MFJ MFJ-1625 Manuel utilisateur

MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

MFJ-1625 Window/Balcony Mount Antenna

Introduction

The MFJ-1625 Window/Balcony Mount Antenna was designed to provide portable or permanent HF

communications on 80 through 10 meters and VHF on 6 meters. The universal mount design allows the

user to install the antenna in many ways. The mount will easily attach to window frames, balconies, and

railings. The MFJ-1625 works well indoors mounted to a desk or table as well.

The antenna consists of a whip tuner designed for tuning short whips as well as virtually any random

length wire antenna, collapsible whip, universal mount, and counterpoise wire. The operating frequency

is found by turning the knobs on the whip tuner and setting them for maximum RF current. The

counterpoise wire length can also be adjusted for maximum RF current. The MFJ-1625

Window/Balcony Mount Antenna will allow the operator to get on the air from locations where antenna

size is limited.

The whip 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-1625 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.

An RF Current Meter indicates the summed antenna and counterpoise antenna currents, making tuning

particularly easy. Simply tune for maximum RF current.

MFJ-1625 Supplied Components (80-10 meter operation)

•MFJ-1956 12 ft. telescopic whip antenna

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

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

telescopic whip antenna

Choosing a Mounting Position

WARNING:ALWAYS ATTACH THE SAFETY ROPE TO A STABLE SUPPORT

BEFORE ATTEMPTING TO ATTACH THE UNIVERSAL MOUNT TO A

WINDOW FRAME OR RAIL. INJURY AND DAMAGE COULD OCCUR

IF THE ANTENNA WERE TO FALL.

1. Locate the MFJ-1625 in a convenient location. The best performance will be obtained by

placing the antenna outside, however the antenna may be used indoors if necessary. Avoid

placing the tuner near microphones, speech processors, computers, TNC's or other RF

sensitive devices.

MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

2. The design of the antenna allows it to be installed in many ways. It can be easily attached to a

window frame, window box or balcony railing. A Wooden fence is another common mounting

location. The counterpoise is simply placed on the floor. Some installations may require the use

of a C-clamp or vice-grips to secure the base plate.

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

touching these terminals while transmitting!

Important: Always remember to keep the antenna away from metal objects and out of

reach to prevent injury.

WARNING: SERIOUS RF BURNS AND INJURY CAN OCCUR IF CONTACT IS MADE

WITH THE ANTENNA.

Installation

IMPORTANT: WHILE INSTALLING THE ANTENNA TO A WINDOW OR BALCONY

CONNECT THE SAFETY ROPE OF THE BASE PLATE TO A

SUPPORT.

1. Choose a location to mount the antenna.

WARNING: NEVER MOUNT THE ANTENNA IN A LOCATION CLOSE TO POWER

LINES. SERIOUS INJURY OR DEATH MAY OCCUR.

2. Connect the safety rope to a good support.

3. Attach the mounting bracket in position by placing the bracket over or around the surface of the

support.

NOTE:THE ANTENNA SHOULD BE ORIENTED AWAY FROM WINDOWS AND OTHER

OBJECTS THAT ARE WITHIN CLOSE RANGE IF POSSIBLE.

4. Tighten the screws on the rear of the base plate against the surface of the support. The screws

should be tightened in equal increments to keep the force on the spacer plate proportioned.

5. Loosen the Counterpoise Attachment.

6. Insert the end of the counterpoise wire

7. Tighten to secure the counterpoise.

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

TRANSMITTER on the back of the tuner.

MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

9. Decide which mount hole will be used on the mounting bracket according to your situation.

There are five holes available.

10. Connect the MFJ-63 Loading Coil Assembly and the MFJ-1956 12 ft. telescopic whip antenna

to the 3/8x24 stud on the top of the mounting bracket and extend to its full length.

Using the MFJ-1625

CAUTION:Never Change The Antenna or Inductor Selector Switch Position While

Transmitting! Never Apply More Than 200 Watts To The MFJ-1625.

Preset the controls on the MFJ-1625 as follows:

•ANTENNA to maximum inductance -Position "A".

•MATCHING to minimum capacitance –Position “10”

•NORM/+C switch to NORM

•COUNTERPOISE to minimum inductance –Position “L”

•Hi-Z/Lo-Z switch (back of unit) to Lo-Z.

•SENSITIVITY control fully clockwise (maximum sensitivity)

Most modern solid state transceivers do not require tuning and loading adjustments. If the transceiver

has a built in antenna tuner, be sure it is turned off or disabled. If your transmitter has an adjustable

output circuit, it must be properly tuned to a 50 ohm load at the operating frequency before 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 receiver noise.

Note: If no noise peak is evident, try adding extra capacitance with the NORM/+C

switch. Then reverse the HI-Z/LO-Z switch and re-try with both positions of the

NORM/+C switch.

2) Apply just enough power on CW (or AM/FM/RTTY) to obtain a noticeable deflection on the RF

CURRENT meter.

3) Carefully adjust the ANTENNA, MATCHING and COUNTERPOISE controls for maximum RF

current as follows.

MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

•Adjust the MATCHING capacitor for maximum RF current.

