MFJ Super Hi-Q Loop Instruction Manual Download Page 2 | Manualshive

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MFJ Super Hi-Q Loop Instruction Manual Download Page 2

MFJ

Super Hi-Q Loop

™ Antenna Instruction Manual

2

PATTERNS, POLARIZATION AND LOCATION

This loop antenna can be mounted to provide either vertical or horizontal polarization. To mount this
antenna for vertical polarization the loop should be mounted standing up. To mount the loop for
horizontal polarization the loop should be mounted so it lays flat.

The radiation pattern of a small loop
antenna is essentially omni-directional with
the exception of two very narrow nulls in
the axis of the loop. If you visualize the
loop as a "wheel", the nulls are in the same
directions that the "wheel's axle" would run.

Figure 1

Figure 2

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Summary of Contents for Super Hi-Q Loop

Page 1: ... resistive losses in a small loop antenna are kept low a small loop antenna will transmit nearly as well as a full size dipole MFJ was able to make this small loop antenna radiate nearly as well as a full size dipole by paying special attention to the electrical and mechanical construction of this antenna Because radio frequency currents primarily flow near the thin outer edges of flat conductor l...

Page 2: ...olarization the loop should be mounted standing up To mount the loop for horizontal polarization the loop should be mounted so it lays flat The radiation pattern of a small loop antenna is essentially omni directional with the exception of two very narrow nulls in the axis of the loop If you visualize the loop as a wheel the nulls are in the same directions that the wheel s axle would run Figure 1...

Page 3: ...l sky wave signals Because of the constantly changing angle and direction of sky wave signals the nulls of the loop are probably most useful for eliminating ground wave interference although they can be effective on some sky wave signals Other examples of using the null can be understood if we consider a loop antenna located on a roof By mounting the antenna horizontally above the middle of the ro...

Page 4: ...d loop antenna or mounting the loop vertically over a large metal roof HORIZONTAL POLARIZATION Horizontal mounting of the loop antenna results in an omni direction horizontally polarized pattern that has a null straight up in the air and straight below the center of the antenna This means that any ground reflection will tend to cancel the radiation along the horizon and also at low wave angles unl...

Page 5: ...r Some improvement in lightning protection of the loop electronics can be achieved by coiling and taping the coax into a two turn one foot diameter loop between the antenna and the mast Be sure this lightning retarding loop is below the plane of the antenna and at right angles to it 6 If you use coax seal use it sparingly Seal only the area near the top of the loop s female connector and the knurl...

Page 6: ...sulation to protect you Stay away from all power lines This antenna can be used inside a wooden or non metallic building with some reduction in performance Caution must be used when this antenna is used indoors because the antenna generates strong electromagnetic fields These fields can induce considerable RF currents into wiring and other metallic items A secondary concern is that the effects of ...

Page 7: ... will not effect the operation or SWR of the system However if you use lossy cable adjustment of the control head may be necessary If you are using a lossy cable between your antenna and controller and have problem tuning the easiest way to correct the problem is to get better quality cable If changing the cable is impractical adjustment of R10 to the minimum may correct the problem If you still g...

Page 8: ...top When you release the latched button after the low SWR point is crossed a MOVE LED near the FINE TUNE buttons will be lit The control head also contains circuits that allow the motor to move in slow steps To optimize the SWR the FINE TUNE buttons are used The MOVE LED s that indicated which way you needed to move after using the AUTO BAND SELECT will extinguish after the proper FINE TUNE button...

Page 9: ...ng lightning storms and unplug the power supply 6 Always ground the control head to the station ground buss 7 Never transmit with more than 150 watts through the control head 8 Always ground the shield of the feedline to a good earth ground at the entrance of the building for lightning and RF protection TESTING AND OPERATION WARNING Connecting a power supply that has outputs grounded to chassis or...

Page 10: ... the top of it s tuning range by pressing the AUTO BAND SELECT UP button The FREQ UP LED should light until the loop reaches the highest frequency and then extinguish approx 20 45 seconds RELEASE THE UP BUTTON 7 Cycle the SLOW UP and DOWN buttons The FAST UP or DOWN LED should flash off and on while the loop is tuning The flashing FAST UP LED will extinguish when the upper tuning range limit is re...

Page 11: ... the best power range Although very little power will be radiated until the loop is tuned use the least power necessary during tuning Always check frequency before tuning to avoid causing interference GENERAL OPERATION AND TROUBLESHOOTING After you have tested the loop as described in the TESTING AND OPERATION section you are ready to learn the short cuts necessary for easy day to day use of this ...

Page 12: ...e handled by using the FINE TUNE buttons TUNING WITH A KNOWN DIRECTION OF FREQUENCY MOVEMENT This method of tuning should be used when you know what direction the antenna needs to move If the change is small then only the FINE TUNE buttons need to be used goto step 4 1 Adjust the transmitter to the new frequency and transmit a steady unmodulated carrier 1 50w is ideal Be sure the RANGE switch is s...

Page 13: ... dim suddenly any time during operation Check that the coax is connected properly Check for a short from the antenna coax center conductor to ground Check for a short from the DC power supply to chassis ground If you push a Tune button and the Tune LED stays on for more than 40 seconds Check for moisture in the feedline or antenna If you press a Tune button and an LED does not light Make sure the ...

Page 14: ...t The loop may be circular or elliptical Compress or extend the loop until swr is at an acceptable level Replace the cover 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 problem or your problem is not solved by reading the manual you may call MFJ Technical Service at 601 323 0549 or the MFJ Factor...

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