Antenna height

[Staybolt]

My 5 element beam is up 50 foot on my tower and on ssb on a good night I can talk to Richmond, Ind 150 miles away.

 

[SIX-SHOOTER]

View attachment 41261

As I said,Slightly Over 36 Ft for the 11 meter band.I Love being Right. {:>)

SIX-SHOOTER

 

[Marconi]

The closest local would have been around 8km it was a base station but could always hear mobile units running close around my building.

Thanks for the answer Tin_Can.

My Pop had a field services business in far South Texas for years. He used and old 200' tower that the Light company abdomen on his property, in the back water marshes of the Gulf.

He had an old Starduster put up there so he could use his radio to stay in touch with his 5 crews harvesting crops for farmers out a 100+ miles and more.

He once told me he could hardly hear a soul, mobile, in Kingsville, Texas, about 20 miles away to the West while the tower was right near the Gulf water mash land.

He could hear lots of traffic in Corpus Christi about 50+ miles due North. 100 - 200 miles for his crews in the fields was easy contacts with that old Starduster however.

This is the reason for my question, just curious.

 

[Slowmover]

Thanks for the answer Tin_Can.

My Pop had a field services business in far South Texas for years. He used and old 200' tower that the Light company abdomen on his property, in the back water marshes of the Gulf.

He had an old Starduster put up there so he could use his radio to stay in touch with his 5 crews harvesting crops for farmers out a 100+ miles and more.

He once told me he could hardly hear a soul, mobile, in Kingsville, Texas, about 20 miles away to the West while the tower was right near the Gulf water mash land.

He could hear lots of traffic in Corpus Christi about 50+ miles due North. 100 - 200 miles for his crews in the fields was easy contacts with that old Starduster however.

This is the reason for my question, just curious.

And you used to walk barefoot to Petronila with a half bit you’d saved?

.

 

[Marconi]

Nope, Pop's place was south of Balfin Bay, Texas, deep in cotton farms.

 

[TIN_CAN]

Thanks for the answer Tin_Can.

My Pop had a field services business in far South Texas for years. He used and old 200' tower that the Light company abdomen on his property, in the back water marshes of the Gulf.

He had an old Starduster put up there so he could use his radio to stay in touch with his 5 crews harvesting crops for farmers out a 100+ miles and more.

He once told me he could hardly hear a soul, mobile, in Kingsville, Texas, about 20 miles away to the West while the tower was right near the Gulf water mash land.

He could hear lots of traffic in Corpus Christi about 50+ miles due North. 100 - 200 miles for his crews in the fields was easy contacts with that old Starduster however.

This is the reason for my question, just curious.

Mother nature is truly wonderful...Cheers!!

 

[edfiero]

I came across a printed article from the late 60's or early 70's that covered this topic. The article indicated that assuming flat ground (I guess think Kansas), that you need to TRIPLE your antenna height like from 20 feet to 60 feet to get almost DOUBLE the range (1.8x) to be exact.

So practically speaking, if your antenna is 20 feet or less, there is a lot of range to be gained relatively easily. But if you already up 40 or 50 feet, going up another 10 feet is not likely to make a noticeable difference.

 

[Marconi]

I came across a printed article from the late 60's or early 70's that covered this topic. The article indicated that assuming flat ground (I guess think Kansas), that you need to TRIPLE your antenna height like from 20 feet to 60 feet to get almost DOUBLE the range (1.8x) to be exact.

So practically speaking, if your antenna is 20 feet or less, there is a lot of range to be gained relatively easily. But if you already up 40 or 50 feet, going up another 10 feet is not likely to make a noticeable difference.

Here is my SP 500 with a tapered radiator.

1. is the model in Free Space that reports the Average Gain Test = 1.

2. is the same basic model as #1, over (average) Real Earth at 36'. 40', 50' feet above Earth.

I also added overlays comparing these 3 models for gain and angle. Note the angle increases as the antenna is raised and the maximum gain angle drops by 1* with each interaction in height.

IMO, these models show very little differences between the maximum gain and angle patterns produced and you would be hard pressed to see a difference just using your radio.

From the minimum to the maximum gain and angle...it may not be unusual to hear one operator produce a bit <> audio...a lot of things might effect such effects.

