On 2/7/2012 12:11 AM, Larry Cochrane wrote:
> Hi Everyone,
>
> Last year I incorporated Bob McClure's inverse filter into WinQuake 
> and WinSDR. See 
> http://sites.google.com/site/bobmcclure90/inversefilter for more 
> information on Bob's filter. You can try the filter in WinQuake if you 
> install this beta release:
>
> 32-Bit: http://www.seismicnet.com/software/wq323b_32bit.exe
> 64-Bit: http://www.seismicnet.com/software/wq323b_64bit.exe
>
> And if you have a PSN ADC board you can use the filter in real-time by 
> using the current WinSDR beta release available here:
> http://www.seismicnet.com/winsdr/winsdr4x.html.
>
> Please Note! In WinQuake the pendulum frequency is entered in seconds 
> so a 4.5 Hz geophone would be entered as 0.222. In WinSDR the 
> frequency is entered in Hertz, so a 20 second Lehman would be entered 
> as .05. I should normalize this, I'm just not sure if I should change 
> WinQuake or WinSDR...
>
> In WinQuake the inverse filter can be found in the Time-Domain Filter 
> dialog box and in WinSDR the Channel Settings -> Integrate / Filter 
> tab dialog box.
>
> A few days ago there were some emails on the list regarding what 
> numbers to use for the pendulum frequency and high-pass filter. The 
> pendulum frequency is the undamped period of your sensor. If you have 
> a geophone this would normally be 4.5 Hz (WinSDR, .222 in WinQuake) or 
> maybe 1 if you gave a 1 Hz geophone or AS1 type of sensor. This number 
> sets where the filter starts to boost the lower frequencies to 
> compensate for the drop off of sensitivity below the period of the 
> sensor. The high-pass filter sets how much you want to extend the 
> period of the sensor. It should be set to some number below the period 
> of the sensor. Depending on the sensor and electronics, mainly the 
> first op-amp, you might be able to extend the period by one decade.
>
> Before adding the software filter to WinSDR and WinQuake I played 
> around with the Robert's circuit. My results regarding using this 
> filter, both in hardware and software, can be found here: 
> http://www.seismicnet.com/epf/
>
> Below is some information on the event files on my system that use 
> this filter in WinSDR:
>
> *.LCSV1.psn - This is a volume set from a Kinemetrics SV-1 5-Second 
> intermediate-period vertical sensor. The LCZS1 channel is the raw data 
> from the sensor. The LCZS2 channel has been period expended to 25 
> seconds (.04Hz) and then a 2 pole 2 Hz low-pass filter is applied to 
> the data. This helicoder plot (updated every 5 min) 
> http://www.seismicnet.com/quakes/images/lczs2.png shows the 24 hour 
> graph from this channel. Teleseismic events show up much better on the 
> inverse filter channel then the raw data channel.
>
> *.LC45v.psn - This is a volume set from a horizontal 4.5 Hz geophone. 
> The LCEG1 channel is the raw data from the sensor and the LCEG2 
> channel has been period extended to 5 seconds or .2 Hz. This PSN event 
> file
> http://www.seismicnet.com/quakes/1201/120126.021845.lc45v.psn is a 
> good example of an earthquake recorded from this sensor.
>
> I would like to thank Bob McClure for supplying the Visual Basic code 
> so I could add this feature to my programs.
>
> Regards,
> Larry Cochrane
> Webtronics
>
> On 2/6/2012 5:20 PM, Len Polucci wrote:
>>
>> Hi Chris,
>> reading your response to David regarding Geoffreys inquiry about a 
>> damping resistor,
>> you say that the Roberts circuit will lower the frequency response x 
>> 10 but I thought
>> I read it was x 4 or 5 for a geophone? Do you know of ANY other 'bass 
>> boost' analog
>> seismo amp? I do have Mariotti's EQ PCB unassembled,but I am 
>> wondering what it will
>> do for an SP instrument with a natural period of 5 sec. Will it give 
>> me 25 sec. or 50
>> possibly?*/
>> /*
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It is certainly a step up, Larry and Bob. It allows new areas of 
display. But how do I access epf files!
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