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Sloping Terrain vs Feedline Losses

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Edward A. Dauer

Sloping Terrain vs Feedline Losses

So long as antenna discussions on the reflector haven’t been met with the “OT” cloture lately, I have an antenna question of a different sort. I am contemplating a ¼ wave vertical with four elevated radials for 80 meters. My choices for siting it are two – one is near the top of the property (about 8,600 feet ASL), somewhat in the clear, and within 100 feet from the operating position. The other is in a meadow near the property boundary, which is much more open and a just a bit higher – but it has two other significant characteristics. One is that the land slopes away from that site, over about half the compass from NNW to SSE, at a slope of 10 to 15% for about a half mile. According to ON4UN’s text, that slope could give me a significant gain in that part of the azimuth with no significant terrain obstruction on the other half. The second characteristic, however, goes the other way – that site would require about 500 feet of feedline from the house to the antenna feed point. I have been looking at the loss factors in hardline and in “direct burial” coax, which on 80 meters seem modest but not irrelevant for a run of that length – maybe a dB or so per 100 feet. What I can’t quantify – because I don’t have enough life expectancy to learn how to adapt antenna modelling software to a Mac or even to learn it if I could – is whether the gain from the sloping near field would make up for the feedline loss. In case it matters, the ground likely has very poor conductivity. It’s decomposed granite – a specialty in the Colorado mountains – with a very thin layer of usually very dry soil. (Our well has a static level of 142 feet, so there’s no ground water anywhere near the surface.) Anyone have opinions, guesses, estimates, advice, or whatever – should I accept the feedline losses and enjoy the half-hemisphere low-angle gain? Or would the poor soil quality negate that advantage?

Ted, KN1CBR

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Craig Smith

Re: Sloping Terrain vs Feedline Losses

Ted …

I think you are overstating the coax losses. Even stock RG-11 should be perhaps 0.3 dB/100ft on 80 meters - around 1.5 dB for the 500 ft. run.

Even so, I would probably gravitate toward the closer location. With the elevated radials, the effects of the ground conductivity should be minimal. Not sure if ON4UNs data assume elevated radials or many on-ground radials. It could be that his estimate of the sloping ground advantage is for the later. With the closer location, you will have perhaps 1 dB stronger signal in all directions because of the lower feedline loss.

73 Craig AC0DS

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N5CQ

Re: Sloping Terrain vs Feedline Losses

The elevated radials should help reduce near field I2R losses, but the sloping terrain will help far field reinforcement and produce 'gain' in some directions, although at 80M it should slope for further than a mile away to really make a difference. I do not think elevated radials will change the far field reflections from the sloping terrain in any way.

At 80M, even small hardline should have very low loss, so I would go for the location that has the better terrain profile.

73 John N5CQ

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Craig Smith
Sent: Tuesday, July 12, 2016 5:50 PM
To: Dauer, Edward <[hidden email]>
Cc: [hidden email]
Subject: Re: [Elecraft] Sloping Terrain vs Feedline Losses

Ted …

I think you are overstating the coax losses. Even stock RG-11 should be perhaps 0.3 dB/100ft on 80 meters - around 1.5 dB for the 500 ft. run.

Even so, I would probably gravitate toward the closer location. With the elevated radials, the effects of the ground conductivity should be minimal. Not sure if ON4UNs data assume elevated radials or many on-ground radials. It could be that his estimate of the sloping ground advantage is for the later. With the closer location, you will have perhaps 1 dB stronger signal in all directions because of the lower feedline loss.

73 Craig AC0DS

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Ken G Kopp

Re: Sloping Terrain vs Feedline Losses

Don't forget about scrap 72 ohm CATV aluminum hard-line -or- open wire to
feed the vertical.

73!

K0PP
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Elecraft mailing list

Re: Sloping Terrain vs Feedline Losses

In reply to this post by N5CQ

Elevated radials will do more by establishing a fixed array configuration on match and pattern. The orientation of the ground is another issue but with a fixed orientation the pattern will be more subtle. I run multiple antennas with vertical orientation and find that the ground conductivity has more to change the pattern than the radials. That said, look at the ground conductivity in your area and see if it is constant over a year or widely wet to dry. If the ground is highly variable, the elevated radials will help give you a more stable operating platform or match.

Mel, K6KBE

From: John Langdon <[hidden email]>
To: 'Craig Smith' <[hidden email]>; "'Dauer, Edward'" <[hidden email]>
Cc: [hidden email]
Sent: Tuesday, July 12, 2016 6:36 PM
Subject: Re: [Elecraft] Sloping Terrain vs Feedline Losses

The elevated radials should help reduce near field I2R losses, but the sloping terrain will help far field reinforcement and produce 'gain' in some directions, although at 80M it should slope for further than a mile away to really make a difference. I do not think elevated radials will change the far field reflections from the sloping terrain in any way.

