Noise canceller advice
 

Im just about ready to give up on radio due to newly introduced
"mystery" static in my area.... S-9 worth of noise! But before I give
up on my ham and SWL career I would like to give it a last shot and
try a noise cancelling unit.

I would like to hear all the input you guys can give me on one of
these units, which one works better and do they really work as
advertised?

Thanks...Gil

"mystery" static in my area.... S-9 worth of noise!

What do you (not) know about this noise?

"0ff_Ramp" wrote in message ...
"mystery" static in my area.... S-9 worth of noise!

What do you (not) know about this noise?

Not sure where its coming from. It ususally starts late morning and
lasts up to midnight, its very much on time every day.

gil wrote in message
m...
Im just about ready to give up on radio due to newly introduced
"mystery" static in my area.... S-9 worth of noise! But before I give
up on my ham and SWL career I would like to give it a last shot and
try a noise cancelling unit.

I would like to hear all the input you guys can give me on one of
these units, which one works better and do they really work as
advertised?

Thanks...Gil

I got hold of a MFJ unit and played with it---properly used it is VERY
effective. I could null a local AM brodcast station into the noise. If
your static is from a point source you won't have any problem nulling it.
Powerline noise propagating along the powerlines might not be as easy to
null completely.

It might take awhile to become familiar with how to tune it as it requires a
fine touch.

Maybe you can borrow one and try it out.

Its an idea that's been around for a long time. My memory is vague but I
think there was a boatanchor Hallicrafters or Hammerlund reciever that had a
noise canceller built in.

RG

"0ff_Ramp" wrote in message ...
"mystery" static in my area.... S-9 worth of noise!

What do you (not) know about this noise?

This is a superb question, because the ability of the device to remove
noise has alot to do with the nature of the noise. If the noise is
local and well-defined, if it is coming into your system via the
antenna (as opposed to the electrical lines) and especially if it is
the *only* bad noise you have, then a noise canceller will probably
take it out quite nicely. If the noise is distant (such as an
offending HF station via skywave) and the other two criteria still
apply, it will still work, but not quite as well.

If any two of these criteria are not met, then it is unlikely that the
unit will give satisfaction. For two different noise sources, two
units in series might work, but I have never tried this. For this, it
is probably preferable to have a radio that has noise-cancelling
devices (Noise blanker, DSP, etc) plus a single external unit.

Also, some units (the MFJ-1026 notably, which I use) comes with a
built-in aux "noise" antenna. It works, a bit (especially on certain
wavelengths such as 25m and 60m - 90m, where it works quite well) -
but for serious noise, it is best to have a dedicated external antenna
that comes reasonably close in character to your main antenna. This,
because you want both antennas to be "hearing" the same noise. Two
roughly parallel 40-foot (12m) or longer random wires about 20-50 feet
(6m to 16m) apart would be nearly ideal; but I use a DX-Ultra
(essentially a center-fed dipole assembly) with a random wire of about
60 feet as the aux antenna, and it works pretty well for most noise.

The way the units are configured, you can phase one, the other or both
antennas together for the best noise reduction. On the MFJ units, the
aux antenna has both a gain control and a preamp, which is nice, but
it would be even better if these features were switchable from aux to
main sometimes (a fairly simple modification inside the unit can
achieve this, if you aren't afraid to do minor surgery).

With my unit in stock condition and with the internal jumpers
configured per the instructions, I can reduce most constant modest
static 3 to 5 S-units; strong static or impulse noise from S-9 down to
below the noise floor at S-1 or less (a good noise blanker will
accomplish about as much); offending groundwave stations (on SW or MW)
a comparable amount; and offending skywave stations about 3 S-Units
(typically). These correspond to dB reductions of about 18 up to 50
dB or more, depending on the noise.

When I have an obnoxious noise that cannot be remedied by the noise
blanker, notch or DSP, I tune off the desired station frequency to a
quiet spot nearby 5 or 10 kHz away), adjust the noise levels and phase
according to the directions until the noise is reduced maximally, then
tune back to the station. You don't want to tune very far away to
adjust the device, because the settings are frequency-dependent. Done
properly, this works very well.

The unit advertises that it can take out static crashes from lightning
and other intermittent noise sources, and it may be true, but the
nature of these noises makes it very difficult to adjust the device
with any precision.

