Re: Tail ending my signal #FT8


Jim Shorney
 

Time division multiplexing. Not a new idea. Kids these days just don't understand technology. :D

73

-Jim
NU0C

On Fri, 29 Jan 2021 08:15:50 +0000
"Philip Rose via groups.io" <gm3zza=btinternet.com@groups.io> wrote:

Well said, Reino.

What I have highlighted below is the significant factor, that some people seem not able to get their heads around. People transmitting on the same frequency as you but in the other timeslot will NOT interfere with your signal, and you will still receive on all the frequencies in your filter bandwidth.

73 Phil GM3ZZA

Sent from Mail for Windows 10

From: Reino Talarmo
Sent: 29 January 2021 08:08
To: main@WSJTX.groups.io
Subject: Re: [WSJTX] Tail ending my signal

Personally I see this as cutting the available bandwidth in half. It’s similar to telling everyone to run split. Takes 2 frequencies to make a QSO that way
Hi,
Personally I am a selfish person and prefer to select whom I answer, but that is not the issue. Let me explain how FT8 is different to many other digital modes. The biggest difference is multi decoding that covers the whole waterfall and even overlapping signals. You still got a RX frequency where the first decoding is tried. RX frequency need not to be same as your TX frequency for successful QSOs. You receive and try to decode all stations over whole waterfall bandwidth.
Now let’s see what happens, when I call CQ. If all stations answers at my TX frequency they will QRM each other and none may not be decoded or only some close by station I am not currently interested in. On the other hand, when answering stations are spread over waterfall range, my receiver will decode most of those and I have nice opportunity to select one.
By the way I totally disagree any statement about cutting available bandwidth in half. Bandwidth is *used* only, when you or anybody is transmitting. When you receive, you don’t *use* any bandwidth. There is another essential difference to most other modes. All transmissions happen in timeslots either even or odd. In effect band is divided timewise into two independent “bands”. QSO uses alternating those “bands” and using a single frequency on each. On the usage point of view it is totally irrelevant, whether those frequencies are same or not. They cannot QRM each other due the time division.
So use split, please. It is more efficient at QSO setup time and after that there is no difference at all.
73, Reino OH3Ma                      

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