[time-nuts] Rebroadcasting time signals [WAS: La Crosse Clocks - ]

[Charles Steinmetz]

Hal wrote:

> Transmitting on the same frequency you are receiving on seems like asking for
> troubles.

Difficult perhaps, but not impossible.  As /tvb notes, one solution is 
time domain multiplexing; and, as Alex says, phase domain multiplexing 
is another (although the phase discrimination of 60kHz antennas this 
size is problematic).  There are others.

> How far apart would the antennas have to be?  How would you calculate that
> distance?  Or what is the right question?

I've watched discussions of this topic for several years, and have 
always been surprised that nobody has ever once mentioned the potential 
for harmful interference extending beyond one's own property.  (Tom 
mentioned it today, including the possibility of legal implications.) 
This is especially true of people, like some on this list, who 
reportedly run a big loop around their house ("so that all their WWVB 
clocks can hear it").  But really, any scheme with leakage can (and 
likely does) create harmful interference beyond your property.

I can say positively that if anyone who has such a system lived down the 
block from me, I would be most unhappy about it and would be in a very 
foul mood by the time I figured out what was causing the interference I 
was receiving.  (I know whereof I speak -- I spent quite a lot of effort 
a few years ago chasing down a leaking 10MHz reference of very dubious 
quality in use by a local ham nearly a kilometer from me.)

So, please, if you are going to rebroadcast a time signal to your 
receivers, make sure the modulator and RF generator are in 
well-RF-sealed enclosures and that you use good coax (or, preferably, 
triax) to send the signal to each receiver individually.  BTW, this 
applies to *any* such signal, not just LF but HF and GNSS rebroadcasters 
as well.

Best regards,

Charles