[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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> 
> -- 
>  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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> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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