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MFJ-1642 Portable Whip Tuner 

Instruction Manual 

MFJ-1642 Portable Whip Tuner with Artificial Ground 

 

IMPORTANT:  

Please read entire manual before attempting to operate this equipment.  This unit does 

not provide a dc or low frequency earth ground from the counterpoise terminal.  A separate wire should 
be connected from the station ground bus to an electric ground.  Do not place any counterpoise or non-
coaxial feed wires near metallic or RF sensitive devices. 

Introduction 

 
The MFJ-1642 is a 150 watt, 80-10 meter antenna tuner designed for tuning short whips as well as 
virtually any random length wire antenna.  It is perfect for either fixed station or portable use, and, with 
its built-in artificial ground tuning system, will match any transmitter or transceiver to virtually any 
antenna.   
 
The MFJ-1642 tuner section uses a reversible "L" network.  The advantage of the “L” network is that it 
has only two tuning controls, and only one tuning solution for given impedance match.  The MFJ-1642 
has rear panel connectors for coaxial input and a “Hi-Z/Lo-Z” switch for reversing the “L” network.  An 
internal input-isolating current balun provides isolation of DC and RF grounds for optimum tuning of the 
RF counterpoise. 
 

MFJ-1642 Supplied Components (30-10 meter operation) 

• 

MFJ-1956 12 ft. telescopic whip antenna 

• 

Counterpoise assembly (6, 14, and 26 ft. long wires)  

 

 

MFJ-1642 Optional Components ( 40-80 meter operation) 

• 

MFJ-63 Loading Coil Assembly for 40-80 meter operation with the MFJ-1956 12 ft. 
telescopic whip antenna 

 

Installation 

 
1.  Locate the MFJ-1642 in a convenient location at the operating position.  Avoid placing the tuner 

near microphones, speech processors, computers, TNC's or other RF sensitive devices. 

 

WARNING:  High RF voltages exist at the antenna and counterpoise terminals.  Avoid 

touching these terminals while transmitting! 

 
2.  Connect your transceiver’s output to the SO-239 (UHF female) connector labeled 

TRANSMITTER on the back of the tuner.  You will need an external SWR Wattmeter connected 
in line between the transmitter and whip tuner. 

 

Summary of Contents for MFJ-1642

Page 1: ...s and only one tuning solution for given impedance match The MFJ 1642 has rear panel connectors for coaxial input and a Hi Z Lo Z switch for reversing the L network An internal input isolating current balun provides isolation of DC and RF grounds for optimum tuning of the RF counterpoise MFJ 1642 Supplied Components 30 10 meter operation MFJ 1956 12 ft telescopic whip antenna Counterpoise assembly...

Page 2: ...ore adjusting the tuner This should be done with a dummy load Tuning Procedure WARNING Never transmit while changing the INDUCTOR SELECTOR 1 First tune for maximum receiver noise as follows While listening to your desired receive frequency adjust the ANTENNA control for maximum receiver noise Adjust the MATCHING control for maximum receiver noise Adjust the COUNTERPOISE control for maximum receive...

Page 3: ...nd provided by the counterpoise when using any whip or long wire antenna This is because the MFJ 1642 tuner needs something to push against in order to force current into the antenna If a good RF ground is not available RF will usually find its way back into the power line RFI transmitter audio circuits RF feedback or the operator RF burns Water pipes provide good dc and ac safety grounds but they...

Page 4: ...or less or as complicated as several wires cut for different bands Always insulate counterpoise wires and keep them from accidentally contacting animals people RF sensitive devices and wiring For best performance try to position the counterpoise wires in a straight line if possible A counterpoise wire must be well insulated For best performance several wires a quarter wavelength long on different ...

Page 5: ...is possible for RF to flow down power cables into the house wiring This may cause TVI Stereo VCR or other RFI problems As a precaution a ferrite core can be clamped around power leads The MFJ 701 RFI FREE CHOKE KIT makes it easy to eliminate common RFI problems Technical Assistance If you have any problem with this unit first check the appropriate section of this manual If the manual does not refe...

Page 6: ...a copy of this page and place it near the tuner Insert your own values for each frequency according to your station Freq MHz Counterpoise Matching Antenna Hi Lo Z switch Extra cap switch 1 8 1 8 2 0 2 0 3 5 3 5 3 5 3 75 3 75 3 75 4 0 4 0 4 0 7 15 7 15 10 1 10 1 14 2 18 1 18 1 21 2 21 2 24 9 28 5 ...

Page 7: ...MFJ 1642 Portable Whip Tuner Instruction Manual 7 Schematic ...

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