Hemisphere GPS Vector V113 - Environmental Considerations; VHF Interference

V103/113 Vector User Guide Chapter 2-Installation Page 6 of 35
The V113’s internal beacon receiver calculates a signal-to-noise ratio (SNR), measured in decibels (dB), that
indicates the receiver’s performance. The SNR is the height of the signal above the noise floor: the higher the
SNR, the better your beacon receiver demodulates the signal.
The optimum antenna location will be a position where your average SNR is highest. You should turn on all
accessories you intend to use during normal operation when locating the best position for the antenna. By
monitoring the SNR, you can determine the optimum location with respect to beacon reception. The SNR is
available in the $CRMSS NMEA message described in the Hemisphere GNSS Technical Reference Guide.
Environmental Considerations
Hemisphere Vector compasses are designed to withstand harsh environmental conditions; however, adhere to
the following limits when storing and using the V103/ 113:
 Operating temperature: -30°C to +70°C (-22°F to+158°F)
 Storage temperature: -40°C to +85°C (-40°F to+185°F)
 Humidity: 95% non-condensing
VHF Interference
VHF interference from such devices as cellular phones and radio transmitters may interfere with GPS
operation, however the Vector compass can still track GLONASS satellites maintaining heading and position.
For example, if installing the V103/113 near marine radios consider the following:
 VHF marine radio working frequencies (Channels 1 to 28 and 84 to 88) range from
 156.05 to 157.40 MHz. The L1 GPS working center frequency is 1575.42 MHz. The bandwidth is +/-
2MHz to +/- 10 MHz, which is dependent on the GNSS antenna and receiver design.
 VHF marine radios emit strong harmonics. The 10th harmonic of VHF radio, in some channels, falls
into the GPS working frequency band, which may cause the SNR of GNSS to degrade significantly.
 The radiated harmonic signal strength of different brands/models varies.
 Follow VHF radio manufacturers’ recommendations on how to mount their radios and what devices to
keep a safe distance away.
 Handheld 5W VHF radios may not provide suitable filtering and may interfere with the V103/113’s
operation if too close
Before installing the Vector Compass use the following diagram to ensure there are no nearby devices that
may cause VHF interference.
Figure 2-1: V103/113 Distance from nearby VHF Radios