[time-nuts] WWVB BPSK Receiver Project?

Jim Lux jimlux at earthlink.net
Fri Mar 16 05:17:25 UTC 2012


On 3/15/12 9:41 PM, Chris Albertson wrote:
> On Thu, Mar 15, 2012 at 8:45 PM, Jim Lux<jimlux at earthlink.net>  wrote:
>
>>
>>> http://dttsp.sourceforge.net/
>>>
>>
>> documentation for dttsp is less than wonderful
>>
>>   http://www.oz9aec.net/index.**php/gnu-radio/grc-examples<http://www.oz9aec.net/index.php/gnu-radio/grc-examples>
>>>
>>
>> seems to be a bit more diverse usage for gnuradio, so more examples and
>> documentation
>>
>
> dttsp has by far the larger in-use user based because it is the engine used
> by PowerSDR by Flex Radio.  It is also used by the HPSDR group.  See these
> links
> http://www.flex-radio.com/
> http://openhpsdr.org/
>
> But you are right in that using dttsp is something that might take a long
> tome to learn.   The above user group tends to have many "appliance users"
> and a few programers so learning is not so much of an issue

If there are more than half a dozen people actually using dttsp, in the 
sense of modifying it, or doing something other than creating a UI for 
it, I'd be pretty surprised.  It's pretty much a product of the two main 
authors.  As you say, the learning curve is exceedingly steep, 
especially if you want to understand the architecture and internal 
structure.  You could probably go in and do "spot changes" without 
breaking too much, but any sort of radical change (like adding a new 
demodulator) would be a pretty big challenge.

The fact that it's the core of PowerSDR means that over the years, it's 
had a lot of customization for that particular application.  Someone 
trying to decode PSK WWVB isn't going to be interested in the latency of 
the CW keyer or the performance of the automated notch filter.


>
> GNU Radio is popular in Universities where as soon as something works they
> toss it out.   It's quite a bit easier to program or if you like there is
> GRC that allows visual programming.    I think this is better because it
> allows a wider number of people to contribute.

it's much more "componentized" and the source of the components is broader.

Probably not as "finished" as something like PowerSDR, but much easier 
to bite off small chunks.

For simple tasks, there are also tools like DL4YHF(?) spectrumlab.
http://www.qsl.net/d/dl4yhf/spectra1.html
it has:
# Decoder for some time-code transmitters: MSF(60kHz), HBG(75kHz), DCF77 
(77.5kHz) can now be used to set your PC clock to a high accuracy. All 
you need is your longwave receiver and the soundcard.
# Modulator and decoder for some 'experimental' digital communication 
modes like PSK31, BPSK, QPSK, FSK,  multi-tone HELL, MSK (minimum shift 
keying since 2004-12), transmission and reception of letters with a 
small 'terminal' window.

I've used it a lot for a variety of tasks (a Doppler radar, for one thing)

>
> My suggestion to use a platform where these two libraries run was really to
> say that you should not write this on bare hardware.  It's a good way to
> paint yourself into a corner and have to start over to add some new feature
> we can't think of today.


Another idea, if you have access (e.g. student licenses or thru work) is 
Matlab/Simulink and real-time-workshop.

All the building blocks are there, you just hook them up.

Pretty pricey if you're not in the educational bucket, though.  And 
Octave doesn't really have all the cool toolboxes that Matlab does.



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