[RFI] Damned Amtrak

Jim Brown jim at audiosystemsgroup.com
Sat Dec 29 19:46:08 EST 2012

On 12/29/2012 1:25 PM, dalej wrote:
> You might consider a Timewave ANC-4 noise canx device.

Perhaps -- the MAJOR problem with these boxes is that the RF detection 
circuit that does T-R switching is a NASTY key click generator that will 
make your neighbor hams very unhappy. An easy cure for this is to put 
the noise canceller in the RX antenna input, if you have one.

The MFJ equivalent is supposed to be better at noise cancelling, but I 
haven't seen one and don't know about clicks. And, of course, be aware 
of their QC problems and prepared to fix cold solder joints.

As Dale has mentioned, the key to these working well is having a noise 
sense antenna that is as close as possible to the noise. You want the 
ratio of "noise" to desired signal on that "sense" antenna to be as high 
as possible so that you cancel more noise and less desired signal.  :)

73, Jim K9YC

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