Get the noise antenna right, and the noise canceller will do its job. It’s simpler than you think.
Setting up the external noise antenna for your ANC-4 or MFJ-1026 is the most important part of reducing RFI from noisy neighbors. There is lots of advice available, some good, some not. You should start by looking at the recommendations from the manufacturers.
According to MFJ, “If the primary problem is removal of local noise, it is preferable the noise (AUXILIARY) antenna hear the noise much louder than it hears desired signals. The noise antenna should be located as close to the noise source as possible, so the noise antenna picks up the least amount of desired signal and largest amount of noise possible. In this case the polarization is unimportant, and the spacing between antennas can be any convenient distance.”
According to Timewave, “For noises generated outside the home, we recommend that you mount a small noise dipole outside perhaps down in the shrubs or some other area a foot or two above ground, and broadside to the noise source, such as
parallel to power lines. Any noise antenna that works, including combinations of horizontal and vertically polarized antennas, may be used.”
After conducting lots of experiments, I agree with these recommendations, particularly that from MFJ, and summarize my findings as follows:
- Your noise antenna should do a good job of picking up the interference you want to cancel, and a lousy job of picking up the signals you want to hear. An easy way to find out what your noise antenna receives is to disconnect your main antenna, and just use the noise probe as an active antenna.
- Polarization is not that critical, but RFI tends to be more vertically polarized. Start with a vertical noise probe.
- You should not worry about impedance matching for the noise antenna. As long as it picks up lots of noise, it works. If the noise is too strong or not strong enough, you can easily attenuate or amplify to get the level right.
Unfortunately, users will find lots of “advice” on the Internet about using a “proper” antenna for the noise probe. Don’t, unless you plan to use the phasing devices for signal enhancement. For cancellation, users get best results from lousy antennas that just hear mostly noise.
Noise Antenna that Works for Me
At my location, the main noise sources are located in two neighboring houses. One is about 150 feet to the west, the other is about 75 feet east. I have put up a noise antenna for each source. The antenna is a 4 foot ground plane. The vertical element is a #14 wire inside a ½” plastic conduit. I 3D printed mounts for the wire that snap onto the top and bottom of the pipe. Each antenna is as close as I can get to the noise source, and vertically mounted on a fence post using a ½” clamp. See the picture above.
The noise probes are connected to runs of RG6 coaxial cable. I can switch between them in the shack, using “A” or “B” with my ANC-4. The antennas are largely hidden by surrounding foliage. Gray plastic conduit is not very noticeable, either.
These noise probes do nothing for RFI from within my house, but they work wonders on interference from either neighbor over the range of 6 – 25 MHz.
John, I just watched your excellent video on the ANC-4. I wonder if you might offer any advice…
My main antennas are in my attic (composition roof, OSB sheathing, stick framing) and the noise renders my basement station nearly unusable. There’s little wiring near those antennae, just a 120V runs for an incandescent attic light and another for an in-line radon blower fan – so I assume my noise is coming from beyond my house. I do have a transformer pad behind my back fence about 60’ away (buried electrical service in this neighborhood) so that may be one offender.
Near the entrance point for my shack, I have a vertical 12’ aluminum downspout connected to a 30’ horizontal gutter. I realize everything is an experiment but would you think I’d have better odds with a noise antenna such as yours, or instead just connecting to that downspout?
Any advice will be greatly appreciated. I bought the ANC-4 knowing it would be the start of a learning curve, but you might be able to give me a push.
Sure, try it. Any antenna that picks up a lot of the noise and very little of the desired signal may work.
I have an issue with a neighbour that has his stereo on all night from 10:30 pm to 6am and I have measured the level on my iphone at 32 to 35 hz will your antenna work to reduce the thump sound that keeps us awake all night, we are in our 70’s and have had enough , the police and noise control are unable to help as they say it needs to be well above the level we are experiencing but its a constant thumping .
Will your antenna work , we are about 8 mtrs from the room .
We have double glazing and yet the sub bass still comes through.
One last question what cost and what are they known as we may be able to purchase in New Zealand.
Ray from NZ
Sorry, Ray but these systems only work on radio, not audio. However, you might try some noise cancelling headphones and see if they might help. Cheers.
I’ve read your article here and was very encouraged. I bought the MFJ 1026 last week, to try to get rid of power line noise (at least that’s what I suspect it’s is). To little antenna that comes with that unit is doing something, but not enough. Could you provide a little more information on how you build your noise antenna? Specially, could you explain how you connect the element to the coax? Is it connected to the core or three braid? Is the remaining portion of the coax connected to anything? Is there a ground plane or a ground connection? So many questions.
Paul, may be worthy of a future post. I will answer your questions directly by e-mail or call.
Great article and Youtube video! I have the same question about the construction of your antenna system. Would love the additional information you have offered, as well.
Regards and Thanks,