[time-nuts] 60 KHz Receiver

[J. Forster]

Paul,

I'd bet there are 50+ LORAN timing receivers in the Boston area that could
receive and lock to an erzatz 5W signal from a simulator and small amp.

-John

=============


> A great thread by everyone. Oh to make the loran receivers work. But that
> is
> indeed the past. Can not hear Europe on east coast.
> But the question really is, what do you want to accomplish? I don't think
> its a time stamp. Its just to easy to get it from GPS or the network. But
> that could be a secondary use. I believe the primary goal would be
> frequency
> distribution with perhaps a tick.
> If this is the goal then I am 100% in agreement that there are far more
> efficient modulation and recovery methods today. The trick is you need
> something that does not effect the accuracy of the timing and may improve
> the various transmission issues at these frequencies. By the way this list
> has a heck of a brain trust so its very very possible.
> Someone mentioned spread spectrum. Thats very interesting as it is what
> GPS
> uses and could work at these lower frequencies.
> Like the  "Hey this is just telemetry" comment. You know the FCC does
> indeed
> give temp authorization for quite long periods of time. Years in fact.
> So I would be in the keep it simple mode.
> Great a single carrier with a id every 10 min. Maybe that could be waved
> to
> 1 per hour or 24 hours. Unfortunately then we have nothing better then
> wwvb.
> The modulation method may be key and then what freq we would use. BPSK at
> higher frequencies is also impressive.
> My first contact was in the indian ocean on 5 whats from boston.
> Regards
> Paul
> WB8TSL
>
>
> On Tue, Oct 5, 2010 at 6:59 AM, Bob Camp <lists at rtty.us> wrote:
>
>> 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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