[digitalradio] Re: Another plug for JT65A ... the spectrum efficient mode
--- In digitalradio@yahoogroups.com, John Becker, WØJAB w0...@... wrote: Just * how many * modes would like to put on one frequency at a time? If the frequency is in use then find another. That's just the point. There isn't another. The space we have to use on HF is limited. All the frequencies we have are already being used by somebody. Look at all the trouble ROS mode has had trying to find a place to operate that didn't upset somebody. We should be looking to develop better narrower modes that allow more people to make contacts using the space we have, instead of wide ones which will simply create conflict by forcing existing users into ever narrower corners of the available spectrum. Most people are not interested in experimenting with new modes. They just want to make contacts using the modes we already have. They don't take kindly to being squeezed off the bands by new wideband modes and I entirely understand and sympathize with that. Julian, G4ILO
[digitalradio] Re: Another plug for JT65A ... the spectrum efficient mode
That seems a bit theoretical to me. If you have a mode that is very wide but gets its information across in short bursts, it could be said to be very efficient, but in practise it is efficient only if others are able to make use of the gaps between transmissions. If that mode needs that frequency to itself and cannot exist with other modes then it really makes no difference if it transmits on a 100% duty cycle or a 1% duty cycle it is preventing users of another mode from using the same spectrum. I think this argument is valid for the amateur bands because most digital modes do not have exclusive use of a part of the spectrum. They have to share space with other, different modes. A wide, bursty mode will prevent narrow, continuous ones from having a contact on the frequency (and vice versa) therefore from the point of view of the users of the narrow mode struggling to find somewhere to operate, the wide mode is occupying all of that space. Julian, G4ILO --- In digitalradio@yahoogroups.com, Rein Couperus r...@... wrote: Hi Andy, well, I don't agree... as soon as you talk efficiency, you have to define what that means. For me bandwidth efficiency is 3-dimensional, it defines how much information can be transferred within a certain time span, within a certain bandwidth.
Re: [digitalradio] Re: Another plug for JT65A ... the spectrum efficient mode
At 01:01 PM 3/25/2010, you wrote: That seems a bit theoretical to me. If you have a mode that is very wide but gets its information across in short bursts, it could be said to be very efficient, but in practise it is efficient only if others are able to make use of the gaps between transmissions. If that mode needs that frequency to itself and cannot exist with other modes then it really makes no difference if it transmits on a 100% duty cycle or a 1% duty cycle it is preventing users of another mode from using the same spectrum. Just * how many * modes would like to put on one frequency at a time? If the frequency is in use then find another.
[digitalradio] Re: Another plug for JT65A ... the spectrum efficient mode
Thanks Andy, And here I thought it was my superior receive capability :) Actually that was about the limit of resolution as I had the multi decoder spacing at 20 Hz. 73, Bill N9DSJ --- In digitalradio@yahoogroups.com, Andy obrien k3uka...@... wrote: I know many are already aware of this, but take a look N9DSJ-1 (EN52ti) Heard N6TE(DM12) on 3576.23 KHz -8dB at 03:32:00Z using JT65A N9DSJ-1 (EN52ti) Heard K3UK(FN02) on 3575.99 KHz -5dB at 03:32:00Z using JT65A Bill N9DSJ decoded two stations within 24 Hz of each other, how is that for spectrum efficiency? I was transmitting 5 watts, Andy K3UK
