Bob Dobbs EC42 wrote:

On Wed, 30 Aug 2006 16:32:14 +0000, Mark Zenier wrote:

In article .com,
Steve wrote:
In some contexts, when noise is a problem, people will say that you want
to keep the "noise antenna" that you use with the ANC-4 as small as
possible. This is because you want the noise antenna to hear *only* the
noise, which will be phased out, and not the target signal, which you
don't want to be phased out. The suggestion here is clearly that, if
your noise antenna *does* hear the target signal, you're going lose
signal along with noise.

Answering Steve;
since I seem to have either lost or never saw his original post.

What you say above is correct.

However, when people use the ANC-4 to establish phased arrays of two or
more antennas, this is usually with a couple of serious antennas, widely
separated, *both* of which can hear the target signal.

In this case they aren't using the ANC-4 as much for noise reduction
alone, but for signal enhancement, and phase select for desired signal
versus unwanted interference, noise and other stations.

Hence my
question: When the ANC-4 is connected to two largish antennas, both of
which are capable of hearing the target signal, what prevents the
desired signal from simply being phased out? Is determining what gets
phased out just a matter of carefully adjusting the controls on the
ANC-4?

They aren't trying to phase out the desirable signal.

A noise bridge works by subtracting the noise from the signal.

He's not talking about a noise bridge, which seeks an impedence null in an
antenna system, and is sometimes used as a tuner tuner.

Yep, a noise bridge can be quite handy for setting up an antenna tuner.

dxAce
Michigan
USA

Bob Dobbs EC42 wrote:

On Thu, 31 Aug 2006 13:30:49 -0400, dxAce wrote:

Yep, a noise bridge can be quite handy for setting up an antenna tuner.

And is a lot simpler device,
usually a wideband noise source (a diode abused until it hisses)
and a calibrated bridge to indicate impedence or sometimes SWR.
Generally cost about a third of an ANC-4

I used an MFJ-202B and a Drake MN-75 tuner. If I were to go back to using a
large dipole or inverted V that's probaby the combo I would again employ.

It was easy to set up the antenna for various bands and I simply marked the
basic settings on a card which made it very handy to hop from band to band.

dxAce
Michigan
USA

www.devilfinder.com Tavis Swiley's boobs

I have to watch the Waterworld movie on Radio tv Bravo channel now,and
the movie comes on Radio tv again at 9:00 PM this evening.I like the
part where that old guy is checkin the oil level and that fire comes
blazing in and he says,Oh,Thank GOD!
cuhulin

Bob Dobbs EC42 wrote:
On Wed, 30 Aug 2006 16:32:14 +0000, Mark Zenier wrote:

In article .com,
Steve wrote:
In some contexts, when noise is a problem, people will say that you want
to keep the "noise antenna" that you use with the ANC-4 as small as
possible. This is because you want the noise antenna to hear *only* the
noise, which will be phased out, and not the target signal, which you
don't want to be phased out. The suggestion here is clearly that, if
your noise antenna *does* hear the target signal, you're going lose
signal along with noise.

Answering Steve;
since I seem to have either lost or never saw his original post.

What you say above is correct.

However, when people use the ANC-4 to establish phased arrays of two or
more antennas, this is usually with a couple of serious antennas, widely
separated, *both* of which can hear the target signal.

In this case they aren't using the ANC-4 as much for noise reduction
alone, but for signal enhancement, and phase select for desired signal
versus unwanted interference, noise and other stations.

Hence my
question: When the ANC-4 is connected to two largish antennas, both of
which are capable of hearing the target signal, what prevents the
desired signal from simply being phased out? Is determining what gets
phased out just a matter of carefully adjusting the controls on the
ANC-4?

They aren't trying to phase out the desirable signal.

A noise bridge works by subtracting the noise from the signal.

He's not talking about a noise bridge, which seeks an impedence null in an
antenna system, and is sometimes used as a tuner tuner.

snipprd the rest unrelated to the ANC-4's operation.



--

Echo Charlie 42
San Diego, California

Thanks for the info. Very interesting. I look forward to trying the
ANC-4. I'm going to try it with a variety of short wires, but I will
probably also try to use it in conjunction with a good quality active
whip (H-800 Skymatch). Should be fun figuring out what works best...I
love doing this sort of thing.

Steve

David wrote:
On Thu, 31 Aug 2006 15:02:46 GMT, Ron Hardin
wrote:

David wrote:

On Thu, 31 Aug 2006 08:27:40 GMT, Ron Hardin
wrote:


It doesn't matter. Precision doesn't come into it any more or less
with random wires.

A random wire is already full of nulls and nodes. Much easier to
phase vertical omnis.

No, if one antenna isn't hearing the signal you want to eliminate, the
job is done for you. If it is hearing it, you phase it away with the
other antenna.

Nothing in the operation changes. You diddle the knobs the same way
in either case, and respond the same way.

The ANC-4 doesn't care where the signal comes from, just that it's
present.

Very imprecise and technically minimalist.

Yes, but it's also correct. I have the MFJ equivalent, and the
contraption works just as Ron describes. I have two antennas up thar,
one a random wire and the other a multiband dipole, and except for the
lower HF bands, where the random wire just isn't quite long enough, I
can cancel out most any *single* obnoxious local noise. For the MW
station nulling, by and large it works fine, despite the mismatched
antenna length...it will chew a big bite out of a pretty big local
signal and leave the weaker station 'neath intact.

