[Lowfer] Sampling Rate and Frequency Calibration

[John Andrews]

JR,

Not tested for other clock frequencies. The clock cycles should scale 
with the external clock, though. Upper limit would be 20 MHz for this 
part, so I'm not sure how useful the different clocking would be.

The one thing that it doesn't do is provide a 1 MHz output. The reason 
is the overhead in instructions doesn't allow clocking that fine. The 
100 kHz output is interestingly weaved into the code as it is. 
Everything below that is simple divide by 10.

Anyway, glad to be able to put this old code to a new use.

John A.

On 1/25/2014 2:56 PM, jrusgrove at comcast.net wrote:
> JA
>
> Just wanted to offer feedback on how well your preprogrammed pic works.
> The setup here is GPS disciplined 10 MHz > 74HC4046 > your programmed
> PIC16F84A. It's sure handy having calibrated outputs all the way down to
> 1000 seconds ... didn't have the patience to check that particular
> output but all others are working ;~) . This simplified circuit replaces
> a number of divider chips that were required to give me just 10 kHz.
>
> FWIW, in the system here, the 10 kHz output from the pic feeds the right
> channel of SpecLab (in stereo mode) which is then used by the Frequency
> Error Compensation utility to discipline the soundcard sampling rate to
> 10 kHz. With the RF-590 receiver already disciplined at 10 MHz and now
> the soundcard at 10 kHz I'm seeing frequency accuracies in the uHz.
>
> Curious if you 'tested' the input frequency range for the programmed
> pic? It would make an excellent general purpose divider 'test
> instrument' where frequencies other than 1 Mhz, 100 kHz, 10 kHz, 1 kHz
> etc are needed ... if the input can be adjusted over a wide frequency
> range.
>
> Jay W1VD  WD2XNS  WE2XGR/2  WG2XRS/2
>
>
>
>
> ----- Original Message ----- From: <w1tag at charter.net>
> To: <lowfer at mailman.qth.net>
> Sent: Tuesday, January 21, 2014 8:52 AM
> Subject: [Lowfer] Sampling Rate and Frequency Calibration
>
>
>> In response to the recurring question about how to calibrate sound
>> card sampling rates and check receiver audio output frequency "on the
>> cheap," I have put up an article on a simple calibrator circuit that
>> provides 1 kHz and 100 kHz outputs. See:
>> http://www.w1tag.com/Calibrator/Freq_Cal.htm
>>
>> As the article notes, I can provide small quantities of  programmed
>> divider chips. Anyone interested should contact me directly, not
>> through the mail list.
>>
>> John, W1TAG
>> ______________________________________________________________
>> Lowfer mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/lowfer
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Lowfer at mailman.qth.net
>> Post must be less than 50KB total for message plus attachment!
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> Lowfer mailing list
> Home: http://mailman.qth.net/mailman/listinfo/lowfer
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Lowfer at mailman.qth.net
> Post must be less than 50KB total for message plus attachment!
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
>
> Internal Virus Database is out of date.
> Checked by AVG - www.avg.com
> Version: 8.5.455 / Virus Database: 271.1.1/5970 - Release Date: 07/06/13 16:46:00
>