[time-nuts] ThunderBolt question

[Dana Whitlow]

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


On Sat, Jun 6, 2020 at 9:11 AM Wes <wes at triconet.org> wrote:

> 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 be sure they will work with quad-shielded.  I bought some
> (blue) that
> were claimed to work and there was no way in hell that I could get them
> on.  I
> had to buy another batch (purple) that do work.
>
> Regarding mismatches; my recently installed antenna is a PCTEL
> GPSL1-TMG-SPI-40NCB.  This is advertised as a "timing" antenna, so I
> assume
> they're worried about timing. The data sheet says the "nominal impedance"
> is 50
> ohm.  But....the VSWR spec is <2.0:1. Of course this antenna has an
> internal
> amplifier (40 dB), whose match to the helix antenna is unknown but I'm
> guessing
> it's for NF optimization.  So is the spec the nominal output Z (s21) of
> the
> internal amplifier or is it the load the amplifier needs to be presented
> with to
> deliver advertised gain?  Who knows?  Either way, my 75 ohm coax is within
> limits.
>
> Wes  N7WS
>
>
>
>
>
> On 6/5/2020 4:56 PM, DON MURRAY via time-nuts wrote:
> > Robert...
> >
> > Try to find QUAD SHIELD RG-6.
> >
> >
> > 73
> > Don
> > W4WJ
> >
>
>
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