Nissei RS-50M User manual

WHAT IS IT?
The RS-50M SWR Power Meter helps to ensure your radio
installation is transmitting at it's best possible performance. By
testing your VHF radio at the radio, and at each junction point of
your antenna cable, you will quickly be able to determine if there is
an issue with your radio, a cable segment, or antenna that is
preventing your radio from transmitting to its maximum range.
QUICK GUIDE
FWD –Forward Power is the amount of power being transmitted
from the radio to the antenna in Watts.
REF –Reflected Power is the amount of power being reflected back
from your antenna in Watts.
SWR –Standing Wave Ratio is the ratio of FWD to REF power.
HOW DOES IT WORK?
The RS-50M will detect when the microphone button on the VHF
radio also known as PTT (push to talk) has been pressed, and
measures the Forward Power, Reflected Power and Standing Wave
Ratio.

The Forward Power (signal output) from the VHF radio is shown in
Watts under FWD. The power reflected back from the antenna due
to incorrect impedance between the VHF radio, antenna cable,
connectors and antenna is shown under REF for Reflected Power.
The Standing Wave Ratio which is a measurement of how efficiently
your radio is radiating the power it produces when you transmit is
shown under SWR. It is generally referred to as the ratio of FWD to
REF power. The smaller the number, the better the SWR reading.
An SWR reading of 1.00 is ideal but rarely achieved, meaning 100%
of your signal is transmitted with no reflected power.
1.00 to 1.50
Very good reading.
1.50 to 2.00
Okay, some issue may exist.
2.00 to 3.00
Significant loss. Serious issue exists.
3.00 and up
Potentially damaging amount of REF power to the
transceiver.
Note: The highest SRW values occur when the antenna is
disconnected or short circuited. Operating a VHF radio with the
antenna disconnected or short circuited can damage the radio.
Testing the radio with the RS-50M without the antenna attached
can also damage the radio.

Battery Installation:
1. Remove the black screw from the rear cover to open
the battery compartment.
2. Be sure to check polarity of batteries before installing.
3. Install 2 x AAA batteries. Batteries may be alkaline
(1.5v), NiCad or NiMH (1.2v) rechargeable batteries.
Power can also be supplied using the included USB
cable. The USB port is intended for continuous power,
but will not charge the batteries.
4. Remove the batteries if the unit will not be used for an
extended period.
Measurement:
1. Connect the transceiver to the “TX” connector on the RS-
50M meter using a 1 meter length of 50-ohm cable (sold
separately)
2. Connect the antenna or load to the "ANT" connector.
3. Turn on the RS-50M power and optionally the LCD back-
light switch.

4. Turn on the transceiver and tune to Channel 72. The RS50M
has been calibrated for Channel 72 as the center frequency
and will be the most accurate on this channel.
5. Monitor the channel prior to transmitting to ensure you are
not disrupting ongoing communications during the test.
6. Press the microphone (PTT) button for 1 to 2 seconds and
release to read the results on the display. The Forward
Power (FWD), Reflected Power (REF) and Standing Wave
Ratio (SWR) will be displayed for 5 seconds. While the PTT
button is pressed the RS-50M is constantly calculating and
averaging the results for the most accurate reading.
Note: If the meter is not used for 30 seconds, the back-light
will automatically turn off. After pressing the PTT
button, the back-light will turn back on.
7. Be sure to turn off both the Power and Light switches
after use to conserve battery power.

WHY IT IS IMPORTANT
In a marine emergency, when you press the VHF radio’s Digital
Selective Calling (DSC) button, you want the radio to transmit your
unique MMSI number identifying your boat and GPS co-ordinates
with the strongest and clearest signal to facilitate a marine rescue.
However, your MAYDAY call may not be received if…
1) Antenna isn’t high enough
4) Obstructions
2) Radio isn’t receiving enough
voltage from your battery to
generate a strong signal
5) Antenna cable / connection
issues
3) Weather conditions
The RS50M will help you test your radio.
We tested a sailboat and found that the radio was only producing
18 watts of power due to low battery voltage. Corrosion on a short
antenna cable leading from the radio to the base of the mast
reduced the signal strength by a further 6 watts, and at the antenna
at the top of the mast, the signal strength was only 6 watts.
Replacing the cable increased the signal strength substantially.
Note: You should test your radio circuit in the Spring after launching
and stepping your mast, and before embarking on a cruise.

Troubleshooting:
Symptom
Solution
FWD Power less than 25
Watts
a) Make sure that you are testing on
Channel 72, a 25 Watt Channel. Some
channels are limited to 1 Watt.
b) Check battery voltage on Radio. Most
VHF radios will only transmit full power
(25 Watts) with 13.8 volts DC power.
REF shows “--.--“
a) Check to make sure you are testing on
channel 72 (25 watt) instead of a 1 watt
channel
b) Make sure radio and antenna
connections are not reversed
c) Make sure wiring and connections from
radio to antenna are in good condition.
SWR shows “99.99“
Antenna cable may have a short.
No display on RS50M
Check batteries. Replace with 2 x AAA
Alkaline (1.5v), NiCad or NiMH (1.2v)
rechargeable batteries, or use the Micro
USB cable supplied.

Specifications:
Frequency Range
155 –158 MHz
RF Power:
0 –30 Watts
Testing functions:
Forward Power, Reflected Power, SWR
Impedance:
50 ohms
Accuracy:
+ / - 5%
Power source:
2 x AAA Alkaline (1.5v), NiCad or NiMH (1.2v)
rechargeable batteries, or Micro USB
Connectors:
SO-239
Taiwan Nissei Sokki Co.
No.2, Lane 21, Cheng Kung Rd. Banqiao District,
New Taipei City, Taiwan.
TEL: [phone] FAX: [phone]
Homepage：http://www.meterexpert.com
e-mail：[e-mail]
Manual written by CTEX Innovations for Taiwan Nissei Sokki Co.
© 2017 Taiwan Nissei Sokki Co.