PI coil DD

[Anonymous]

I know how to balance and tune DD VLF. On the PI how do you tune the coil? VLF you use what ever the transmitting frequency. White's for example GM series, 50khz is the frequency. On the PI you don't want the coils to oscillate. So the question is how do you tune the coils or DD to any particular PI? I have read the post for past years on this site and Carl's site on DD construction, but nothing on tuning PI coil like SD series does. Any help would be appreicated.
Rick S

 

[Anonymous]

Rick,
I tried to e-mail you twice. Both times my message came back to me! Please send me your e-mail address to devilbat@bellsouth.net Dave. * * *

 

[Anonymous]

Dave,
Sorry for the mistake on my email address. It is rks6636@netzero.net. I tried your email and I couldn't get though to you. Try again is all I can say.. Thanks for your persistance.
Rick S

 

[Anonymous]

Hi Rick,
An easy method that I use, is to look at the output of the wideband amp in the receiver with a scope. With a mono coil you will see a step up for the duration of the TX pulse, followed by a short step down and then the RX returns to the zero level where you do the sampling. Using a DD coil you simply adjust the overlap until the step caused by the TX pulse disappears and the RX is showing zero level. i.e. the TX is inducing equal positive and negative signals in the RX. When you get this far wave a piece of non-ferrous metal over the coil and observe the response at the wide band amp output, both during the TX on period as well as the TX off. Next try a piece of ferrous metal and observe the difference. That should give you something to think about <IMG SRC="/forums/images/smile.gif" BORDER=0 ALT="">
Eric.

 

[Anonymous]

Eric,
Thanks for the reply.
Rick S