[time-nuts] Re: Time Signal Transmitter (low power)

[Brooke Clarke]

Hi Anthony:

For efficient transmission of radio signals the antenna should be at least 1/4 wavelength in size.  At 60 kHz a 
wavelength is 5,000 meters so a 1/4 wave is 1250 meters (4100 feet).  If the antenna is smaller than 1/4 wavelength the 
efficiency goes down.  So if you were to wrap a room/house with a coil of wire and with an impedance match drive it with 
a 60 kHz signal the signal would fall off very quickly.

There's a license free band in the US between 160 and 170 kHz (1750 meters) where you are limited to a 50 foot antenna 
and one Watt input to the transmitter.  It's quite a challenge to be heard a hundred miles away.  Instead of the 37 Ohms 
antenna impedance of a 1/4 wave vertical you have an antenna resistance that's a thousand times smaller.  That means the 
effective radiated power is in the milliwatts.

-- 
Have Fun,

Brooke Clarke, N6GCE
https://www.PRC68.com
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 --------
> G'day time nut friends
>
> I wonder if one of you could point me in the right direction on how to purchase (if one exists) a Time Signal 
> Transmitter for use at the local level (range 20m) for synchronising watches and radio clocks using the various 
> standard radio frequencies?
>
> And for the transmitter itself to receive / synchronise it's time using NTP?
>
> I am in Australia and we are out of range for the normal transmissions...
>
>
> Kind regards to you all
>
>
> Anthony Dunne
>
> Sydney, Australia
>
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