Wed May 23, 2018 3:53 pm
#1613276
Marvin wrote:...What your describing is Fruit and Garble.
Ground Based Receivers and Extractors as well as this used in TCAS are a little more complex in their front end design to address the issues as well as changes being made in the interrogate frequencies and therefore reduction in replies required to determine a SSR position.
A software tuned receiver is not even close to the same level of firmware in the decoding process.
Can any one guarantee - no.
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Ahaa, you fell into my carefully laid trap Mr Bond
I am in agreement, on your statement regarding Ground based receivers (I am not so familiar with the front end TCAS design), but I believe you are right: in order to make sense of the overlapping data you need incredibly high quality front end receivers and huge compute power in the digital signal processing at the back end, in order to differentiate.
You are not going to get that kind of equipment sat on the coaming of your average GA aircraft.
In fact some of the early tests which were done regarding congestion on 1090Mhz (I have the reports somewhere), the analysis could not even be done realtime, it required post processing of the data in order to analyse effectively, with the caveat given as (I'm paraphrasing here from memory) :-
'at some point in the future computer power will be capable of handling the data in realtime'
its kind of like leaving the Nuclear waste cleanup to future generations!
So ground (or space) based stations will possibly make sense of the ADS-B data, in-aircraft systems, will not be able to differentiate and disambiguate the ADS-B data
I understand that their is a discussion regarding whether the 1090Mhz frequency could be used to handle simultaneous transmissions of OOK and FSK - this could be a solution, but I am sceptical that this would work, I would have thought that the harmonics generated during the switch between the 2 FSK frequencies would interfere with the 1090 OOK receivers
Thx
Lee
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