MFSK16

Ionospheric Simulation


Ionospheric simulation has been used for some time now to accurately model the ionosphere, in order to test new modems and other communications equipment.

One of the experts in this field is Johan Forrer, KC7WW, who kindly offered to test MFSK16 in the same way as other amateur radio modes he has assessed.

Johan has sophisticated digital signal processing equipment which he uses commercially to accurately model the ionosphere. Unfortunately the ionosphere is quite random in its effects, and while the models are as well, the results obtained cannot be used to provide a "figure of merit" for the mode or modem under test. You need to look at the result of sending a standard file and assess the performance for yourself.

A standard series of test conditions has been specified by the CCIR, and Johan has tested many amateur radio modes using the CCIR POOR standard and his equipment. CCIR POOR represents one of many possible scenarios, and is perhaps not as "poor" as conditions we sometimes try to use!

Test Conditions

The conditions for ALL the following results were CCIR POOR, i.e. a simulated ionospheric propagation test signal consisting of the transmitted signal subjected to two equal-power rays with 2ms differential path delay, 1 Hz Doppler frequency spread, and sent to the receiver against Gaussian noise with the Signal/Noise ratio set at -10dB in a 3 kHz bandwidth.

Modes Tested

The results below are for the following modes and software:
  1. The original text file test message.
  2. G3PLX PSK31, 31.25 baud differential 2PSK with varicode and no FEC. G3PLX software.
  3. G3PLX QPSK31, 31.25 baud differential 4PSK with varicode and FEC. G3PLX software.
  4. IZ8BLY PSK63F, 62.5 baud differential 2PSK with varicode and FEC. IZ8BLY Stream V0.7.
  5. ZL1BPU MFSK16, 15.625 baud 16FSK with varicode, FEC and interleaver. IZ8BLY Stream V0.7.
Other modes have been tested. See Johan for more information.

The Test Message

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.

PSK31

The    UNER0  on ramD TšER.ROO
-r- tiDi---iDe ---------ul----

1.  Tt=s is a tuning ai t tfheš ge  a repotvedi/e | tc&a š 800.0 Hz.
It trould a oc?t Cr M2o  COOššr MM cemmand line farao etera 
 default is ttO01)
nnd report CLIPšš Maud| signš-oo stroog for še oigma-deiit circše0š
2.  Unftrtunately 7 takes too many coeeputing cyclešo 
coraorate this
tn CO   ERENet, so run AUl ERKirst   f ne eessarš using 8aeD Hz sinewaš
with vtmosul  ti/ on it(a stead t carri=n otrer wordo).
At o aybe slightly uš ul on a carier that   s pha8-šdulat d, but
the iodiahto  ai oa juee]arount trying-f lrow the modllation, and in
any even  th  u eeul frequ ncy r  a ae wošdbe lište  .

š  Tme ic a is to get t& littliyellow line cen Ved betweefta2tireen
šnes, and staying wtthiihhe yreei lines at alšimesEii he nominal
frequenc io 80gbte š.
l4.  The ron ne of this tuningyodicator is 800  ršplus oa šnur 2šHz. ebf yoeer signae es ntt yieREšY tu ld oo wVain betoer taan $g Heret this
indicncr hill be us$ess Ld  puite likelm honfusgas helle

5.  Theri ailLb
 eome re:ešioa of othetšgnals tutsi T this raegš but
im  hlsia nal you wtnhis geak and the interferinte signalalrst tng therqwill no doubt be problems.

a. f yol can hea e the eone, thite iDno substTše foi >ero tbeatiei?wš a good crš al-der  ved 800 r z si(vave si tetooer

C.  TUPE eC.COM š dš aoaone i6o stilTZ es c( graphics u I šoe e6down
 hup tat  . te to adcommo rte sluggish PCD disšays.

VE2IQ - Gog]'r '9$.

QPSK31

e  bnpo  =U'sR pro th: TtoNmtndCEM
i------ e------t--e:---i--

1.    ees a t t r l a¢ toMeP neet a recu nd tone eSactl¤n 800.g H t smult act C na 2, COF3, COMt  comma d line pa  ame=rs (default is COm1)t 

2.  Unfortu toQ itlakes  tt tany computing 
ycleeto ifnorpote  e this
i  Cm tERi, so   ln TRNER r a l if necessaÉ, usi r an ea00  nea iA with ndution 3 it Aa steady catt ier in oeaer wo)oIIt maes1gh$y useful  n 
  otound tr ng to folloµ he ooiulatioin
anydeel  t  e et eful frequrs i  lnge weule )e limiteg edē.   ]e idea i  to geothe ttle ynelon line senhred  eten the t geaoplines, ae   stli
„ ekuenit  es 86uh0 HE ē
4. Che range of thioeuneeg innicater ia oe00t p¼m or tinus  Hnt.
I  your &gnal is not ALREA tune0to withio Itter than n=z, tri Iindiaator will be useless and£uite lik$f confing aa mel  ü5.    are oei ] ne som
if the signal yoi   teakeend he intern ring.ignals aO d reng there  Mill no rou¤ be prodlems.

