[sci.electronics] Conductive paint question

mann@eskimo.celestial.com (Tom Mann) (06/24/91)

Hello, all.
After a number of years as an inactive 'ham', I'm getting the
urge to get back on the air. In particular, I'm interested in
packet and other 'digital' communications modes. Naturally, this
means having a computer/terminal etc running at the same time as
my transceiver   - and there's the rub. All of my computer/terminal
stuff throws so much RFI garbage that my receiver is nearly useless.
I've already installed toroids on the power leads, cleaned up the
shielding and improved my grounds ... all with marginal success.

What I'm looking for now is the next level of suppression. Do conductive
spray paints work? If so, any particular brands and where can I find
them? Also, are there other possibilities (besides putting the computer
in a screen room)

Thanks for any help
73,
Tom KD9NL/7

durham@w2xo.pgh.pa.us (Jim Durham) (06/25/91)

In article <762@eskimo.celestial.com> mann@eskimo.celestial.com (Tom Mann) writes:
(stuff deleted)
>my transceiver   - and there's the rub. All of my computer/terminal
>stuff throws so much RFI garbage that my receiver is nearly useless.
>I've already installed toroids on the power leads, cleaned up the
>shielding and improved my grounds ... all with marginal success.
>
>What I'm looking for now is the next level of suppression. Do conductive
>spray paints work? If so, any particular brands and where can I find

I suggest this test: Remove the coax from the back of the "rig". Terminate
the coax connector with a plug and 50 ohm resistor. If the RFI is still
there, you need shielding. If not, you probably need to move or
improve your antenna system. 

I moved my dipole farther away from the house. This helped a lot until
the balun failed and I removed it. "Who the heck needs a balun?"
Without starting a "balun vs no-balun" war, removal of the balun
on my dipole made it impossible to operate. That's quite a difference.
Feedline unbalance made the coax, which was much closer to the
noisy computer equipment act like an antenna and pick up the birdies
(Long explanation omitted).
(Balun Haters..cool it..I ended up with a tuner out under the antenna).

I would try this before spray-painting your equipment. Remember the
plastic panels!

Good Luck
Jim Durham  W2XO