If I wanted a CoCo for myself only, it was very easy for me to do it. I can easily afford to spare $50 to purchase a roll of good quality coax online, made by a good manufacturer, which has a datasheet, and which has copper wire and copper braid.
However my objective has been “Easy Antennas for Beginners”, and a CoCo definitely does not fall into this category due to lack of datasheet for commonly availble and reasonably priced Coax in stores around the globe.
Users who make a Coco using coax without datasheet, and use VF they see on web site guide or Youtube tutorial, and still get a good Coco is merely their good luck.
The 1/4 wavelength ground plane wire antennas definitely fit the criterea “Easy Antennas for Beginners”.
If a good quality coax with known VF is in hand, making a good Coco is not a problem. Let us hope one day I will find it in our local stores/suppliers.
Did you use a 75Ω balance resistor (based on the fact you used 75Ω RG6)? That site is the most prominent in the search engines, but not much else out there that doesn’t almost restate that link word for word and frankly, much of it is somewhat confusing and jumbled together. (No offense to the author of course). I’d like to see a thread here exploring different techniques, tests and sweeps as we have for the other DIY’s. Be good to put more effort in this design - maybe as a thread for the DIY headbangers and not only beginners.
ADD: I inquired about the Sewell cable I use and one of the reps sent me the following, SW-30173/SW-30174, readily available and not too expensive (have also had it outdoors in Phoenix, AZ for the last 4 years and it still looks new):
Thanks. I will brows it. Hopefully I can get a coax of known VF at a reasonable price.
My key problem still remains: The coax used for Satellite & tv is the most readily available and low cost coax worldwide. How many hobbyist worldwide will be able to afford to purchase the coax of known VF? We in North America & Europe can afford this, but difficult for other countries of the world.
In addition, people dont realize importance of using accurate value of VF, so they just use whatever value suggested in the web sites / youtube, and apply it to whatever satellite cable they have or can get easily.
A ball of string is also readily available and cheap - doesn’t mean it’s suitable for making antennas.
In a previous post you said you buy your coax from a $1 store (or similar), so it’s no wonder your antennas fail. That’s fine and it was still worth a try, but you write off the design as “to difficult for hobbyists” when you’ve only tried building it (knowingly) with crap cable; That’s very poor advice.
Good quality cable is not expensive - if you can’t afford $1.50/ meter (LMR400) (you only need a meter or two for the antenna), perhaps you should stop building antennas? (or at lest stop writing about them)
Is there an advantage to using lower-loss cable for a collinear construction? Asking for a friend
Many of the more recent replies in this thread should be moved into a dedicated collinear antenna construction thread so it ends up constructive. No sense in railing each other, nobody learns that way.
I built a collinear based on the same link @vkirienko listed and it sucked. I had the cable specs (listed above), did the math, cut to perfection, checked every segment as I was putting it together and I’m about as OCD as a person can get… I didn’t add the balance resistor either, so in theory it should have ended up like @vkirienko’s and maybe it did, but I’ve also done the sweeps and side-by-side tests to make sure.
Bottom line is that it would be fantastic to have a constructive collinear construction thread where those that have the experience making them can chime in - just like this thread was before the diversion. I cant start it because I don’t know what I’m doing evidently, but will try again with some direction and can do side-by-sides and sweeps. Hug it out.
The Satellite RG6 is not at all bad for making a Coco. The problem is that its VF is not known to almost any seller.
I replicated the situation in most parts of the world where the only readily available and affordable coax is that which is used for satellite tv.
The hobbyists of North America and Europe have completely different situation. Good coax with known VF is available easily, and is affordable for most. Please do not limit what I said to only these regions, rather exclude these regions from my conclusion “difficult for average hobbyists”.
Given I normally live in a country where brand name cable is unavailable, I assure you, I am not excluding any regions.
When I need to know what I’m using, I have to import it myself.
I don’t get this argument. Even with your designs you need to cut wire to specific dimensions (maybe not so precise) but you can’t go from 135mm to let’s say 175mm without issues. You need to realize that dimension is important. With coco you need to realize that VF is important and it drives dimension. Any sane person realizes that design is based on some specific thing (dimension, VF, type of cable, etc.) and you usually can’t substitute it with something else. So why importance of VF is more difficult to grasp than dimension?
That is exactly what most of beginners fail to realize.
Dimension is a physical thing and easily understood and complied with, even by a beginner. It is very unlikely that any beginner will make an error more than a few mm from what mm is given in diagrams.
On the other hand VF is taken from data sheet (or web sites / youtube). It cant be seen & verified by a beginner like he can verify the length. Also Coco is more intolerant to dimensional error than the 1/4 wavelength ground plane. Few mm error in a 1/4 wave ground plane will not make a drastic drop in performance, while few mm error in Coco is enough to knock it down.
A good 8-element Coco has gain and radiation pattern comparable to most commercial antennas like FA-antenna & Jetvision antenna. Does not this fact tell you anything that in spite of claims that a good Coco is easy to make, most user opt for a commercial antenna and do not make a Coco?
Please brows the following old thread which was started in 2014. It is a long thread, difficult to read, but to summarize, most of the posters followed a path more or less like this:
Started with: mag mount whip in window or attic - Range 50 nm
Next step: Built a CoCo - Range doubled to 100nm
Next step: Built 1/4 wavelength ground plane (Spider) - Range increased to 150 nm
Next step: Purchased commercial antenna - Range increased to 250 nm
$13-15 dollars will buy you enough cable to have a few goes. It would be interesting to see if using the ‘default’ velocity value for that type of cable gets you something that works.
I will throw the post i made many years ago on flightradar in here if anyone wants a guide to how i have made mine in the past.
There is another complication if you intend to use it outdoors.
A polymer pipe around the colinear antenna commonly used for weatherproofing will change the velocity factor / tuned frequency.
That obviously depends on the diameter / thickness / material of the pipe used.
