - FlightAware user avatar

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Posts: 62
myalias wrote:
biekerc wrote:
The reason for this is that on either side is a relatively small windows. This way, I thought, it can "look out" of both of the windows.


Glass attenuates the 1090 MHz signal. Wood blocks it less.


In my case the roof is made of clay tiles and some insulation, (and the walls are solid red brick masonry).

In this case, I guess being close to a single glazed window is still an advantage, but only for the reception in this direction, and a disadavante for the reception in all other.

Being close to the top reduces the distance to the tow sides of the roof, which should also reduce the signal loss. In sum, this seems to be the best option.

It is like a triangle, if you move to the left or right hand corner, you increase the distance to the other side, only if you move upwards to the top, the distance to the left and right are reduced.


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Tue Dec 06, 2016 11:21 pm 
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myalias - FlightAware user avatar

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abcd567 wrote:
myalias wrote:
Glass attenuates the 1090 MHz signal. Wood blocks it less.

For details of attenuation, please see this post:
RF Signal Loss in Penetrating a Building


Thank you for the heads-up on that thread. I hadn't come across it yet. No doubt it will come in useful!


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Sat Dec 10, 2016 7:28 pm 
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aldoir - FlightAware user avatar

Joined: Sat Oct 29, 2016 5:54 pm
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Folks,

After a couple of weeks running this antenna I would like to see how it performs for you too.

I started this thread http://discussions.flightaware.com/ads-b-flight-tracking-f21/disappointing-results-with-my-setup-what-s-wrong-t38177.html after some unsucessful atemps with the Coaxial Collinear and after some research found the antenna I would like to share here.

I's a J-Pole Collinear, an easy to build and tune antenna.

Here is its diagram and 1090Mhz lengths
Wire: 16 AWG copper (enameled if available)
Coils: 16 turns of 5mm inner diameter 53mm long

(you can build with 2 to 4 elements (1 to 3 coils)
Image

The feed line should be connected at 6mm from the bottom (shield to the short element, as per this image).

Image

If anyone is interested in building it please let me know and I'll update the needed details.

EDIT: Updated dimensions to reflect new tests.


Last edited by aldoir on Fri Dec 16, 2016 7:11 am, edited 3 times in total.

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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Sun Dec 11, 2016 7:39 pm 
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k6rtm - FlightAware user avatar

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what size wire did you use for this?

--bob k6rtm


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Sun Dec 11, 2016 8:44 pm 
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aldoir - FlightAware user avatar

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Ops, sorry, 16AWG enamelled copper


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 12, 2016 7:15 am 
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triggers - FlightAware user avatar

Joined: Sun Dec 21, 2014 2:37 pm
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@aldoir

Just about to make your antenna.

I have a question for the experts. I have the orange Pro-stick on my test system which is currently connected to a 6 element CoCo. The J pole is a "shorted" antenna. Do I need a DC blocker to make sure the amp in the Pro-stick doesn't fry?


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 12, 2016 9:03 am 
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aldoir - FlightAware user avatar

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Location: Curitiba/Brazil
You dont need dc blocking for the ProStick. It's only needed for tee bias sat amplifiers

I've tested both, currently I'm using a 20dB amp with a std rtlsdr stick


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 12, 2016 9:30 am 
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triggers - FlightAware user avatar

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aldoir wrote:
You dont need dc blocking for the ProStick. It's only needed for tee bias sat amplifiers

I've tested both, currently I'm using a 20dB amp with a std rtlsdr stick


Thanks, the antenna is on test.

I only had 1mm wire so built it to your dimensions.


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 12, 2016 9:56 am 
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aldoir - FlightAware user avatar

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Location: Curitiba/Brazil
triggers wrote:
Thanks, the antenna is on test.

I only had 1mm wire so built it to your dimensions.


How many elements did you make?


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 12, 2016 10:45 am 
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triggers - FlightAware user avatar

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aldoir wrote:
triggers wrote:
Thanks, the antenna is on test.

I only had 1mm wire so built it to your dimensions.


How many elements did you make?


Just the one coil for now.


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 12, 2016 11:14 am 
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aldoir - FlightAware user avatar

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I believe the 2 elements will perforform something around 30% more messages than a 1/4 ground plane, not that great.


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 12, 2016 1:16 pm 
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triggers - FlightAware user avatar

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Preliminary results show the Collinear J pole is not as good as my 9 element CoCo. I will add another 2 elements tomorrow.
ImageImageImage

Here is my CoCo for comparison
Image

What is the length of the wire used to make the coil? Is it half wavelength or something else?


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 Post subject: Re: Three Easy DIY Antennas for Beginners
PostPosted: Mon Dec 12, 2016 2:37 pm 
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aldoir - FlightAware user avatar

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Fairly good results, 70% of the message rate of a 4 elements CoCo

This article trys to explain the black magic behind these antennas and was the main source of my findings. Search for a section named "Wire length in Collinear J-Pole Phasing Coil"

http://www.hamradio.me/antennas/improvi ... per-j.html

I've tested 18turns / 60mm and the gain decreased significantly, meaning poorer SWR. Will try another sizes to see if is there any improvement, but so far this was the best results I got.


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