New Antenna - 10x Increase (Not even outside yet)


#16

Any one interested to make Easy & Reliable DIY antenna? Try these:

http://discussions.flightaware.com/ads-b-flight-tracking-f21/3-easy-antennas-for-beginners-t20177.html


#17

… Doesn’t need much, I was setting up the PiB - using the supplied magmount (cut down to 68mm) stuck on a can of tuna on the outside window cill … and was getting almost 150nm


#18

[quote=“PeterHR”]

In past I have also tried the same thing and got similar results, but limitation is the small length of stock antenna’s cable, which puts constrains on equipment setup.


#19

SIMULATION OF 2 DIY ANTENNAS

Simulation 1 of 2: SPIDER (8 Legged )
Gain = 1.7 dBi
SWR (75 ohms) = 1.3


Simulation 2 of 2: CANTENNA
**Gain = 1.9 dBi
SWR (75 ohms) = 1.5
**


#20

These pics did not turn out the best due to the high contrast outside. Will see if I can get some better ones during the evening.

https://www.dropbox.com/sh/7px5jnzhs86drcp/AAAKOc1DdNtcHhtfmaSU7vlIa?dl=0


#21

Here is my INDOOR Cantenna & Its Range
Range Rings are 50 nm apart. Outermost red ring is 300nm radius
Gmap screenshot: Aug 02, 2015, 12:26pm local time (US/Canada Eastern Time)

My setup:
Indoor Cantenna > 12 ft RG6 Coax + 20 inch RG316 pigtail to DVB-T > DVB-T directly inserted into RPi > 15ft Network cable from RPi to router



Note about Cantenna Whip: The Whip of Cantenna looks like a piece of Coax, but it is not. It looks like coax because I made it from core wire + white core insulation of Coax (important: the braid and foil were removed from the whip). What is actually required is bare copper wire. The core insulation can also be removed if desired. I left the white core insulation to make whip more visible in photos :slight_smile:

Note About red/blue range rings: Please see my post: http://discussions.flightaware.com/ads-b-flight-tracking-f21/how-to-get-alternating-blue-red-circles-in-dump1090-t20403.html

Note about how to make Cantenna: Please see my post http://discussions.flightaware.com/ads-b-flight-tracking-f21/3-easy-antennas-for-beginners-t20177.html

.


#22

The Spider has existed for a long time, frequently used by amateur radio operators.

A close relative of Cantenna, the “Coaxial Dipole” has also existed for a long time, but was not so popular as the Spider. It was mainly used in rubber ducky antennas of Hand-held radios. It has a very narrow diameter sleeve, which was made of a copper tube or pipe, slightly bigger in diameter than coax. It did not have the performance as good as it’s newly discovered wide-bodied relative, the Cantenna.

The Cantenna was born only about an year ago, as a result of series of my experiments on CoCo. In June 2014, I added a decoupling sleeve, made of Pepsi can cut to 69mm, at feed point of my CoCo. This experiment was not successful, possibly as the sleeve was too large in diameter for decoupling purposes.

Instead of discarding the sleeve (Pepsi can cut to 69mm), I decided to use it to make another type of antenna, the sleeved dipole, and it proved very successful. It’s performance was much better than “Coaxial Dipole”. This was birth of Cantenna.

After 2 months I renamed sleeved dipole to “Cantenna”.

**(1) Cantenna Invented by me - The Very First Cantenna ever made (June 2014): **
http://forum.flightradar24.com/threads/3831-best-antenna?p=53094&viewfull=1#post53094

(2) Name “Cantenna” chosen by me (Aug 2014) - Originally I called it “1/2 λ sleeve dipole”:
http://forum.flightradar24.com/threads/3831-best-antenna?p=55872&viewfull=1#post55872


#23

Isn’t your antenna just a smaller version of this one?

amateurradio.bz/coffee_can_antenna.html


#24

Similar, yours uses an SO-239 as opposed to a F-type inline female barrel connector. Different enough to get a patent granted on a busy day.
But then again: Ecclesiastes 1:9 :wink:


#25

Thanks for pointing out. Yes the two antennas look very similar, but the “2 meter coffee can antenna” is a random design, not a proper engineering design.

