[RFI] RFI Digest, Vol 119, Issue 35

[Patrick]

FWIW I've used the MFJ-1026 in line with a IC-746 using the MFJ-1026's 
internal RF relay without problems.  I did not use the RF sensing 
feature but hooked up a separate keying line. I used this mostly on 75 
and 40 meters.  I use a 50 ft long wire for a sense antenna with my 75 
meter dipole. The unit can work wonders but expect to spend a lot of 
time fiddling with the setup.

Since you are adjusting amplitudes and phase angles from two separate 
antennas, anything that changes the arrival time or phasing from either 
antenna effects the null. Touch up the tuner to minimize SWR and you may 
be tweaking the noise null again.  Change frequency too much and  the 
null also changes so you are tweaking again.

If you have more than one source of noise the best that you may do is 
null the worst source. If your sense antenna does not hear the noise 
then you will not get a null. (If your sense antenna is quieter than 
your transmit antenna you can use the 1026 as a TR relay and just listen 
to the sense antenna and forget trying to null the noise.)

Just now I tried it on S5 line noise on 75 meters. It's quiet enough 
today that I wouldn't normally bother with a noise canceller; however,  
I could not get a null.  The noise actually sounds a little different on 
the dipole as opposed to the longwire so the sense antenna (longwire) is 
not hearing the noise the dipole is hearing.

As a test of the unit, I tuned in a local highway info station on 1620 
kHz.  Starting with both aux and main antenna gain at minimum, I set 
each gain to just light up the S9+20db segment on the 746. From that 
equal RF amplitude start and with a little tweaking I could get a null 
of this station to S7. That should give an idea of what you might expect 
given a point noise source and a well located sense antenna.

I didn't have a quality control issues.

Pat
wa4tuk



On 12/30/2012 3:12 PM, George wrote:
> For a diagram of how to hook up an ANC4 or MFJ1025/1026, see:
> http://va3cr.net/accessories/ANC-4.htm
> Should work with any rig having a separate RX jack and eliminates the need
> for TR switching in the noise canceller box.
>
> The external noise antenna is critical for effectiveness - the MFJ whip
> antenna is not enough.  Also, as noted, it's only good for one source.  Like
> peeling off the layers of an onion, some crying may result.
>
> Noise is just one of the joys of centre of the city DXing...
>
> 73, George VE3YV / K8HI
>
>
>