Inverted V Noise Problem
 

Hello, all....

My first HF antenna (still in use) is an inverted V cut for 40
meters. This very quiet antenna is constructed suspended from three trees
in front of my home - the tree in the middle supports the apex while two
somewhat evenly spaced trees support the ends. The center of the antenna
is approximately 30' above the ground, and the angle of the V is about 120
degrees. The antenna is constructed of #14 stranded jacketed wire fed with
450 ohm window line. This antenna has worked quite well for me on 10-40
meters using a transmatch.

Several months ago, I tried to raise the antenna's center to around
40'in order to improve performance. I also raised the antenna's ends
proportionately. My transceiver's noise level increased dramatically. I
then tried a "flat top" dipole configuration without any lessening of the
noise. When I returned my antenna to its original configuration, all was
quiet again. To me, the noise sounded electrical in nature.

There is a power line feeding a street lamp about 25' away and
perpendicular to the original dipole. The street lamp power line is about
35' high. Power lines to all of the homes in our neighborhood are buried
except for the home adjoining our back lot. The power company strung a
conventional pole-to-house feed to their home. The feed to the street light
also runs from this pole.

I am planning on stringing an 80 meter dipole in our back yard. This
new antenna would be constructed of the same components, and parallel to my
original wire antenna. The apex would be strung between trees with the
middle about 40' above the ground. However, I am leery of doing this
project considering the noise problem experienced when I raised my original
antenna. I would like to add a 80/75 meter antenna however.

Is my problem related to a noisy power line feeding the street light,
or is it be something else?

Thanks in advance for your suggestions!


Warren - KC8YKQ

Warren Bowery wrote:
... My transceiver's noise level increased dramatically...
Warren - KC8YKQ

Warren -

To solve this kind of problem in the real world, you need to eliminate
things one by one.

With the antenna back up in the noise, see what happens when the street
light comes on at dusk - is this when the noise starts? Or is the noise
there before the light turns on?

If it's there without the light, some device in your neighbor's house
may be sending the noise back up the power line. Thermostats, fishtank
heaters, yard lights - the variety of noise sources is impressive.

Could also be loose or rusted connections on the pole/transformer.

You might be able to trace the source with a pocket transistor radio
tuned between stations.

ARRL has some good stuff on interference - have you checked their website?

Would like to hear other opinions on this one - I'm still learning.

73 -

Lee H, NB7F

Warren,

You may not have a problem.

The signals level MUST also have increased with the increase in height.

Did the signals go up together with the noise, the signal-to-noise ratio
remaining unchanged?
----
Reg

Reg - any increase in signals certainly did not increase enough to overcome
the noise. Like I mentioned, the original configuration I is very quiet.
In fact, the noise level went from not registering on the meter at all at
the lower height to an S9+ when I raised the antenna.

Warren





Reg Edwards" wrote in
:

Warren,

You may not have a problem.

The signals level MUST also have increased with the increase in height.

Did the signals go up together with the noise, the signal-to-noise ratio
remaining unchanged?
----
Reg

"If it's there without the light, some device in your neighbor's house
may be sending the noise back up the power line. Thermostats, fishtank
heaters, yard lights - the variety of noise sources is impressive.
Could also be loose or rusted connections on the pole/transformer."

To the above, add the photocell on the street light. depending on how
it was designed, it could make noise waiting to turn 'on', or when 'on'.
'Doc

On Sun, 28 Nov 2004 00:20:56 -0600, Warren Bowery
wrote:

Hello, all....

My first HF antenna (still in use) is an inverted V cut for 40
meters. This very quiet antenna is constructed suspended from three trees
in front of my home - the tree in the middle supports the apex while two
somewhat evenly spaced trees support the ends. The center of the antenna
is approximately 30' above the ground, and the angle of the V is about 120
degrees. The antenna is constructed of #14 stranded jacketed wire fed with
450 ohm window line. This antenna has worked quite well for me on 10-40
meters using a transmatch.

Several months ago, I tried to raise the antenna's center to around
40'in order to improve performance. I also raised the antenna's ends
proportionately. My transceiver's noise level increased dramatically. I
then tried a "flat top" dipole configuration without any lessening of the
noise. When I returned my antenna to its original configuration, all was
quiet again. To me, the noise sounded electrical in nature.

There is a power line feeding a street lamp about 25' away and
perpendicular to the original dipole. The street lamp power line is about
35' high. Power lines to all of the homes in our neighborhood are buried
except for the home adjoining our back lot. The power company strung a
conventional pole-to-house feed to their home. The feed to the street light
also runs from this pole.

I am planning on stringing an 80 meter dipole in our back yard. This
new antenna would be constructed of the same components, and parallel to my
original wire antenna. The apex would be strung between trees with the
middle about 40' above the ground. However, I am leery of doing this
project considering the noise problem experienced when I raised my original
antenna. I would like to add a 80/75 meter antenna however.

Is my problem related to a noisy power line feeding the street light,
or is it be something else?

Thanks in advance for your suggestions!


Warren - KC8YKQ

C.Crane Co. has a helpful page on receiving noise:

http://www.ccrane.com/radio-noise-problems.aspx

bob
k5qwg

On Sun, 28 Nov 2004 06:47:45 -0600, Warren Bowery
wrote:
Reg - any increase in signals certainly did not increase enough to overcome
the noise. Like I mentioned, the original configuration I is very quiet.
In fact, the noise level went from not registering on the meter at all at
the lower height to an S9+ when I raised the antenna.

