Hello all,
Thought I would weigh in on this thread.?
I have an ANC-4 that I decided was not working. Sometimes there seemed to be an effect, othertimes none. So I sent it back to the factory for evaluation. This was $60 plus shipping both ways to learn there was nothing wrong with the unit.
I did chat with two folks at TimeWave and learned the following:
As the ANC-4 works by sampling noise, then inverting the noise signal and adding it to the main signal, it will only be successful if the noise on both antennas is matched. The manual recommends a short dipole close the ground for the noise antenna, but the folks at TimeWave said to use whatever works. That is to say, you should arrange the noise antenna as vertical, horizontal, or whatever just so you can ge the same noise signature and level on both antennas.
There is a level control on the ANC-4, but the range may not be sufficient to match both signals.?
I was told that the unit only works properly if there is a well characterized single noise source. That is, ?there should be something "tangible" to detect, invert and cancel.?
For random grunge from scores of SMPS sources coming from all directions in your neighborhood, the ANC-4 is likely to be ineffective. On the otherhand, if your neighbor's garage plasma cutter runs 24/7 you might just be able to zap it away.
This is the best case to sign off with "YMMV", as it certainly will.
Cheers,
=Randy=
WB6MAI
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On Sat, 2024-06-15 at 20:41 -0400, don Root via groups.io wrote:
Hello all. I just read the ANC-4 ?blurb.? ?It seems to me that if the noise comes from? wiring in the house, use a small noise ¡°antenna /wire near the¡± sourse or maybe near the wiring, but if the noise is from outside power lines, use a longer outdoor wire.? They ??leave the whole type of main antenna to be a mystery. No wonder ?there are reports that it works well and others that it is bogus. ?IMO the noise? location[s] and the antenna combinations used is missing, and must be a very big topic.???? don
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The ANC-4 by Timewave is a very effective device for limiting local noise. ?I get more than 40dB reduction, sometimes more, so that weak signals stand out against an almost silent background. ?MFJ makes a similar device. ?These devices use an active RF circuit to amplify the offending noise from a separate antenna, and then beat it against the same noise in your main antenna. ?They really work. I see some used ones online around 125 bucks. ?
Preston WJ2V
On Jun 10, 2024, at 1:52 PM, Maynard Wright, P. E., W6PAP via <ma.wright@...> wrote:
?
The use of a noise antenna and associated circuitry is independent of
the nature of the noise, whether or not it's periodic and whether or not
it's random.
Ideally, the signal antenna would receive the signal plus the offending
noise and the noise antenna would receive just the noise. The combining
network would be adjusted to combine the two signals so that their time
domain noise components would be equal in amplitude but opposite in
polarity so that they would cancel and leave only the desired signal at
the input to the receiver.
There are several potential difficulties that make this system less than
perfect in most, if not all, implementations, but it may reduce the
noise enough to be useful in some situations.
73,
Maynard
W6PAP
On 6/9/24 17:11, Mike Feher wrote:
It seems to me, that since noise is neither correlate-able or
stochastic, elimination is not possible. Also the multiple antenna
theory is out the window since RF generated noise travels at the speed
of light. 73 ¨C Mike
Mike B. Feher, N4FS
89 Arnold Blvd.
Howell NJ 07731
908-902-3831
*From:* [email protected] <[email protected]>
*On Behalf Of *Maynard Wright, P. E., W6PAP via
*Sent:* Sunday, June 9, 2024 7:31 PM
*To:* [email protected]
*Subject:* Re: [HallicraftersRadios] SX-117 noise limiter behavior
Another technique for reducing or eliminating noise was to introduce
local noise to the front end of a receiver from a local "noise antenna."
The amplitude and phase of that noise could be adjusted to, hopefully,
cancel the noise received by the signal antenna.
Early BC-342 and BC-312 receivers featured a noise suppression circuit
of this type. War Department TM 11-850 states that the noise antenna
was intended to eliminate ignition noise when the receiver was mounted
in a vehicle.
By the time my BC-342-N was born (1942), the noise antenna and
associated circuitry were omitted, so that circuit may not have worked
well. The September, 1946 revision of the TM notes that spare parts
were no longer available for the noise suppression circuit and
recommends removing it if any of the components fail.
MFJ has featured at least one similar unit, the MFJ-1026, which is now
listed as sold out. There are other such units available but I have no
experience with them.
73,
Maynard
W6PAP
