Hi Chris,=0A=0A=A0=A0=A0=A0=A0Thank you so much for=A0providing the incredi=
ble information so that now I can resume the project that I had started ove=
r a year ago!=A0I will=A0go to John's website as you suggest. I use Bob McC=
lures program that=A0he did for Dataq and=A0as you know it is great for tel=
eseismic events!=A0You and Bob have really advanced amateur seismology and =
made it's data so much more meaningful in many ways. I dumped the resistor =
and now use your magnetic damping that=A0works great on an old 3-5 sec. ver=
tical (Times Instrument, Washington, DC).=A0I=A0think AmaSeis is a fabulous=
 program especially it's involvement in school programs. I use that frequen=
tly as well.=A0Thank you=A0once again, Len=A0=A0=A0=0A=0A=0A=0A=A0=0A=0A___=
_____________________________=0AFrom: "chrisatupw@......." =0ATo: psnlist@.............. =0ASent: Monday, February 6, 2012 9:44 PM=
=0ASubject: Re: Robert's circuit=0A=0A=0ALen Polucci lenpolucci@..........
=0ASubject: Robert's circuit=0A=0A=A0 =0A****Hi Chris,=0A=0A=A0=A0=A0=A0You=
 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?=A0 =0A=A0=0AHi Len, =0A=A0=
=0A=A0=A0=A0 I don't know where you read it, but Roberts' article - if you =
read it on John's web site - quotes a 1 Hz geophone extended to 0.1 Hz. And=
 I use x10 on 4.5 Hz ! =0AWith the gain increasing as 1/f^2, long period 1/=
f amplifier noise is the main limitation.=0A=A0=0A****Do you know of ANY ot=
her 'bass boost' analog seismo amp? =0A=A0=A0 =0A=A0=A0=A0 Yes. The Roberts=
 circuit uses parallel amplification. You can do exactly the same job with =
a serial circuit.=0A=A0=0A****I do have Mariotti's EQ PCB unassembled,=A0bu=
t I am wondering what it will do for an=A0SP instrument with a natural peri=
od of 5 sec. Will it give me 25 sec. or 50 possibly?=0A=0A=0A=A0=A0=A0 You =
will have to recalculate the circuit values. Getting 25 seconds should be e=
asy. =0ATrying to go to 50 seconds may run into 1/f noise in my experience,=
 but you could add a 2 pole high pass=A0filter to limit it. The problem doe=
s not usually arise with geophones.=0AI extended the response of a 1.5 to 4=
..5 seconds AS-1 out to 20 seconds without any problems.=A0=0AYou can also d=
o the same job digitally, but you may tend to run out of signal resolution =
/ have noise problems. 100 x 0 =3D 0 !=A0=0AIsn't there digital compensatio=
n provided=A0on Winquake these days ?? There is on AmaSeis, but you have to=
 extract the trace first. =0A=0A=A0=A0=A0 I hope that this helps,=0A=0A=A0=
Hi Chris,


 &n=
bsp;   Thank you so much for providing the incredible i=
nformation so that now I can resume the project that I had started over a y=
ear ago! I will go to John's website as you suggest. I use Bob Mc=
Clures program that he did for Dataq and as you know it is great =
for teleseismic events! You and Bob have really advanced amateur seism=
ology and made it's data so much more meaningful in many ways. I dumped the resistor and now use your magnetic damping t=
hat works great on an old 3-5 sec. vertical (Times Instrument, Washing=
ton, DC). I think AmaSeis is a fabulous program especially it's i=
nvolvement in school programs. I use that frequently as well. Thank yo=
u once again, Len   


 



From:=
 "chrisatupw@......." <chrisatupw@.......>
To: psnlist@.............. 
Sent: Monday, February 6, 2012 9:44=
 PM
Subject: Re: Robert'=
s circuit



Len Polucci lenpolucci@.........<=
BR>Subject: Robert's circuit





 =20
****Hi Chris,


    You say that the=
 Roberts circuit will lower the frequency response x 10 but I thought I rea=
d it was x 4 or 5 for a geophone?  
 
Hi Len, 
 
    I don't know where yo=
u read it, but Roberts' article - if you read it on John's web site - quote=
s a 1 Hz geophone extended to 0.1 Hz. And I use x10 on 4.5 Hz ! 
With the gain increasing as 1/f^2, long =
period 1/f amplifier noise is the main limitation.
 
****Do you know of ANY other 'bass boost=
' analog seismo amp? 
   
    Yes. The Roberts circ=
uit uses parallel amplification. You can do exactly the same job with a ser=
ial circuit.
 
****I do have Mariotti's EQ PCB unassemb=
led, but I am wondering what it will do for an SP instru=
ment with a natural period of 5 sec. Will it give me 25 sec. or 50 possibly=
?

 
    You will have to recalculate the circuit values. Ge=
tting 25 seconds should be easy. 
Trying to go to 50 seconds may run into 1/f noise in my experience, bu=
t you could add a 2 pole high pass filter to limit it. The problem doe=
s not usually arise with geophones.
I extended the response of a 1.5 to 4.5 seconds AS-1 out to 20 seconds=
 without any problems. 
You can also do the same job digitally, but you may tend to run out of=
 signal resolution / have noise problems. 100 x 0 =3D 0 ! 
Isn't there digital compensation provided on Winquake these days =
?? There is on AmaSeis, but you have to extract the trace first. 
 
    I hope that this helps,
 
    Chris Chapman
 
 
 
 
 
 
 
 
 

 



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