I like mine alot - for the city/suburb dweller or the random person
with horrid noise, it works minor miracles.

Bruce Jensen

Well of course hunting down mystery noise is fun too. But for
noise cancellers, the Timewave ANC-4 works great (formerly JPS ANC-4).

The best arrangement is use two external antennas, arbitrarily
connecting one to the ``noise antenna'' and the other to the
``main antenna.''

That gives you a two-element phased array, and you simply steer
its null over your noise source, and it's magically gone. This
is actually something of an entertainment itself.

You _might_ get by with the onboard noise antenna but that's more
speculative. It depends on how well indoor noise copies what the
outdoor antenna is hearing. Two real antennas always works better.

I myself have found this amusing enough to build an 8-element
phased array with 7 ANC-4's. Talk about versatile! I can
null two stations and hear a weaker third under them, with some
diddling, and have half the array left over.

The ANC-4 works down to MW and below, which the MFJ version does not.
MW is the most entertaining place of entertaining places to do
nulling and digging out.

Incidentally, for nulling distant stations, it doesn't work for SW
because the variability of direction of arrival with skip is bigger
than the size of the null you're steering; it works on MW though,
and at any frequency for local sources (ie with a stable direction)
like your noise source.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

con't

on antenna spacing : any spacing at all works for cancelling,
but the gain of the resulting system for things you _do_ want
to hear is reduced if they're separated by less than a quarter wave.

That reduction may be of no importance whatever, however, with
modern sensitivities and low internal noise receivers. Try any
separation you have room for. On MW you can rarely get a quarter
wave but it works fine nevertheless.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

Howdy Ron:

Have you written up that phased array of yours? I've been reading your
comments about it for quite awhile and you seem to be quite proud of your
antenna (as you should be). It seems just the ticket for an article in PC,
MT, CQ or perhaps QST.

I've been wanting to set up a shortened beverage array with the noise
canceller as per Vic Misek, W1WCR "Beverage Antenna Handbook" I think it
should work out quite well with his Steering Wave Array. If you don't have
a copy of his book I think you would find it interesting and become a
worthwhile addition to your collection of references.

Sincerely,
RG

"mystery" static in my area.... S-9 worth of noise!

What do you (not) know about this noise?

Not sure where its coming from. It ususally starts late morning and
lasts up to midnight, its very much on time every day.

With the timeframe you mention, seems like a business establishment -
restaurant/bar?
Any new electric signs in the neighborhood? Can you isolate the noise to
any degree???
I'll assume you have already eliminated your own residence by shutting off
all the power?

I recall one day certain cable TV channels were being obliterated. Then at
night I turned on the AM radio and intermittent noise was 20 over. From the
noise pattern and time of use I had speculated that the noise was caused by
an electric blanket thermostat. This went on for days before I couldn't
take it anymore. I used a small portable receiver and isolated the noise to
my neighbors home. They had recently had a newborn baby. Turns out they had
started using a baby wipes warmer (cheap, made in China, junk, fire
hazard.). As soon at it was plugged in for the evening diaper routines all
hell broke loose.

Ron Hardin wrote:

Well of course hunting down mystery noise is fun too. But for
noise cancellers, the Timewave ANC-4 works great (formerly JPS ANC-4).

The best arrangement is use two external antennas, arbitrarily
connecting one to the ``noise antenna'' and the other to the
``main antenna.''

That gives you a two-element phased array, and you simply steer
its null over your noise source, and it's magically gone. This
is actually something of an entertainment itself.

You _might_ get by with the onboard noise antenna but that's more
speculative. It depends on how well indoor noise copies what the
outdoor antenna is hearing. Two real antennas always works better.

I myself have found this amusing enough to build an 8-element
phased array with 7 ANC-4's. Talk about versatile! I can
null two stations and hear a weaker third under them, with some
diddling, and have half the array left over.

The ANC-4 works down to MW and below, which the MFJ version does not.
MW is the most entertaining place of entertaining places to do
nulling and digging out.

Incidentally, for nulling distant stations, it doesn't work for SW
because the variability of direction of arrival with skip is bigger
than the size of the null you're steering; it works on MW though,
and at any frequency for local sources (ie with a stable direction)
like your noise source.
--
Ron Hardin

There were plans in past issues of Monitoring Times and QST for a
homebrew version of the ANC-4.


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