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Author Topic: Antenna for sloping lot  (Read 4199 times)

Posts: 12

« on: July 13, 2013, 07:31:42 PM »

I've just moved to a new place, and am thinking about what sort of antenna to install.

The main characteristic of this place is that it's on a sloping lot. The rear of the property is well above the roof of the house. The slope is downward toward about 30 degrees magnetic. This is in suburban Sydney, so Southern Hemisphere. The generally northern exposure is good, and a quick WSPR experiment with a small, portable vertical showed reasonable propagation.

There's already a tower for the TV antenna on the roof, so I can run a wire, probably a full size G5RV, from the back fence to that, no problem.

There is another lot behind me, further up the hill, so that's a consideration.

My question is, should I consider a larger vertical? My budget and space would allow something like a Hustler 5BTV or (maybe) a Butternut HF6V. I could put up a 43-foot vertical, as well, and have some radials.

Is a vertical on a hillside a good idea, or should I work out a way to do something more directional? I am not sure there's room for a beam, though maybe a rotating dipole is possible.


Posts: 7718

« Reply #1 on: July 14, 2013, 06:42:06 AM »

The verticals you mention as well as the G5RV will yield many contacts. You might install both antennas - a vertical and a horizontal - and compare them.

Posts: 2276

« Reply #2 on: July 14, 2013, 03:17:59 PM »

I would locate the 5btv at the high point of your property and add as second antenna a rotatable trap dipole on the tower.

The two antennas will serve you very well and since the dipole can be rotated would certainly help when Not IF the conditions warrant.

Since the two antennas are roughly at equal heights the skywave variations can be seen and properly accounted for with a/b switching.

If the horizontal rotatable dipole is high enough on the lower bands such as 40m you may notice minimal difference here.

If the horizontal dipole is only a quarter wave above the surface below it then the vertical will show improvementsduring a/b switching comparisons, relative to longer skywave dx over the sampled period on average.


Posts: 12

« Reply #3 on: July 15, 2013, 03:33:34 AM »

Thanks to both of you. I am pretty happy with the new QTH, as it seems like the biggest risk will be annoying the guy uphill, and I think I can manage that.

Some questions:

1. There is no reason not to go with a longer vertical if I can, right? A DX Engineering 43-foot vertical is better than the shorter Hustler in all cases, if I can afford it, I think.

2. Can an aluminum antenna be painted with some sort of dull spray enamel to make it less visible, without affecting its performance?

3. What is the take-off angle of a vertical antenna on a slope?

Thank you. Apologies for my ignorance.

Posts: 17476

« Reply #4 on: July 15, 2013, 08:19:22 AM »

There were some studies in one of volumes of the ARRL Antenna Compendium on
the radiation pattern of vertical antennas on a slope, but I'd have to dig out the book
to see what it said.

Ground slope can make a significant difference in the angle of radiation for horizontal
polarisation, however.  With a steep enough slope you can get low angle radiation from
a relatively low antenna, at least in the downhill direction.  (Uphill is much more difficult.)
G6XN discusses this in his book, HF Antennas for All Locations.  A friend of mine
put his 20m yagi at 140' and it worked very poorly: because of his sloping ground the
optimum height was about 55' instead. 

There is a software package called something like HF Terrain Analyzer that allows
you to look at the vertical radiation angles due to different antenna heights and ground
topography that might help to answer some of your questions.

Posts: 203

« Reply #5 on: July 15, 2013, 09:27:43 AM »

I've never had to paint an antenna, but others have.
Here's one from another eham thread.  And there are lots more if you search eham.,24144.0.html

73 & GL
de K3ANG
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