FlightAware Discussions

Veggie Cantenna + Collinear Mark II


Your story is similar to most DIY antenna hobbyist’s story (including mine).

DIY Collinear antennas are “A Shot in Dark”. Mostly missed, rarely hit.

Your Spider is a neat built. Looks very nice :+1: :+1: :+1:

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That spider is the same as most- what I did was cross drill the holes for the ground plane elements 90 degrees apart into the sides of the cap, just far enough down the side that the drill diameter missed the thickness of the end of the cap. Stuck the 2 excess length element wires straight through the center, bent around inside the cap to clear the F connector, bent the elements down, soldered the elements, installed the F connector then trimmed the ground plane elements to “proper” length. For this one the top surface of the cap itself was not factored into the 68.8mm measurement.

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This interesting CoCo design was posted by @mem0tap in FR24 forum. Unique design: using copper water pipe as shield, and bamboo stick as core insulation

Two days ago (July 14, 2018)


Today (July 16, 2018).


Photo 1 of 3


Photo 2 of 3

Photo 3 of 3


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I don’t know how you guys solder anything, i fail at getting enough heat into them to get it to melt…

I used nuts and bolts on my SO239.

Certainly is unique.

A few questions if I may;

  1. What advantage does this construction have over coaxial cable?
  2. What is the Velocity Factor?
  3. How do you keep the centre conductor straight and on the centre line of the outer conductor?
  4. Why?



Soldering is problem with me also.
That is why I developed Quick Spider and Cantenna - No soldering :smile:

I am not in a position to answer any of your questions.
Better ask these in FlightRadar24 forum where the CoCo builder @mem0tap has posted the above antenna design:

It’s important to use a soldering iron with the proper wattage. The typical 25-30 Watts soldering iron, used for soldering semiconductors, is not ‘strong’ enough for these kinds of jobs.

Too ‘strong’ a soldering iron, or gun, will melt everything.

Also, the cheap plugs/connectors are not solder ‘friendly’. A silver plated type is preferred, but it costs more.

Yes, Velocity Factor is how fast the signal moves along a transmission line.

For the construction of a Coaxial Collinear made of coaxial cable segments each segment needs to be a half wave transmission line. Hence the need for a known, accurate Velocity Factor and accurate cutting to length.

Each segment is an exact half wave transmission line and an approximately half wave dipole radiator. The higher the VF, the closer the segments come to being half wave dipoles in free space which is better.

My question was to find the actual VF for a coax segment made of copper pipe and wire with a bamboo di-electric. With the wrong VF or a variable VF depending on the bit of bamboo is likely to end in a typical home-made CoCo failure.

Over time specifications such as RG58 and RG59 and RG6 in various formats have been made with different dielectric properties and hence different Velocity Factors. For most transmission line applications, the VF does not matter. It makes a significant difference if the project involves a cable length of a particular number of wavelengths such as a CoCo or a multi antenna phasing harness.

It is much easier if a known, branded coaxial cable is used as the manufacturer can usually supply the actual VF.

Hillary only had to climb a mountain. Big deal, he was the first.

I’d suggest more people have now climbed Everest than made a successful CoCo fro coaxial cable.

I’d sadly suggest that more have died trying to climb Everest than have expired making a CoCo.


Air insulated coaxial cable (VF=1)
Foamed PolyEthylene (FPE) coax, RG6 has the highest VF (0.83 ~ 0.86)
The Polyethylene (PE), the VF is low (0.66)

True :+1: :+1: :+1:
Coaxial collinear is “A Shot in Dark”, mostly missed, rarely hit.

Vf (not VF) is relative to the speed of light in a vacuum.

The speed of light in air is for practical purposes (a sharp knife and wooden ruler) the same, but shouldn’t be confused as being the same thing.

Kick-ass coax looks like this and has Vf of 0.92

Andrews HJ-50

I used a 100 watt soldering iron on the copper pipe cap and even that was marginal heat. You have to realize that any piece of metal is a “heat sink”, meaning that in order to get the solder contact point up to temperature to flow the solder, you have to overcome the fact that heat is being conducted away into the whole mass of metal at a rate only slightly slower than you are putting heat in. The wire will heat rapidly, the pipe cap will take a lot longer. Bias the heat towards the larger mass and be patient- remove heat just after solder flows.

I also made my SO239 spider with bolts because I didn’t want to melt the center insulator getting it hot enough to flow solder, plus the connectors I purchased were made of the cheapest cast garbage mystery metal and would never in a million years take solder. The bases used to all be made of plated brass and you could file off the plating to much more easily solder to it.

Pipe cap spider came about as there is no place near me anymore where I can walk in and buy components like SO239 chassis connectors. No one fixes or builds anything anymore and if they do its all online parts orders.

TLDR: Choose your battles

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You realize you just caused me a spate of google searching :rofl:…that coax is sexy stuff but I wouldn’t want to pay for it or be wrestling it into a bend!

But of course I went down another internet rat hole when I was curious to know how the skin effect of the outer shield surface area relates to that of the center conductor- would appear that the net surface area of both is different. At the moment that stuff way over my head.

What i do soldering cans is setup a electric heat gun to “prewarm” what i’m soldering.

So i bring it up mostly to soldering temperature and the use a good iron. Or even setup the heat gun so it can keep on blowing the entire time i’m soldering.

With cans it’s not a problem but with connectors it depends what plastic is used.

You are right, but for the purpose of making a CoCo, such finer details are unnecessary.

Andrew Heliax LDF is very costly and not sold by common stores. It is rarely used for making a DIY Coco. A hobbyist who lives in my area did make a Coco from LDF1-50, but only after he got a length of it free of cost from a friend. Here are two photos of his 14 element Coco made of LDF 1-50 Andrew Heliax cable (the one with black outer jacket). The other made of brass tubes is a commercial antena for Wifi



True, but there lots of off-cuts every time a cellsite goes up.
When it’s free, you can use it for everything / anything.

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The Andrew Heliax has a corrugated shield, which effectively increases shield’s length as compared to a plain shield. This makes Adrew-Heliax’s radiator closer to half wave than the radiator of a standard plain shielded coax.

Local policeman: “What are you doing here rummaging around the communications tower ?”
Me: “Collecting wire”
Local policeman:" Did you cut that stuff off the tower intending to steal it ?"
Me: " No, they left scraps around"
Local policeman: “What do you think your doing with those ?”
Me: “Tracking airliners”
Local policeman, becoming alarmed : “Excuse me, did you say tracking commercial airliners ?”
Me: "Yes, I can see exactly where they are and where they are going and… "
Handcuffs. Dragged off never to be seen again.

Joking of course, but I think unless someone cleared me picking them up not something Id personally go hunting for…

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No joking at all. We are not in Kansas anymore.:grinning:

The same applies to other innocent hobbies, like geocaching. Not a problem in Canada, the US, or Western Europe. But in some other countries, the last thing you ‘need’ is to be caught with a GPS receiver, checking behind bushes, inside holes or digging. Ever heard of ‘dead drops’? :rofl:

Then there is/was Pokemon Go. The places people would go, oblivious to anything else. There is an ‘iconic’ picture of a guy in an area where the big sign clearly said: Danger. Stop. Do not enter. Mined field.

Sorry for the off-topic. Back to our regularly scheduled programming.:joy: