[time-nuts] GPS Interference Question

Tom Holmes tholmes at woh.rr.com
Fri Sep 30 15:35:34 UTC 2011


My question had nothing to do with cost or design, but only that you can't
filter out a signal that is in the passband you need for your own channel.
Even a square passband won't help that problem, fantasy that it is.

Tom Holmes, N8ZM
Tipp City, OH
EM79


> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Chuck Forsberg WA7KGX N2469R
> Sent: Friday, September 30, 2011 11:20 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] GPS Interference Question
> 
> A wider filter with steep skirts tends to cost more.
> Constraints on noise figure, dynamic range, group delay. and flatness
> add more cost
> and power consumption.
> 
> 
> On 09/30/2011 08:11 AM, Bob Bownes wrote:
> > Exactly. The narrower the filter, the more it will cost. In general.
> >
> >
> >
> > On Fri, Sep 30, 2011 at 11:10 AM, Tom Holmes<tholmes at woh.rr.com>  wrote:
> >> Sticking with the intent to keep this non-political, what good is a
filter
> >> if the offending signal is within the necessary passband?
> >>
> >> Tom Holmes, N8ZM
> >> Tipp City, OH
> >> EM79
> >>
> >>
> >>> -----Original Message-----
> >>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]
> On
> >>> Behalf Of Chuck Forsberg WA7KGX N2469R
> >>> Sent: Friday, September 30, 2011 10:55 AM
> >>> To: Discussion of precise time and frequency measurement
> >>> Subject: Re: [time-nuts] GPS Interference Question
> >>>
> >>> If LightSquared deploys their high powered LTE network in the
satellite
> >> band
> >>> the GPS world will become very interesting indeed.  Are LightSquared
> >> willing
> >>> to spend $20,000 to upgrade the GPS on my Skylane to a new model which
> >>> does not yet exist?
> >>>
> >>> With that many transmitters we may experience areas where RF from
> multiple
> >>> high power transmitters creates hot spots.  In some places pieces of
metal
> >>> with non Ohmic bonds will create mixing products, some of which may
fall
> >>> directly within GPS bands.  These effects have not been simulated.
> >>>
> >>> Who knows who the FCC is listening to - the GPS industry including
> >> millions
> >>> of current users, or those who appear to have bought under the table
> >> favor.
> >>> This could make Solyndra look like small change.  Film at 11.
> >>>
> >>>
> >>> On 09/30/2011 07:02 AM, Marco IK1ODO -2 wrote:
> >>>> At 15:44 30-09-11, Jason wrote:
> >>>>
> >>>>> To filter out the L2 signal, would an actual GPS receiver have to be
> >>>>> replaced / modified?
> >>>>>
> >>>>> Or would a more simple and cheaper alternative be to get a new
> >>>>> antenna (with fancy filtering) to replace my existing roof-top
> >>>>> antenna and expect all my old equipment to be happy?
> >>>> I think that a new antenna/filter/amplifier unit would be ok. But the
> >>>> problem is the installed base of receivers, including all those
costly
> >>>> units used for geodesy or navigation, that have embedded antennas.
> >>>> Those will be hard to modify.
> >>>>
> >>>> 73 - Marco IK1ODO
> >>>>
> >>>>
> >>>>
> >>>> _______________________________________________
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> >>>>
> >>> --
> >>> Chuck Forsberg WA7KGX N2469R     caf at omen.com   www.omen.com
> >>> Developer of Industrial ZMODEM(Tm) for Embedded Applications
> >>>     Omen Technology Inc      "The High Reliability Software"
> >>> 10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430
> >>>
> >>>
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> >>
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> 
> --
> Chuck Forsberg WA7KGX N2469R     caf at omen.com   www.omen.com
> Developer of Industrial ZMODEM(Tm) for Embedded Applications
>    Omen Technology Inc      "The High Reliability Software"
> 10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430
> 
> 
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