SD2000 front end mod #3

[Woody.au]

Here is another modification that improved the detector both in depth and sensitivity. One the main circuit board near the input wire from the coil connector is an small wound choke. I noticed that by shorting out the choke with a small blob of solder the sensitivity increased by around 10% on small target response, a similar increase in depth on large targets would also be expected.

The choke is an "attempt" at stopping radio interference but it is next to useless and all it does is add series resistance that causes signal loss and the series inductance slows down the receive signal. If you need radio suppression install a ferrite bead with 5 turns of wire and this will knock out most of the high frequency radio interference but not impede detector operation.

I have attached a pic showing the choke, notice the small solder blob in front of it shorting it out.

[Elie]

I have been looking at the mods which you have posted, and am wondering how practical it would be to install switches in the case for some of them. For example, for this, switch the shorting on and off, and for the frequency mod, use a switch to select from several crystals of different frequencies.

[Woody.au]

You could use a switch if you used shielded cable. To much wire on the input inside the detector may pick up unwanted electronic noise.