MFJ MFJ-817C User Manual

MFJ-817C Deluxe VHF/UHF True Peak Reading SWR/Wattmeter Instruction Manual

NOTE:

IMPORTANT:

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

unit does not provide a dc or low frequency earth ground. A separate wire

und bus to an electric ground. Do

MFJ-817C Deluxe VHF/UHF True Peak Reading

SWR/Wattmeter

Introduction

The MFJ-817C is a true peak reading SWR/Wattmeter designed to operate on
144/220/440 MHz. This meter uses our TrueActive peak reading circuit to read true

peak/average forward and reflected power and SWR simultaneously. It has 300/30 Watts
forward and 60/6 Watts reflected power scales. The MFJ-817C utilizes a large
illuminated three-inch Cross-Needle meter to read the SWR from 1:1 to ∞.

should be connected from the station gro
not place any non-coaxial feed wires near metallic or RF sensitive devices.

Installation

1. Connect your transmitter to the connector on the back of the unit labeled
TRANSMITTER and your antenna to the connector labeled ANTENNA. It is
important that you use good quality coax and properly installed connectors.

2. The MFJ-817C has a TrueActive peak reading circuit that requires a DC power
supply such as the MFJ-1312B in order to function. A 9 VDC may also be
installed inside the meter with a battery clip that is included. The rear panel
accepts a 2.1 mm coaxial plug with the center conductor positive (+) and the
sleeve negative (-). The negative lead is grounded inside the meter. There is no
need to disconnect the battery when using external power.

3. An internal lamp backlights the meter scale. The lamp circuit requires 12 VDC
and will not illuminate with the 9 VDC battery alone.

4. 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 MFJ­817C.

The wattmeter must have a power source in order to function. A nine-volt
battery may be installed in the compartment on the rear panel, or an external
12 VDC source, such as the optional MFJ-1312D power supply, may be used.

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MFJ-817C Deluxe VHF/UHF True Peak Reading SWR/Wattmeter Instruction Manual

Operation

1. With the DC power supply or 9 VDC battery installed, push the ON/OFF button
in to turn the unit ON. If 12 VDC is used, the lamp will also be turned ON.

2. The meter’s full-scale forward and reflected power range is controlled by the
300/30 Watt 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. If your transmitter/amplifier runs more than 30 Watts of output
power, push the button in for 300 Watts. If your transmitter runs less than 30
Watts of output power, push the button out for 30 Watts.

3. Average power is measured when the PEAK/AVG button is pushed out. Peak
envelope power (PEP) is measured when the PEAK/AVG button is pushed in.
Peak and average power values are equal with steady unmodulated carriers, FSK,
or FM. The meter reading on these modes will be the same whether the
PEAK/AVG button is pushed in or out. On SSB, the PEP meter reading should
be twice the average power with two-tone test modulation. On SSB, the ratio of
PEP to average power varies with different voice characteristics. With most
voices, the PEP reading is three to five times higher than the average voice power
reading. The most accurate PEP readings are obtained only with sustained carrier,
voice or two-tone test modulation. During normal voice modulation, the
wattmeter will typically indicate only 70% of the true Peak Envelope Power.

4. Forward power is displayed on the left-hand FORWARD meter scale. This scale
is calibrated from 0 to 300 Watts and is read directly in the 300W (in) position.
Each picket (scale mark) represents 5 Watts below 10 Watts, 10 Watts between 10
and 100 Watts, and 25 Watts between 100 and 300 Watts. In the 30W (out)
position, the forward power scale must be divided by 10. Each picket represents

0.5 Watts below 1 watt, 1 watt from 1 to 10 Watts, and 2.5 Watts from 10 to 30
Watts.

5. The reflected power is read on the right-hand REFLECTED meter scale.
Reflected power is 60 Watts full scale when the 300W (in) power scale is
selected, and 6 Watts full scale when the 30W (out) power scale is selected.

6. The most accurate power readings occur in the upper half of the meter scales.
When trying to measure power with a less than perfect match, the reflected power
should be subtracted from the forward power reading in order to find the true
power.

7. The SWR is read directly from nine red SWR curves that range from 1:1 to ∞.
SWR is measured by observing the point where the forward and reflected power
needles cross. The SWR is indicated by the red curve closest to the needle
crossing point.

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