MFJ-416 Instruction Manual
IMPORTANT NOTICE
Some versions of the MFJ-9406 require a minor change on the main pc board before installation of the
MFJ-416 CW adapter. To determine if this change must be made to your transceiver, locate R54-about 1" to the right of HDR1 (HDR1 is the header where the CW adapter plugs in).
[ ] If no part is installed at R54 on your MFJ-9406 pc board, than you must make the modification
outlined in this sheet.
[ ] If a 4.7 uH molded choke is installed at R54 on your MFJ 9406 (yellow, violet, gold, silver), then
disregard this notice and proceed with CW adapter installation.
Modification:
To modify your MFJ 9406, find the 4.7uH molded choke included with the CW adapter kit (yellow,
violet, gold, silver). Install this choke, following the diagram below. The choke is needed to
complete the key-line connection between your CW adapter and the MFJ-9406 balanced
modulator. Without it, your transmitter will not generate RF power when the key is
depressed.
Be sure to keep chok e leads as sh ort as possible, and position t he body of the choke cl ose to HDR2.
This completes the modification, and you may now proceed with normal installation of the
CW adapter.
Note: Do Not attempt to install the 4.7 uH RF C at R54 on your circuit board.
MFJ ENTERPRISES, INC.
300 Industrial Park Road
Version OA
Starkville, MS
39759
Tel: 601-323-5869 Fax: 601-323-6 551
USA
COPYRIGHT ® 1996 MFJ ENTERPRISES, INC.
MFJ-416 Instruction Manual
MFJ-416 CW Adapter
Introduction: The MFJ-416 adapter le ts you commun icate on CW usin g the MFJ 940 6. No mode
selectio n is neede d-simply tune in and start send ing. Semi-QSK switching activates the transmitter and
in se rt s t h e c or re ct fr eq u en cy - of fse t (o f fse t ma y b e ad ju st ed t o preference by resetting an internal
trimpot). The MFJ-416 works with manual or semia utomatic k eys, and with mo st electronic k eyers. A
built-in sidetone generator provides audible feedback. The CW note generated by the MFJ-9406 is Al
carrier, not an audioder ived tone. C ontrol gates ar e ti med to ensure st rong first-character attack,
chirp-free offset switching, and comfortable QSK-hold time. FET cont rol gate s prevent ada pter
interaction with the MFJ-9406's normal SSB operation.
Installation: The diag ram bel ow illu strate s how to instal l your adap ter. Simply slip th e ad ap te r bo a rd
socket onto the 4-pin header at the rear of the transceiver's main pc board, as shown. Secure in place with a
#6 screw, using the mounting stud located at the rightrear corner of the main board. Tack-solder the
attached wire lead to the right-hand pin of the radio's
Fine Tuning
Sidetone: If you wish to use the sidetone g enerator built
into
control
your electronic keyer, remove the shorting
pin from HDR1 on th e adapter board. This will d isable the sounder.
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MFJ-416
Instruction Manual
Theory of Operation: Please refer to the schematic shown below:
Key Switch: A ground-path through the key jack activates DC switch Q1, providing logic-high
output. This, in turn, activates PTT switch Q3, balanced-modulator keying switch Q2, VFO
frequency-offset switch Q4, and sidetone generator P1.
Semi-Q SK Switc h Q3: When Q3 conducts, it provides a ground path that activates the transceiver's
relay driver. RC cir cuit R4/C 1 delays PTT dr op, providing approxima tely 1/2-second semi-QSK holdtime between CW characters. Bl ocking diod e D2 isolates th e LC hold circuit from other gates on the Q 1
control line.
CW Keying Switch Q2: Wh e n F E T- s w i t c h Q 2 c o n d u c ts , i t u nb a l a n c es t h e tr a n s m i tt e r ' s modulator
(U5), forcing carrier generation.
Transmit Offset Switch Q4: When Q4 conducts, it passes a DC bias to the radio's Fine Tune
control. This overrides the control's normal bias, forcing the VFO to oscillate approximately 600-Hz
higher in frequency (offset bias can be adjusted by R6 to suit operator preference). R5/C2 provides a
short hold-delay to the gate of Q4 to ensure that offset bias persists beyond CW-character completion.
Blocking diode D3 isolates Q4 from receive-mode bias, and C4 bypasses 50-MHz RF pickup on the
control line.
Sidet one Gener ator P1 : When Q1 goes high, piezoelectric sounder P1 activates to emit a 2.4-kHz
sidetone note. Current-limiting resistor R7 sets volume level, and C3 bypasses AF hash
generated during oscillation.
General: Once installed, the MFJ-416 is powered at all times. Under normal operating
conditions, you can expect y our MFJ-9406 to del iver 5-8 Watts CW output int o a 50Ohm load. The
ad a p t e r h a s b e e n te s t e d fo r R F i m m u ni t y , a nd m a y b e u s e d w i t h t h e MF J 9406 to drive
six
meter
linear a mpl ifiers such as the Mirage A1015-G.
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MFJ-416 Instruction Manual
Operating Cross-Mode CW: While the MFJ-9406 is fixed in the USB mode, many
imported multi-mode transceivers automatically switch from USB for voice to LSB for CW operation.
This mode difference does not disrupt your ability to work those stations. However, CW signals
received on LSB radios will appear inverted from how they are received on the MFJ-9406. Thus, if
you tune a station for a low CW ton e (below the normal 600 Hz offset), you'll sound correspondingly
high (above the 600-Hz offset) to that station. Like wise , up-fre quency QRM on your radio will
sound down-frequency on LSB-mode radio s. The dia gram below may help you visuali ze how
this works:
No special operating adjustmen ts are necess ary to oper ate "cross-mod e", beyond an awareness that L SBmode stations have an upside-down view of the spectrum you share.
In Case of Trouble:
Replying CW stations are consistently off frequency: Reset offset control (R6).
[
I
Remember, most 50 -MHz stations oper ate CW on L SB, so increase offset to lower average pitch
(clockwise ), an d decrease it for higher-pitch (counter-clockwise).
[ ] Continuous carrier heard between CW characters: Poor carrier null. To rebalance
modulator (U5), turn m i c -g a i n f u l ly down , k ey your m i c' s P T T s w i t ch , a n d a d ju s t Carrier Balance
R57 for mini mum sig nal using a sec ond re ceiv er or sp ectr um ana lyz er as a monitor. Carrier should be
at least 40-dB down from full RF output.
[
Ambient audio on CW note: Your microphone should cut the audio line--as well as the PTT
I
line--when the P TT button is released. I f your micr ophone do es not do this, unplug it when operating
CW.
[
QSK-hold too slow: Reduce value of R5 (try 2.2M) or C1 (try .05 uF).
I
If you have any problem with thi s unit first check the approp riate section of this manual. If the
manual does not reference your problem or your problem is not solved by following the
manual, you may
MFJ Technical Service at 601-323-0549 or the MFJ Factory at 601323-
call
5869. You will be best served if you have your unit, manual and all information on your station
handy so you can answer any questions the technicians may ask.
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