[RFI] [Fwd: noise in HF]

[Scott Ginsburg]

If my noise were coming from an air conditioning
device of some kind, that might explain why it's not
as loud, or even not present, in the early morning when
the temperature is cool...


-------- Original Message --------
Subject: noise in HF
Date: Wed, 16 Jun 2004 18:42:56 +0530
From: "jaygee" <jaygee at powersurfer.net>
To: <k1oa at arrl.net>



Hi Scott
Pl refer to ur ongoing discussion on rfi at listing.com

i am facing a similar problem with heavy noise on 7mhz to 21 mhz. It has
been traced back to control system of the elevators in the high rise
apartment complex i live in.
The  speed variations in AC motor of these elevators are controlled by
varying voltage and frequency of the main ac power supply and are called
variable voltage variable frequency drives(vvvf drives.) These systems
are used in elevators, escalators, industrial fans, and many other
industrial or consumer uses where  the speed of motor has to be varied.
The timings of noise which u mention are typical of those involving
industrial or similar activity.
Unlike India, in USA there are strict laws for emmission of RF thru such
equipments(part 15 of FCC) but there could be an exception and someone
might be using an equipment or a device(probably imported) which is
emitting lot of rf.
Hope this info helps.
73's
jag
vu2 kib