FlightAware Discussions

2M J-Pole & LMR400

So right now I am running a 2M J-Pole that I already had up, with about 50’ of LMR-400. I am getting around a lot within the 100NM range, a little in the 150nm range.

I have a new antenna to go up for 1090Mhz, but I am curious if I will see a big improvement with it. Receive is a lot less of an issue than transmit, when it comes to antennas.

Right now I am using a Pi2, Flight Stick Pro and 1090Mhz filter. The antenna is right at the roof line.

Curious what a difference a shorter feed line would really make with LMR-400 already, and swapping out the antenna.

Thoughts?

An antenna built for 1090 mhz should give much better adsb reception than the antenna built for 2m.

Which make/model of 1090 mhz antenna you have?

I have the FlightAware antenna, waiting on the N-Type connectors so I can either swap out the PL-259 ends, also have an adapter for PL-259 to N-Type (coming).

I have a mount on the roof, but don’t have all the connectors yet, just don’t want to put it on the roof if my reception isn’t going to be that much better. Might just use the LMR-400 and mount the Flight Aware antenna on the same mount as the J-Pole and see how that works first as well.

I have not done any fine tuning of the receiver yet either, not sure if I should or not. Just turned it on last Thursday.

NOTE: Current J-Pole is on 2nd floor, balcony. The roof mount is only about 5’ higher, the apex of the roof would still block the north end a little.

The current 1090mhz antenna other than the FlightAware one is the little mag mount. Thats the one I have been comparing to the J-Pole and haven’t seen that much difference, but its also a mag mount antenna :slight_smile:

flightaware.com/adsb/stats/user/zenom

Friday / Saturday was the small antenna sitting on the deck.

Sunday was the 2M J-Pole, with 50’ or so of LMR-400 (through 4pm today)

4pm today moved back to the small antenna but sitting a few feet higher on the railing of the balcony.

One of my recent tweaks was shortening my feed line, it was 5m (15 ft) and I effectively halved it by using a powered USB extension lead and mounting the Flight Stick Pro in a box on the actual antenna mast.

It has made a slight improvement but nothing major, an increase in messages received, especially ground traffic at my nearest large airport, also got my longest hit at 441.6km (238nm).

It is the box on the lower part of the mounting as you can see below

https://dl.dropboxusercontent.com/u/50785283/Antenna1.jpg

@zenom:
I use Flightaware Antenna and it improved my reception considerably. I am pretty sure Flight Aware antenna will improve reception in your case also.

The LMR400 has an attenuation of 4.5 dB/100 ft at 1090 Mhz. Your 50 ft LMR400 will have an attenuation of 2.2 dB. The FlightAware Antenna has a gain of 5 dBi, and the built-in RF pre-amplifier of FlightAware ProStick has a gain of 19 dB. This will more than compensate the attenuation of 50 ft of LMR400, and you may even have to reduce gain setting to prevent overload of the front end/tuner chip.

Meanwhile, try this tweak with your mag mount:

How to improve performance of whip antenna of DVB-T

You can also try indoor, an easy to make antenna (Cantenna), made of a 12 oz/66 mm dia drink/beer can and a F-female to female barrel connector:

EASY ANTENNA #2 : CANTENNA

.

Thanks, I might mess with one of the DIY antennas tonight just for fun.

Thanks!

Be cautious of adapters. Lesser quality adapters can introduce more loss than everything else in your antenna system. Ideally, you would get coax terminated with the connectors you’re using (no adapters).

Also, be careful about too much gain. As others have stated and illustrated, the key to maximizing reception is to maximize the signal-to-noise ratio. Bringing up the noise floor is sometimes very destructive.

Lastly, getting the antenna ABOVE the roof line (unobstructed line-of-sight to the horizon), and additional height is much more significant than a dB or two of line loss. You chose well with the LMR-400.

Let us know how it goes…

I have adapters and connectors coming, the connectors were on back order from DX Engineering.

I have a roll of LMR-400 from my ham radio projects so it was a no brainer :slight_smile:

I also have the filter , any suggestions on what the gain should be set at?

There is a post on gain optimisation. Run the script to get the best idea.

Thanks, found that last night and ran it. So far with the stock stuff, it seems to be right around the 45 mark.

Based on the results of this script, following are my gain settings:
37 For Flightaware 26" antenna (5 dBi) + FA Filter + FA Pro Stick
42 For Cantenna and Quick Spider (both 2 dBi) + FA Filter + FA Pro Stick

NOTE:
Gain settings are specific to each installation, and optimum gain figures of one installation may not be optimum for another installation.

Just switching from the small antenna or the 2m J-Pole to the Flightware antenna, I went up to 600+ msgs sec. From about 300-400 tops before.

Definitely better and seeing farther than before.