Good point. What you have defined , Rein,is the occupancy efficiency in terms of time.. I was measuring efficiency in terms of bandwidth used. Obviously the othe rmeasure is wether the message was deleivered. Using 5 watts for a 300-400 miles trasmission on 80M at night , PSK250 may have needed sveral repeats to send 13 chracters . So even in term so time PSK250 may have been close to 0.001547619 . I'll do a test tonight. Andy K3UK
On Wed, Mar 24, 2010 at 4:27 AM, Rein Couperus <[email protected]> wrote: > > > Spectrum efficiency must be measured in time necessary to get the info > across, > length of info transferred, and bandwidth. > ((characters/second)/ bandwidth) or characters/(seconds * bandwidth). > The bandwidth includes a certain guard band(minimum distance between 2 > different > signals), which for JT65 is quite small ... but the time is a large > factor... > > To give a small example: > > Pskmail using PSK500 ARQ has a spectrum efficiency of 23/500 = 0.046 CPS/Hz > ... measured on 14094.0 kHz running 100 mW connected to SM0RWO (>1000Miles) > ... > > The longest message in JT65 is 13 characters... and a message takes 48 > seconds.. > the bandwidth (according to the mode description) is 65 * 2.7 = 175 Hz > ...which calculates to (13/48) / 175 = 0.001547619 CPS/Hz > > I would say this is a pretty bad value... :) > > Rein PA0R > > > >Bill N9DSJ decoded two stations within 24 Hz of each other, how is > >that for spectrum efficiency? I was transmitting 5 watts, > > > > >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 > > > > > >------------------------------------ > > > >http://www.obriensweb.com/digispotter.html > >Chat, Skeds, and "spots" all in one (resize to suit)Yahoo! Groups Links > > > > > > > >