First of all I would like to give credit to Dave Tadlock of conceiving the idea of using an inverted can as groundplane in 2012, about two years before I independently, and without knowing Dave Tadlock’s work, have also conceived of same idea in 2014. However Dave Tadlock’s design is not based on any sound engineering analysis/synthesis, rather on trial-and-error method. I based my design on sound engineering analysis/synthesis, followed by confirmation of performance by trial runs.

The fundamental difference is that in “2 meter coffee can antenna” the length of sleeve (coffee can) is much less than 1/4 wavelength ( at 2 meters, the 1/4 wavelength = 1/2 meters). Hence it is not a tuned antenna. The much smaller than 1/2 meter coffee can provides some amount of groundplane, but is not an optimal design. Hence performance of “2 meter coffee can antenna” sure will be less than Cantenna.


#26

First of all I would like to give credit to Dave Tadlock of conceiving the idea of using an inverted can as groundplane in 2012, about two years before I independently, and without knowing Dave Tadlock’s work, have also conceived of same idea in 2014. However Dave Tadlock’s design is not based on any sound engineering analysis/synthesis, rather on trial-and-error method. I based my design on sound engineering analysis/synthesis, followed by confirmation of performance by trial runs.

2 Meters Coffee Can Antenna Simulation
I have done a quick simulation of “2 meters coffee can antenna” using the whip & coffee can dimensions given on quoted web page. The results are as I have expected. The coffee can has been used just randomly, and not based on any engineering analysis/synthesis.

Gain = 2 dBi (almost same as Cantenna’s gain of 1.9 dBi)
SWR = 2.6
- Very High, will give poor performance (Cantenna has a SWR = 1.5 which is a very decent value).



#27

[quote=“abcd567”]

Gain = 2 dBi (almost same as Cantenna’s gain of 1.9 dBi)
SWR = 2.6
- Very High, will give poor performance (Cantenna has a SWR = 1.5 which is a very decent value).[/quote]

Recalculate to 50 Ohm, please. As usual, HAM’s equipments use 50 Ohm impedance.


#28

At first - historically name “Cantenna” used as name of “dummy loads”, “dummy antenna” or a “radio frequency termination” :slight_smile: Take a look here (for example - 1965 magazine) : nostalgickitscentral.com/hea … F-1-65.pdf. Original Heath “Cantenna” produced from 1961 till ~1991.

Now name “Cantenna” used to short description of waveguide antenna, made out of an open-ended metal can (most often for Wi-Fi purpose).

In second - your antenna is modification of well known coaxial antenna originally by A. BAILEY (US patent US2184729 A).


#29

(1) I coined and used term Cantenna independently and without being aware of its previous uses. This re use has been done by waveguide antenna designer also as he also seems to be unaware of its use by dummy load. You mentioned the name cantenna was already in use by a dummy load device as far back as 1961, hence the objection you have made for my use of name cantenna, also applies to use of name cantenna by waveguide antenna.

(2) As far as “coaxial antenna” is concerened, I have already acknowleged its existance and closenes to cantenna in my post on page #1, and again quote it here:

A close relative of Cantenna, the “Coaxial Dipole” has also existed for a long time, but was not so popular as the Spider. It was mainly used in rubber ducky antennas of Hand-held radios. It has a very narrow diameter sleeve, which was made of a copper tube or pipe, slightly bigger in diameter than coax. It did not have the performance as good as it’s newly discovered wide-bodied relative, the Cantenna.

To clarify the difference between Cantenna & Coaxial antenna, I am attaching two images showing the construction of “Coaxial Antenna” using a narrow dia cage/tube/pipe, slightly bigger in diameter than the diameter of coax.

