Anyone here use the MFJ 1026 Noise Canceller?

[Moleculo]

I saw G4ILO's blog on his use of the MFJ 1026 Noise Canceller with his K3 station and I got intrigued. I believe my new neighbor (of 6 months or so) has a plasma TV just outside my radio room because I've now got horrible noise on bands that I never had before...so bad that the K3 noise blanker can't deal with it all. I'm thinking this device may be what I need. I've also read the information on eham already.

Has anyone here used this device extensively and able to give some insight or report?

 

[unit248]

I have one of these. When it works, it can make the difference between a station being completely drowned out by noise and being clear as day, but it takes a little time and careful setup to get the best results.

Ideally, you need a second 'noise' antenna that can pick up the offending noise source with about the same strength as your main antenna. If the noise is highly localized (e.g. someone in the apartment upstairs running a vacuum cleaner), then the built-in whip antenna may be good enough. But for more distant noise sources, you definitely need an external antenna. For example, I typically hear an annoying 'whooshing' sound on 75 meters, right around 3950 or so. With the whip antenna, I can't do anything to reduce this at all, but with an external noise antenna I can null it out pretty well. (Unfortunately, this noise tends to shift in frequency over time, which forces me to keep adjusting the phase control to keep it at bay.)

There's a jumper inside that controls which noise antenna input is used. The factory default is to use the built-in whip: if you want plug in an external noise antenna instead, then you need to take the cover off and shift the jumper position.

Also, inside the unit, in series with the external antenna connector, is a small light bulb. (I don't remember the exact specs on it, but it's documented in the manual.) This bulb is intended to act as a fuse, because when an external antenna is used, it will easily pick up RF from your transmitter antenna, and the resulting high RF voltages can damage the device's circuitry. I've seen this bulb glow pretty brightly a few times when operating on 40 meters, and managed to burn it out once. It's not that hard to find suitable replacements though (I found some at Radio Shack with similar specs).

It's probably a good idea to set up a relay that grounds the noise antenna when the transmitter is engaged. If you can't help but having a lot of RF picked up by the noise antenna, this might be a good way to deal with it.

There is a relay inside the unit that activates when it senses a transmit signal. When it engages, it bypasses the phasing circuitry and shunts the transmitter input directly to the main antenna output. (Why they didn't also have this relay ground out the noise antenna I have no idea.) There's a delay control knob that adjusts how long it takes for the relay to disengage. This is for use when operating in SSB mode, to avoid relay chattering.

Figuring out how to null out a noise signal takes some practice. You're basically trying to tune it so that the noise is detected in your receiver at the same level on both the main antenna and the noise antenna. If you're lucky, you'll be able to just keep the main antenna gain at maximum, and then bring up the noise antenna gain until it matches. At that point, you can use the phase control to find the 'sweet spot' where the noise is canceled out. I was one of those people who went from "this thing is a worthless piece of junk" to "holy cow, that's amazing" when I finally got the hang of it.

Note that it's not the sort of thing that can lower your overall noise floor: it only works to cancel out one noise source at a time. You'll have to re-tune it as you move between different frequencies and encounter different noise signals.

Unfortunately, since I live in downtown San Francisco, my main problem is just a generally high noise floor. I occasionally pick up motor or alternator noise (I live right near a busy intersection), but I can deal with that pretty effectively using the noise blanker in the TS-850. Consequently, I haven't had the MFJ 1026 in line a lot lately.

-Bill

 

[KM3F]

I use an ANC 4 which is the same type device.
To go over it again, this type device has a seperate antenna input that amplifies the noise signal on a broadband basis (no selecitivity) and has a phase selection at the output to another amplifier.
It is then combined with the same interfereing signal from the radio's antenna 180° out of phase.
When phase nulled it cancells the interfereing signal to a high degree not always perfect but often a good help in preventing the interference from getting to the radio and shutting down the AGC thus receiver gain.
With my unit the higher the frequency the less effective it may work but still will offer some cancellation on 10m.
The unit can be used as an amplifier as well for receive.
Many feel the unit does not work but often don't understand what it is meant to do.
I will not make the receiver quiet or reduce the radio noise floor.
Uses are attuenuating Broadcast stations, power line leakage etc as long as the unit can get a good enough sample to arrive to the tranformer to cancel.
The unit has an RF detecting circuit to do T/R switching with adjustable time delay and handles about 100 watts so use it between the radio and the amplifier if you use one.
Good luck.