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 <[email protected]> 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 <[email protected]> wrote:
On Mon, Aug 13, 2018 at 8:52 AM Peter Laws <[email protected]> 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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