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Author Topic: Antenna Help/Advice Needed Please  (Read 2121 times)
K4KMG
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Posts: 16




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« on: September 21, 2010, 06:26:37 AM »

Hello. I recently moved to the house shown in the links below. I have high tension electrical wires running along one side of my property. I have not been active for many years, for the usual reasons, and have forgotten most of the little bit of antenna knowledge I used to know. I'm essentially looking for advice/site survey to determine my antenna options. As you can see, I not only have power lines, but many large and high oak trees. I'm assuming a wire is not feasible, but I do have an approximately 50x50x50x50ft area in the back rear, behind the carport, of my property that is open to the sky. This area would be available for a tower. I'm thinking a 60 ft crankup would be a good choice. (affordable) My main concern is the effect, if any, that the power lines would have on operation.


Any advice would be appreciated.
Tom
« Last Edit: December 18, 2011, 11:26:55 AM by K4KMG » Logged
W5FYI
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Posts: 1044




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« Reply #1 on: September 21, 2010, 07:27:45 AM »

FWIW, when I got back into ham radio, I had high tension lines in my back yard. I was able to put up a 10-15-20 tribander on a 40-foot tower, stuck a 2-meter Isopole up there as well, and hung a 40-meter inverted V, and had absolutely no problems working HF. Maybe I was just lucky, but I think the electric utility also kept an eye on things as well.

Why not erect a low antenna just to see if you get RFI from the power line, then go from there? GL
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WA3SKN
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« Reply #2 on: September 21, 2010, 07:46:08 AM »

OK, single story dwelling.
The power lines are a potential noise source.  Probably not a problem, but you want your atenna away from them.
Deteremine where the power is feeding your house, and stay away from that.
Determine where your shack will be located in the house, and how you will get the feedline out.
Now start looking for a good antenna location... away from all the noise sources the house provides.
You do not want the tower/antenna falling onto power lines of ANY kind!

-Mike.
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K4KMG
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« Reply #3 on: September 21, 2010, 07:54:31 AM »

Thanks! The power lines would be at least 200ft from the tower. Even if it fell over, it would not be anywhere near the lines. If I put the tower at the rear of the property, as opposed to up against the house, I'd be 80 ft from the electrical entry into the house.
Tom
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AB9PM
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Posts: 27




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« Reply #4 on: September 21, 2010, 07:55:18 AM »

I think FYI gave you the best advice any person could give you, and that is erect a trial antenna and see what your challenges could be from the power lines. Power lines are deceiving. Depending on just how high of voltage they carrying. I have a sub station close to me with major transmission lines, and then secondary lines. It will give you an idea of how much you wish to invest.

Dave
AB9PM
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K4KMG
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« Reply #5 on: September 21, 2010, 08:10:22 AM »

I agree, it's good advice, but I've got large trees almost everywhere.  Those power lines sure do a lot of 'crackling'!

Any way to check the power lines without setting up any antenna?
Tom
« Last Edit: September 21, 2010, 08:14:34 AM by Tom Foglesong » Logged
WA3SKN
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« Reply #6 on: September 21, 2010, 08:19:12 AM »

Usually, high voltage power lines are not the problem.
Usually, power to the house is not the problem.
Usually all the cute little digital gadgets and gizmos that are in the house ARE the problem!
So having your antenna away from the house and power feeds solves a lot of noise issues.
And it looks like you have the room to install an antenna system in a good location.  Not everyone can!
But it would be a good idea to get an antenna and radio connected just to check for noise problems, then get the tower up.
Good luck with the project!
73s.

-Mike.
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K4KMG
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« Reply #7 on: September 21, 2010, 09:57:42 AM »

One more question. How much effect will the large trees have on a wire antenna. I can't get a wire out in the open.
Thanks
Tom
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AB9PM
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« Reply #8 on: September 21, 2010, 04:42:07 PM »

I have never dealt with many trees. I have been told to use insulated wire when running through trees, but my experience though limited in trees is when they get wet, they can still throw off swr in antennas. As far as reception/transmitting, most people claim they do quite fine despite heavy tree coverage.

If you want to know how noisy your area can be, stick a single wire in the back of your rig and extend it across your yard. A single wire antenna verses a dipole, will give you a much higher noise level,  a balanced dipole is a quieter receive option for noise, not signal strength.

Good luck and have fun.

