[PCR-1000] packet output

Wed, 29 Jan 2003 21:30:09 -0000

Hi Matty,

..... except that the argument doesn't seem to hold up in the real world :)
!!

Others recent comments have left me doubting my sanity.  Although clearly
the packet output should be "better" (greater bandwidth) than speaker output
for these digital signals, they are only 2400 bps modulated signals after
all, so I would have thought the speaker output should be easily "workable"
for this purpose.

I would think the audio stages should be wide enough to handle recording for
11 kb but there must be some other stuff going on here.  I can't imagine
there is de-emphasis or any other kind of audio shaping happening in this
kind of receiver - its not meant for audiophiles after all - there are no
hardware or software "tone" controls.  Are these audio stages screwing phase
response across the audio band - group delay ?   I suppose it could be
somethign to do with driving the speaker output into high impedance load
rather than 8ohms (any audio engineers like to comment ?).  Would a low
value resistor make any difference or is that what the software switch for
speaker/line does anyway?

I am at a loss to understand the dramatic differences reported - I guess
levels have been set similarly in both cases ?  After a mighty good
whipping, its back to the draining board for me :) (is that just a British
thing?)

I have a PCR100 (ie with no packet output) currently dedicated to satellite
stuff - time to experiment with that and possibly reconsider equipment usage
I suppose.  I am particularly impressed at the report of horizon to horizon
coverage.  Now that really would be worth having.

thanks for your kind comments anyway
bw

----- Original Message -----
From: "Robbins, Matty" <[email protected]>
To: <[email protected]>
Sent: Wednesday, January 29, 2003 9:54 AM
Subject: RE: [PCR-1000] packet output

> Thanks for the info
> great explanation
>
> -----Original Message-----
> From: Brian Winter [mailto:[email protected]]
> Sent: Monday, January 27, 2003 2:27 PM
> To: [email protected]
> Subject: Re: [PCR-1000] packet output
>
>
> > 1. Should i connect to the packet output for recording the Satellites?
>
> either should work well enough. try both.  the important thing to note is
> that, whichever you use you don't overdrive the analog input to your audio
> card or later stages so that clipping distorts the audio before you sample
> it and save digital representation to file.
>
> as you want to use 11k sampling rate the highest freq component that you
> will record is half that (5.5khz says nyquist).  in a non-scientific way
> think of the sound quality you get from your telephone (highest freq
3.4khz)
> and from your hi-fi (for simplicty limited by your hearing - around 10k or
> so if youre young and havn't blown your eardrums away with Black Sabbath
or
> Eminem)    Now imagine what your pcr100/1000 sounds like when you connect
> speaker outpu into your sound card "Line In" and play a wide FM broadcast
> station back through decent speakers - much better than your telephone
right
> ?    So this setup should be all you need to satisfy 11 khz sampling rate
as
> long as the signal is 1) loud enough to satisfy the sampler  2)not
corrupted
> by overdriving the sampler.  I reckon theres more mileage in getting th
> elevels right than worrying about which output gives best response.
>
>
>
> > 2. is the a program that converts from different audio formats?
yesterday
> i
> > finally got a good signal from NOAA17 but  i recorded it with the
default
> > talkpcr audio CODEC in order to decode it i need to convert it to PMC
> 11Khz
> > mono are there any conversion programs for this?
>
> Path of least effort: wait 'til tomorrow and try again.  i suspect the
> default you used is a windows (not talkpcr) defalt.   if the sampling rate
> is too slow on the original recording you cant properly recreate the bits
> that are missing to give you a 11k sampled file.  If its slightly faster
(eg
> to x2) your 11k file will be full of sampling errors, resulting in noisy
> pictures.  If you have used a compression technique (codec) you will also
> introduce noise in the decompress/compress process.  Think of it like old
> fashioned analog audio tape recorders. Best you record the original than
> re-record a mates recording (even with Dolby compreesion techniques).
>
> hope this is helpful
> bw
>
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