FlightAware Discussions

Advice for first antenna (spider 4 legs)

Hi! I’ll start telling you about my current setup:
My splash/sun blocker (?) pringles mini can with the dongle attached to a USB 3.0 extension with a power source switch so it doesn’t depend on RPI4 power:


The default Nooelec mini antenna attached (magnet) to the outmost part of an air conditioner that is always off when I have the antenna there, for a base.

I have a clear view of around 45° to S and 45° NW (as you see In the photo, the other quadrants are blocked by my building or the one in front of me, sometime maybe I could try to get this to the roof, but no so simple right now. Max contact with this setup is at 45nm, max one-time range 77nm.

For my first project I’m buying this:

Plus an F female-female connector, and the screws, obviously

The idea is to start working with the cable I have a home (an RG58) and then upgrade to an RG6, will be using the core of this cable for the “legs and top” of the antenna too.

This is my scan with my current setup, maybe I’ll add a filter later when I get one that ships to my country.

Any recommendation will be much appreciated

Thanks!!!

ADSB transmissions are vertically polarised so the first thing you should do is get the antenna vertical rather than horizontal.

1 Like

  1. As the ADSB signal is vertically polarized, the antenna whip should be VERTICAL. A horizontal antenna picks very little of this vertically polarized signal.
  2. The gauze at left, if metallic, will block most of signal
3 Likes

Now it’s vertical, thanks to both of you! the gauze is plastic :slight_smile:
Will rescan on this position.

Any recommendations, things I can be forgotten? Thanks!!!

Looking at your RF scan, and with magnetic base whip you have, and the Spider you are going to built, most likely you will NOT need a Filter. Both these antennas are low gain, and pick little of GSM 800 signal. First try these with proper orientation (vertical) and at different locations in your home to find where you get the best reception.

If possible install antenna on roof so that it has a clear view of horizon all around. Also try to keep length of coax from antenna to dongle as short as possible/practicable.

I live in a urban area with lot of RF noise. I have tried low gain antennas (2 dBi or less), like the Magnetic base whip of dongle, the Spider, and the Cantenna, and all performed good without a filter. I needed a filter only when I used high gain antennas like Flightaware 6 dBi antenna and V-Stub 4 dBi antenna.

V2, now with more “regular” base and vertical


There are not a lot places in the apartment to set up this, right now the RPI 4 is serving another services and has the limitation of a network cable. The good of this side is that is under the approach route to an airport, planes pass at ~1000ft here, and have line of sight to most approach routes, and lost them around 600ft

Will measure again! Somewhere I read about unscrewing the antenna from the base and attaching a cable (I’ll use an rg58 core) with the appropriate size for 1090 can improve a little (don’t want to cut the antenna yet), can’t find the post, is this correct?

Any recommendations for this or spider still welcome, I’m having a lot of fun and trying to learn the most of this.

To install it on the roof I’ll need 30-35 meters of RG6, I think I’ll loss all without some kind of amplifier (?)

Question, the spider antenna, should be over a metal base too?

Thanks!

No. The SO239 and 45 deg slanting radials provide the base (ground plane). Nothing else is required.

 

With such a long run of coax, you will sure need an RF amplifier (also called LNA) installed close to the antenna. Power to the amplifier can be fed over the coax using a Bias-T installed near the dongle, and a dc adaptor to feed dc to the Bias-T

 

The core of RG58 is about 1mm dia and hard to wound on screw stud of base. Better use thin wire like one of the cores from a scrap network cable, or thin steel tie wire. The wire need not be made of copper, it can be any metal.

image

 

ALTERNATIVE -1

Optimized Whip Steel Tie Wire-461x500

 

ALTERNATIVE-2

1 Like

Just what I was looking for, thanks!
What is the difference between the 2 options (how can I better understand it?)
Thanks!!!

Alternative-1 is Low gain antenna (2 dBi)
It is a 1/4 wavelength ground plane antenna tuned to 1090 MHz. It’s vertical element is 1/4 wavelength at 1090 MHz, which is 67 mm. Out of this 67mm, 15 mm is hidden inside the base, and 52 mm is the portion above the screw i.e. 15 + 52 = 67 mm.

Alternative-2 is a higher gain antenna (4 dBi)
It is a wire collinear antenna with two vertical wires connected through a phasing element (the V shaped stub).

Alternative-1 is easier. First make and use it for few days. Later try the Alternative-2 (V stub). As it requires trimming the length of top wire to get the length for best reception, it is a bit difficult than alternative-1. It is a trial-and-error method. It is easy for those who have an SWR meter.

1 Like

Great, thanks! I’ll try the first as you say. For the second I understand that without special equipment I’ll need to count hits+watch coverage, trim and repeat.

The items I’m buying for the antenna are ok? If I seal the connections, can it be outside?
Thanks!

Try setting your antenna on top of the air conditioner. You may pick up some aircraft from the east quadrants. If you can get the antenna above refrigerator height, that might help too.

I’m at fourth floor, to put that 1m higher will make the cabling and stability difficult at almost not height gain…I think
Thanks!

1 Like

All 3 seem OK.

 

 

How-to Protect Outdoor Connectors and Cable From Ingress of Moisture (Due to Rain & Snow) and Resulting Short circuit, Corrosion, and Drop in Performance.

 

 

1 Like

I agree you’ve got good height. your ADS-B antenna can be blinded to the east if there are large metal objects between the antenna and the aircraft (PC cases, refrigerators, steel doors, etc). With the antenna on top of the air conditioner, you’ll have a better chance of receiving those aircraft from the east.

V3,

Almost same result as stock antenna after 24hs, will give one day more because the weather wasn’t the best today.
There is a possibility that a twisted cable is not the same as a wire for this? Either way I’ll look for a wire to test.

Thanks!

Twisted multi-strand wire and solid wire should perform more or less the same.

It will make a difference if it is enamelled copper instead of bare copper. If enamelled, you have to remove enamel from the part which is wound over brass stud of the base to make a direct electrical connection.

It was a cheap cable, with no treatment, or insulation on the copper. Maybe the contract with the base isn’t strong enough…I didn’t want to apply much force there…but even if I can move it it’s always making contact.
Will give it one day more after I’ll try something new.
Thanks!

If it makes any difference, I got pretty good results with a straightened out paper clip. I wrapped it as tight as I could around the threaded part of the base, bent it vertical, and trimmed it off to the correct length.

It worked well for me for a couple of months till I got the itch and moved up to the 26" FA antenna.

2 Likes