The design of the AS1 "black box" is not published, but you can 
design an amplifier that will work in a similar way by setting the 
peak gain at 20 seconds period.  I think Chris Chapman has the most 
experience with amplifier/filter design, so he might be able to 
suggest a circuit for you.  You will be fighting electronic noise to 
get out to 20 seconds and even the AS1 will see 20 second surface 
waves only for the very largest events.  Usually the surface wave 
recorded on an AS1 are in the 12 to 16 second range (very rough estimate!).

Cheers,
John

At 04:03 PM 8/6/2005, you wrote:
>Question,,,   I understand that the 1 sec AS-1 vertical uses an 
>amp-filter which compensates for the signal rolloff so that it works 
>out to about 25 or 30 sec.,,,,   is the schematic for it, or a 
>similar amp-filter available anywhere????   I'd like to adapt it to 
>use with my 4.5 sec vertical!!   I can do it after the fact, using 
>Bob McClures excellent software, but would like to fix the signal 
>before the A/D converter,  to save a few steps!!   Interesting that 
>they give details on building the AS-1 sensor, but not the 
>electronic,,  that I can find??
>   Thanks in advance,
>     Stephen Mortensen
>     PSN Station #55
>     near Pilot Hill Ca.  USA
>     38.828N  120.979W
>
>John or Jan Lahr wrote:
>
>>I've posted some pictures of a 1 Hz vertical seismometer that 
>>leaves a lot to be desired but is relatively quick and easy to 
>>build: http://jclahr.com/science/psn/wooden/ .  If it does a 
>>reasonable job of recording earthquakes I'll post added details.
>>Cheers,
>>John
>__________________________________________________________
>
>Public Seismic Network Mailing List (PSN-L)
>
>To leave this list email PSN-L-REQUEST@.............. with the body 
>of the message (first line only): unsubscribe
>See http://www.seismicnet.com/maillist.html for more information.


__________________________________________________________

Public Seismic Network Mailing List (PSN-L)