[time-nuts] NIST

Thu Aug 30 21:56:20 UTC 2018

Hi

Well, designing jammers on a public forum is an “interesting” thing to do…..

With WWVB, you are fine with a “near field” solution. You don’t need something that propagates for 
miles and miles. The other thing you have in your favor is that coming up with a KW at 60 KHz is 
quite easy. All those 60 KHz switchers we complain about … there’s your dirt cheap source of parts. 

The next part of the “solution” is to feed your signal into the local power grid. Your switcher is happy
with a low impedance load. The power line looks fairly low impedance at 60 KHz. It goes the RF and 
out and about it flows. Indeed it works pretty well over a good chunk of ground. At least as good as your
typical GPS jammer and no more expensive. Been there end done all that, though not for a WWVB jammer. 

Bob

> On Aug 30, 2018, at 5:20 PM, Brooke Clarke <brooke at pacific.net> wrote:
> 
> 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!
>>> 
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> 
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