Transponder transmission strength/range

[Pinza]

Do some aircraft's ADS-B transponders have a stronger range than others?

The reason I ask is because my supplied antenna (seated outside a bay window groundfloor flat in the Midlands) has a reasonable Polar Diagram towards the North but rubbish towards the South (as expected given surrounding properties and terrain).

And yet, every evening I pick up Wizz Air A320s (albeit at high altitude) at a much more southerly distance than any other flights?

[Fenris]

There are different output powers for different classes of aircraft.

You may see this effect because the Wizz Air A320s have a more powerful transponder Tx, but it could also be due to a different antenna fitment that happens to send a bigger signal in your direction.

[meagain]

Transponder output is pretty the same on today's commercial aircraft equipment. One new A320 is much the same as another new A320. The limits are 48.5 to 55 dBm, given the signal degradation over range this would not make a big difference for extreme ranges.

[Pinza]

Thanks Fenris and megain.

Perhaps just a coincidence that I was seeing Wizz Air A320s much further south than anything else with my internal aerial!

Sitting in my local Royal Mail sorting office is a 10m Westflex103 cable assembly (for collection in the morning).

Just need to beg, borrow or steal a long ladder and large drill bit to get an external antenna installed over the weekend...

[Fenris]

Transponder output is pretty the same on today's commercial aircraft equipment. One new A320 is much the same as another new A320. The limits are 48.5 to 55 dBm, given the signal degradation over range this would not make a big difference for extreme ranges.

Actually 6dB translates directly into a halving of range!

[meagain]

There is no range behind the horizon

[Fenris]

No, but if an aircraft at high altitude is just line of sight a reduction in transponder transmit power of 6dB will reduce the range at which the minimum discernable signal is received by a factor of 2.

Simple physics.

[radarspotter10]

Do some aircraft's ADS-B transponders have a stronger range than others?

The reason I ask is because my supplied antenna (seated outside a bay window groundfloor flat in the Midlands) has a reasonable Polar Diagram towards the North but rubbish towards the South (as expected given surrounding properties and terrain).

And yet, every evening I pick up Wizz Air A320s (albeit at high altitude) at a much more southerly distance than any other flights?

hi Pinza.
As they say in ham radio "height is might" as radio signals are concerned,
i remember the astronauts on the space shuttle doing an experiment
on the ham band 2 meters? there power was micro volts or less?, then there's refraction from layers about the earth, now i know theirs a few well renowned ham radio personal on this site that have had personal experience in this field that can enlighten us.
hope that helps Pinza
from pat

[meagain]

No, but if an aircraft at high altitude is just line of sight a reduction in transponder transmit power of 6dB will reduce the range at which the minimum discernable signal is received by a factor of 2.

Simple physics.

My company provides and services the transponder equipment for WZZ and other fleets through a worldwide LRU pool for more than 500 A320 family aircraft. Rest assured there is no specific WZZ equipment.

[Fenris]

No, I didn't think there was. I suspect that whatever the OP is seeing is simply coincidence or perhaps a different antenna fitment. I assume that Airbus don't have a single supplier, and that this sort of thing is a customer option?

[viking9]

Most USAF ac landing at Mildenhall disappear from my RB at around 1000'. However, I have noticed that some aircraft can be tracked right down to almost runway height. I suspect antenna placement on the aircraft to be the defining factor but have no firm evidence for this.

Tom

[Fenris]

That certainly explains it on different aircraft, but not when they are all A320s.

[t1mb0]

equipment fitted to each airframe I hope would have to conform to limits as previously mentioned ie between x and y (Watts?) of output power. I would imagine you are seeing signals from equipment calibrated at each end of those limits, combined with the other factors such as atmospheric conditons and altitude.
Some days I see RyanAirs down to 0ft at Bournemoth 30 miles away, while other days I lose them at 800ft or more.

[Pinza]

Many thanks to all who have responded to this thread that I started!

Have been monitoring the situation over the past few evenings.

It would appear that my north facing indoors groundfloor stock aerial in the Midlands has an inexplicable narrow window that reaches out to just south of the CPT Compton VOR.

I am picking up anything that flies over that very narrow window on my polar diagram - not just Wizz Air A320s!

Pretty impressive results from the included ANRB internal antenna - can't wait to get my external antenna erected!

[meagain]

Some days I see RyanAirs down to 0ft at Bournemoth 30 miles away, while other days I lose them at 800ft or more.

Other reason, but weather or tx power, called QNH.

that this sort of thing is a customer option?

True, but as I said, we operate the pool that serves WZZ and Mode-S could be either RC, Honeywell or Thales (not sure for A320). The pool is huge and for any OEM many other airlines are served through it. Antenna installation is replicable to the jota.

I am picking up anything that flies over that very narrow window on my polar diagram - not just Wizz Air A320s!