[time-nuts] WWVB remodulator for the Spectracom 8170...
Bob Camp
lists at rtty.us
Tue Jun 18 10:41:58 UTC 2013
Hi
I don't know of any phase tracking receiver that would be bothered by the modulator in Paul's schematic. You could implement it a couple of ways, but the net result would be the same. The AM is a bit more square wave than the WWVB signal. Modulation depth and timing would / could be dead on.
Bob
On Jun 17, 2013, at 9:29 PM, David I. Emery <die at dieconsulting.com> wrote:
> On Mon, Jun 17, 2013 at 06:11:15PM -0400, Bob Camp wrote:
>> Hi
>>
>
>> The Costas loop already has the AM component available. There's no
>> need for a second receiver, just wire the AM output over to the output
>> modulator.
>
> That is standard for most Costas loops with an I arm... haven't
> looked at his schematics carefully yet... possibly one might need some
> kind of AGC to use it as input to a second double balanced mixer
> serving as modulator in order to get the right 14 (?) db AM as signal
> fades slowly. Not sure how deep the diurnal fades are...
>
> But I guess if everything is quite linear over enough of a range
> one could perhaps just remodulate without AGC and create a replica of
> both the modulation and fades on the local 60 KHz carrier.
>
>
>
>
>>
>> Bob
>>
>> On Jun 17, 2013, at 5:57 PM, "David I. Emery" <die at dieconsulting.com> wrote:
>>
>>> On Mon, Jun 17, 2013 at 02:41:13PM -0700, Burt I. Weiner wrote:
>>>> Chris,
>>>>
>>>> The 8170 was originally intended to be a frequency reference source
>>>> tied to the USFS (United Stated Frequency Standard). It also gave
>>>> the time of day, but I believe that wasn't it's primary purpose. As
>>>> I recall, there were some versions that did not have the clock
>>>> readout and some that had a chart recorder. Back in the 80's I used
>>>> to drool (it was a disgusting sight!) over the Spectracom receivers
>>>> with the chart recorders. At that time I was usuing a Gertsch RLF-1
>>>> with an external Moseley 680 chart recorder. The remodulator
>>>> precludes it from being used as a frequency standard, but in my
>>>> opinion, so does the fact that WWVB is now phase shifted a bunch.
>>>>
>>>> The 8170 uses a coherent detector and that's where the problem
>>>> lies. While the 8170 still locks to the WWVB carrier, the new BPSK
>>>> scheme causes the detector to output bad data in spite of the
>>>> original dips in the carrier still being present. I had always
>>>> wondered how it was able to pull the data out the noise, but never
>>>> had a manual until just recently. I had naively assumed that the
>>>> WWVB new BPSK scheme would not affect the time of day aspect of the
>>>> 8170. Like I said, I only use it as a clock in my shoppe, and being
>>>> an old dog I don't easily learn new tricks such as looking in a
>>>> different direction for one of the other clocks.
>>>
>>> I suppose I am stating the obvious, but why not combine Paul
>>> Swed's Costas loop and this scheme to output a phase locked 60 Khz
>>> with the right AM modulation ?
>>>
>>>
>>>
>>> --
>>> Dave Emery N1PRE/AE, die at dieconsulting.com DIE Consulting, Weston, Mass 02493
>>> "An empty zombie mind with a forlorn barely readable weatherbeaten
>>> 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
>>> celebration of what could have been, but wasn't and is not to be now either."
>>>
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>>
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>
> --
> Dave Emery N1PRE/AE, die at dieconsulting.com DIE Consulting, Weston, Mass 02493
> "An empty zombie mind with a forlorn barely readable weatherbeaten
> 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
> celebration of what could have been, but wasn't and is not to be now either."
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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