[time-nuts] NIST

Brooke Clarke brooke at pacific.net
Thu Aug 30 17:20:04 EDT 2018


Hi Bob:

I would disagree in that ease of jamming/spoofing is strongly related to wavelength.  That's because antenna efficiency 
goes down as the size of the antenna gets smaller than 1/4 wave.
So, it's easy to make a GPS jammer (1,100 to 1,600MHz) since a 1/4 wavelength is a few inches, something that  you can 
hold in your hand.
It's harder to make a WWV jammer (.5, 5, 10, 15, 20 MHz) since a 1/4 wavelength in in the range of  500 to 12 feet, 
something that can be mounted on a vehicle for the higher frequencies.
But it's extremely hard to make a jammer for WWVB (60 kHz) where a 1/4wavelength is over 4,000 feet.  This means an 
antenna that can be vehicle mounted will be very inefficient. Note this also means that it's extremely hard to make a 
Loran-C jammer.  Note that the WWVB and LORAN-C transmitters run very high power and the antennas are massive.

This also means that if someone makes a WWVB simulator for their house the signal at the next door neighbor's house is 
probably going to be too small to effect their clocks.

PS. Some decades ago I maintained a beacon transmitter "LAH" on 175 kHz where the rules for unlicensed operation limited 
the input power to 1 Watt and total antenna length to 50 feet.  Under these conditions the effective radiated power 
might be 2 milliwatts, orders of magnitude less if a portable system.
http://www.auroralchorus.com/pli/1750meter_antennas.pdf

-- 
Have Fun,

Brooke Clarke, N6GCE
https://www.PRC68.com
https://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

-------- Original Message --------
> Hi
>
> When infastructure GPS *does* get jammed these days that source gets tracked down a lot faster
> than a month or so. Anything that goes on for more than a day gets booted up pretty high
> pretty fast. Indeed I’ve been in the middle of that more than I would have wished to be …..
>
> The same sort of RFI issues that take out GPS from a TV preamp  can equally well take out WWVB or WWV.
> With WWVB, there are a *lot* of 60KHz switching power supplies out there to create problems. There is nothing
> unique about any of these services in terms of being jam immune.
>
> The bigger issue with any of them is spoofing. A proper GPSDO will go into holdover when RFI jammed. I would
> *assume* the same would be true of a fancy WWVB device. I’m not at all sure that’s true of a real WWVB standard,
> they haven’t been for sale new for a really long time. If your time source is in holdover, you can go out and track down
> the issue. If it simply locks to the new signal …. not so much.
>
> There is a subtle distinction in some of this. Newer systems do indeed want time. Older systems were generally after
> frequency. The only WWVB standards I’ve seen were aimed at frequency (and frequency holdover) rather than time and
> time holdover. Getting reasonable (1 to 10 ppb) frequency from WWVB is a very different task than getting the sort of time
> that modern systems are after.
>
> Bob
>
>> On Aug 30, 2018, at 2:46 PM, Scott McGrath <scmcgrath at gmail.com> wrote:
>>
>> The port of Long Beach CA was jammed wrt GPS for several months by a malfunctioning 29.95 TV preamplifier on a boat.
>>
>> GPS was completely unusable when this unsuspecting guy was watching TV on his boat.
>>
>> He had quite the surprise when the coasties with guns showed up.
>>
>> The fact is civillian GPS Is trivial to jam and jammers can be bought ‘under the counter’ at any truckstop along with illlegal linear amplifiers.
>>
>>
>>
>> On Aug 30, 2018, at 12:58 PM, Peter Laws <plaws0 at gmail.com> wrote:
>>
>> On Mon, Aug 13, 2018 at 8:52 AM Peter Laws <plaws0 at gmail.com> wrote:
>>
>>
>>> I have yet to hear anyone make a case for retaining the HF system that
>>> isn't backed by nostalgia.
>> Still looking for this.  Most of the "OMG IF WWV GOES AWAY MILLIONS
>> WILL DIE" posts (elsewhere, not here ... quite ...) are the type of
>> hysteria that is usually reserved for, I don't know, the EMP folks.
>> :-)
>>
>>
>>> As for solar flares taking out the various GNSSs ... wouldn't a solar
>>> flare only take out the vehicles that were on the "sunny" side of the
>>> Earth?  Wouldn't the (approximately) half of the SVs that are in the
>>> Earth's shadow be unaffected?  Serious technical question - I have no
>>> idea.
>> One of the responses to my initial message pointed out that the
>> effects of solar flares and CMEs take a while to get from Sol to Sol
>> III and don't arrive all at once, so potentially all GNSS spacecraft
>> could be affected.
>>
>> Since then, I've been poking around for papers on the effect
>> (observed, potential, theoretical) of these events on the Navstar or
>> other GNSS constellations but am not having much luck.  I assume it's
>> because I'm not putting the right magic incantation into the google
>> machine.
>>
>> Anyone got some cites?  Looking for the effect of solar flares and
>> CMEs on the spacecraft themselves and not how the GNSSs can be used to
>> measure the effects on the ionosphere, etc (those seem plentiful).
>> IOW, I'm curious about the resiliency of the systems to solar events.
>>
>> I did note that at the time of the 1989 solar event that took out a
>> lot of Hydro Quebec's grid, only the "Block I" experimental GPS "SVs"
>> were in orbit.  Well, maybe a couple of the later ones - the
>> operational constellation started launching about a month before that
>> flare.
>>
>> As I said initially, I'll be sad if WWV* goes away but it won't affect
>> my life in any measurable way that I can see.  I mean, other than the
>> mantle clock slowly losing time.
>>
>> -- 
>> Peter Laws | N5UWY | plaws plaws net | Travel by Train!
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
>




More information about the time-nuts mailing list