I will put on my EE hat and surmise that the reason that Garmin
advises against chopping your cable is a simple one.
GPS RF is on the north side of 1.5 GHz. Quality cable like RG400
double braid is essential as is perfection in creating the tiny crimp
connections. If you do not have the equipment and expertise
to do the work, dont even try it. These are not your fathers
PL-259/SO-239 radio shack connectors. A bad connection will
have more attenuation than a few feet of RG400.
The dc voltage to the preamp is not a relevent factor, as
a rusty nail could carry that.
Yes, I think we have all heard that trope about specific cable lengths.
It is, IMHO, just marketing nonsense with no technical basis, since A) the
lengths are no where near a tuned wavelength Feedline, and B) All
modern receivers have AGC(automatic gain control).
Full disclosure: I despise GARMIN avionics for their abysmal
Human factors design and their absurd data pricing.
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Ira N224XS
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