best antenna

[abcd567]

Do I need a filter?
Here is my data capture record
Screenshot 2021-09-17 195508.png

Yes you do need a filter. Heavy mobile phone signal present in GSM850 band.

Optional: You may conduct this scan also. It covers full band of DVB-T (24 Mhz to 1800 Mhz)

In thread "Do I Need a Filter":
OPTION-4:
DVB-T plugged into Windows Computer - Using GUI Spektrum.exe

[bg6snj]

Same wire data as above, simulated in software MMANA-GAL, gives Gain = 7.35 dBi, & very high SWR = 133 !!!!!!

Which software to trust????

Wire dia = 3mm
Gap between stub wires =6 mm (center-to-center distance between stub wires = 1.5 mm + 6 mm + 1.5 mm = 9 mm)
Optimum cable tap position = 45 mm from open end (or 69 mm -45 mm = 24 mm from shorted end)


[ATTACH=CONFIG]4509[/ATTACH]. [ATTACH=CONFIG]4510[/ATTACH] . [ATTACH=CONFIG]4511[/ATTACH]

I used 3.5mm diameter copper wire with 6mm spacing, built the Franklin antenna according to your size, and tested it with a 50ohm feeder. The resonance point is 1080MHz, and the SWR is as high as 3 at 1090.

Can you tell me where there might be a problem?

[Bill@2020]

hello gentleman...
i would like to show you my results of my development because of antennas. Years ago I started this development because of the unreliable ADS-B data during flying sharp u-turns, curves.
The ads-b signal is generally vertical polarized. During flying curves the antenna is not vertical. Rod antennas and all other antennas on the market have all a vertical polarization.
To avoid that problem I developed a new antenna which is very tiny, has a perfect pattern, can be used as sector antenna and no more filter is needed.
attached I have a video which I made 2 days before ...the result was perfect and follows all simulated parameter ....

Have fun

Bill2002

Sorry I have made comments in german....but you will understand :-/

[Lufthansa]

20220403_180505.jpg


Does anyone have an idea how I can shorten this antenna for 1090 MHz? Bought this antenna through Amazon a few years ago for some bucks, but it has performed / performs TERRIBLY....

I don't know how to count the coils in the total length of the antenna (λ/4=6.88 cm or λ/2=13.75 cm). I've already read/searched a bit about coiled antennas/whips here in the forum, but didn't found a solution.

I am grateful for any suggestion!

[abcd567]

No need to cut the whip.
Unscrew the whip and use a thin copper wire like one of 6 wires from a scrap network cable, or a thin steel tie wire like the one in first two photos below.

Optimized Whip Steel Tie Wire.jpg




Optimized Whip Steel Tie Wire-Dimensions.jpg


Dimensions of Optimized Whip.png




Use one of the many wires in a Scrap network cable





category_5e_ethernet.jpg

[SlackDarren]

Wow what a interesting thread. Thanks.

[SlackDarren]

Here are results of my 3 antennas WITHOUT AMPLIFIER, and short (12 feet) Coax from antenna to Receiver.
As you can see, the Franklin & 5/8 wavelength Coil-Tuned are much inferior to Sleeved dipole when run WITHOUT AMPLIFIER.

This shows that:
(1) Half-wave Dipole is inherently tuned with SWR=1 if its two legs are cut at 69mm. This is very easy for any DIY hobbyist.
(2) Franklin & coil tuned (and coco also) require tuning which depends on dimensions & alignments. Little errors caused by DIY hobbyist throw them far away from optimum. These can be best made accurately only in Factory environment with all jigs, tools, templates & sophisticated test equipment.


Half wave Sleeved Dipole (Pepsi-can)
[ATTACH=CONFIG]4594[/ATTACH]

5/8 wavelength dipole with tuning/matching coils
[ATTACH=CONFIG]4593[/ATTACH]

4-element Franklin with Matching stub.
[ATTACH=CONFIG]4592[/ATTACH]

#1443 What is this program and where can I get it. Thanks

[abcd567]

#1443 What is this program and where can I get it. Thanks

It is called adsbScope

https://www.sprut.de/electronic/pic/projekte/adsb/adsb_en.html

Downloads

Latest Version 2.7

• ZIP-File with all relevant data (15 MB)

pepsi can halfwave dipole in radome-NO AMPLIFIER short (12 ft) Coax.jpg




.

[SlackDarren]

Are these any good. image.png

[maltim]

[QUOTE=SlackDarren;n227993]Are these any good. image.png[/QU

Hi! Is there a cover for working outdoors and if not -how can I protect it from external influences?

[SlackDarren]

No there isn't. I used a Half liter plastic bottle, with some hot melt glue on the top. So when i pushed into the bottle it stuck to the inside top of the bottle. I then pushed some 15mm Plastic pipe in the bottom fitted lovely. then hot glued around the pipe and the bottle. Looks ugly but works a treat. Cable comes out through bottom pipe. Oh and also getting around 900 planes a day, previously using a quarter wave ground plane around 500.Thanks for your question.