© Microhard Systems Inc.
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7.0 Installation
Fade Margin
When all radio path numbers are being considered and hardware assumptions are being
made, another factor to consider is the ‘fade margin’ of the overall system. the fade margin is
the difference between the anticipated receive signal level and the minimum acceptable re-
ceive level (receive sensitivity). Being that the Nano Series performs to exacting specifica-
tions, the overall deployment should be such that the modems may be utilized to their full po-
tential to provide a reliable and robust communications link. A typical desired fade margin is
in the order of 20dB, however oftentimes a 10dB fade margin is acceptable.
Frequency
The 900MHz and 2.4GHz frequency ranges are not effected by rain to any significant degree,
and is also able to penetrate through foliage and ‘around obstacles’ to a certain degree. This
being the case, some may choose to scrimp on the physical deployment, particularly when it
comes to antenna (tower) heights. Path calculations provide results which specify ‘required’
antenna heights. For cost savings and in taking advantage of the characteristics of the fre-
quency range, sometimes the height requirements are not adhered to: this may result in un-
reliable communications.
Power Requirements
The Nano Series may be integrated into a system (Development Board, or custom) which
accepts a range of DC input voltages (supply current requirements must also be met). In
some deployments, power consumption is critical. A number of features related to minimize
power consumption are available with the Nano Series: sleep/sniff modes, LED dimming,
and the ability to operate at less transmit power given the receive sensitivity of the distant
modem.
Interference
The frequency hopping spread spectrum (FHSS) operation of the Nano Series most often
allows it to work well in an environment within which there may be sources of in-band interfer-
ence. Frequency Restriction is a built-in feature which may be utilized to avoid specific fre-
quencies or ranges of frequencies; the Spectrum Analyzer function may be used to identify
areas of potential interference. Cavity filters are also available if required: contact Microhard
Systems Inc. for further information.
