[time-nuts] 60 KHz Receiver

[Bob Camp]

Hi

If you were starting from scratch there are a lot of things you could do. If the intent is to put out something a Loran receiver will recognize ... not so much. 

Bob


On Oct 5, 2010, at 6:44 AM, Poul-Henning Kamp wrote:

> In message <B69FDCAF-2B39-4575-B5CD-66A87FA1B332 at rtty.us>, Bob Camp writes:
> 
>> Even though it's pule, the RF power is way beyond the sub 1 W
>> outputs currently contemplated on those bands. Signal to noise
>> *does* matter.
> 
> You know, there are other ways to skin that cat these days.
> 
> Old-time signals had to be grossly inefficient because the receivers
> were inefficient, in particular the "ear-wristwatch" kind of time
> receivers.
> 
> These days we have spread-spectrum modulation, and if our only goal
> is to transmit a timestamp, you can spread pretty wide and far and
> need very little power to produce a receiveable signal at long
> distances.
> 
> The QRSS hams are playing around with numbers like 17,840,000 miles
> per watt, and all it takes to turn that into a time/frequency
> services is a spreading function with a really good autocorrelation.
> 
> Obviously, you will not get second by second measurements, but the
> measurements you do get, say once per hour, will have much higher
> precision because of the averaging that goes into them.
> 
> And equally obvious: propagation effects will take their toll, but
> still...
> 
> Somebody with a license should try that on 137kHz...
> 
> Poul-Henning
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
> 
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