Hemisphere GPS V104n, User Manual

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V104n GPS Compass User Guide
7
VHF Interference
VHF interference from devices such as cellular phones and radio
transmitters may interfere with GPS operation. For example, if installing the
V104n 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 GPS antenna and receiver design (see
next page).
• 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.
• Hand-held 5W VHF radios may not provide suitable filtering and
may interfere with the V104n’s operation if too close.