Crude coil sheilding paint

[golfnut]

Hi Kev,

What resistances are you seeing with your shield?
Is it for use on a Minelab PI, VLF, or other?



As mine is a vlf DD there is more conductive potting in central area at opposing ends of tis part is ~10k
on perimeter opposing sides ~20k

from centre to gnd pin on plug ~8k

Working well, got 7 small coins earlier, all thumnail or smaller.

Tested on really wet saturated lush short lawn this am and was ok very usable - as mentioned conductive potting is on outside and touches ground/grass everything.


S

[6666]

TV balun cores maybe F29 material.

[6666]

The Litz wire was given a single wrap of plumbers Teflon thread seal tape before winding the coil.

Wow Kev thats a Labor of luv, what process did you use to wind the teflon tape on ?

[6666]

Today just for fun I tried making a crude shielding paint using ordinary wood varnish (not marine varnish) and graphite powder.

I used four teaspoons of varnish and two teaspoons of Pressol brand (made in germany) graphite powder,
mixed it up and painted some snail trails about half inch wide on some printer paper .
It still has to dry properly but some initial testing with the multimeter looks good,
more to report later.

[6666]

Well the varnish has dried and the results appear to be ok.
The long snail trail is roughly 56 inches or 1.4 meters long
and has a resistance of 7.83K AA, it is painted on very thick,
you can alter the resistance by varying the thickness of the paint

BB is 16K I painted this very thin

CC is 800 ohms

EE is 1.5K

[6666]

If you hold the paper up to the light you can see how thinly painted patch BB is
and you can see some brush marks in the snail trail to.

The only real difference I can see between "marine" varnish and ordinary varnish
is marine varnish is supposed to be more flexible and UV resistive
but I can bend the paper over and it does not effect the resistance