ADS-B CoCo on a PWS pole

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.

Just thought that I would keep you all up to date on the filter project. Domestic considerations dictate that this a slow build, and, unlike kaptenkurk, I have few of the items required so am having to buy them. I suspect that it will cost me more than a commercially made one, but I wouldn’t have learned what I have so far, nor had half the pleasure in the building. The following few photographs show the progress so far:

Photo 1 is the final cut. I was using a Woolworths special from some years ago and was it MUCH cheaper than a Dremel. Photo 2 shows the tools I was using and lastly the box after using the jaws of my bench vice and a 1lb claw hammer as the bending tool. That was okay for the long sides. For the end plates I cut a piece of aluminium bar I had to the length of the box and secured it with two wide clamps in order to have something to hammer against. It seemed to work well.

I’m now awaiting delivery of the brass expansion plugs, as shown in keptankerks photo. Once I have confirmed that everything “should” fit then i’ll drill the various holes and start assembling/soldering things. Unfortunately I haven’t worked out how to secure the top of the box other than soldering it, which could be a pain if i have to take it off again in order to change anything inside. I have a question: I’m not sure if the pipes should be fixed exactly in the middle of the walls or should the be biased closer to the top or the bottom of the box?

I’m being pretty verbose in this thread, purely in the hope that someone who has been considering doing something like this will see that it really is possible and learn from trigger and others as I have, and enjoy doing it.

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You should open a new thread about this filter. However, this is a pic for inspiration:

http://pe1rki.com/1090mhzfilter.html

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I suppose I should. Or copy it across to triggers original thread on building his. As for inspiration, I wish I could afford the milling machine that produced such a beautiful finish to a block of aluminium.

.

Great. This is the sprit of this forum. :+1:

Adding to @triggers thread is better, instead of having multiple threads on same subject.

Err, emm Ehh- - - How do I go about this?

It will be difficult to copy so many posts from here to there, so easier option is continue here, and in @triggers thread post a link to this thread, and here a link to @triggers thread.

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Hi Mike,

Looking good :grinning::grinning:

I found the soldering of the components the most difficult. The trouble with copper is that it is a great conductor of heat :wink:. I’d get one piece soldered then whilst soldering the next one, the first piece would unsolder and drop off.

Good luck with the rest of the build.

I put mine in the middle of the walls.

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Triggers, thanks for the heads up on the soldering. Once i’ve finished this I shall gather all the bits of suitable spare metal and clamp them to the walls as heat sinks. Hopefully this will reduce the propensity for the solder to drop off. Rather than using my blow torch I might try using a soldering gun, to sort of “spot weld” enough of these and with a bit of patience, you’ve got a continuous weld. (I hope)

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If you want to go that way you might want to use a hot plate set to a low setting or a heat gun for preheating.

Otherwise using a soldering iron to solder copper sheet is gonna be tough :slight_smile:
Also depends on your soldering gun i suppose!

An electric soldering gun will have to be at least 100W to be able to heat up that copper.

soNic,
Yep. I just discovered that However I have found that my trusty bench vice seems to be a good heat sink. Ive got one joint complete, so i’ll try another one with the box in the vice and with additional heat sinks and hope that joint #1 doesn’t melt. Still, if it does, i’ll sit back in my man cave with a nice cold beer and contemplate the next move.

A342

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Better to use the vice as heat sink than your fingers :smiley:

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Tried to be tidy and use the old plunbers trick of “wiping” the joint. It didn’t work. Tomorrow, i’ll file the excess😅

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