[RFI] RFI from Astron power supply

[Tom Rauch]

.....and what is always most important is HOW the RFI is 
getting into the system.

My own experience is that electronic ballasts are generally 
noisier, not less noisy. The older conventional systems are 
quieter unless defective.

73, Tom W8JI
----- Original Message ----- 
From: "Andrew Ingraham" <ingraham.ma.ultranet at rcn.com>
To: <rfi at contesting.com>
Sent: Monday, June 04, 2007 9:37 AM
Subject: Re: [RFI] RFI from Astron power supply


>> I was told by the City Manager that they are going to 
>> have the ballasts in the
>> fluorescent lights in the radio room replaced with 
>> electronic ones. Not sure
>> what he meant by electronic.
>
> Here is my crude understanding.
>
> Fluorescent lights require a somewhat large voltage to 
> fire, but the voltage
> then drops way down.  The ballast I think allowed that to 
> happen, and was
> basically a large inductor inside a box in the fixture.
>
> Some modern fluorescent lights (in particular the compact 
> fluorescents that
> screw into conventional lamp sockets) use an electronic 
> circuit of some
> sort, instead of the big inductor.  What they actually do, 
> I don't know, but
> I believe they are more than merely an active inductor or 
> a current source.
>
> The inductor itself probably doesn't cause RFI (unless 
> it's got a bad
> contact), but the combination of inductor and the 
> fluorescent tube, which
> snaps into and out of conduction, tends to generate large 
> voltage spikes
> which might be responsible for the RFI.  Perhaps the 
> electronic ballasts
> do this in a more graceful way without the large spikes.
>
> Past experience with fluorescents and "carrier-current" 
> radio says that the
> RFI may be conducted over rather large distances so 
> replacing only the ones
> in the radio room may not totally fix it.
>
> Regards,
> Andy
>
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