@abcd567 Got it. Before you replied I already built V-Lad with 82mm and simply connected it with electric tape to quick spider laying around. Still no miracle, it performed 2-3 times worse than my homemade 10 element co-co I’m currently using. I think I tried at least 4 or 5 your designs (found here and on other sites) and they all were in the same ballpark compared to co-co.
I’m not sure if tuning can make up for such big difference so I did not try to tune it. Maybe tomorrow.
Also not sure if coax can be a culprit. For V-lad I used 2 feet piece that came with my cable modem.
If you have made a good 10 element coco, then all the wire antennas I have posted here will perform inferior to it. A good 10 element coco can have a gain of 6 to 9 dB and a very favourable radiation pattern. In this case I will suggest you dont try any DIY wire antennas.
Still interesting to try to see myself and hope for the miracle. What else left? Buy FA-antenna and prove co-co is better or FA is better and call it a day? Not fun.
When you introduced this as a COLLINEAR ANTENNA I tried to understand how it works and hence my question about the wavelength of the lower and upper wire.
The lower wire being 0.13 wavelength means the top of it is not a high impedance point and the coil would not just be a phase shift.
At least now I understand what I don’t understand.
Actually I tried to simulate an approximate clone of FA Antenna (for simulating frequency sweep, and not for building it).
I dont have FA antenna’s dimensions, and dont want to spoil mine by opening it to measure. I just approximated dimensions from photo given below as follows:
1/2 𝛌 upper wire
4 turn 1" dia coil
1/4 𝛌 lower wire
1/4 𝛌 long, 15mm dia decoupling sleeve
These dimensions gave poor results. As I was not interested to build it, but to use model for frequency sweep through software, I modified upper & lower wires to get results good enough to go ahead with frequency sweep.
The other option was to keep upper & lower wires 1/2 𝛌 and 1/4 𝛌, and vary the coil diameter and length (number of turns is clearly 4 in photo so no need to change it). This option is tough as I had to create a very lage number of coils of different diameters & length combinations, which is very tedious, and not necessary as I did not create this model to built it, I created it to make a very wide range frequency sweep from 100 Mhz to 2500 MHz
FlightAware Antenna With Platic Pipe Removed
CLICK ON IMAGE TO SEE LARGER SIZE CLICK AGAIN TO SEE FULL SIZE
No miracles. It will only be a big disappointment.
That will be real fun. Without the side-by-side comparison of coco & FA-antenna, you dont know where your coco stands, better than or worst than FA-antenna.
If coco is better than FA, keep it and sell FA-antenna.
If coco is worst than FA, use FA and throw coco in trash
Maybe I’ll do it later. But before I’ll move co-co to attic instead of having it inside facing one side of the house. That would be interesting to see what improvements I’ll get.
@abcd567, I just don’t get why you are trying to improve inferior antenna designs instead of getting to the bottom of issues with co-co. For my it was a very simple to build it as soon as I found coax with known velocity factor. So I’m not sure why others struggle with co-cos.
Coco is a shot in dark, and only few lucky ones (like you) end up in making a good coco. The reasons are velocity factor not know accurately and dimensional errors caused due to this or poor workmanship. Coco is verry intollerant to dimensional errors. A millimeter or two plus or minus, and it is disaster.
The DIY antennas I suggest are mostly 1/4 wavelength, which are not very sensetive to dimensional errors, and do not require tuning. This is ideal for a beginner.
I’m not an expert but it is not very difficult to find coax with known velocity factor (unless you telling me that specs provided by manufacturer is total BS). IMHO to cut 4-6-8 straight pieces of coax and measure it with caliper is not a rocket science. Argument that co-co is difficult to make sounds strange to me.
Maybe I need to try to make another one to suffer “a big disappointment” to see your point.
During first few years of this hobby, I have made over a dozen CoCos. None of these performed better than a 1/4 wavelength grouund plane, and some performed even worst.
The main problem is that the coax which is readily available everywhere, and is reasonably priced, is that RG6 which is used for TV and Satellite Dish. This coax comes from lot of different manufacturers, lot of these unbranded, and the branded ones without any specs available.
To have a good start with coco, the very basic requirement is that a coax which is from a good manufacturer, and whose data sheet is available should be procured.
Very few hobbyists make such an effort, and use the coax already available with them, or purchase whatever is readily available in local stores.
But did you ever try to make coco from coax with well known data sheet? If so, did it fail as well? I can’t be so lucky to make it good on the first try (need to admit I won $10 lottery once ).
Don’t see the point of making inferior product when effort is so low to get it right doing better one (unless it is pure luck at all to get coco right).
No, I did not make any coco with coax of known velocity factor. The reason was that I was trying to replicate what majority of hobbyist will do. How many will order a 5m piece of coax from a seller/manufaccturer who provides coax data also? Most will go to super market like Walmart, Home Depot or a Dish TV installer.
That is a valid point. It stands to reason that any comparison should be against that of a known and widely available entity.
I have no doubt that a correctly built collinear performs very admirably - it’s a tried and true design, but they do take a brain to build and can be frustrating due to conflicting construction information. I’d really like to see a side-by-side with an FA unit myself. I only mention the FA antenna because it is usually the most widely available and popular of the manufactured units and there is a lot of data and testing behind them.
Also a very valid point. I really haven’t seen clear and concise build instructions with the necessary base measurements and VF calculation adjustments for a 1090Mhz specific coco in one easy to find place besides a couple external links, but none of them show anything close to side by side tests. Also a 10-element is somewhat rare to find - most everything is 8. I’d love to learn more about your particular build as well.
I can tape a couple hubcaps together on a stick and probably pick a few planes up, but that’s not the point. Perhaps I suck at searching, but I’ve seen a ton more when it comes to spiders and coke cans, which are inherently inferior by design but truly easier to build. I’d like to see more on the collinear designs as well as 5/8, jpole, etc. We’re dangerously close to being off track for this thread.
@Nitr0 For measurements I used information from this site - [https://www.balarad.net/]. I did not use any lambda/4 protection stubs and etc. since antenna is indoors. I connected coco directly to short piece of coax → filter → LNA → SDR → Raspberry (initially just coco → SDR → Raspberry). I think I went from 6 to 8 and then to 10 elements probably without significant gain in reception just to fill PVC pipe I used to hold coco.
True, and not only amazon, but other sites also, but the cost of shipment to canada and duties make total cost prohibitive. In example you quoted, the cost alone is 49.99, and shipment+duties will make it much more. I can buy a FA-antenna in less than this price.
Thank you very much. I have the “Noise Source”, so I will try it this weekend.
OK, me and so many other hobbyists can do it. However most of hobbyists, particularly the beginner do not have enough technical know how and equipment to do it. They normally “guess” the VF from google search or from the web site/ youtube they are using as guide. This is the main cause of failure.
I have visited lot of stores in my area like Walmart, Home Depot, Satellite dish supplies, electronics hobby shops. All of these have good quality Coax double & quad shielded, but no data for vf available. Also all these coax have Aliminum foil+ Steel braid, no copper. The core wire is copper-clad steel. Core can be soldered, but braid wont hold the solder.
What else left? Buy FA-antenna and prove co-co is better or FA is better and call it a day? Not fun. 
