Garmin CNX80 GPS Receiver User Manual


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GARMIN USA, Inc. 1200 East 151
st
St., Olathe, Kansas 66062 913/397.8200 Fax 913/397.8282
CNX80 User Newsletter
Fourth Edition for the CNX80
5/4/04
Paul Damschen, CNX80 Certification Manager
In this edition:
1. Common Installation Problems with GPS/VHF Systems.
2. GTX 32 and 33 interfaces.
3. Auto SUSP in Holding.
4. Operating on the fringes of WAAS coverage
5. Meggitt Magic Interface
Common Installation Problems with GPS/VHF Systems
This topic is not really specific to the CNX80. However it bears putting forth some of
this information as the CNX80 installations we have seen can and have been affected by
some of these common installation problems. If you are in the process of installing your
CNX80, you may wish to discuss these issues with your installer, or if you are a
distributor, be aware of these types of issues.
In almost all cases, the majority of problems are related to the Radio Frequency (RF)
signals used by the VHF Nav/Comm and GPS signals from the GPS satellites. Serial
data connections between systems typically are less problematic, as they tend to either
work or not work at all in which case wiring, poor seating of the unit in the tray, or a bent
or broken pin is usually the cause.
Reuse of Old Coax and Connectors
If it’s not broken don’t fix it, right? Most of the time this approach works, but reliability
of reused coax and connectors tend to be hit and miss. Old coax and connectors that are
reused in a retrofit upgrade with new equipment usually result in an acceptable
installation, but it’s a common point of failure and complaint that we hear.
Coax is not expensive and frayed/chafed coax or marginal crimps on the connectors will
substantially degrade system performance or drive you crazy with intermittent or
complete loss of function problems. If the airplane is open and the coax accessible it is
far cheaper to replace it than leave what’s been in the airplane for many years and hope
for the best.
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