MFJ MFJ-415B Instruction Manual Download Page 6

MFJ-415B CW Adapter 

 

Instruction Manual 

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  Module Adjustment for CW Offset (R103): 

Offset is preset at the factory for roughly 600 Hz.  However, if you prefer a different beat 
note--or if stations consistently respond to your CQs off frequency--you should reset 
R103. 
 
To reset the offset, connect your MFJ radio to a dummy load and set it up to 
"communicate" with a second transceiver.  Begin by tuning in the CW signal generated 
by the second radio to a comfortable pitch on your MFJ radio--as you would do when 
tuning in a station calling CQ.  Then, while sending a reply with the MFJ radio, adjust 
R103 for a 600-Hz tone in the second radio's speaker.  That way, you'll hear incoming 
signals at the pitch you prefer--and your transmitted signal will sound on-frequency to 
other stations listening for you.  To approximate the factory-default adjustment for R103, 
set the arrow pointer on the trimpot so that it points to the "R" in the "R103" silkscreen 
marking on the pc board.  Then, adjust from this starting point.  
 

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  Module Adjustment for QSK Hold (R102): 

This establishes how long the TX relay holds in after you stop sending.  QSK hold is set 
to approximately 1/2-second at the factory--a typical delay for 13-20 WPM sending.  
However, you may set this for personal preference by adjusting trimpot R102.  To 
approximate the factory default position, set the arrow on the trimpot to the "2" in the 
"R102" silkscreen marking on the pc board. 
 

Important VFO-setting Note: 

 Radio amateurs are solely responsible for knowing the 

frequency they transmit on.  If you work DX at the low edge of the band or if you are 
restricted to a sub-band within the CW allocation, make sure you know where your band-
limits are.  MFJ cannot be held responsible if your radio is miscalibrated or if you 
accidentally transmit outside the prescribed frequency allocation for your class of license. 
 

Important Tune-button Note:  

When powered on, the CW module's keying circuitry will 

interact with--and disable--the radio's front-panel 

Tune

 button.  If you need to generate a 

continuous carrier in CW mode for ATU adjustments, use the key to activate a carrier.  
The 

Tune

 function will work normally when the CW adapter is turned off. 

 

Important Microphone Note: 

 If the push-to-talk switch in your microphone doesn't 

disable the mic element during receive mode, you must unplug your mic before operating 
CW.  If you do not, stray voice signals and noise may be picked up and transmitted on 
SSB along with the CW signal!  The recommended MFJ-290 and Radio Shack 21-1172 
microphones normally disable the mic line and may be left plugged in (so do many other 
PTT type mics).  However, if you are aren't sure of your mic's switching circuit, check! 
 

Summary of Contents for MFJ-415B

Page 1: ...d Installation 2 Shorting Plugs 2 Adjustment and Calibration 2 Transceiver Recalibration of VFO 2 Module Calibration for CW Band 3 Module Adjustment for CW Offset 4 Module Adjustment for QSK Hold 4 In...

Page 2: ......

Page 3: ...to the transceiver s VFO circuit to shift frequency coverage into the CW portion of the band The specific components required to make the VFO shift are selected by the jumper plug on header J105 You...

Page 4: ...no sidetone remove it For MFJ 9440 place a shorting plug on center and rear pins of J105 For MFJ 9420 place a shorting plug on center and front pins of J105 Adjustment and Calibration Your MFJ 415B C...

Page 5: ...O dial are set to 14 000 MHz MFJ 9440 Signal source and VFO dial are set to 7 000 MHz If your MFJ radio lacks a CW band dial scale on its faceplate set the VFO dial to the low end of the phone band Th...

Page 6: ...personal preference by adjusting trimpot R102 To approximate the factory default position set the arrow on the trimpot to the 2 in the R102 silkscreen marking on the pc board Important VFO setting Not...

Page 7: ...e at least 40 dBc or 40 dB down from full CW output Technical Assistance If you have any problem with this unit first check the appropriate section of this manual If the manual does not reference your...

Page 8: ...MFJ 415B CW Adapter Instruction Manual 6 Schematic...

Page 9: ...5 Jack Stereo PCB 3 5 mm J104 612 0102 Header Pin Straight 375 1 2 Position J105 612 0103 Header Pin Straight 375 1 3 Position K101 408 1011 Relay Reed Type 12 V SPST L101 402 2710 Inductor Coilcraft...

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