[time-nuts] WWV/CHU

paul swed paulswedb at gmail.com
Thu Mar 29 15:14:48 EDT 2018


I'll add to the conversation. CHU is easier to deal with because its not a
subcarrier as the 100 Hz WWV signal is.
Its FSK and bell 103 modem style.
Regards
Paul
WB8TSL

On Thu, Mar 29, 2018 at 10:08 AM, jimlux <jimlux at earthlink.net> wrote:

> On 3/29/18 3:49 AM, Attila Kinali wrote:
>
>> On Thu, 29 Mar 2018 03:12:24 -0700
>> Hal Murray <hmurray at megapathdsl.net> wrote:
>>
>> What do I need in in order to get time from WWV or CHU?
>>>
>>> Do I need a fancy receiver as a front end?  Do I have a chance with one
>>> of
>>> the low cost USB thumb drive size receivers?
>>>
>>> Is there an obvious software package to start with?  (Linux)
>>>
>>
>> I think the easiest is GnuRadio... A quick googling lead
>> to https://github.com/jasonabele/gr-wwvb
>> I don't know anything about it so use at own risk :)
>> But at least it seems like something that can be done easily
>> on a rainy evening.
>>
>> Normal RTL-SDR's do not work for WWVB as they have a lower cut of
>> frequency in the range of 20-50MHz...unless you bypass the tuner
>> chip and feed the signal directly to the ADC. As IIRC all RTL-SDR
>> give you something like 2Msps, that should be more than plenty to
>> decode WWVB and related signals. If you feed the RTL-SDR from an
>> external frequency source, you should be able to related that
>> frequency source to WWV.
>>
>
> The RTL-SDR is an interesting device - I'm putting together a hobby HF
> interferometer with GPS to provide time tags.
>
> Yes, most of the newer parts (RTL-SDR v3, for instance) provide a
> programmable bypass of the front end downconverter (the part is actually
> designed to tune TV signals and the L-band output of a consumer dish LNB)
> The backend chip (RTL2832U) is a digital downconverter which mixes and
> filters the nominal 3.5 MHz IF which is sampled at 28.8 MHz
>
> You can actually adjust the output sample rate - something around 2
> Msample/second is the default, but there's lots of other rates available.
> For WWV you could crank it down, but..
> The ADC is 8 bits (7 ENOB) and the output is 8 bit I/8 bit Q.
>
> Folks have modified the RTL-SDR to accept an external frequency reference,
> so you could take the output from your ensemble of Cesium references to
> discipline a hydrogen maser (so your close in phase noise is better),then
> use that to drive a 28.8 MHz discrete divide/multiply chain, and run that
> into your $30 receiver to improve the frequency accuracy.  (not for nothing
> are we called time-nuts)
>
>
>
>
>
>>                         Attila Kinali
>>
>>
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