FlightAware Discussions

Confused about antenna design

I like this presentation, range plot with antenna shown on the same picture.


Well, finally cut my can, and coax, it’s ugly in terms of accuracy, but hopefully it’ll be a bit better than it was before… Next attempt will be to put the system in the attic(currently on the second floor inside).

You forgot to remove from WHIP, the black outer jacket, the braid & aluminm foil. The whip should be either BARE wire, or wire+core insulation.

Ok that should be easy enough to do… I didn’t remove it since in several other diagrams/pictures the shielding was left on… and what’s impressive it seems I’m getting better receiption with it on than the packaged antenna.

**@slookabill: **
Your reception will improve after you remove the braid & foil from the whip.

I found this simple and easy to make antenna from another forum.
The Range mentioned below by the antenna maker is remarkable for such a simple antenna.

"Mine is made with 33cm unshielded TV coax and as a ground plane the bottom of a thunafish tin. More than 200nm."

Now that is what I would call “cutting edge technology” :unamused: :unamused:

Well said! :laughing: :laughing: :laughing: :laughing: :wink:


Here comes the Platenna

Range Rings are 50 nm apart. Outermost ring is 300nm radius

Collect the Stuff
(1) For RG6 coax lengths in excess of 5m/15ft, coax attenuation will be high, and an amplifier may become necessary.
(2) Even with short lengths of Coax, use of amplifier increases plane count & range.

Assemble the Platenna
The whip at top is ¼ wavelength (68mm)

I’m curious if there is an advantage to leaving the core around the center conductor? I see that often in people’s antenna design.
I personally just use a 68mm stub of electrical wire for mine.

No, there is no advantage in leaving the core insulation around center conductor. I think I am the first one who started this practice, and other are copying.

The reasons why I do not remove core insulation are:
(1) It makes the whip visible and look more beautiful than the thin bare core wire of 1 mm dia.
(2) I am lazy and want to save the effort to remove it :smiley:

I use spare 12 or 14 ga Romex, strip a bit of the end going into the connector, and cut it to length leaving the insulation for visibility. I need all the help I can get :slight_smile:

Just wondering: Would leaving the insulation on affect the velocity factor and thus optimal length? I would think so but never measured.

VF depends on the material through which the electromagnetic signal passes.

In the case of Coax, the electromagnetic field, due to rf signal travelling along the cable, is totally confined within the space between core & shield. This space is filled with core insulation. Hence VF of the core insulation applies.

In case of whip wire with insulation, but no shield, the electromagnetic field exists in the space between core and the transmitting antenna of aircraft. Hence the material through which the signal from an aircraft at a distance of 100 km passes, is composed of 100,000,000 mm of air + 4 mm of core insulation. This makes medium of propagation 99.999996% air and 0.0000004% core insulation, which, for all practical purposes, is same as air, hence VF=1

Edit: Removed formulas to make description easy to understand.

Makes perfectly sense to round that! Thanks for clearing!

I’m fairly new to this myself and have been online for less than a month. My first few days were with the “stock” antennas that came with my “noo” dongles. (have both the R820T and R820T2) Since I had a bunch of RG6 laying around, my first attempt at building an antenna was a COCO based on the dimensions here balarad.net/ . My range results without amplification are below. (50nm rings)

Great! Conratulations on being amongst few lucky ones who get good results from their first DIY CoCo.

150nm to 200nm max without amplifier is very good.

What is:
(1) Antenna location (indoor or outdoor).
(1) Height of antenna.
(3) Length of coax between antenna & receiver.

  1. outdoors on roof. Not as High as it should be but that will change when the ice/snow are gone.
  2. Currently about 15 feet above ground. partially blocked to north by roof and west by neighbor’s house.
  3. I’m going to have to guess about 40 feet of coax to the receiver with a ground block before entry.

Would really like to put it on my Dad’s 60 foot ham tower on other side of town. :slight_smile:


PS: 8 segment, unterminated, encased in pvc. All RG6 quad shield 3.0 Ghz rated cable. (will find exact specs one of these days)

**@karllitterer: **
Thanks for details. Seems you made a good CoCo, which gives 150 to 200 nm with 40 feet coax, and no amplifier!

Great. Now add an amplifier, and your max range will increase by 50nm to 100nm over your current max range.