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[hfsig] RE: Bytes/Minute (Correction)

DuBose Walt Civ AETC CONS/LGCA Walt.DuBose at RANDOLPH.AF.MIL
Wed May 18 14:48:29 UTC 2005


I'll get my math right yet...

Throughput at -5 dB SNR on a poor or average CCIR channel.  Pactor I/II/III
has been measured/graphed at -5 dB on an average CCIR channel.  MT63 has
been measured at -5 dB SNR on a poor CCIR channel.

So Net bytes per minute is the number of USER bytes per minute vs RAW bytes
per minute or time period.

Looking at Pactor III and MT63...

Throughput at -5 dB SNR on a poor or average CCIR channel.  Pactor I/II/III
has been measured/graphed (by KN6KB) at -5 dB on an average CCIR channel.
MT63 has been measured (by KC7WW) at -5 dB SNR on a poor CCIR channel.

So, MT63 has 200 WPM in ASCII so a word is 5 characters plus a space or 6
characters per word.  Thus 200 WPM times 6 characters is 1200 characters per
minute or 20 characters per second.

Pactor III is 500 net bytes/minute at is 500 characters/minute or 8.33
characters/second using 6 characters per word.

Walt/K5YFW

-----Original Message-----
From: DuBose Walt Civ AETC CONS/LGCA 
Sent: Tuesday, May 17, 2005 12:29 PM
To: 'hfsig at lists.tapr.org'
Subject: Bytes/Minute
Importance: High


On page (17) from KN6KB's SCAMP presentation at the DCC in Nov. 2004
(ftp://winlink.org/SCAMP/SCAMPdccPresentation.ppt), it shows the throughput
of Pactor I/II/III as measured by KN6KB using KC7WW's channel simulator.

I am unsure about his Net Bytes/Minute...if that is different that
Bytes/minute?

The chart shows, as nearly as I can determine, a throughput of about 500 net
bytes/minute for Pactor II/III and somewhat less (perhaps 250 net
bytes/minute) for Pactor I.

MT63 has an advertised throughput of 200 WPM at -5 dB SNR on a poor CCIR
channel as shown by KC7WW in his testing on MT63 on his channel simulator
(http://www.johanforrer.net/hfpsk.htm).
And the copy appears to be error free when comparied to the original "test
text" and "MT63-2K  -5 dB SNR text" below.

If I am correct, 200 WPM is 1200 CPS or 1200 bytes/second or 7200
bytes/minute.  

Is something wrong with my math?  Surely MT63 can't be 14 times faster than
Pactor III at a 
-5 dB SNR on a poor CCIR channel?

Please advise.

Walt/K5YFW

============================================================================
==============
Test Text
=====

The TUNER program - TUNER.COM

-----------------------------



1.  This is a tuning aid to help get a received tone exactly on 800.0 Hz.

It should accept COM2, COM3, COM4 command line parameters (default is COM1)

and report CLIPPING (audio signal too strong for the sigma-delta circuit).



2.  Unfortunately it takes too many computing cycles to incorporate this

in COHERENT, so run TUNER first if necessary, using an 800 Hz sinewave

with no modulation on it (a steady carrier in other words).

It may be slightly useful on a carrier that is phase-modulated, but

the indicator will jump around trying to follow the modulation, and in

any event the useful frequency range would be limited.



3.  The idea is to get the little yellow line centered between the 2 green

lines, and staying within the green lines at all times.  The nominal

frequency is 800.0 Hz.



4.  The range of this tuning indicator is 800 Hz plus or minus 20 Hz.

If your signal is not ALREADY tuned to within better than 20 Hz, this

indicator will be useless and quite likely confusing as hell!



5.  There will be some rejection of other signals outside this range, but

if the signal you want is weak and the interfering signals are strong there

will no doubt be problems.



6.  If you can hear the tone, there is no substitute for zero-beating it

with a good crystal-derived 800 Hz sinewave sidetone.



7.  TUNERC.COM is for anyone who still uses CGA graphics - I slowed down

the update rate to accommodate sluggish LCD displays.



VE2IQ - November '95.

============================================================================
==============
MT63-2K  -5 dB SNR
=====

The TUNER program - TUNER.COM

-----------------------------

 

     1.  This is a tuning aid to help get a received tone exactly on 800.0
Hz.

It should accept COM2, COM3, COM4 command line parameters (default is COM1)

and report CLIPPING (audio signal too strong for the sigma-delta circuit).

 

2.  Unfortunately it takes too many computing cycles to incorporate this

in COHERENT, so run TUNER first if necessary, using an 800 Hz sinewave

with no modulation on it (a steady carrier in other words).

It may be slightly useful on a carrier that is phase-modulated, but

the indicator will jump around trying to follow the modulation, and in

any event the useful frequency range would be limited.

 

3.  The idea is to get the little yellow line centered between the 2 green

lines, and staying within the green lines at all times.  The nominal

frequency is 800.0 Hz.

 

4.  The range of this tuning indicator is 800 Hz plus or minus 20 Hz.

If your signal is not ALREADY tuned to within better than 20 Hz, this

indicator will be useless and quite likely confusing as hell!

 

5.  There will be some rejection of other signals outside this range, but

if the signal you want is weak and the interfering signals are strong there

will no doubt be problems.

 

6.  If you can hear the tone, there is no substitute for zero-beating it

with a good crystal-derived 800 Hz sinewave sidetone.

 

7.  TUNERC.COM is for anyone who still uses CGA graphics - I slowed down

the update rate to accommodate sluggish LCD displays.

 

VE2IQ - November '95.



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