Re: [RFI] NOISE GADGETS

[David Jordan <wa3gin@erols.com>]

Yes, Tom I can't disagree with these most recent comments of yours.

I typically use cormcom EMI/RFI AC line filters.  But I've used some 
surplus jobs from Fair Radio with similar success. Decades ago I spent a 
good amount of time in a lab comparing some of these filters types, even 
the K-coms.

We had one telephone line problem where the line had so much RF on it 
that you could pull an arch off the line with a graphite pencil. We 
placed seven K-COMS in series in an attempt to remove the RFI. But seven 
wasn't enough...the RFI was there, reduced but still there...one Corcom 
totally removed the RF.  It was amazing!

I'll dig around and see if I can find the type and model info...most of 
the stuff is now down on the farm.

Here is the info from one of the surplus filters:

LINE
RNF - 5PI
2X5 AMPS
125/ 50VAC
50 400hz
RTRON CORP

I bought a couple dozen of these years ago.  They have been solving 
phone RFI problems for many years.

73,
dave
wa3gin

Tom Rauch wrote:

> > I've used these filters for decades and they blow away
>
> everything
>
> > discussed on this thread to date. And I've tried them all.
>
> So, I'm
>
> > speaker from practical experience.
>
>
> Hi  Dave,
>
> If you tried them all, then you have tried more than I have!
> I've probably only sampled and measured a few dozen types of
> brute force line filters, and none were really suitable for
> general telco use. I suppose there are types that work is
> some cases, I just haven't run into them. I'm a little
> reluctant to believe it's OK to just use any old brute force
> line filter in the world, especially when most I've seen
> won't work reliably.
>
> It would be helpful if you gave a brand and part number of
> something that does work.
>
> A power line operates at 60 Hz, has very low impedance, and
> is not critical at all for balance.
>
> A telco line runs at 300-3500 Hz, has reasonably high
> impedance (600 ohms), and that is very load impedance and
> balance critical.
>
> 73 Tom
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