[time-nuts] Antenna for t-bolt

Azelio Boriani azelio.boriani at screen.it
Tue Apr 3 20:04:31 UTC 2012


Absolutely true, that's why it is advisable to dare with the elevation mask
and set it rather high (upto 20 deg?) if the antenna is clear above but
there is the possibility for multipath or reflections (i.e. surrounded by
buildings). Of course the choke rings antenna is better... guess how much
the Trimble Zephyr gained starting at $250? It's gone for $1050: we can say
that 10 degrees more of elevation mask are worth $800. Anyway, the Zephyr
antenna doesn't have rings but there should be a sort of absorbing plane
made by those expensive microwave absorbing sheets.

On Tue, Apr 3, 2012 at 9:38 PM, <shalimr9 at gmail.com> wrote:

> If the satellite is above the mask, the signal will be used in computing a
> solution even if it got in through reflexions and multipath. That's why a
> good antenna with choke rings is desirable.
>
> Didier KO4BB
>
>
>
> Sent from my BlackBerry Wireless thingy while I do other things...
>
> -----Original Message-----
> From: Azelio Boriani <azelio.boriani at screen.it>
> Sender: time-nuts-bounces at febo.com
> Date: Tue, 3 Apr 2012 21:27:26
> To: Discussion of precise time and frequency measurement<
> time-nuts at febo.com>
> Reply-To: Discussion of precise time and frequency measurement
>        <time-nuts at febo.com>
> Subject: Re: [time-nuts] Antenna for t-bolt
>
> Of course the elevation mask is only software and doesn't prevent the bad
> signal from entering the antenna but then the signal will not despread and
> should cause no harm to the computations.
>
> On Tue, Apr 3, 2012 at 9:19 PM, <shalimr9 at gmail.com> wrote:
>
> > The elevation angle filter is based on the satellite position, not the
> > actual direction the signals come from.
> >
> > If you have reflections and multipath, but the satellite is otherwise
> high
> > in the sky, you are out of luck regardless of elevation angle filter.
> >
> > Of course, the higher the sat, the less likely you will have reflections
> > from roofs and such, so it is definitely not useless, but it is not the
> > same as having a good antenna in the first place.
> >
> > Didier KO4BB
> >
> > ------Original Message------
> > From: Hal Murray
> > Sender: time-nuts-bounces at febo.com
> > To: Time-Nuts
> > ReplyTo: Time-Nuts
> > Subject: Re: [time-nuts] Antenna for t-bolt
> > Sent: Apr 3, 2012 12:15 AM
> >
> >
> > caf at omen.com said:
> > > Presumably a timing antenna would block low elevation signals to reduce
> > > multipath.
> >
> > Maybe, but there is a software aspect to the filter.  You get to select
> the
> > elevation angle.
> >
> > I don't remember seeing any specs about the filtering angles of various
> > antennas.  Has anybody seen something like that?
> >
> >
> > --
> > These are my opinions, not necessarily my employer's.  I hate spam.
> >
> >
> >
> >
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> >
> > Sent from my BlackBerry Wireless thingy while I do other things...
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