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Installation | HS80/HS80A/MX575C/MX575D User Manual
Environmental considerations
The Smart GPS compass is designed to withstand harsh environmental conditions; however,
adhere to the following limits when storing and using the GPS Compass:
• 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. For example, if installing the Smart GPS compass 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 GPS working center frequency is 1575.42 MHz. The bandwidth is +/- 2MHz to
+/- 10 MHz, which is dependent on the GPS 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 GPS 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 Smart
GPS compass’s operation if too close.
Before installing the Smart GPS compass use the following diagram to ensure there are no
nearby devices that may cause VHF interference.
Use these minimum distances
to determine where to place
the Smart GPS compass
1.5 m radius at top
(minimum)
1.0 m radius at base (minimum)
VHF antenna
Figure 2-1: Smart GPS compass minimum distance from nearby VHF radios
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