Dealing with RFI
I am glad to see that the
problem of RFI
is being considered seriously
(80-BUS News Vol.2, Iss-5) and delighted to learn that we may get an issue
devoted to Amateur Radio. For a starter, may I suggest the following
additional hints on the problem of RFI.
- A metal case to enclose your computer is vital. Mine came from a Radio
Rally, custom-made out of l6swg steel except for a 1/8th aluminium front
panel for #15. This vast box measures 19x14.5x9 inches and leaves a lot
of room for all the expansion boards.
- Multi-core screened cable for keyboard, printer and etc, may be obtained
from Maplins whose catalogue may be read (and purchased) at W.H.Smiths.
Screened cable is a must for stopping RF radiating from lovely aerials
dangling from your computer.
- Ferrite rings (try Ambit International) are effective. All leads (power,
cassete, tv/monitor) emerging from your case to be wound a few times
around the rings, as near as the case as practicable.
- A mains filter (Ambit). This is effecitve both ways. It stops RF-escaping
into the mains where the house wiring acts as a massive aerial
and prevents the mains crud getting at your computer.
- Desperate measure. In Wireless World, September 1983, G3NRW recommends a
150 pF capacitor between the +12 V rail and ground.
- Another desperate measure. Try earthing all your bits (computer proper,
tv/monitor, cassette, etc) at only one point.
RFI appears worst for amateurs at 70 MHz. I achieved a measure of
success for that band with some of the above, plus critical computer/radio
spacing and complete success by executing HALT! ON 144 MHz, I have a few S1
whistles, but presently the lid is off the box and a Hobbit mechanism dangling
on an unscreened lead.
By the way, has anyone made Hisoft
Pascal talk to the Hobbit?
Yours, G. Orford, Bristol.
A Lunatic Writes
Oldsters, who are, like, total vacuum-heads and do not understand the
problems of a young person of today, often get the wrong idea about Waldo
‘D.R.’ Dobbs, who is like me, man. They think that I have no romance in my
soul, which is, like, this incredibly strange thing that I have inside my
body. To them I say: “You are totally incorrect, man”. It is, like, the
total lack of 80-BUS NEWS that causes these sauzzball manifestations, man!
Why, when I see these utterly horrible PLASTIC BOXES, I am, like, totally
overcome with emotion. There are these worthless diseased MOLLUSCS all over
the magazine stands in W.H. Nasties, reading about these disturbingly
repulsive micros, man.
Degenerate reptile, man, I ask you to stop this senseless deprivation of
REAL COMPUTERS that you are, like, doing to me, man.
Monstrously, hazardously, like, yours, man.
Waldo ‘D.R.’ Dobbs [No address given.]