MFJ -818 Instruction Manual

Mobile swr/wattmeter

MFJ-818 Mobile SWR/Wattmeter

Introduction

The MFJ-818 Mobile SWR/Wattmeter measures forward and reflected power and SWR

simultaneously and is designed to operate on 1.8-30 MHz. The MFJ-818 has two power

scales, which are selected with the top panel push button switch. The high power scale

measures 0-300 Watts forward power and 0-60 Watts reflected power. The low power

scale measures 0-30 Watts forward power and 0-6 Watts reflected power. The MFJ-818

utilizes a large illuminated three-inch Cross-Needle meter to read the SWR from 1:1 to

∞. A slide switch turns the back light on or off. This compact SWR/Wattmeter is rugged

enough to take the abuse of brutal mobile and portable operation.

1. Connect your transmitter to the connector labeled TRANSMITTER and your

antenna to the connector labeled ANTENNA. It is important that you use good

quality coax and properly installed connectors.

2. An internal lamp backlights the meter scale. The lamp circuit requires 12 VDC

supply such as the MFJ-1312B. Use a 2.1 mm coaxial plug with the center

conductor positive and the sleeve ground. A slide switch turns the internal lamp

on or off.

3. To measure the power output capability of a transmitter/amplifier you should

connect a quality 50-ohm dummy load to the ANTENNA connector of the MFJ-

818.

Figure 1: MFJ Mobile SWR/Wattmeter

Instruction Manual

Table of Contents

Do you have a question about the MFJ-818 and is the answer not in the manual?

Page 1 The MFJ-818 Mobile SWR/Wattmeter measures forward and reflected power and SWR simultaneously and is designed to operate on 1.8-30 MHz. The MFJ-818 has two power scales, which are selected with the top panel push button switch. The high power scale measures 0-300 Watts forward power and 0-60 Watts reflected power.
Page 2 MFJ-818 Mobile SWR/Wattmeter Instruction Manual Operation 1. The meter’s full-scale forward and reflected power range is controlled by the POWER RANGE button. When the button is pushed in, the forward power scale is on 300 Watts and the reflected power scale is on 60 Watts. When the button is pushed out, the forward power scale is on 30 Watts and the reflected power scale is on 6 Watts.
Page 3 MFJ-818 Mobile SWR/Wattmeter Instruction Manual Calibration The MFJ-818 has been calibrated at the factory. If it should ever need to be recalibrated, then follow this procedure: Equipment Needed 1. Transmitter capable of supplying enough power to obtain ½ to full-scale reading at 14 or 21 MHz.
Page 4 20 Watts. 8. SWR requires no calibration. Transmitter/ Standard MFJ-818 50-Ohm Reference Mobile Transceiver Dummy Load SWR/ Wattmeter Wattmeter Figure 2: Test Setup LO REF HI REF LO FWD HI FWD Figure 3: Trim Pot Location (Side View of MFJ-818)
Page 5 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 techinfo@mfjenterprises.com.