Jeff Liebermann wrote:
Building a store and forward repeater for WWVB (or the EU equivalent)
60Khz is a waste of time. The storage delay needed to regenerate the
signal will result in the sync pulses arriving too late. However, a
system that uses GPS, GLONASS, or Galileo as a reference, and
generates a simulated time code format will work. The problem is that
at 60Khz, the necessary antenna farm would be huge and the
transmitters rather power hungry. WWVB runs at an EIRP of about 70kW.
That's sort of what I was thinking of. Get the time from NTP, generate
a fresh time code signal, which would not be accurate enough for someone who
wanted truely accurate time code, but to keep a clock that displays to the
minute, or even to the second on time, it would be good enough.
As for the transmitter, how much power do you need to transmit a signal from
a time code generator to a receiver next to it, connected via a coax cable?
A microwatt? A milliwatt?
limited abilities of a commodity router. Methinks you would be better
off with a SBC (single board computer) or common PC (ITX, Mini-ITX,
etc).
It depends. A cheap router, such as the Linksys WRTG-54L (note the L at the
end it's the enhanced model that runs Linux) would do it. It sells new for
not much money, will be obosolete as the 802.11N routers come into general
useage, has an ARM processor, two ethernet interfaces (one connected to a
4 port hub), a WiFi radio and a bunch of status LEDs. The advantage of it
is that there are several alternate Linux packages for it and you can easily
compile your own programs, build your own "flash" (firmware image) and load it.
There are also distributions for other routers, I recently bought a $30 EDIMAX
wired router that had a distribution for it.
Actually, a 60KHz xmitter is fairly easy to design. The problem is
that all the components would be huge. There's also the not so easy
problem of getting Ministry of Communications approval. It's not on
the designated ham radio frequency list:
If it is directly connected to the input of the receiver, it needs no
license.
I'm sure that nearby users that went through the trouble of obtaining
large antennas, will not be thrilled with your transmissions. Even a
"local" transmitter can carry a substantial distance at 60KHz.
I also expect there are none. Around here the noise level is so high that
they would never hear it until I got into the "real antenna" type system.
A microwatt with true isotropic radiator antenna (a short wire) would not
leave my apartment, let alone go anywhere. But if it is connected directly,
then it is a moot point.
I was thinking of something simple, such as flashing the LED at 60kHz, and
wrapping a pickup loop around it. That's about the same power level and
frequency of a TV remote control and no one from the MOC has come and
complained about any of the ones I have. I'm talking about the RF leakage
from it, not the optical signal.
The GC-1000 used WWV at 5,10, and 15 MHz, all of which are still on
the air. I'm not sure what a 60KHz system would do for you.
Not here. I have never heard them here, nor have I heard CHU (yes, I know it
moved), any of the European stations, etc. I'm not talking about a cheap
portable shortwave, I'm talking about a Kenwood R-5000 with a 75 foot random
wire, or other equally as sensitive ham receivers either with a 20m resonant
dipole or 1/4 wave vertical, or a 40m resonant dipole.
I'm not actually familar with the clock in question, the discussion (I think
it was on this newsgroup) focused on them using WWVB (VLF) radios.
I've given up asking "why". Some of the strange things I've seen on
the internet defy logic and explanation.
I'll agree with that.
Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel
N3OWJ/4X1GM