Peter wrote:
The antenna has a pretty clear sky view right now. I have about 75
feet of cable, 25 feet that came attached permanently to the
antenna, might be RG-59, and a 50 foot extension which is a new
piece of good quality RG-6 CATV cable.
Perhaps the antenna (came with the tbolt in the ebay deal) is not
that good and I should get something better before taking the effort
to get it up in its permanent location?
If you are not using a timing-grade antenna, changing it would be a
good idea -- but be prepared for your c/n numbers not to change
dramatically. If you get a new one, make sure it is a 5 V antenna.
You say that the E and S exposures are pretty much clear, but the
plot shows poor c/n below 30-45 degrees elevation. You may find that
your ADEV improves if you change the elevation filter to 30 degrees
(it is at 10 degrees now), or change the signal strength filter to
something >= 3.0 AMU (it is at 0.0 now; 3.5-4.0 is often
recommended). Either of these would reduce the number of satellites
used by the Tbolt at any given time, but getting rid of the noisiest
signals may improve overall performance as long as it does not cause
the Tbolt to go into holdover for lack of satellites.
One of my Tbolts is in a location surrounded by tall trees and I have
an indoor backup antenna in case the external antenna fails. Using
the backup antenna, its c/n plot looks not too different from
yours. After much experimentation, I found that the best performance
with the backup antenna is achieved with the elevation filter set to
30 degrees and the signal strength filter set to 3.0 AMU.
Best regards,
Charles
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