 

[Marconi]

Do not mount groundplane antennas at heights between 0.25 and 1.25 wavelength. At those levels above ground most of the energy will be radiated at angles of 27° to 45° into the ionosphere. This phenomenon seems to be independent to the number of radials or other counterpoises. Further simulations indicates that this is true for all other variants of vertical antenna systems too.

https://www.qsl.net/df3lp/projects/vertical/index.html

Here I set the SP 500 at 1.25% wavelength.

This looks like a little benefit to me, and I sure don't see the maximum gain and angle shooting up to 27* - 45* degrees, but it does produce an additional lobe at a high angle. Adding high angle lobes is sometimes what we see when we go higher.

 

[edfiero]

Here is my SP 500 with a tapered radiator.

IMO, these models show very little differences between the maximum gain and angle patterns produced and you would be hard pressed to see a difference just using your radio.

Thanks for the plots. Unfortunately I don't know how to read them. I thought these showed the radiation pattern, not the expected distance.

I believe the point of the article I found was that by raising the antenna height the horizon becomes increasingly farther away, and with a increased horizon comes an increased range. The article did not imply the gain or the pattern of the antenna was changed by raising the height.

 

[BJ radionut]

Height versus take off angle (dx-antennas.com)

 

[Marconi]

Thanks for the plots. Unfortunately I don't know how to read them. I thought these showed the radiation pattern, not the expected distance.

The antenna pattern plots only show the maximum gain and angle at the lowest point on the horizon (Earth) and the values are relative.

Imagine you are standing about 50' feet away and on the ground looking at your antenna. In the model for the Antenna Pattern...you will be seeing the RF pattern generated by the software.

There is no distance indicated in models at this level of modeling.
Any ideas for distance will have to be somehow determined in Real World testing, if at all.

Does the antenna in the Antenna View look familiar to you?

Does the Source Data Report (matching at the feed point) look familiar to you?

Does the Bandwidth Curve Report look familiar to you?

Thanks for the questions edfiero

 

[Marconi]

I believe the point of the article I found was that by raising the antenna height the horizon becomes increasingly farther away, and with a increased horizon comes an increased range. The article did not imply the gain or the pattern of the antenna was changed by raising the height.

Raising the antenna can produces a lower angle to the horizon. I can also produce more lobes at higher angles above the horizon. That said, the lowest angle noted as maximum gain is generally considered as the better antenna for distance, but in some situations like in valleys or on hills and mountains...other angles can be important.

The surface is also filled with "stuff" that can either increase RF signals or decrease RF signals at unknow points.

This is complicated stuff, and predicting results can be scientifically determined I'm sure, but I don't see many CB'rs doing real science.

Observations, comparisons, opinions, and experiences are acceptable discussion points...don't you think?

 

[edfiero]

Height versus take off angle (dx-antennas.com)

Interesting article. If I understand it correctly, the focus of the article is about DX (skip). Do the conclusions hold true for non-skip (local) conditions? My original question is specifically about local effects of antenna height.

 

[TheBlaster]

There is an oddity to this model that does not seem to relate to what is written..

Do not mount groundplane antennas at heights between 0.25 and 1.25 wavelength. At those levels above ground most of the energy will be radiated at angles of 27° to 45° into the ionosphere. This phenomenon seems to be independent to the number of radials or other counterpoises. Further simulations indicates that this is true for all other variants of vertical antenna systems too.

https://www.qsl.net/df3lp/projects/vertical/index.html

Specifically this image, the third model (fig 4) on that page.. by eye alone that looks like MORE gain at a lower angle (like a hat rim) than the prior 2 images. (despite less gain and a bit of a null at a higher angle)

Though the text relating to that model does not confirm that, it says:

"But now have a look at Figures 4 to 6! At those usual heights most of the transmitting energy is radiated at high angles. There is only a small amount of radiated energy at low angles which could bring you up into DXCC highscore. Figure 4: Height: 0.5 x wavelengths (ca. 10m at 14MHz).Impedance: 25.7 - j0.7 ohms Max. Gain: 1.9 dBi at 45°."

What do you believe the image or the text ?

This is of special interest to me as I have just recently made and used a GPA antenna and it seems to work quite well in my first test.