Improving my coco antenna

[abcd567]

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[Stealth]

An increase of 2-3 metres can have a significant benefit if it takes you above local obstacles. I increased progressively from 9 to about 14 metres and in certain directions get returns out to 200+ nm. However, that 14 metres still doesn't take me clear of some very adjacent trees that effectively wipe out any coverage beyond 40nm in a westerly direction.

The theoretical coverage versus actual is shown in the attached diagram, yellow is 20,000 and Red 40,000. Actual coverage is shown in black. The diagram is a bit out of date and actual coverage has improved a bit to the North since I increased the height from 12 to 14 metres.

actual vs real 200_400.jpg

[petercr]

Have added the power inserter, amp and DC blocker and managed to get the antenna another 1.5m higher (top is now nearly 7m above ground level). VRS give me the following;
ADS-B range.png

(range circles are 50km) Range to the SE is blocked due to a very large mango tree two houses away, the west by the D'Aguilar Range which is only about 10k's away

and for comparison from HeyWhatsThat
HeyWhatsThat Range.png
FR24 stats now say I'm getting an increased number of hits between 150 and 200Nm and I'm now seeing some planes over 200Nm.

At some stage if I can borrow a ladder to get on the roof, I might see if I can co-locate the antenna with the TV aerial which sits about 1.5m above the top of the roof line.

EDIT: added other image

[petercr]

That was the second one I tried after the 'Mexican Beans' cantenna (which was a perfect size but too heavy to sit on top of the pipe, kept bending in the wind) ... Was only getting around 60Nm but that was using RG59 coax for the downlead...

[abcd567]

Have you tried Quick Spider. It requires about 1 meter of RG6 coax, two cable-ties, and a twist-on F-connector. It costs hardly a dollar! I got very good results from it. No harm in trying. Instructions to make it are in this thread:

Quick Spider - No Soldering No Connector

[petercr]

Hi abcd, that was one of the things I noticed when reading through the other thread and my current range is somewhere in between the blue and orange lines so I know there's some room for improvement... It's a hobby for me so I'm not going to go out and spend lots of money to achieve maximum results when I can get reasonable results... (and I've only really been getting into this over the last few weeks). We have a mobile phone / cellular tower about a km away (line of sites from my house) so that might have some impact too...

[abcd567]

@petercr:
I suggest you determine the maximum range you can get at your location using method described in the following thread. This will serve as a reference for you to judge how good or bad your system is.

What is the Maximum Range I can Get?

[petercr]

Get any 5dB antenna that is tuned properly and you will get 200+ nm with a decent cable and an FA Prostick.

Your system is underperforming and adding a SAT amp is not going to solve that unless you have terribly high cable attenuation today.

/M

I'm trying the least costly options first - if you notice above the coax cost me nothing and the amp only cost $6 (the power supply was lying around from a previous TV installation). Since ordering that, I've also ordered a FA Prostick+ from a local Australian supplier which I'm hoping won't take too long to arrive. The antenna would be the last option as that'd be another $100 on top.

All the cabling is RG6 with the run from the antenna connector to the DVB-T stick being quad-shielded and the length being kept as short as possible. There's also local geographic and arboreal conditions that I've had to take into account so I humbly think 140Nm isn't too bad considering.

[Stealth]

Get any 5dB antenna that is tuned properly and you will get 200+ nm with a decent cable and an FA Prostick.

Your system is underperforming and adding a SAT amp is not going to solve that unless you have terribly high cable attenuation today.

/M

I can vouch for that. The FA antenna opened my eyes yesterday, right after that I was turning down the Pro Stick gain!

[MrMac]

... 8 element CoCo ... 130-140Nm ... 20db satellite amps

Get any 5dB antenna that is tuned properly and you will get 200+ nm with a decent cable and an FA Prostick.

Your system is underperforming and adding a SAT amp is not going to solve that unless you have terribly high cable attenuation today.

/M

[petercr]

Just exercise a little caution when using PVC conduit to enclose your coco. Some, but by no means all, PVC conduit can degrade the signal you're attempting to receive. There is plenty of advice on the net re testing of these conduits but I've found the safest (buggered if I'm sticking it in the microwave oven) is to try it inside the property with and without it for comparison before hoisting it up the mast.

Some also require painting as they aren't UV protected and that too can be problematic depending on the paint used.

Sounds like you've got everything else pretty well covered. It is indeed fun isn't it?

Regards,
Gregg

Gregg, I'm a late-comer to this but have built myself an 8 element CoCo out of left-over RG6 (left over from when we'd cancelled our Foxtel) using the dimensions given by abcd in the other thread. I've got it installed in some Holman 15mm PVC-U pipe that I got from Bunnings. As far as I can tell there doesn't seem to be too much signal degradation - I'm getting around 130-140Nm with about 2m sticking out of a J-bracket that I bought from Jaycar. Next step is to add one of those 20db satellite amps that I got off ebay for around $6 and a Kingray power injector that I bought from Jaycar.

[abcd567]

@MrMac:
Fully agree.

Flightaware 26 inch Antenna: Wire Collinear, with Decoupling Sleeve.

[MrMac]

It's better to start with something easier!


The problem is, even if you DO have an SWR meter, the small phase differences messes with the radiation pattern so that all that theoretical gain will never materialize. This is not visible on SWR, it can be perfectly resonant but still not give the expected gain in any direction.

I have seen this well demonstrated, worked for a major antenna manufacturer and we made a 10dB collinear. It was a b*tch to assemble correctly and we had a fully automated compact range (anechoic chamber) with an ABB robot that made automated over-night 360x360 gain measurements that we invested 3 million USD in. Unless you have access to that kind of equipment that can actually measure gain in different directions, it WILL be sub-optimal.

There is a reason both FR24 and Flightaware decided that the best performance comes from 5-6 dB collinear antennas. I know for a fact that FR24 tested a lot of different ones before they made that choice.


BR /M

[PiRad108]

Jeez, even with a full RF lab it's almost impossible to get a collinear with that many elements in phase. IF you are building "blind", try 3-4 elements. If you have a good SWR meter, maybe 5-6.

/M

I am just starting to learn what I does and does not work as you know there is lots of misleading info out there. On that note my 8 element RG8 coco which is on its first day test in the carport because it is raining at the moment is getting the best results so far for that location having used the supplied short whip antenna, and a Spider in that location which only has decent Northern line of sight and getting 40 NM max, this one has already given me 62 NM.

[MrMac]

... my first antenna 16 element coco array failed on examination...

Jeez, even with a full RF lab it's almost impossible to get a collinear with that many elements in phase. IF you are building "blind", try 3-4 elements. If you have a good SWR meter, maybe 5-6.

/M