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VK5QX > CURE 04.05.03 19:48l 72 Lines 2286 Bytes #999 (0) @ WW
BID : 010617VK5QX
Read: DB0FHN GUEST
Subj: Re: RF noise cure trick !
Path: DB0FHN<DB0ZWI<DB0HOT<OK0PKL<OK0PPL<RZ6HXA<SP7MGD<IK6PYS<7M3TJZ<HA3PG<
VK3AVE<VK5UJ<VK5BRC<VK5SPG<VK5LZ
Sent: 030428/0747Z @:VK5LZ.#ADL.#SA.AUS.OC #:62292 [Elizabeth] $:010617VK5QX
From: VK5QX@VK5LZ.#ADL.#SA.AUS.OC
To : CURE@WW
POWER SUPPLIES AND RFI
Andy G0FTD commented on ways of overcoming RF noise and made suggestions
as regards connections to a computer and the use of the "Hamcom"
interface.
For some time now I have been meaning to make up one of these interfaces
and have had the PC board and parts tucked away. However I still have not
found time to out it all together.
It seems to me that I remember the circuit for the board that I have put
aside, as having opto-couplers for connection with the other devices.
It is my guess that use of a system along these lines would go a long way
towards overcoming noise problems such as Andy has been experiencing.
I will make some further enquiries of a friend of mine who I believe is
well versed on such matters, particularly as regards the "Hamcom"
interface approach.
Needless to say, I will report on any useful findings.
I also would suggest that good shielding of the various components of a
system would go quite some way towards obviating a fair deal of noise.
HOWEVER. I was very puzzled at Andy's comments in reply to G0ANS, as
follows:-
__________
" Maybe so. But here I suffer badly. No doubt you are using a desktop
which usually contains a linear psu.
I use laptops here, and they usually come with a small switched mode psu
which generates oodles of rf trash.
If I run the laptop on it's battery then all is fine, thus proving it's
the smpsu.
No doubt this is to allow a much smaller physical size than a linear
psu and transformer. Not usually a problem for "normal" users but for
radio people it's not so good.
__________
I would argue that Andy may well be incorrect in his understanding as
regards the various power supply units in general use.
It was my belief that pretty well ALL computers, namely of the PC desktop
and laptop types, use switched mode power supplies.
A quick enquiry to the "experts" at my local high quality computer service
confirms my belief and suspicions.
YES. ALL the PC's that they know of, laptop and desktop, DO USE SWITCHED
MODE PSU's.
I imagine that it is the same with PC's in most parts of the world. e.g.
Europe, USA, Asia, SE Asia Oceania etc.
Regards,
Ian
__________
73 de Ian, VK5QX
@ VK5LZ.#ADL.#SA.AUS.OC
28 Apr 2003
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