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Feed forward

A

Anonymous

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Hi Eric,
I'm not sure if I should post this here or on your forum as most of the activity seems to have moved back to there.
You recently said you were a proponent of the feed forward method. Can you expand on why that is? Is it better to have a higher spec op amp in the front end and then amplify with high gain in a 2nd stage than to have a large signal gain in one front end amp? You are obviously doing something right with the kind of reports you are getting on the deepstar. The front end circuit you posted and the Goldpic kit both seem to get about the same range which is about half of what your detectors seem to get.
Thanks,
Charles
 
Hi Charles,
Post here by all means. It does seem to have gone a bit quiet but that is how it goes. Some one will eventually raise a subject that will fuel a long debate and things will liven up again. Still it
 
Eric,
Thanks for yet another excellent posting. Your comments have directly addressed my current musings.
My latest Tx coil effort is wound with 7 x 0.1mm PVC hook-up wire. I paralleled three strands of this in a vertical sense and edge-wound a section of ten turns. I have stacked these sections with approx. 1mm+ spacing and series-connected each wire through the sections. Three sections provide around 340mh and four sections measured 750mh (Not happy with this eems high - and will have to repeat)
The Rdc is low - around 0.6ohm. I like the results, though I have yet to finalise an Rx coil.
The Tx coil looks quite fast and what has impressed me is that critical damping is achieved with 660ohms - it looks between 6-10msecs.
I have been thinking a lot upon an Rx coil. A paragraph by Ian Hickman (page 27, Jan 98, WE) impresses me with a statement that a balanced-input is less susceptable to noise.
I am hung-up on matching. Topical inputs around an inverting amplifier provide a relatively low impedance to the coil. Can uou see/have you experienced efforts following his fig.10 - with balanced source-followers?? Comment would be much appreciated.
g
 
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