Dave
AB9PM
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N1LO
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« Reply #9 on: September 22, 2010, 08:43:24 AM »

Hi Tom,

A single mast in that clearing would support an 88' doublet, leaving 10 or 15' hanging tails on each end. Put up as an inverted V and fed with window line, current balun and tuner, this will quickly and cheaply deliver you 80-10m as a test while you save up for your tower.

You could also set lines in the trees bordering the clearing and pull the same antenna up as an inverted U (flattop with tails).

A 40m horizontal loop (45' on a side) fed at a corner with window line would also play nicely 40-10, but would require 3 suspension points.

There is also plenty of room for a nice trapped vertical and radials there.

Good Luck,

- - · · ·  M A R K · N 1 L O · · · - -
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K4KMG
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« Reply #10 on: September 23, 2010, 07:13:13 AM »

Thanks Mark. I have the $ for the tower, just want to make sure I have no interference problems. I went ahead and got a G5RV for testing purposes. I'll be interested in seeing how it performs with regard to all my trees.
Tom
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K4KMG
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« Reply #11 on: December 18, 2011, 11:21:23 AM »

Update: (yes, I know, it's been awhile!)

It appears I have a huge noise problem that I can't figure out.

Current setup:
Omni VII
Gap Titan at approx 30ft high, and 100ft horizontally from high tension wires.

High tension wires are closer than I originally stated. About 100ft horizontally from the house and about 60ft high.

Noise is a good S8+ most times, on all bands, although it does vary some depending on time of day. To eliminate as many possibilities as I could, I've done the following:

Hooked radio to battery and killed the main breaker to house. NO difference in noise level.

Using an AM radio, I wandered around outside and got the same type/level of noise. (bacon frying) When rotating the radio, I got the noise in all but 2 directions, and only for a degree or two in those 2 directions, (NE and SW), where the noise dropped significantly.

Sure would like to get on the air, but at these levels, it's just not enjoyable. Any suggestions would be appreciated

Thanks.
Tom K4KMG

Picture of the high tension wires here: http://k4kmgweather.com/images/wires.gif Antenna is above the peak of the house. (not the garage)

Mods: This might be better placed in the RFI forum. Feel free to move if necessary.
« Last Edit: December 18, 2011, 11:40:16 AM by K4KMG » Logged
WB6BYU
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Posts: 12979




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« Reply #12 on: December 18, 2011, 02:30:37 PM »

Quote from: K4KMG

Using an AM radio, I wandered around outside and got the same type/level of noise. (bacon frying) When rotating the radio, I got the noise in all but 2 directions, and only for a degree or two in those 2 directions, (NE and SW), where the noise dropped significantly.



Was that the way the radio was FACING, or the direction off the EDGES of the case?

You've successfully taken a bearing on the offending source:  the nulls will be off the
sides of the case (the ends of the built-in ferrite rod antenna.)  Unless you are standing
under the lines themselves, in which case the null will be when the rod is in line with
the power line.

Move some distance and try again - see if you can triangulate the source.  Start by
moving at right angles to the initial bearing, as that is more likely to help you determine
which direction it is in.  (It could be either direction.)

At some point you'll have problems taking a bearing because the signal will come
from along a wire rather than a point source.  Then you can just walk around listening
for where the interference is strongest.  From that point an AM or SSB/CW VHF radio
is probably best for pointing to the source with a directional antenna.
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AC5UP
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« Reply #13 on: December 18, 2011, 03:01:40 PM »

Your AM radio has a ferrite bar antenna and reading the null is the most effective method of tracking down a noise source.

                  North

West  <== ferrite rod ==>  East

                  South

Rotate the radio until you hear a sharp null in the noise. The source will be along the axis of the rod and by the illustration above East or West of the radio... Assuming you know how the rod is oriented inside the radio.

Your next step is to move 50 feet or so (depending on the location) to the North or South. Find the new null direction. Assuming it's now NE/SW or NW/SE at the second location, you should be able to draw a line for the antenna axis as seen from the first location and another as seen from the second location. The noise source will be near the intersection of the two lines.

If you have trouble hearing a good null, you're probably too close to the noise. Try it from two new locations.
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K4KMG
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Posts: 16




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« Reply #14 on: December 18, 2011, 03:32:26 PM »

Thank you. Antenna was facing directly away from me in a horizontal position. (although, horizontal or vertical made no difference) I just went out and tried again. The farther away I get from the wires, the noise quickly reduces considerably in any direction. (say 200ft+)

If I'm close to or even standing under the wires, I get nulls at 90 degrees off of parallel, (in either direction), with the wires. As I swing around to parallel with the wires, the noise increases considerably and quickly.

Tom
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