s9 noise problem related to position of antenna tuner?
 

Can you please advise on the optimal position for my atu. I'm a novice ham,
and at the moment I've got a random length of wire slung between my attic
roof and a garden tree (about 40 feet high), with a connection to the centre
wire of a 50 ohm coax cable as soon as it enters the attic roof, down to my
antenna tuner. My problem is a very high level of electrical noise across
most HF bands, especially the lower ones. We have a lot of electrical
cabling in the roof for lights, satellite tv etc, and switching them all off
would provoke a family riot. Would it be any better if the atu was between
the wire and the coax where it enters the roof (although it would be
difficult for me to get a power supply up there)? Any other possible
solutions to the noise problem? Thanks for your help.

On Mon, 1 Mar 2004 05:52:05 +0000 (UTC), "tedoboxer"
wrote:
Can you please advise on the optimal position for my atu. I'm a novice ham,
and at the moment I've got a random length of wire slung between my attic
roof and a garden tree (about 40 feet high), with a connection to the centre
wire of a 50 ohm coax cable as soon as it enters the attic roof, down to my
antenna tuner. My problem is a very high level of electrical noise across
most HF bands, especially the lower ones. We have a lot of electrical
cabling in the roof for lights, satellite tv etc, and switching them all off
would provoke a family riot. Would it be any better if the atu was between
the wire and the coax where it enters the roof (although it would be
difficult for me to get a power supply up there)? Any other possible
solutions to the noise problem? Thanks for your help.

Hi OM,

First, confirm your source of noise. During the wee hours, throw the
breaker to those electrical and electronics devices and see if the
noise goes away. No use in blaming the innocent. Use a battery
powered receiver if throwing the breaker also means killing your
shack.

Much of noise actually arrives through the Mains power connection
(typically a ground loop). If you can, move your rig's power to a
different breaker (break ALL grounds to do this, it may be more subtle
than you might imagine at first glance to do this). Dimmer noise (and
other sources) often is conducted through sharing a common breaker.

Radiative noise (not coming in through the mains, but over the air)
can be snubbed by using a choke at the coaxial far end (try moving
your feedpoint out and away from the attic, and placing a
choke/current BalUn on it).

73's
Richard Clark, KB7QHC

Immediately upon moving to my new QTH, I was also struck with an S9+ noise
problem. Although it was not present all the time, I was certain that it was
caused by the electric company's high voltage lines just above my back yard
fence. After much investigation, they were convinced that their system was
clean and was generating no noise. They were right. One night, late at
night when everything in the house was still and quiet, the S9+ noise came
back, right in the middle of a QSO. I tore off my headphones in disgust,
just in time to hear the familiar clunk sound that was made by the ice maker
when its motor was running, dumping the ice cubes out of the trays into the
bin below. When it finished, I put my headphones back on. Yep, no noise. 40
meters was as quiet as the rest of my house. I replaced the ice maker and
never had the problem again.

After you try the helpful recommendations by KB7QHC, try to isolate the
noise by turning off one at a time every piece of equipment that you have in
your house, being careful to test for the presence/absence of noise after
each one. Remember that some items are still powered after you turn off
their power switches. You will have to unplug these. Be sure to unplug your
house's heater. Check that lightbulbs are completely screwed into their
sockets so that there is no electrical arcing when it is turned on. Turn off
and unplug your computer, video displays also.

If I were you, I would temporarily remove the ATU from the antenna feedline
completely and unplug it so that it cannot draw any power. If it is an
automatic unit, it will have motors in it. If your ATU is not itself the
cause of the noise, changing its location will have no effect on the noise
at all.

Another thing that comes to mind is the ARRL publication on RFI. We usually
think of RFI as something that we hams cause to someone else, but it can
often be the case that we are the ones affected by noise caused by others or
other electrical items in the house. That book has been very helpful to me.

Oh, yes. About the family riot. You can prevent this by enlisting the help
of the kids in hunting down the problem. This puts them on your side. I'll
bet they will be thrilled in being asked to help you solve a problem.
Children don't often get a chance to help parents solve a problem.

One last thing. Don't give up. You can solve this.

VY 73 DE N6UF

On Mon, 1 Mar 2004 05:52:05 +0000 (UTC), "tedoboxer"
wrote:

....snip My problem is a very high level of electrical noise across
most HF bands, especially the lower ones.

Look for any "Touch Lamps" that are in your home and get rid of them.
They are wide band noise generators - on or off.

73,
Bob

Can you please advise on the optimal position for my atu. I'm a novice ham,
and at the moment I've got a random length of wire slung between my attic
roof and a garden tree (about 40 feet high), with a connection to the centre
wire of a 50 ohm coax cable as soon as it enters the attic roof, down to my
antenna tuner.

From what you have written, I surmise that you do not have
a ground connection for the coax shield at the antenna
feedpoint, that is, at the attic roof. I would add such
a wire from that point down to a ground rod outside your
house. Attaching some buried ground wires to that rod
would help even more.

You might also add a balun between the coax line and the
antenna feedpoint. This can be simply another length of
coax coiled up at the feedpoint and connected between the
existing coax and the antenna. You didn't mention the
frequencies you are using the antenna on. For lower
frequencies, you would need more coax. Assuming a lower
frequency of 7 MHz, a 20-foot length of coax formed into
a 12-inch diameter coil should suffice. Commercial baluns
are relatively cheap and small. If you use one of those,
get a 1:1 type and make sure you connect the ground wire
to the wire on the balun that has a DC connection to
the coax connector shield. Or get a special form of the
balun called an UNUN and connect the ground wire to the
shield of its isolated coax connector and the antenna
to the center pin.

The antenna you have constructed, although having a
horizontal wire, actually responds to signals that
are vertically polarized, particularly at the lower
frequencies. Unfortunately, noise is also predominantly
vertically polarized, so the antenna is somewhat inherently
noisy.

Of course, I assume you have already followed the mainline
advice offered to you by other posters here that you
eliminate, reduce the effect of, or at least identify the
noisy appliances in your own house.

Would it be any better if the atu was between
the wire and the coax where it enters the roof (although it would be
difficult for me to get a power supply up there)?

I wouldn't do that unless you were having trouble getting
an impedance match on the higher frequencies. And to make
the ATU work at the feedpoint, a ground connection from
there is absolutely required.

Hope this helps....

Jim Bromley, K7JEB
Glendale, AZ, USA

"Robert Lay W9DMK" wrote in message
...
On Mon, 1 Mar 2004 05:52:05 +0000 (UTC), "tedoboxer"
wrote:

....snip My problem is a very high level of electrical noise across
most HF bands, especially the lower ones.

Look for any "Touch Lamps" that are in your home and get rid of them.
They are wide band noise generators - on or off.

Aquarium heaters are known to be bad noise
makers. Any electrical device where the contacts
are not cleanly opening/closing can cause it.

I recently had the power company come out and,
lo and behold, there was a problem in the HV side
of the circuit supplying my house. I had a radio on
the back porch, battery-powered, while the serviceman
tightnened connections. He redid everything on the
low-voltage side, no help... then he got out the fiberglas
extend-a-pole and touched the HV cutout (big knife switch)...
instant crunch in the receiver (tuned to 50.125MHz USB).
He cycled the big switch and the power noise has been
much better (still comes and goes some).

I found a bad circuit breaker contact in my outside
service panel after that... buss bar had been installed
without bending the cable properly, resulting in bad
contact where the breakers clip on to the bar.

My point is, you could have three different sources of noise... use
the battery-powered receiver to isolate the noise source. Once
you know the source of the noise, you are most of the way to
solving your problem.
__
Steve
KI5YG
..