[time-nuts] Re: Antenna return loss

[Dana Whitlow]

Andy,

Good point, up to a point.  But even if the antenna's amplifier itself has
a good return
loss, cheap cables like RG-174 are pure garbage and could be doing just
about
anything along their length.  And if the bottom end connector is put on by
a person
without training and the correct tooling, very bad things can happen there,
too.

Complicating the situation is the mismatch likely to occur when one tries
to power
said antenna through a bias tee or whatever.  Fortunately, if the right
kind of splitter
is used, such mismatches will occur in a "safe" location (downstream of the
splitter).

Nothing's ever simple ...

Dana


On Thu, Jul 29, 2021 at 3:42 AM Andy Talbot <andy.g4jnt at gmail.com> wrote:

> Much talk about source return loss and splitters.
> All active GPS antennas I've met have masses of gain at the top end, 40dB
> or more.   Most of the small puck ones come with several metres of RG174
> thin coax.
>
> This is so lossy at 1.6GHz that that several metres may have perhaps 10 -
> 15dB loss.   So there's your good source impedance for the splitter 20 -
> 30dB RLoss without even considering the head amp itself.
>
> Even several metres of UR43 should have enough loss to constitute a decent
> match.
>
> Andy
> www.g4jnt.com
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