MFJ MFJ-784B User manual

ME
FS Tunable DSP Filter
Model MFJ-784B
INSTRUCTION MANUAL
CAUTION: Read All Instructions Before Operating Equipment
MFJ ENTERPRISES,
300 Industrial Park Road
Starkville, MS 39759 USA
Tel: [phone] Fax: [phone]
VERSION 1B COPYRIGHT © 1995 MFJ ENTERPRISES, INC.

MFJ-784B Instruction Manual
Contents
Before Reading. TRIS. MaNMUal ea nicatuctes atieoetecssaientinaiapomitenadaaation Ny
Pes Gel G cesar tase Baca Alec tocahnlat a entree tara iat soa nek bed ventana 1
Chapter 1 Introduction ....escssscssescssssesssssscssarssssessocensesvessessssseseess 1-1
IER OCIICHION CONDISP 2, ccrtacs- ca schee deca eaewaneateninnauatonmnnemen 1-2
FPOGIICE CIV SRV GW oy cceceassaesintasoastioy veleshatannerets roe tance dneen ethan nie Mectatleidora st 1-3
QS EA Ia a sa 8s mca te a De a5 Rosendahl eca sGu Sk Sach Sol rh nal soso ata 1-4
FP lle SPIN CUM ea cxassnss sve astm csats nrcpaanaateae wd una a veeimeruncdaueracueian: 1-5
Bacie Panel LAVOUt titans cart eied cannes aly waar art alee: 1-6
FIRST SPECIICS ORS tas teticunec et ian tient cyl eee ededl amet ctr and 1-7
LITE SPECICATION Gee terrecrasst Meta tetra ela attest ocr rn Sacenatinth ners 1-8
GENEral SOSCi CAO wiscion.ch acai cieimsccssteninirh ar nedacasatuiontenosesens 1-8
IUG/ DUE GUE SPEC CAG MS :cxcctet, cseanctativcorectetshicdaantaiacecacaeeania 1-8
Chapter 2. Installations sisiescicccssissccsisasssonscsdivesicasernsssincsseonstenssands 2-1
Back Pariel Comme ctions ......sscsssssesssssssesssssesssssssssssssssssessesssssssvesssseseseassee 2-2
Basic CONNECTIONS ca2tatincets tal blnastinds ie th asnae la bamiaternnin as o-3
Setting Receive Audio Level (Input Level)... eee o-4
Increasing Headphone Audio LeVel uw. eee ecceeseeeeeceesteeseeeeneen 2-4
FSS SING ICS LCC saa av scorer czocedcasconschvmnsinscn aonanrciptraesdadeictnaleeretneuts 2-5
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CSIC ROHS UC esac avhes echt geno ucts set dicataboiay eertonmdnatieelenacien, 2-6
DSP to: TING Conmpections aii aes en ea ea neliacreineee 2-6
CHaApEEr SOC RAGIN ac ccscccieviesicseainsecseccesvsvsnasccadenntechocenctnseesnntensse 3-1
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CVV TOC OIN seca as te taste ase ts yeastartacspateeeeal noetesie cas tescaieebimnsemerenateai 3-3
SSB [and other voice modes) Operation Destin sihiAAar kite did 3-4
PRONG Mariel DSseriptlonn .scitset ex tess ssenitecdacts a axishia en heuanineuiatedatean 3-6
Pa iy Ec path DSc aces Scat teal oat oa coats haa NON NA ccdtcbite ae asate 3-6
Input EET 18 21s Sere tC lot ge IE he RP 3-6
PBC BUGCOM Aes. ets bled Qea tate eves ateca hacen alata 3-7
ae 215 | Brel p Rat co{ 19100] a Penner eri rce nae Rae en Re RDS ctr aa eno rea 3-7
MBtORY BUTOOI sitet eaciennaaraan rane ieeN Gatti butanol siasccanl 3-8
TES PSs UICC Iacacsent Genie la ea cseaadtas antl ceataresuh Suite ccasnae ks acrreranduntaataadlaaetie 3-8
Tea ble Fibers: GomGrl Se csi iit cscs ee cere cctlets ce dnactte ehues ested 3-9
aribiaMINOEGI. BUTTON sincere neis cuss en tae, we aaa 3-10

