Dana,
I have about 45 feet of RG6 into a two-way splitter, currently feeding two
receivers, a BG7TBL GPSDO (U-blox) and a TAPR/Synergy GPS Timing Kit (M12+). So
each device has about 7 dB loss in front of it. As a crude test if I add a
stepped attenuator in the line to the TAPR receiver and look at the dBc report
in LH, a 10 dB step is hardly noticed, but a 20 dB step makes a noticeable
change. I still see tracking at 30 dB but at 40, gone.
So there is a lot of margin but I don't see any issues and the plan is to go to
a four-way split and add a couple of devices. I'm in a rural area outside of
Tucson so hopefully Ligado won't be an issue. We'll have to see if their
technical expertise is as good as the PR and lobby lawyers are.
Wes
On 6/6/2020 8:49 AM, Dana Whitlow wrote:
Wes, it sounds like you're in pretty good shape with one thing that
concerns me.
Unless your transmission line is long enough to have substantial loss, that
40 dB
gain figure seems awfully high and you may find yourself overloading the
front
end of your receiver.
Most modern receivers are sensitive enough to do just fine with no antenna
LNA
at all, in the absence of line loss. I remember reading a note from
Garmin on this
topic years ago when they were recommending no more than about 15 dB net
gain
between the antenna and the receiver.
With your receiver and 40 dB antenna, even if it seems to work well now,
beware of
Ligado! If/when they go on the air near you, you may find yourself needing
an
attenuator.
Dana
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