It doesn't work worth a hoot for general band noise (no surprise), and
for things like distant lightning that theoretically should be
nullable, it is so tricky that it isn't really worth the trouble.

Bruce Jensen

Bob Dobbs EC42 wrote:
On Thu, 31 Aug 2006 15:06:17 -0700, bpnjensen wrote:

It doesn't work worth a hoot for general band noise (no surprise), and
for things like distant lightning that theoretically should be nullable,
it is so tricky that it isn't really worth the trouble.

That's because the DX noise is coming from the same direction as the
desired signal so there's not enough parallax to work with.
BTW: Lightening is usually impusle rather than plasma noise
and your blanker should deal with that.

Bingo on both counts. The NB does a decent job on the lightning, but
on the R75, it is not quite as broad in its powers as it could be. Not
bad, but not perfect. Luckily, or maybe unfortunately, lightning isn't
*usually* the worst noise I have to deal with at this QTH.

Bruce Jensen

In article pan.2006.08.31.17.10.46.51000@Quetzalcoatl,
Bob Dobbs EC42 wrote:

They aren't trying to phase out the desirable signal.

A noise bridge works by subtracting the noise from the signal.

He's not talking about a noise bridge, which seeks an impedence null in an
antenna system, and is sometimes used as a tuner tuner.

OK, "noise cancelling bridge", according the page off the web that
I built mine from. (Something like Doug's Noise Cancelling..., and
the "ARRL RFI handbook").

A "bridge" is a old general name for a circuit that works by subtracting
one signal from another by means of two "arms", (ie. matching networks).
The output could be a meter, or in my case, a transformer winding that
feeds the antenna input.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

Steve wrote:
Bob Dobbs EC42 wrote:
On Wed, 30 Aug 2006 16:32:14 +0000, Mark Zenier wrote:

In article .com,
Steve wrote:
In some contexts, when noise is a problem, people will say that you want
to keep the "noise antenna" that you use with the ANC-4 as small as
possible. This is because you want the noise antenna to hear *only* the
noise, which will be phased out, and not the target signal, which you
don't want to be phased out. The suggestion here is clearly that, if
your noise antenna *does* hear the target signal, you're going lose
signal along with noise.

Answering Steve;
since I seem to have either lost or never saw his original post.

What you say above is correct.

However, when people use the ANC-4 to establish phased arrays of two or
more antennas, this is usually with a couple of serious antennas, widely
separated, *both* of which can hear the target signal.

In this case they aren't using the ANC-4 as much for noise reduction
alone, but for signal enhancement, and phase select for desired signal
versus unwanted interference, noise and other stations.

Hence my
question: When the ANC-4 is connected to two largish antennas, both of
which are capable of hearing the target signal, what prevents the
desired signal from simply being phased out? Is determining what gets
phased out just a matter of carefully adjusting the controls on the
ANC-4?

They aren't trying to phase out the desirable signal.

A noise bridge works by subtracting the noise from the signal.

He's not talking about a noise bridge, which seeks an impedence null in an
antenna system, and is sometimes used as a tuner tuner.

snipprd the rest unrelated to the ANC-4's operation.



--

Echo Charlie 42
San Diego, California

Thanks for the info. Very interesting. I look forward to trying the
ANC-4. I'm going to try it with a variety of short wires, but I will
probably also try to use it in conjunction with a good quality active
whip (H-800 Skymatch). Should be fun figuring out what works best...I
love doing this sort of thing.

Steve

I've got the ANC-4 unit now and will be experimenting with it over the
weekend. I'll use a variety of wire antennas of different lengths and
configurations. My first impression is positive. I've attached it to
short wires and sure enough, the noise floor goes way down.
Interestingly enough, though, I find that it will not work at all in
conjunction with the H-800 active whip. I'll try it again at some
point, but the whip is nowhere near as effective as a wire, at least in
my preliminary tests

Steve

There's no trouble with active antennas, in fact they're handier because you can
get exactly the location you want when you construct your phased array of two.

What's most likely is that you're nowhere near the right gain to make the signal
you want to cancel the same strength in both antennas, and so you get no indication
of a null direction.

The ANC-4 has linear gain pots, which unfortunately means that the phase control
also changes the gain (strong at the ends, weak in the middle), which makes
searches for the null harder than it has to be.

A technique called successive overrelaxation is the most successful in searching
for a null.

Say, step the phase, and at each step minimize the S-meter with the gain, but going
a little past the minimum each time (choose a direction for this and stick to it).

Go back to the best phase, and repeat with smaller steps. Hairline changes will
be necessary at the end.

And finally notice that there's a phase button, and searching with the opposite
phase might surprise you. Having the wrong hi-lo frequency setting also changes
things, giving you less than a complete phase control.

Successive overrelaxation works when the search controls aren't orthogonal, which is
what most of the time happens.

--
Ron Hardin


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

Bob Dobbs EC42 wrote:

On Sat, 02 Sep 2006 10:47:49 +0000, Ron Hardin wrote:

The ANC-4 has linear gain pots, which unfortunately means that the phase
control also changes the gain (strong at the ends, weak in the middle),
which makes searches for the null harder than it has to be.

This statement in addition to being an internally contradicting paradox,
is inapplicable to the ANC-4's operation.
Your description "(strong at the ends, weak in the middle)"
is anything but linear. Plus the phasing isn't linked to the gain,
therefore two separate pots.

No, linear pots are linear in voltage, and you want linear in power, which they are
not.

The result is that the gain is small with the phase centered, and big with the
phase at either end.