[AMRadio] Receiver Noise Reduction Devices


Patrick Thompson wa4tukhr at gmail.com
Fri Jan 25 07:12:53 EST 2008


I have the MFJ-1026 that was bought to use against power line noise. If the
noise is radiated externally to your house and not conducted into your house
via the power lines and if the noise is from a particular direction the 1026
will help and sometimes dramatically.  If the noise is from no particular
direction you'll not see much benefit.

You might get an idea if the noise is directional by rotating a BCB receiver
with internal loopstick to see if it peaks in one direction. (See if you can
find a null.)

If you decide to try the 1026 you'll need an external sense antenna with
similar pattern to your main antenna. If you use a transceiver you'll be
transmitting through the 1026 using its internal relay. So far it's been
okay at 100 watts SSB but you would want to put it between the TR relay and
receiver for anything AM or before the amp for SSB higher power. 

The adjustments are critical and take a while to master.  They are also
frequency dependant so going from 160 to 80 is a retuning proposition. Of
course you could log the knob settings to get back close. On the higher
bands at full throttle using the preamp decreases the s/n ratio so if the
noise is minor you wouldn't want to use the 1026. Just turn its power off to
put in bypass.

The manual is online so that might help your decision.  I was reluctant to
spend money on something that might not help but in my situation it was
worthwhile. 

There is an RFI mailing list that is worth joining even if you mostly just
"read the mail".

Pat
wa4tuk


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Mike Duke, K5XU
Sent: Thursday, January 24, 2008 8:27 PM
To: Discussion of AM Radio
Subject: [AMRadio] Receiver Noise Reduction Devices

I'm looking for a way to reduce a received noise which is being back-fed
into a nearby powerline from something inside a house about a block away.
I've been working with my power company, and we are in agreement that it is
coming from the owner's side of the meter.

This noise is killing all but the strongest signals on 160 and 80 meters,
and is almost as bad on the lower half of 40.

The noise sounds like a strong white noise on 80 and 40, and more like an
electric motor on 160 and the AM bc band.

Will a device such as the MFJ 1025 or 1026 reduce this noise enough to be
worth spending the money for it, or should I just prey for lightning in the 
next block?





Mike Duke, K5XU
American Council of Blind Radio Amateurs


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