Fwd: Tuesday Tech Net

[Dave]

    A simple SDR(crystal osc  and a 74hc74 plus FST bus switch + 2 
opamps) like a softrock and one of the free SDR programs should do it. 
If the signal is not very weak, you might get by with connecting an 
antenna to one of the inputs of your sound card.  They have a recording 
option plus DSP processing.

Dave - WB6DHW
<http://wb6dhw.com>

On 6/8/2015 9:05 PM, Nan and Sandy Sanders wrote:
>
>> From Hal WB3KDU
>>
>>
>>
>> Tuesday Tech*Net   8PM AMRAD repeater (21/81) and Echolink.
>> ======================================================
>>
>> Built in 1927 SAQ is VLF station operating on 17.2Khz generating its 
>> signal with a
>> mechanical Alexandrian generator.  AMRAD members have been DXing SAQ for
>> a number of years and some have been the repent of its special QSL 
>> which can
>> only be obtained by copying accurately most of its transmission.  SAQ 
>> operates
>> twice a year, Christmas Eve and the first Sunday of July which is 
>> rapidly approaching.
>>
>> There are practical problems to receiving SAQ.  First you need a 
>> receiver that
>> covers 17.2Khz with adequate sensitivity.   Next, there is a large 
>> amount of
>> noise to contend with - simple radio static, weather and man-made.  This
>> requires a very narrow filter, usually around 50hz to limit the 
>> noise. If the signal
>> strength is not strong (this happens from time to time) you may be 
>> unable to
>> hear the transmission or you may discern it but be unable to copy it 
>> because
>> it is so weak.
>>
>> Attempts have been made to record and digitally process the signal 
>> attempting
>> to apply DSP techniques to recover the station's audio.  This hasn't 
>> proved
>> successful in the past due to various technical issues. However, it 
>> might be worth
>> trying this route if the signal is too weak to copy by ear.
>>
>> It also might be possible to have several stations record whatever 
>> audio they can
>> and then combine a number of recordings made by receiver in different 
>> parts
>> of the country.  This could be done processing just the audio. A more 
>> ambitious
>> idea is to record the RF baseband and combine and process it. It 
>> would require phase
>> references to be recorded along with the signal.  It would involve some
>> tricky DSP code too.
>>
>> http://en.wikipedia.org/wiki/Varberg_Radio_Station
>>
>> Besides SAQ we will have our usual exchange on digital modes and SDR.
>>
>> Should we sponsor a "Learn Verilog" project of some kind?  This is one
>> of the popular languages for programming an FPGA.
>>
>> Last week we had a couple of station check in so attendance on the net,
>> while still small is definitely up.
>>
>> ======================================================
>> Tech*Net meets Tuesday 8PM on the AMRAD repeater (21/81) and
>> via Echolink on the W4CIA conference point.  WB5MMD is conference
>> coordinator and net control.
>>
>
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