MIFJ-7846 Instruction Manual
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Chapter 4 = Advanced Featuress........ssceccsscccssssssessesseserserscesssessess 4-1
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PA SCCUIN GS sic snctnatermenuutnsladmniitvcrtadeduiiendsnderistrcts tule: 4-8
Auto Notch Aggressiveness un... scsessssescescescnsssseseceesseeeseteesceaeres 4-8
Normal JUMpEr Settings ....canccdacstenntiuivsaiigeiciwacaind tener 4-8
Normal Jumper Settings Chart... cceceessseseesesneeenen 4-9
Setting the CW Sidetone Filter ou. sseessescseeeseessecneeeneennen 4-10
PCS SCE FICCRS seo viccns chateaus china cddecan aide onalant cen telinaanenieass 4-11
Factory FILER DCA UIES iow anees oho eaes alae cen cel, 4-11
Data Mode Jumper Settings Chart... ccc 4-12
Chapter 5 = Filter Description .........scssssssssssssessesncessssensneesseseeses 5-1
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MFJ-784B Instruction Manual
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Radio to TNS Caples soisccsc feet tala tasce ttn titten ahs dea tanuceeneiamnae A-5
MFJ-7B84B to PK-232 Connections wc sceseseesesen A-D
MFJ-784B to PK-BB Connections wn ccscssssssstssesceseessens A-5
Pre-set and Memory Filters Settings Chart... eee A-6

MIFJ-7 84B Instruction Manual
Before Reading This Manual
This manual is divided into two parts. The first part, called Fast Start, Is
meant far people who need to know nothing except how to minimally install
the unit and operate it on CW and SSB. The second part, chapters 1-5, is
meant for operators who want or need more information. Detailed
description of the unit and its operation are described in these chapters.
The first chapter is an introduction to DSP and the MFJ-784B. The second
chapter tells about the back panel and how to install the unit with a radio or
TNC. Chapter 3 tells how to operate the unit in CW and SSB and describes
the various controls. Advanced Features, chapter 4, tells how to use the
special features of the MFJ-784B. The last chapter is a description of the
digital filters used in this unit.
The appendix has two important sections, troubleshooting and technical
assistance. There is also a self-test for the unit's digital circuitry and controls.
Refer to these sections if you should have any problem with your new MFv-
7848.
Important: Please read this section to become familiar with the terms
and mechanics used in this manual.
Whenever the manual text discusses a control, jack, or level adjustment, the
name will appear in Bold.
Example: Plug a headphone into the Headphones Out jack for ...
The Memory/Normal Filters button will be referred to simply as the
Memory button throughout this manual.
Definitions for the abbreviations used in this manual are listed below:
LR = Low Reject (Cutoff Frequency)
HR = High Reject (Cutoff Frequency)
f1 = Center or Notch Frequency #1
fe = Center or Notch Frequency #2
fe = Center Frequency
BW = Bandwidth
FIR = Finite Impulse Response
IIR = Infinite Impulse Response
LMS = Least Mean Square
WPM = Words Per Minute

MFJ-784B Instruction Manual
Explanation of graphical symbol:
alert you ‘of conditions that eee be ‘damaging to th product or
resulting in a risk of electric shock to persons. ea

Amplifier
This T/R connection is used to pass sidetone.
The amplifier connection and diode are optional.
See the text on page 2-5.
1N4001 Diode
or equiv.
Transceiver |
i
Nt SPEAKER Gray - Shield
yo
AUDIO
OUT
Black
-
Conductor
RLY
(oc)
SRREEok
©)
|
TIR (Pin 5)
gemaneramemunaenscantnarn: Qasenvrerraminlecoe
ad
N-NMR ODE RCO IEA
“Ground (Pin 2)
MFJ-7846 DSP Filter
may cause undesired operation.
This device complies with part 15 of the FCC 1-TNC XMIT AUDIO 1-TNC XMITA
Rules. Operation is subject to the following two NTERPRISES, INC. 2- GROUND 2- GROUND
conditions: (1) This device may not cause harmful 3-PTT 3-
Interference, and (2) This device must accept any
| Interference’ received, Including interference that - BECEWE Uaioe EUDIO OUT
FILTERED AUDIO
OUT
HEADPHONES
SPEAKER
OQ
ADJUST
(02 ©
Center Conductor. +12 Vdc
Outside Sleeve: Ground
Warning: The MFJ-7846 will be damaged by
reverse polarity or voltages over 18 volts