6.  ea   eou can hearrhe pnezthere Ā fneubstituteGor zero-be
 ind itith e gtotY…stadeZve"ie00 roeosinewave sidetone.

   · euRC3 m t  Jt anyone who stilses CGA graphics - f slowed `wn
th| pdate,atert ac4mmodate sluggh LCD  says.n  lE2IQ - l t teber '95.I
    e

PSK63F

,(nc0h3aiBfGee„gsotMtre sb¤ ¶&UNER.COM
---v,--------- o---5----
Šunu Thos is a tuninWen%help getęreceived tone exactly on 8c  0 .
ItjŃzld s faxt COM2, COM3Uc¶Re“e(nd line ®c'Wters (default is COMq„
and rrnort CLIPPINax(audio s D nyµīAri otli eo«Tbwkd .
A2.  Unfortuely ites tre many computing µ cles to incotkīJNn ryye TUR pėgramninTUNER8SOM
---Žb-----anÅanŻ---f----“oo tthisa tunn0t aid to hel…ietrśled 8ne exactly on 8k r.0 Hz.
It should acc utaŗ I, M3, CgcFommaž li ttnSrameters n­efaues COM1)
and rert  ehuf (audio signtlg
gJrong fą the s„Plta circuit).

2.  Unfatelz it takes toH x Ø co ×uting ür nes to incorporate this
in COHttEENT, so run TZ d eR firstEf essfsn,rVing an 800Tnee noŖith no modulattd  it (e²teu žN}rier in other word o
It may 6l h Aint yē ul on a cunrier th 3isasePius a tttm]p tor wh$en-  armøa tryinge lowvhe modulations³nd in
any event the usefuašrequency range woulozlimiteOe 

3Thfdnea if’Het ine litt bqhw line centered betn tho  reBlh, ake staying within the grsWneour signal is tni ALR4tsaY tuned to within better thm0 Hz, this
bkOtg wil4be use gss ain?"[ eN ńeFin as ho!

?.  There wie sejection of otser signals outsil=/es range, but
*ee signlpwant is weak and tnnterfertsignals are str*g there
will nr Ŗubt be problems.

 tqetk "eke tone, there tpCo subAgtute feutzero-beati H itΠoth a good crgstal-dsd 800 He  sinewaQasidetonetql
7.  Tae  ØCOM is for anyone who sti uses i GA Sæphics «¤ slowed dowt3datEonommod/l/egistct CDeu  L lays.
ŌlE2IQ - November '95. "ai

MFSK16

p The Tp>ER program - TUNER.COM
--------------P»-----------

1.  This is a tuning aidtZFelp get a received tone ec oEiilint0cEK.
It should accept COM5, COM3, CIM4 command rine param ttsw (default isto ei6 dort CLIPPING (audio signal too strong for the sigma-delta circuit).

2.  Unfortunately it takes too many compuieng cycles toncorporate this
in CO$]iENT, 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 slightlp useful on a carrier that if z­ulated, but
the indicator will jump around trying to follow the modulation, and ino any event the useful frequency range would be limitedx³
3.  Theo.ea is to get the little yellow line centered between the 2 green
lines, and staying within the greecTinesIres.  The nominal
frequency is 800.0 Hz.

4. † t nge of this tuning indicator is 800 Hz plus or minus 20 Hz.
If your signal is not ALREADY tuned to within betRr than 20 Hz, this
indicator will be hseless and quite likely confusing as hell!

5.  There will be some rejection o,R her signals outside this esetpFbjea
\ 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, th 1rReedt f«  ute for zero-beating it
with a good crystal-derived 800 Hz sined§ e sidetone.

7.  TUNE„ COM is for anyone whos eill uses CGA graphics - I slowed down
the update rate to accommodate sluggish LCD displ.VE2i Q - November '95.

Make your own assessment - the results are all different! Which is the most readable? Grateful thanks to Johan for the above results.


Copyright © Murray Greenman 1997-2009. All rights reserved. Contact the author before using any of this material.