Hi Warren,

Then it appears you upset the balance of the antenna (hard to believe
it was balanced before) such that common mode noise is finding its way
in.

It seems entirely unlikely that you achieved any more gain, nor more
highly resolved angular discrimination to now be focused on a source
of noise that has "always" been there.

The way I read your statements, it's as if you raised your antenna to
the equal horizon of a noise your antenna in its former position just
couldn't see. At HF and at those heights, this just isn't in the
cards. Signal intensity follows square law and for your noise to rise
from nothing to S-9 does not correspond to any dimensional change (or
if it does, there's your clue, but you are within inches of it now
where you were 10's of feet away formerly).

73's
Richard Clark, KB7QHC

Sounds to me like its a not so simple case of more power line noise coupled
into the antenna at it increased height, which at its new height is also
closer to the height of the power line. But the comments about the large
difference in noise observed and also the contradiction to the square law
effect are interesting.

Maybe the question we should be pondering is NOT what the changes in the
antenna pattern are, but what the antenna pattern of the *power line* at the
observed freq is. These things are by nature antennas as well which also
exhibit directivity and gain (I'm cringing at the thought of future BPL
"dx"), but would probably be impossible to model since there are too many
unknowns.

So my 2 cent theory is that the original antenna location lies in a power
line noise pattern null (or no low angle) and at the new height it's now in
a lobe.

John



"Richard Clark" wrote in message
...
On Sun, 28 Nov 2004 06:47:45 -0600, Warren Bowery
wrote:
Reg - any increase in signals certainly did not increase enough to
overcome
the noise. Like I mentioned, the original configuration I is very quiet.
In fact, the noise level went from not registering on the meter at all at
the lower height to an S9+ when I raised the antenna.

Hi Warren,

Then it appears you upset the balance of the antenna (hard to believe
it was balanced before) such that common mode noise is finding its way
in.

It seems entirely unlikely that you achieved any more gain, nor more
highly resolved angular discrimination to now be focused on a source
of noise that has "always" been there.

The way I read your statements, it's as if you raised your antenna to
the equal horizon of a noise your antenna in its former position just
couldn't see. At HF and at those heights, this just isn't in the
cards. Signal intensity follows square law and for your noise to rise
from nothing to S-9 does not correspond to any dimensional change (or
if it does, there's your clue, but you are within inches of it now
where you were 10's of feet away formerly).

73's
Richard Clark, KB7QHC

On Sun, 28 Nov 2004 12:15:40 -0500, "- XC -" wrote:

So my 2 cent theory is that the original antenna location lies in a power
line noise pattern null (or no low angle) and at the new height it's now in
a lobe.

Hi John,

The simple wavelength mechanics of that negate the premise. For any
structure, much less a power line, to exhibit a null due to a dipolar
distribution; then that would have to arise from certain constraints.
Chief among them is isolation from ground by a significant portion of
one wavelength, in this power line case 5000000 meters.

However, the noise is not 60Hz. In the case of the actual frequency
of the interference, it is equally unlikely to be emanating from the
power lines - from the 60 Hz generation end. It would necessarily be
emanating from a load that is using the line as an antenna (although,
not purposely except in your nightmare of BPL).

In this case of higher frequency nuisance, the same powerlines would
present an enormously long structure (unless the noise were snubbed at
the nearest isolation transformer). that would create a huge number of
lobes. And still, it is unlikely that any null to peak of those lobes
would match the characteristic of no noise to S-9 variation. As such,
the odds are on square-law ruled proximity. Where in quieter times
past the noise was 10's of feet away, with change that noise got
within inches. That, or the description of noise levels has been
exaggerated.

A noise survey should be performed with a simple handheld transistor
SW receiver. Walk around and listen. If push comes to shove, then
tie a string to the receiver, turn up the volume and hoist it up.
More can be determined by this than all the arm-chair prognosis.

73's
Richard Clark, KB7QHC

Richard:

Don't forget the harmonics that may be caused and radiated by the power
lines...

Just a thought.

-SSB

Richard Clark wrote:
On Sun, 28 Nov 2004 12:15:40 -0500, "- XC -" wrote:


So my 2 cent theory is that the original antenna location lies in a power
line noise pattern null (or no low angle) and at the new height it's now in
a lobe.


Hi John,

The simple wavelength mechanics of that negate the premise. For any
structure, much less a power line, to exhibit a null due to a dipolar
distribution; then that would have to arise from certain constraints.
Chief among them is isolation from ground by a significant portion of
one wavelength, in this power line case 5000000 meters.

However, the noise is not 60Hz. In the case of the actual frequency
of the interference, it is equally unlikely to be emanating from the
power lines - from the 60 Hz generation end. It would necessarily be
emanating from a load that is using the line as an antenna (although,
not purposely except in your nightmare of BPL).

In this case of higher frequency nuisance, the same powerlines would
present an enormously long structure (unless the noise were snubbed at
the nearest isolation transformer). that would create a huge number of
lobes. And still, it is unlikely that any null to peak of those lobes
would match the characteristic of no noise to S-9 variation. As such,
the odds are on square-law ruled proximity. Where in quieter times
past the noise was 10's of feet away, with change that noise got
within inches. That, or the description of noise levels has been
exaggerated.

A noise survey should be performed with a simple handheld transistor
SW receiver. Walk around and listen. If push comes to shove, then
tie a string to the receiver, turn up the volume and hoist it up.
More can be determined by this than all the arm-chair prognosis.

73's
Richard Clark, KB7QHC