ADS-B CoCo on a PWS pole

Skip,
Many thanks for your reply. Firstly the good news. My antenna is an eight element CoCo suspended in a 20mm polypipe. It has now been up for over 24 hours and I have had no problems with interference The Vantage Vue is transmitting in the frequency range you have stated. The CoCo however is receiving only, and at a frequency of 1.09Ghz. I have to admit that it is now 58 years since I studied any antenna theory (40 (Ulster) Signals Regt. T&AVR II) but I seem to remember that there should be no interference FROM the CoCo. However, if the s had a powerful transmitter rather than the minuscule 30Ma stated it is possible that the signal from the CoCo might be corrupted.

As for the antenna being shielded, another FA respondent has suggested mounting a cranked 1” aluminium pole as near to the top of the Davis pole as possible (I would suggest on the south/solar end to mitigate any flow problem over the anemometer cups) and thereby being able to mount the CoCo above and behind the Vantage Vue, thereby taking it out of any shielding/shadow. I shall try this and also change the somewhat agricultural heavy duty steel mounting clamps provided by my friendly TV man. If you wish I will let you know how I get on with this.

Regards

Mike Wilson

Bangor, Co. Down

Install a horizintal pipe as as extender arm and install your CoCo on it, something like FlightRadar24 user lutorm did to mount his 1090 MHz Franklin on the pipe already having a 2-meter J-Pole.

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Mike, in my case the concern was about the Vantage Vue transmitter possibly introducing noise into the ADSB signal received- there should be no impact on the weather station operation caused by the FA antenna. Many folks ( particuarly in urban environments) have issues with Cell frequencies and other neighboring services swamping the relatively weak ADSB 1090Mhz signal with interference. You will see many conversations here about how to determine whether additional filters are required if you search or browse through the discussions.

Good luck with your installation, and did you build the CoCo yourself ?

Skip,
Thank you for your good wishes. Yes, I built the CoCo myself with eight elements, using RG6 Co-Ax. A 50m reel in our local hardware chainstore cost £8.50 ($6.00 U.S.) I live in a suburban area of Bangor in Northern Ireland and have not noticed much noise (but don’t have the instrumentation to prove it) Suffice to say I am happy with over 230nm to the south and hopefully will get a more circular splat (splot? i’m new to this terminology). I’m fortunate in that I live in an area where the majority of Western European/UK flights from/ to Canada, The U.S.northern east coast and the west coast overfly en-route to their entry/exit points to/from the northern NATS tracks. I have an iComm RC 20 and can listen in to Scottish (Rathlin West Sector) ATCC. With two commercial airports and a GA field close by it’s a rich environment for aviation hobbyists of every ilk.

Regards

If your traffic is predominantly in one direction then installing the antenna on the appropriate side of the pole will minimize missing reports.

For example, 90% of my traffic is E-W so I would mount the antenna on the N or S side of the pole.

Your dongle (DVB-T or Pro Stick) + your computer (RPi or Windows laptop/desktop) is sufficient to find out existing RF interference at your location picked by your 1090 Mhz antenna. Please see this thread:

Do I Need A Filter?

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Skip, Robwell,a567 and others.
That’s what I like about this site, no one flames you for lack of knowledge, rather the reverse. Skip, I spoke with a pleasant chap at Davis who informed that the Vantage Vue ISS on sale in the EU uses a frequency spread of 868 to 868.6 Mhz. As you will see below, I don’t think that the Vue is causing too much trouble, though I would like those with the knowledge to interpret the scan.
Robwell, as I wrote to skip above I live in what, for me, is a fairly intense area of aerial activity, what with the Rathlin West sector of the Scottish ATCC vectoring loads of traffic through my area onto the North Atlantic Track System, via Shanwick.
abcd567, thank you very much for directing me to the “Do I need a Filter” thread. It has greatly increased my theoretical knowledge of receiver antennae (but LOADS of reading to be done in that area) Yes, I think (know) that I do need a filter. Can you advise me which would be best, based on the scan results below. My TV man has installed a Swan Neck pole onto the PWS pole but is reluctant to mount it too far up for fear of any twisting moment affecting the K mounts in a strong wind. He’s the professional so I listen to what he says. Unfortunately the CoCo is still below the level of the PWS and is not only still in the shadow of the main pole but needs to be about two meters higher to clear the buildings immediately above and behind me to the West, North and Northeast. I propose to do that by building another CoCo, but this time using RG6, and mounting it in a 3 metre polypipe, ensuring that it is secured to the top of the pipe, thereby keeping the CoCo itself clear of the ironmongery mount and gaining height with very little increase in weight (twisting moment) Now the big question. Is my eight element CoCo, which is giving me great results compared to what I started out with, OK or would a 12 or 16 element CoCo be more efficient? Oh yes, what’s all that activity between 920 and 960 Mhz. Mobile/Cell activity?

scan1a
scan2A
scan3A

Why do you think you need more elements (gain)? Are you running at the max gain now?

