RIght! (about Ligado).
Well, it sounds like you might be OK with your 4 way splitter and roughly 10
dB of added attenuation. Somewhat of a point can be made in favor of using
attenuation to the extent you can, just so that strong local disturbances
(like
those famous Arizona lightning strikes)
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
Hi
Their engineering group also backs up this statement if you ask them about
it face to face. The answer that comes back is: “We ran a bunch of tests with
75 and 50 ohm cable, we could see no difference in the results”.
Bob
> On Jun 6, 2020, at 1:30 PM, Taka Kamiya via time-nuts
> wrote:
>
In case of thunderbolt, the manufacturer openly recommends use of 75 ohm cable.
The manufacturer openly states not to be concerned with a mismatch. They are
in manuals.
---
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
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
As the chip is a message, not a time hack per se, all the delay can do is make
it more difficult to decode the message. That's how these COFDM-type schemes
work. It's why your digital TV signal (which in the US is not a COFDM signal,
but still behaves similarly) falls off a cliff when things
Hi
A “cable echo” looks like any other multi-path signal. Your local environment
provides *lots* of those all the time. That's regardless of how hard you try to
get
rid of them. If they are *stronger* than the main signal (which they can be in
a “bounce off a building" case) they really mess
Conventional wisdom says yes to this. I'm not so sure, if the cable is
well-made, but some of the stuff is really garbage.
I'm using RG-6 cable purchased at DX Engineering, mainly because I had a gift
certificate for my last order. It's quality stuff, but if you're going to use F
connectors
I wish I could give some numbers. Sadly, I don't know how to calculate
them nor do I
have the equipment to do empirical measurements of that level of accuracy.
But I could do an arm-waving estimate. Suppose that the delayed signal
component
is in phase with the direct signal, but 20 dB down,
No caveats required.
Give some numbers on how loud that MP signal has to be to cause a problem. My
original example of line losses for a relatively short cable still suggests to
me that it is a minimal problem. If the S/N of a satellite is poor, the
receiver algorithm is likely to not use it
Hi
Do a little research and You will find that a 3 db noise figure is as good as
it gets
with a receiver who’s front end is a perfect match to the transmission line ….
(Signal goes down 6 db when you match, noise drops by 3 db ….).
Unless you are using some sort of ferrite isolator on the
Basically true, Tom, but with some caveats:
The GPS system was originally designed, as you say, to provide
positions and velocity
information to military users in the field. Errors of a few meters were of
little consequence.
But now, we have the time-nuts, surveyors, etc, who are decidedly
Dana...
The question that comes to mind is just how much effect a weak a long delayed
reflection will have on overall system performance since it will only matter to
SV’s with poor S/N. The modulation scene which allows all the SV's to transmit
on the same frequency has to be pretty robust in
I must take issue with John's statement that "impedance matching is easy".
It's easy only in the case of very limited bandwidth and if you are willing
to
ignore such issues as getting good IMD performance, good noise performance,
and good broadband AC stability. The last item is critically
It's one thing to maintain lock in a multipath environment, quite another
thing
to get "full" accuracy of GPS measurements of PVT.
An interesting difference between my scenario of poorly matched impedances
and "ordinary" multipath is this: In the poor matching scenario, all the
received
signals
The original question was need for impedance matching between gps antenna and
Tbolt.
The responses were accurate and appropriate. 50 Ohm vs 75 Ohm is a nonissue.
On Sat, 6 Jun 2020 07:11:49 +, John Moran, Scawby Design wrote:
>Everyone ...
>I must admit to being amazed at the cavalier
Everyone ...
I must admit to being amazed at the cavalier attitude to impedance matching. I
dread to think what a state we would be in if the original telecoms networks
were designed with such disregard.
OK, my background is in the old telecoms - land-line stuff where we had a
variety of
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