[time-nuts] WAAS.....

[Brian, WA1ZMS]

Guys-

Thanks for the inputs and the mention of FEI and related patents. I thought the idea was not new but did not remember the details.

As for some answers:
As far as I have seen first-hand, the jamming is short in nature and events that I saw were from trucks on highways trying to defeat any tracking systems in the trucks.  An FCC enforcement issue here in the US resulted in one such user being made an example of by heavy fines since his truck was near a major airport where the FAA was trying to test GPS landing aids.

In my case, SW masking of hold-over alarms may be a shorter fix without any HW fixes. But that said, I wanted to be sure I understood the situation/mitigation at least well enough to talk about it with some info as back-up.

As for Hal's drop-out of GPS in the SFO area, that was a location that I had to address with a customer 18 months ago who was having chronic GPS drop-outs that I traced to GPS jamming and documented. Could be the same or not.

This latest issue is on the East Coast.

Again, there is a wealth of great knowledge here in Time Nuts and I'm glad to be able to call on help!

-Brian, WA1ZMS/4
iPhone

On Jan 8, 2014, at 11:57 AM, Björn <bg at lysator.liu.se> wrote:

> Hi Brian!
> 
> Hmmm... should I finish the thread before commenting...
> 
> The scenario has been discussed on the list before. There are publications from Zyfer (fei) on Waas timing with a fixed dish antenna. There is also a Fenton(Novatel) patent.
> 
> --  
> 
>    Björn
> 
> <div>-------- Originalmeddelande --------</div><div>Från: "Brian, WA1ZMS" <wa1zms at att.net> </div><div>Datum:2014-01-08  09:25  (GMT+01:00) </div><div>Till: Discussion of precise time and frequency measurement <time-nuts at febo.com> </div><div>Rubrik: Re: [time-nuts] WAAS..... </div><div>
> </div>In this case the timing rcvrs are located all with in a 20km radius with fixed known surveyed locations. The problem is GPS jamming that happens at random times. So one "what if" idea is to use a WAAS enabled rcvr and a yet to be selected parabolic antenna to point at a given WAAS sat. The concept is to give all rcvrs a single common view for critcal timing use in a comm system.
> 
> The ultimate goal is to try and reduce the number of times when full sky view GPS antennas are victims of GPS band interference.  This is only a half-baked idea of mine (in my day-job) but wanted Time Nuts feedback to see if it has any merit at all. BTW, the system has Rb for hold-over when there are problems but the frequent system error alarms indicating hold-over events is what I/we would like to reduce. New SNMP traps could mask off the events, but being an RF guy.....I was thinking about a HW solution. :- )
> 
> 
> -Brian, WA1ZMS/4
> iPhone
> 
> On Jan 7, 2014, at 11:05 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> 
>> Brian,
>> 
>> On 2014-01-08 02:25, Brian, WA1ZMS wrote:
>>> Hypothetical question....
>>> For a given set of GPS timing grade receivers at multiple locations, is there any advantage by limiting allowable SVN numbers to only be the WAAS satellites?
>> 
>> Well, if you do common view GPS comparision and is not into monitoring observables separately (which is recommended), then there is some use for it, as you configure the WAAS acceptance statically and only need to update it once a new bird becomes available or one disappears. However, I wonder if they are any good for that purpose anyway.
>> 
>> So, in a more general way, I'd say no.
>> 
>> More importantly, what are you trying to achieve?
>> 
>> Cheers,
>> Magnus
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