[Lowfer] WOLF Sampling Rate Cal

[lloyd chastant]

Nice John...oughta help  as the season starts
Lloyd

On Thu, Aug 7, 2008 at 4:52 PM, John Andrews <w1tag at w1tag.com> wrote:
> All,
>
> Something to do while on vacation stuck in the woods with wet weather...<g>
>
> I have posted a new article on an easy way to find your sound card's actual
> sampling rate at:
> http://www.w1tag.com/WOLFSamp.htm
>
> Here's the idea. Several of us have suggested that an AM receiver tuned to
> Loran-C on 100 kHz provides an excellent spectrum of accurate audio
> frequencies which can be used to calibrate sampling rates. The problem is
> that your rate may be SO far off that you wind up using the wrong Loran
> harmonic. My approach is now to do the cal in two steps: an approximation
> using a very low audio frequency, and then a fine-tuning using one of the
> harmonics. Any comments on the article would be appreciated.
>
> For those who may be unconvinced about the need to nail the sampling rate
> for WOLF, here's an example:
>
> My laptop has an actual sampling rate of 11098.786 Hz instead of the nominal
> 11025 Hz. Here's part of a WOLF run on 185.800 kHz with a weak signal, using
> the correct rate:
> 2008-08-05 19:16:08 >WOLF  -r 11098.79 -f 700.170 -t 1 -d 16 -w 0.0000
> t:  24 f: 0.003 a: 0.0 dp: 60.0 ci:12 cj:120 TAG RAYMOND ME  -
> t:  48 f: 0.001 a: 0.2 dp: 60.8 ci:12 cj:120 TAG RAYMOND ME  -
> t:  96 f: 0.001 a: 0.2 dp: 61.2 ci:12 cj:120 TAG RAYMOND ME  -
> t: 192 f: 0.000 pm:18.06 jm:720 q:  3.5  2.6 TAG RAYMOND ME  -
>
> Now, if I change the rate to the nominal 11025 Hz, and lower the receiver
> tuning to 185.795 kHz to get the signal back in the passband, the following
> results:
> 2008-08-05 18:46:26 >WOLF  -r 11025 -f 700.170 -t 1 -d 16 -w 0.0000
> t:  24 f: 0.312 a:-0.9 dp: 63.9 ci: 8 cj:  0 IUGISRYOZPVHPRF ?
> t:  48 f: 0.312 a:-0.9 dp: 63.3 ci: 4 cj:324 B33I5SPSXY45J4J ?
> t:  96 f: 0.312 a:-0.9 dp: 62.3 ci: 7 cj:325 IYAHR4IM/2KEHH5 -
> t: 192 f: 0.312 pm:1.974 jm:314 q:-12.3 -8.5 XMNE*OAEHZMCPQO ?
> t: 288 f: 0.312 pm:2.533 jm:319 q:-11.5 -8.4 D*CVQ07UFR4FYH* ?
> t: 384 f: 0.312 pm:2.590 jm:319 q:-11.2 -6.1 TWU8DTIFJNF/H9H -
> t: 480 f: 0.312 pm:2.617 jm:319 q:-10.3 -7.8 D*E1YG1QUBSAVZU ?
> t: 576 f: 0.312 pm:3.030 jm:319 q: -9.7 -8.0 H YKU7UJGKQYTSB ?
> t: 672 f: 0.312 pm:3.054 jm:319 q: -9.0 -7.8 .KRK0J *KTMVL4H ?
> t: 768 f: 0.312 pm:3.091 jm:319 q: -8.6 -7.6 U D6FLDZ6X15E/8 ?
> t: 864 f: 0.312 pm:3.221 jm:361 q: -8.2 -7.6 CLCAUBP48BXX1HG ?
> t: 960 f: 0.312 pm:3.478 jm:341 q: -7.5 -7.8 FUCV9734SEY7UP4 ?
> t:1056 f: 0.312 pm:3.574 jm:341 q: -7.1 -8.3 34H*M7GW. /K57X ?
> t:1152 f: 0.312 pm:3.576 jm:341 q: -6.7 -8.1 /X0358UEJ9GCK30 ?
> t:1248 f: 0.312 pm:4.479 jm:386 q: -5.6 -6.0 91XJY0USP7M3UT* -
> t:1344 f: 0.312 pm:4.518 jm:386 q: -5.2 -9.0 UGENBXXY3SQ2OSM ?
> t:1440 f: 0.312 pm:4.554 jm:386 q: -4.9 -8.1 LCFT*NBAM LAKU3 ?
> t:1536 f: 0.312 pm:4.585 jm:386 q: -4.9 -6.1 QJU9MQ.RQNNBX6R -
> t:1632 f: 0.312 pm:4.679 jm:386 q: -4.7 -7.5 EFYE2WHVR/UU5FS ?
>
> I.E., same signal, and it never decodes! The rapidly increasing "jm" values
> show the shifting of the framing, and the "q" values never get above the
> magic -3 or so that it takes to decode a signal.
>
> John Andrews, W1TAG
>
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