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Yes, ALL the activity shown in two pieces of scan below is Mobile/Cell/Pager etc. You SURE need a good filter to get rid of Cell/Mobile signals between 925 Mhz and 965 Mhz
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scan1a
scan2A

Hi A342,

I used to have a home built 16 element CoCo made from a generic coax. I eventually worked out that the Velocity Factor was 0.66 so cut my elements accordingly. I then placed it in some 22mm plastic waste pipe and mounted it at the apex of the roof. It worked very well until we had a winter storm and the pipe snapped just above the mounting point. It used to swing about a lot in light winds so I wasn’t surprised it eventually broke.
Make yourself a 12 and a 16 element CoCo and test them outdoors but not up the pole on the roof. You may have read on this forum that a lot of people have trouble making a CoCo that works, so congratulations on your build :smiley:

As others have said, you need a filter to remove the unwanted signals in the 900 Mhz band. You seem to be a DIYer so take a look at a thread I started about Interdigital filters.
[Note] I have NO experience of radio/physics etc. apart from what I’ve learned on this forum and a lot of reading :wink:

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@A342

I will recommend that you follow @triggers advises and guidance.
He has a long experience in CoCo making, and has successfully built several very good CoCos.

He has also ventured in saw, cavity and inter-digital DIY Filters, as well as Directional antennas like Yagi & Corner Reflector types.

However, most of them ended up in the bin but it was good experience.

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I don’t know. I’m new to this particular bit of following aircraft via ADS-B and am adding, hopefully, to the UK coverage. It’s nice to know that those with knowledge like to share it. I was EXTREMELY surprised when I tried my first cantenna a few months ago and even more surprised when the tin of beans performed better than the tin of peas.

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Triggers, abcd567, thanks for all your advice. Triggers I will most certainly look at the thread you recommend. Yes I will try the various numbers of elements and hoist them above my man cave for comparison. As for experience, I left school at 14 years and ten months of age (armed with a National Bicycle Safety Certificate) to start working life as a Chemists (Drug Store) delivery boy. Since then I have graduated from the School of Hard Knocks and am working on my Masters in the University of Life. Yes, my children think I am a little mad.

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This happens to majority of parents, not only you… generation gap. :slight_smile:

Triggers, abcd567, KeptenKurk and others. I have totally plagiarised the designs that you gentlemen have shared. Triggers thanks for the link to your thread on the filter. I have used KeptenKurks measurements as I also had 12mm copper pipe. I have made a template and a pattern to allow me to see what mishaps and pitfalls could lie ahead. Please see the photograph.
Now that all the Xmas puddings have been mixed and steamed , I can now go ahead and cut the copper sheet. I will be using metal rawls to hold the pipes in place. As said elsewhere it is useful to crimp the tuning screw once perfection (ha,ha!) has been reached. I will use loctite as that can do the job but can easily be broken if further tuning in the future is needed.


On my journey through the theory and design of this filter there are lots of things i don’t understand but have just copied what I thought I needed (monkey see, monkey do!) but I would like to as k a couple of questions. Is the impedance mentioned in the tables that of the co-ax being used or something else? Endplate measurement. Am I to presume that that is the distance from the connecter wall to first an last pipe, and lastly (for tonight anyway), what is Q and Qu

Many thanks for your patience.

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@A342

Your drawing shows the BNC connectors attached through to the adjusting screws. This is wrong. They should be connected to the tubes.

[Edit] I also don’t understand the theory. Seems to me that there is a dead short through the filter. The core is attached to the tubes which are attached to the copper box. The braid is attached to the copper box. :face_with_raised_eyebrow:

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A mistake in the drawing, and yes, now that you mention it it does seem like a dead short. However in the coco the talk is of elements but it is still one continuous length of cable but with the polarity continually changing from element to element??

Not quite. Put a meter between core and braid and there is no continuity except if you short the top element ( I don’t have a shorted top element in any of my CoCos)

Isn’t physics great :wink:

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Actually that description is more like lambda/2 antennas connected together with lambda/2 pieces of coax cable (for phasing reasons, delay the signal with 180degrees). It’s just convenient to use the outside of coax as antennas, because of mechanical construction.