TopBand: ANC-4 Noise Canceller
dick sander
sander@aud.alcatel.com
Mon, 20 Oct 97 08:51:31 CDT
Topbanders:
I received many favorable responses from JPS ANC-4 Noise Canceller
users. Some were direct and some via the Topband Reflector.
>When I point my beam north I pick up noise (10m). On my FT-1000MP the
>noise blanker cuts it out (2-3 S-units). Using the ANC-4 I find a "dip"
>in the noise of about 1 S-unit. If I turn the gain up high and move from the
>"dip", I hear spurious noises. The signals are also about an S-unit down.
>(The manual says about 6 dB insertion loss.)
I had a few requests to post a summary, so here they are:
---------------
Thats about what I found here....after 2 months I got rid of it. Even
tried it on 6M.
Be interesting what you hear elsewhere. Different locations have very
varying requirements...one size does not fit all...even if batteries are
included!
BTW the best DSP I have used sofar was in the TS-870 ( IF DSP, not Audio
like the FT1000MP, etc). It made all those add-on boxes look sick. Now
that KW has "supposedly" fixed the overload/AGC problem I may try one
again.
73 Carl KM1H
---------------
Dick, the "sense" antenna must pick up the same noise as your
receiving antenna on 160m's. The success of the ANC-4 is based soley
on how you can duplicate the reception of your main antenna by the
sense antenna. Many people put up large inv L's just for their sense
antenna. Also, the ANC-4 is only good for man made noise such as line
interference, pulsing generator noise....not good for atmospheric.
Many people in the city use them because of the high degree of local
man made QRN. You might have to play around with it before you see the
results your looking for. Good Luck!
Peter W5PS, Anna, TX
-----------
I wrestled with the ANC-4 too but found out that the pickup antenna is
very important. An eight foot sense antenna on 160M just will not
work. It should be at least 30 foot long!
The JPS folks have a web page. They were extremely helpful to me to get
mine going. You might search for their web page and send them a message
as to your problems.
I think your unit works but the sense antenna is not yet right.
Charlie, W0YG..>>
---------------
I guess an interesting way to test the ANC-4 would be to hook
the TX antenna to the noise antenna. You should be able to
totally null out everything!
You might open up the box and check R2 (I think that is right).
It is a 100 Ohm resistor that acts as a fuse on the input. It
is also possible that the transistor (Q1?) is blown. It is a
J310A FET (not NTE replacement, but JPS will probably send you
some if you thing it is gone).
If you remove the TX antenna, you should hear signals when advancing
the gain with just the noise antenna (you can use the TX antenna for
the noise antenna).
If all of that works, then the unit is working. Make sure the
HI/LO band switch is in the right place (I think 10 MHz is the
cutover frequency).
I use mine with another tower about 105' from my TX antenna. With
the ANC-4, I can create deep nulls in specific directions. KH6CC
seems to be in one of those directions as I can just about make him
totally go into the noise, until I push the reverse button and he
is over S9.
Good ruck! Tree -n6tr
---------------
Hi Dick - I have an ANC-4 too. It works fine, but ONLY on phase-coherent
noise. It will kill TV timebases, computer hash, and single point noise
sources, but the moment you get a wide phase range on the noise - it is
useless. So roughly, you will be very lucky if you can shift power line
noise with it - the noise travels along the line, and gives all sorts of
phase angles at your rx. Also you will never kill ionospherically borne
noise. It needs to be local, and point source.
You also have to be very careful with the size of the sense antenna. I've
found that 6-8 ft is about the maximum before you get spurious signals
generated in the ANC-4 rx.
But on the right noise it is great - I can get 5-6 S points on local noises
and little reduction in wanted signal.
Good luck ! Don - G3OZF
----------
Just throwing an arbitrary noise antenna out there is not unlike, when
trout fishing, just walking up to a river, throwing in whatever bait,
lure or fly strikes you, at whatever spot appeals to you, and then
pronouncing the river devoid of fish when an immediate strike is not
experienced.
[I dig your analogy! My second hobby is Bass fishing -QY]
Finding the right noise antenna may take a great deal of effort, and the
odds are high that, once you find one that "works" for a specific noise
on a specific band, it will be mediocre for any other band or noise. So
you may need an arsenal of noise antennas to battle different noises.
The right one may well reduce the noise dramatically--40 dB is not
unrealistic. I've done that here. My ANC-4 is not on all the time, and
is not helpful all the time, but when it is, it is invaluable.
Just remember---noise cancellation requires summing the
singal-plus-noise with a noise signal which is EXACTLY the same
amplitude and EXACTLY out of phase with the noise component.
Garry Shapiro, NI6T
---------------
You might try shorting the shield to the center conductor on your sense
antenna as the noise signal may not be strong enough since it looks like you
are only attached to the center conductor, but, then you'll have lots of
coupling to the big tower which may confound the ANC4 ability to lock onto a
phase. Try another temp sense wire - 20 foot random wire nearby.
The LOW setting BTW is not very useful I have found - it brings in too much
crud altho if you put an attenuator in line with the sense antenna it can
work fine. The most effective settings for me are usually when the noise gain
control is no more than midway altho at times I need to boost it but then the
crud comes in.
Here in a busy, NOISY, suburban eastern neighborhood - houses all around me -
it is extremely effective - hits 80% or more of the problem noise totally,
some not so totally but it helps and the only stuff it cant touch is the
multiple strong noise sources - the TV signal, my neighbors fish tank and the
other neighbors model trains all at the same time. Then, when that happens,
I fire up my AM rig on 160 and see if they like hearing me in full AM
fidelity coming over their stereos and phones.
73 Pete -W2PM
---------
I have a power line approx 100 ft north of me that I feel is part of my
160m noise problem, so far my noise blanker works best. Tonight I'm going to
clip a short wire on my lawnmower sparkplug to see if it generates some strong
noise and give the ANC-4 a try to verify if it at least works. At this point
I really don't know if my (used) unit is defective of not.
Since I posted this querry, I've tried my 160m Inverted vee as a sense ant
-no help, but 30dB to 40dB/S9 spurious signals. I built a short dipole parallel
to the power lines as per the manual -no help, but no spurious signals.
Thanks to all & 73, Dick -K5QY
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