In a message dated 2006/11/16, davewilley@............. writes:

>  >      You can get Roberts' type period extension amplifiers from=20
> www.sara.pg.it=20
> >These should enable you to receive teleseismic P and S waves, which you=20
> won't other-
> >wise see with 4.5 Hz geophones. See the note about 4.5 Hz geophones on=20
> Larry's website?
>=20
> Are you referring to the 3 channel amp boards (SEMP30) and equalizer board=
s=20
> (SEQUA10)?=20

       Correct and also the PSU supply?

If so, will the eq board work in front of Larry=E2=80=99s 4 channel 16-bit p=
reamp=20
board? =20
> (Which I already have.)   I could hang this EQ board on the unused 4th=20
> channel for teleseismic work.  That would be a neat setup if they play tog=
ether.

       I don't have one of Larry's boards to compare, but from the circuit=20
you would likely have to break the link / rewire the connection between the=20
first and second opamps and wire in earth and supply rails for the SEQUA10.=20=
They=20
are a special type of LF boost amplifier. You usually fit a SEQUA10 between=20=
the=20
first low noise opamp and the low pass filter to get optimum performance /=20
lowest noise.=20

> >       Are you going to solder the metal film damping resistors and any R=
F=20
> capacitors across the=20
> >geophone terminals? Remember to check the input resistance of your=20
> amplifier and use it in the=20
> >calculation for the damping resistor.=20
>=20
> I=E2=80=99m assuming since I bought everything from Larry several years ag=
o as a =E2=80=9C
> turn-key=E2=80=9D system that this has been all done. It=E2=80=99s been pl=
aying fine on the=20
> back concrete patio for 1.5 years. Now it=E2=80=99s time to wrap up the te=
st phase of=20
> this experiment and get it in the ground away from the house and the roads=
.

       I suggest that you cross check EVERYTHING -  BEFORE you seal / bury=20
ANYTHING!

       I start to pick up fast traffic on the main road at about 1 km.

> >   How about protection diodes? Do you get severe thunder storms in your=20
> area? Is the soil=20
> >sandy / rocky / dry? It is over many areas in the USA and this can give=20
> problems with local=20
> >lightning. Your house and system may all be exposed many feet above the=20
> local 'Earth'=20
> >conducting plane.
>=20
>=20
> This I=E2=80=99ll have to check on.  I don=E2=80=99t think there are any c=
lamping diodes. I=E2=80=99
> ll put some a silicon version of a 1N914 diode=20
> =E2=80=9Cnose-to-tail=E2=80=9D across the cables center conductors and coa=
x shield/case=20
> ground.  Good thought.

       I would use fast high current rectifiers to give them a chance of=20
outlasting the first thunderstorm. Having to dig up failed electronics does=20=
not=20
improve your mood. Check with the Ham Radio operators on lightning protectio=
n=20
for your area? How about ferrite rings? I use them on the base unit of a=20
cordless phone to ~protect it from transients. That was after the phone had=20=
failed=20
twice and after the phone company had fitted their own discharge tube=20
protection.....=20

>  >      The outer case must be hermetically sealed and the cable end also=20
> sealed. Some cable=20
> >types allow air to pass through between the wires when under pressure. Al=
so=20
> seal the amplifier=20
> >end of the cable. I suggest that you add a bag of inert silica gel drying=
=20
> crystals inside the case=20
> > to absorb any moisture.=20
>=20
> I=E2=80=99ll check with Belden Cable about Plenum grade RG-174 and see how=
=20
> impervious to water vapor it is.
      =20
       I don't use coax cable. I use six core screened cable which has an=20
external braided copper screen - this one cable services the three geophones=
 and=20
the screen is connected to the geophone cases. CAT5 cable does not provide=20
good enough rejection, even if you can get it screened. The cable supplied f=
or=20
geophones has steel reinforcing but no screen - sigh!=20
      =20
       Regards,

       Chris Chapman
In a me=
ssage dated 2006/11/16, davewilley@............. writes:



 >    &n=
bsp; You can get Roberts' type period extension amplifiers from www.sara.pg.=
it 

>These should enable you to receive teleseismic P and S waves, which you=20=
won't other-

>wise see with 4.5 Hz geophones. See the note about 4.5 Hz geophones on L=
arry's website?



Are you referring to the 3 channel amp boards (SEMP30) and equalizer boards=20=
(SEQUA10)? 




       Correct and also the PSU supply?



If so, will the eq board work in front of Larry=E2=80=99s 4 channel 16-bit p=
reamp board?  

(Which I already have.) &=
nbsp; I could hang this EQ board on the unused 4th channel for teleseismic w=
ork.  That would be a neat setup if they play together.



       I don't have one of Larry's boards to=20=
compare, but from the circuit you would likely have to break the link / rewi=
re the connection between the first and second opamps and wire in earth and=20=
supply rails for the SEQUA10. They are a special type of LF boost amplifier.=
 You usually fit a SEQUA10 between the first low noise opamp and the low pas=
s filter to get optimum performance / lowest noise. 



>    &nb=
sp;  Are you going to solder the metal film damping resistors and any R=
F capacitors across the 

>geophone terminals? Remember to check the input resistance of your ampli=
fier and use it in the 

>calculation for the damping resistor. 



I=E2=80=99m assuming since I bought everything from Larry several years ago=20=
as a =E2=80=9Cturn-key=E2=80=9D system that this has been all done. It=E2=
=80=99s been playing fine on the back concrete patio for 1.5 years. Now it=
=E2=80=99s time to wrap up the test phase of this experiment and get it in t=
he ground away from the house and the roads.




       I suggest that you cross check EVERYTH=
ING -  BEFORE you seal / bury ANYTHING!



       I start to pick up fast traffic on the=20=
main road at about 1 km.



>   How about prot=
ection diodes? Do you get severe thunder storms in your area? Is the soil 
>sandy / rocky / dry? It is over many areas in the USA and this can give=20=
problems with local 

>lightning. Your house and system may all be exposed many feet above the=20=
local 'Earth' 

>conducting plane.





This I=E2=80=99ll have to check on.  I don=E2=80=99t think there are an=
y clamping diodes. I=E2=80=99ll put some a silicon version of a 1N914 diode=20=


=E2=80=9Cnose-to-tail=E2=80=9D across the cables center conductors and coax=20=
shield/case ground.  Good thought.




       I would use fast high current rectifie=
rs to give them a chance of outlasting the first thunderstorm. Having to dig=
 up failed electronics does not improve your mood. Check with the Ham Radio=20=
operators on lightning protection for your area? How about ferrite rings? I=20=
use them on the base unit of a cordless phone to ~protect it from transients=
.. That was after the phone had failed twice and after the phone company had=20=
fitted their own discharge tube protection..... 



 >    &=
nbsp; The outer case must be hermetically sealed and the cable end also seal=
ed. Some cable 

>types allow air to pass through between the wires when under pressure. A=
lso seal the amplifier 

>end of the cable. I suggest that you add a bag of inert silica gel dryin=
g crystals inside the case 

> to absorb any moisture. 



I=E2=80=99ll check with Belden Cable about Plenum grade RG-174 and see how i=
mpervious to water vapor it is.


       

       I don't use coax cable. I use six core=20=
screened cable which has an external braided copper screen - this one cable=20=
services the three geophones and the screen is connected to the geophone cas=
es. CAT5 cable does not provide good enough rejection, even if you can get i=
t screened. The cable supplied for geophones has steel reinforcing but no sc=
reen - sigh! 

       

       Regards,



       Chris Chapman