MFJ-784B Fast Start
Fast Start
Beginners’ Installation and Operation
To install and use the MFJ-784B in the simplest way possible, follow the steps
below. On some steps we give you a choice of CW or SSB. Choose one
throughout this Fast Start section. SSB also works with AM and FM voice.
1. Install the unit. Follow the installation diagram on the facing page.
2. Set the controls as follows:
Control
AGC button:
Program button:
Memory button:
Filters switch:
Tunable Filters left knob:
Manual Notch button:
Tunable Filters right knob:
Auto Notch button:
Noise Reduction control:
Noise Reduction button:
Volume control:
Speaker button:
DSP button:
Power button:
Position
out
N/A
out (normal)
CW or SSB
center
out
full counter-clockwise
out
full counter-clockwise
out
full counter-clockwise
Meaning
AGC off
N/A
Tunable/ Pre-set
CW or SSB filter
middle center freq.
manual notch off
widest bandwidth
auto notch off
minimum reduction
noise reduction off
minimum volume
speaker on
DSP bypassed
MFJ-7 848 off
3. Apply external power and press and lock the DSP's Power button. The
PWR LED on the front panel should light red.
Memory button.
4. Set the input level.
a. Tune your radio to a CW or SSB station.
b. Set your radio’s volume control to a normal level.
If it is green, press the
c. Use a screwdriver to adjust the Receive Audio Adjust (on the back
panel of the DSP) until the Input Level LED [front panel) flashes
mostly green and never red [red is too high, off is too low).
Fast Start 1

MFJ-784B Fast Start
5. How to operate the CW filter. (If you work SSB skip to step 6)
a.
Your radio should still be tuned to a CW station and setup as in step
2 (except Power). Press and lock the DSP button. Adjust the DSP's
volume control.
Press and hold the red Program button. You will hear a tone.
Adjust the left Tunable Filters control (center frequency or fc) until
the tone is the same pitch as the CW station. When the tones are
closely matched, release the Program button.
Slowly adjust the right Tunable Filters control (bandwidth or BW)
clockwise. The CW station's signal should become clearer (less noise
and QRM).
Practice on other single stations and even with several CW stations
sending at the same time. With practice, you will be able to separate
mixed signals and copy signals that were undetectable without the
filter. Also, experiment with the Noise Reduction, AGC, and Manual
Notch controls.
6. How to operate the SSB filter. (If you work CW skip to step 7)
a.
Your radio should still be tuned to a SSB station and setup as in step
2 (except Power). Press and lock the DSP button. Adjust the DSP's
volume control.
Adjust the right Tunable Filters contro! [bandwidth or BW) clockwise
to make the SSB signal clearer (less noise and QRM) while not
making the signal less intelligible.
Adjust the left Tunable Filters control (center frequency or fc) to
peak the signal for maximum intelligibility.
Re-adjust the right Tunable Filters control (bandwidth or BW)
clockwise to eliminate most of the noise and QRM. At some point
decreasing the bandwidth will make the signal less intelligible.
Press the DSP button to the "out" position. Find another station that
has CW or some other tone interference audible with a SSB or voice
signal.
Préss the DSP button to the "in" position and filter the voice signal.
Lock the Auto Notch button "in." Any remaining tones should
disappear or be greatly reduced.
Experiment with different filter adjustments and functions under
various conditions to become familiar with the various controls.
Now that you have used the DSP filter you can read other parts of this
manual to learn to use the other features of the MFU-784B.
Fast Start 2

MFJ-784B Instruction Manual
1
Introduction
Contents of This Chapter
> Introduction to DSP Page 1-2
> Product Overview — Page 1-3
> Block Diagram Page 1-4
>» Front Panel Layout Page 1-5
>» Back Panel Layout Page 1-6
> Filter Specifications Page 1-7
> Unit Specifications Page 1-8
General Specifications Page 1-8
Input/Output Specifications Page 1-8
Introduction 1-1