[CQ-Contest] More on the UPS RFI

Ken N4UK ramirezk at emi.com
Wed Apr 23 09:01:06 EDT 1997

     Some questions that need to be answered regarding the 
"birdie" problem I'm having with a recently acquired UPS system. 
The UPS system I'm using is an APC brand UPS. Others using APC 
brand UPS systems have reported no birdies heard on HF.
  I'm hearing the birdies on the VHF weak signal bands where 
even the tiniest of birdies can be heard in a good receiving 
system. I suppose these birdies may be present on HF but are 
below the ambient band noise. Try listening on 10m at night and 
see if they are heard. According to Zoli (see below) there is a 
good reason why they are every 10KCs. If it is true that it will 
be almost impossible to get rid of the birdies then the wife 
will probably acquire a new UPS and I'll go without!
   73 Ken N4UK

<---- Begin Forwarded Message ---->
From: z.pitman at libertel.nl
Subject: UPS
To: ramirezk at emi.com

Hi Ken,

Sorry to say, but I wouldn't bet on your success. The UPS has an 
(app. 10 KHz) and its signal is used like a switch controller. 
radiates itself and the signals getting out (mains, outlets) 
intermodulation everywhere. The function between the price and 
the EMC
quality is exponential.

If you want to have a professional (=long-term problem-free) 
solution use
accus and get rid of those switching power supplies, UPSs etc. 
In HA we had
lots of problems with PC and PS noise. A major step to clear 
those birdies
up was to use 2 gel-accu's for 12V/105Ah to feed the PCs 
requireing 12V DC). (Altough I suspect that transporting 105Ah 
accus to Cabo
Rojo is not the challange you dream of)

Clearing your spectrum from the UPS noise could be worth for a 
PH.D. on the
field of EMC.  

73s de Zoli PA/HA1AG

Tel> +31 43 355 7012 (between 0930 and 1700 GMT)

Ps> I enjoyed your WPX-story. Keep up posting them!

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