Cave Man is also back on the scene !! Just mention Pipe Dreamers (remember
the Band) plus Moon pull at Perigee and he is OFF.
others are sensitive when Windows is mentioned causing sporadic unreast,
not
to mention CW
Back to normal soon when the Moon goes Apogee.
To avoid conflict the following words should be avoided, Windows, CW,
Opera, Panto, Pipe Dreamer, Sense of humour.
de kev
----- Original Message -----
From: "Graham" <[email protected]>
To: <[email protected]>
Sent: Sunday, May 06, 2012 9:50 PM
Subject: Re: LF: Generating 8970 Hz carrier with Spectrum Lab ?
From the BBC news ,
''The phenomenon, known as a perigee full moon, means the Moon appears up
to
14% bigger and 30% brighter than when it is furthest from the planet.''
They go on to state :-
''Scientists have dismissed the idea the perigee could cause strange
behaviour - like lycanthropy - or natural disasters.''
As yet another 'Dog fight' breaks out, Obviously are not monitoring
Black sheep then ?
G..
--------------------------------------------------
From: "mal hamilton" <[email protected]>
Sent: Sunday, May 06, 2012 6:27 PM
To: <[email protected]>
Subject: Re: LF: Generating 8970 Hz carrier with Spectrum Lab ?
> Does Pipe Dreamer ring a bell !!!!
>
> ----- Original Message -----
> From: "Roger Lapthorn" <[email protected]>
> To: <[email protected]>
> Sent: Sunday, May 06, 2012 4:58 PM
> Subject: Re: LF: Generating 8970 Hz carrier with Spectrum Lab ?
>
>
> Mal, you are talking rubbish again.
>
> Without frequency locking in SL and very very narrow bandwidths
possible,
> there is no way I would have been able to copy the EU VLF amateurs last
> year
> in this semi-urban noise pool. Not many of us live in v.quiet rural
areas.
> You may be able to copy VLF DX at QRSS3 but most of us can not at any
> distance.
>
> Regarding VLF activity in the UK, I continue to do earth-mode tests
> although
> I have been distracted to NLOS optical comms of late. Not sure if G3XIZ
is
> planning further radiated tests. Several stations including G3ZJO
monitor
> EU
> VLF tests regularly.
>
> 73s
> Roger G3XBM
>
>
> -- Via my 2.4GHz transceiver --
>
> On 6 May 2012, at 17:26, "mal hamilton" <[email protected]> wrote:
>
>> Andy
>> All these complications to accommodate the Appliance Operator who
cannot
>> read MORSE or watch QRSS on a screen.
>> g3kev
>>
>> ----- Original Message -----
>> From: "Andy Talbot" <[email protected]>
>> To: <[email protected]>
>> Sent: Sunday, May 06, 2012 4:14 PM
>> Subject: Re: LF: Generating 8970 Hz carrier with Spectrum Lab ?
>>
>>
>> The problem with USB slippage comes about because of the Isochronos
>> mode (yes, that is spelt correctly, it is not IsoSYNchronous) -
>> where it sends puts real time rapid data transfer as more important
>> than lost samples and sends samples in real time without checking
>> This is probably just what music and audio people want, but it screws
>> up using USB based sound cards as precision timed A/D converters.
>> USB does have other modes with full error checking, albeit with some
>> latency, but the latency wouldn't matter here.
>>
>> While it would be a pretty simple task these days to build an external
>> A/D converter and interface to USB properly, the resulting data stream
>> would need a custom driver written, then all the decoding software we
>> know and love would have to be modified to work with this custom
>> interface. Then someone else would come along with another design
>> and we'd have to start again.
>>
>> I suspect it is going to be absolutely impossible to use the soundcard
>> as a guaranteed glitch free A/D converter.
>>
>> Joe Taylor K1JT in the WSJT suite has a dead simple pragmatic
>> solution. Instead of trying to read the data in real time, all the
>> WSJT modes read the entire transmisisons' worth of data to a .WAV
>> file, and the software works on that. While WSJT uses the soundcard
>> to do the job it will suffer from the same slippages (which don't
>> matter' of course' for those modes) the idea of an intermediate buffer
>> file would help.
>>
>> A custom A/D could send its data in its own format via USB, or serial
>> COM port or whatever, to software that saves blocks in the format of a
>> .WAV file. Then the decoding software works on the resulting .WAV
>> files. It won't be real time any more, but none of these slow data
>> modes actually are that real time. The speed of reading and switching
>> (using a pair of ping-pong files if necessary) can make the whole
>> system pseudo real time - in the same way as WSJT appears to run
>> continuously.
>>
>> Now, any A/D design can be used provided the results are written to a
>> .WAV file. Wav files can have any sample rate (so long as it is an
>> integer number of Hz) and do not have to be restricted to 48000, 11025
>> or whatever, so custom LF receivers using quite slow A/D converters
>> and low sample rates are now valid.
>>
>> Just throwing that idea into the ring..
>>
>> Andy
>> www.g4jnt.com
>>
>>
>> On 6 May 2012 16:14, James Moritz <[email protected]>
>> wrote:
>>> Dear Andy, LF Group,
>>>
>>> A bit late, but never mind...
>>>
>>>> Has anyone tried using an external USB soundcard with a separate
>>>> locked clock? Most work from a 12MHz crystal which can be replaces
>>>> with a GPS locked source without too much effort. But I can't help
>>>> wondering if there will be subsequent USB synchronisation glitches
>>>> upsetting the input sampling.
>>>
>>>
>>>
>>> I can confirm that glitches do occur with USB sound cards. I have
found
>> this
>>> to be a perennial problem trying to use such a sound card with the
> laptops
>> I
>>> have available. For 9kHz reception, the relatively rapid temperature
>>> fluctuations inside the laptop, and resulting cyclic drift of the
> internal
>>> soundcard sampling frequency interfere with the operation of DL4YHF's
>>> ingenious sample rate correction facility in SpecLab, making the
>>> internal
>>> sound card unusable for FFT resolution below a few millihertz. I
>>> found
>>> my
>>> USB soundcard solved this particular problem quite well, but
introduced
>>> glitches that made achieving FFT resolution in the uHz range
>>> impractical.
>>>
>>> Watching Speclab's sample rate correction "history" window, the USB
card
>>> sample rate typically starts off a few hundred ppm low (much larger
than
>> the
>>> actual clock frequency error), but remaining stable to within a few
ppm,
>> but
>>> then at unpredictable intervals abrupt jumps in sample rate of a
similar
>>> order of magnitude occur, with corresponding "blips" on the
spectrogram
>>> traces. The reported sample rate is always lower than the nominal
value,
>>> suggesting that some samples are being periodically discarded
>>> somehow.
>>>
>>> The sound card uses a single-chip integrated audio codec and USB
>>> transceiver, using a single 12MHz crystal. I can't really believe in
>>> "USB
>>> slippage" in the hardware - surely losing some of the data would
either
> be
>>> handled quietly by the USB error checking, or result in endless error
>>> messages. The same sound card seems to work in a glitch-free way when
>>> plugged into my desktop machine, where the reported sample rate error
is
>> in
>>> line with the error in the crystal frequency.
>>>
>>> Cheers, Jim Moritz
>>> 73 de M0BMU
>>>
>>
>>
>>
>
>
>
