Lets get back to that GPS antenna mounting. A few days ago various
members fussed about where to put the thing. I had mine on the front
window ledge and it worked OK except sometimes.
I was informed by a member that the cap over the drivers area was
fiberglass (which I did not know) and so there ensued an attempt to put
the Earthmate up against this fiberglass but above the ceiling.
Then it occurred to me to try it just on the underside of the ceiling
pan. This would mean the radiated energy would need transit both the
fiberglass and the ABS plastic of the finish ceiling.
First I made a series of checks with the Earthmate outside, recorded the
numbers from 8 satellites, put it on the window ledge and repeated the
recording then simply held it up against the ceiling about a foot back
from the window.
To my complete astonishment I picked up a couple more SATs, had green
readings from all 9, none were more than 3 dB less than the signal
strength recorded with the Earthmate completely outside.
I then put a good velcro strip on the face of the receiver and held it
in position to record any loss from the velcro. There was none.
So after velcroing the receiver in the center of the ceiling, about a
foot back from the rear view mirror but on the inside I recorded the
following data:
With the coach parked heading north I received green signals from all
satellites except one which was at a 10 degree elevation and directly in
the rear.
Satellites from all other angles and above 10 degrees altitude, from
headings of 160 degrees through north and on around to 200 degrees
produced signals of 30 dB or above.
30 dB is sufficient to properly trigger the data.
dB readings ranged from 30 to 47 dB.
The horizontal error was less than 17' and the vertical error was less
than 32'. The other parameters of PDOP, HDOP and VDOP all were in the
good range.
The simple truth is that you can mount the Earthmate on the ceiling if
the structure is the same as came from the factory, it is easy to afix
the lead to the center window strut.
No fuss, no mess and it works as it should.
Melvin Shaffer