First image is from antenna engineering book “Antennenbuch by Karl Rothammel”, and the second image is from patent by A. BAILEY (US patent US2184729)

Image 1 of 2 (Translation in English in red added by me)

Image 2 of 2


#30

[quote=“Serge77”]

Recalculate to 50 Ohm, please. As usual, HAM’s equipments use 50 Ohm impedance.

“2 meters coffee can antenna” recalculated for 50 ohms:
Gain = 2 dBi
SWR (50 ohms) = 3.1


#31

[quote=“abcd567”]

“2 meters coffee can antenna” recalculated for 50 ohms:
Gain = 2 dBi
SWR (50 ohms) = 3.1

Wow! 3.1 is too big! So strange…

Well, another notes about your calculations:

  1. Take a look at farm4.staticflickr.com/3879/150 … 6e79_c.jpg - the edges of the jars are bent, respectively the amount of bend must be considered in the calculations, but you don’t, and so you construction not equal your calculation.
  2. Take a look on post157719.html#p157719 - you use central wire of coax cable insulator, but not consider reducing coef for cable lenght and recommend 69 мм. Coax on picture looks like foam insulated (coef ~0.8-0.85 in general) so lenght must be lower then 69 mm depending on cable type.

#32

Thanks for pointing out details about calculations.
(1) The can wall & bent edge touch each other and are electrically continuous, like one sheet of metal, but double in thickness. Logically this should not affect performance. However when I made my first few cantennas, in order to check the effect of bent edge, I have removed the bent edge of one of these cans and put on trial run, and did not notice any improvement or decay in performance. The bent edge is to avoid creating razor-sharp edge and risk of injuring the fingers. Bent edge can be removed and adhesive tape applied along the rim to cover the razor-sharp edge of the can without affecting performance.

(2) I have tried whip with core insulation as well as a bare wire whip, both of the same length and diameter, and both gave same performance.

When the shield is present over the core, it prevents electromagnetic field from its inside to extend outside and vice versa. As a result the entire electromagnetic field surrounding core wire is confined within the core insulation. In this case the propagation slows down by Velocity Factor of insulation, and a reduction in length proportional to VF has to be applied.

When the shield is removed, there is nothing to confine the core wire’s electromagnetic field. The electromagnetic field of core wire without shield therefore extends beyond the core insulation into the surrounding air. Almost the entire quantity of the electromagnetic field is in air around the whip and only a very small fraction is inside the core insulation. As a result the VF is almost 1, and practically no reduction in length is required.


#33

(1) I agree with such decision from the point of view for safety reason, but even can wall & bent edge touch each other in geometry, but because of an oxide layer - the aluminum can’t provide proof contact on very low signals.
(2) Of course I don’t urge to multiply length on 0.8, but from my experience of constructioning SW antennas, the same resonance frequency had antenna without insulation and antenna with PVC (0,8 mm thickness) insulation with shorter in length at 2-2,5% then without insulation. In our case the ratio between the thickness of the insulation and the wavelength is much greater so IMHO the coefficient of reduction of length shall be more.

Best regards,
Serge


#34

Thanks very much for the pics. I see where I went wrong. I did not hang the antenna upside down LOL

Anyway, I returned my FA antenna and am expecting a replacement to arrive soon. The range was definitely degraded as compred to the whip.

However, in the meantime I have improved the performance of the whip by only extending it equivalent to 5/8 wave instead of fully extended. I was unable to collapse it to 1/4 wave without cutting it which was something I did not want to do.


#35

Once you get the MCX-male to F-female pigtail, you will have flexibility to experiment with many DIY antennas such as:

  1. Spider - needs special connector like SO239 or N-connector. The 4 leg version do not require soldering, but 8 leg version requires soldering.
  2. Cantenna - needs no special connectors or soldering. Needs only a drink or food can & one F female-to-female barrel connector with 1 nut & 2 washers.
  3. CoCo - needs only 1.5 meters of coax, one F type twist on connector, cutter, knife & lot of good luck :smiley: (may require making and trying many CoCos with slightly different element length till you get a good one).