•Adjust the COUNTERPOISE inductor for maximum RF current.

•Try plus or minus a position or two on the ANTENNA inductor, along with tuning the

MATCHING capacitor to see if higher RF current is achievable.

Note: These controls interact. Go back and forth between these adjustments as required until

maximum RF current is obtained.

4) The transmitter power may now be increased up to a maximum of 200 watts. Make sure you

reduce the RF SENSITIVITY control as necessary to keep from pinning the RF Current meter.

Note: The MFJ-1625 will reduce the SWR of most antenna systems to below 1.5:1. Maximum RF

current also corresponds to minimum SWR. This can be verified with an external SWR meter if

desired.

In Case of Difficulty

If this tuner fails to tune, please double check all connections and follow the tuning procedure again.

The power rating of this tuner is 200 watts on 30-10 meters. If this tuner arcs at the rated power

levels, please double-check all connections and follow the tuning procedure again.

If you are still unsuccessful, please read the following ANTENNA HINTS text.

Grounding Hints

To minimize RFI, antennas should be kept away from other wiring as much as possible. Also, the

antenna should be adequately insulated to prevent arcing or accidental contact if placed near other

objects.

For safety, it is always best to use both dc and RF grounds. A DC ground may not be practical in

some portable locations, however.

It is always important to have a good RF ground, provided by the counterpoise, when using any whip or

long-wire antenna. This is because the MFJ-1625 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 are often inadequate for RF grounding

because they are long single conductors. RF grounds require large "spread out" surfaces with direct

multiple connections to the equipment ground point. Water pipes, heating ducts, or multiple ground

rods may work (especially if they are all connected together with jumper wires), but the best RF

grounds are radial systems or multi-wire counterpoises.

MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

Antenna Hints

WARNING: For operator safety, a goodearth ground should be installed and connected to

the case of the MFJ-1625. Make certain the safety ground connects to the

same terminal that connects to the transmitter and other station accessories.

A binding post labeled "COUNTERPOISE" is provided for counterpoise or

other RF ground connection(s). This post will not provide a safety ground.

Matching Problems

Most matching problems occur when the antenna system presents extremely high impedance to the

tuner. This occurs when the antenna is approximately a half-wavelength long at the frequency at which

you are trying to tune.

MFJ-1625 Artificial Ground

The MFJ-1625 contains a series L-circuit that is used to tune the RF ground system (either a

counterpoise or a ground wire). Maximum ground current will flow through the MFJ-1625 RF current

meter when the COUNTERPOISE switch is properly set.

Installation of a Suitable Counterpoise / Artificial Ground

The MFJ-1625 includes a counterpoise set of wires that will work well from 80-10 meters. It is

important to keep the last few feet of the counterpoise wires as far as possible (two feet minimum) from

each other and other near-by conductors.

You can also build your own counterpoise system if you desire. A RF counterpoise system can be as

simple as a single wire a quarter wave long 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 frequencies should be connected together at the COUNTERPOISE post

of the MFJ-1625.

When counterpoise wires are located indoors, they can be laid on a floor under a carpet, placed in an

attic, or stapled to a basement ceiling. If you place the counterpoise under the carpet or where

MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

someone may contact it, be sure to use well insulated wire and multiple counterpoise wires. Insulate the

far end of the counterpoise wire(s) with electrical tape to prevent accidental contact.

When counterpoise wires are used outdoors, only place them high enough to walk under. Use multiple

wires spaced a few feet apart (at minimum).

DANGER: Touching counterpoise and/or antenna wires while transmitting can cause an RF

burn. The wire must be well insulated and the end properly insulated.

There are cases very little deflection of the RF current meter can be seen. However, even though the

meter may not indicate much RF current change while adjusting the COUNTERPOISE control, even

the slightest RF current peak indicates that the artificial ground is helping.

Tuning Out Reactance of Long Ground Leads

If the station ground has a long lead, you can connect it to the COUNTERPOISE binding post of the

MFJ-1625. Connect the station ground bus and accessories to the GROUND post. Do not reverse

these wires. Follow the same procedure for maximizing RF Current described in the tuning procedure.

WARNING: This unit does NOT provide a dc or ac safety ground through the

COUNTERPOISE terminal. A separate wire from the station ground bus to

an electrical or earth ground must be used.

TVI and RFI Hints

It 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 reference your problem or your problem is not solved by reading the manual, you may call

MFJ Technical Service at 662-323-0549 or the MFJ Factory at 662-323-5869. You will be best

helped if you have your unit, manual and all information on your station handy so you can answer any

questions the technicians may ask.

You can also send questions by mail to MFJ Enterprises, Inc., 300 Industrial Park Road, Starkville,

MS 39759; by Facsimile (FAX) to 662-323-6551; or by email to [email protected]. Send

a complete description of your problem, an explanation of exactly how you are using your unit, and a

complete description of your station.

MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

Schematic

MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

Tuning Chart

You may wish to remove or make 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

2.0

3.5

3.75

4.0

7.15

10.1

14.2

18.1

21.2

24.9

28.5

MFJ-1625 Instruction Manual Window/Balcony Mount Antenna

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