At 80M, even small hardline should have very low loss, so I would go for the location that has the better terrain profile.

73 John N5CQ

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Craig Smith
Sent: Tuesday, July 12, 2016 5:50 PM
To: Dauer, Edward <[hidden email]>
Cc: [hidden email]
Subject: Re: [Elecraft] Sloping Terrain vs Feedline Losses

Ted …

I think you are overstating the coax losses. Even stock RG-11 should be perhaps 0.3 dB/100ft on 80 meters - around 1.5 dB for the 500 ft. run.

Even so, I would probably gravitate toward the closer location. With the elevated radials, the effects of the ground conductivity should be minimal. Not sure if ON4UNs data assume elevated radials or many on-ground radials. It could be that his estimate of the sloping ground advantage is for the later. With the closer location, you will have perhaps 1 dB stronger signal in all directions because of the lower feedline loss.

73 Craig AC0DS

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Vic Rosenthal

Re: Sloping Terrain vs Feedline Losses

In reply to this post by Edward A. Dauer

You might also consider receive noise, which you can check in both spots (unless you are planning a dedicated RX antenna).
As others said, loss for most coax will be much lower than one dB per 100 feet.

Vic 4X6GP

> On 13 Jul 2016, at 01:16, Dauer, Edward <[hidden email]> wrote:
>
> So long as antenna discussions on the reflector haven’t been met with the “OT” cloture lately, I have an antenna question of a different sort. I am contemplating a ¼ wave vertical with four elevated radials for 80 meters. My choices for siting it are two – one is near the top of the property (about 8,600 feet ASL), somewhat in the clear, and within 100 feet from the operating position. The other is in a meadow near the property boundary, which is much more open and a just a bit higher – but it has two other significant characteristics. One is that the land slopes away from that site, over about half the compass from NNW to SSE, at a slope of 10 to 15% for about a half mile. According to ON4UN’s text, that slope could give me a significant gain in that part of the azimuth with no significant terrain obstruction on the other half. The second characteristic, however, goes the other way – that site would require about 500 feet of feedline from the house to the antenna feed point. I have been looking at the loss factors in hardline and in “direct burial” coax, which on 80 meters seem modest but not irrelevant for a run of that length – maybe a dB or so per 100 feet. What I can’t quantify – because I don’t have enough life expectancy to learn how to adapt antenna modelling software to a Mac or even to learn it if I could – is whether the gain from the sloping near field would make up for the feedline loss. In case it matters, the ground likely has very poor conductivity. It’s decomposed granite – a specialty in the Colorado mountains – with a very thin layer of usually very dry soil. (Our well has a static level of 142 feet, so there’s no ground water anywhere near the surface.) Anyone have opinions, guesses, estimates, advice, or whatever – should I accept the feedline losses and enjoy the half-hemisphere low-angle gain? Or would the poor soil quality negate that advantage?
>
> Ted, KN1CBR
>
>
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David Gilbert

Re: Sloping Terrain vs Feedline Losses

In reply to this post by Craig Smith

Agree on the coax losses, but totally disagree on both of your other
comments:

1. Elevated radials will ONLY help reduce near field ground losses ...
they will do nothing to help radiation pattern. The effects of ground
conductivity determine far field pattern (given a particular profile) no
matter what kind of radials he uses.

2. If there is any gain benefit from the terrain profile at all, it
will be much more than 1 db.

Dave AB7E

On 7/12/2016 3:49 PM, Craig Smith wrote:
> Ted …
>
> I think you are overstating the coax losses. Even stock RG-11 should be perhaps 0.3 dB/100ft on 80 meters - around 1.5 dB for the 500 ft. run.
>
> Even so, I would probably gravitate toward the closer location. With the elevated radials, the effects of the ground conductivity should be minimal. Not sure if ON4UNs data assume elevated radials or many on-ground radials. It could be that his estimate of the sloping ground advantage is for the later. With the closer location, you will have perhaps 1 dB stronger signal in all directions because of the lower feedline loss.
>
> 73 Craig AC0DS

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briancom

Re: Sloping Terrain vs Feedline Losses

Hi Dave.

Care to comment on how much benefit vertically polarized antennas might
gain from terrain sloping away from vertical?

For horizontally polarized antennas, where ground reflection gain is up
to 6 dB, the sloping terrain can lower the effective take off angle a
lot- 10's of degrees. There was a program called YTAD that estimated
this effect in one dimension. It's results were quite enlightening.

Vertical antennas have no ground reflection gain. Would one then expect
sloping terrain NOT to alter their already low take off angle much? On
the other hand, folklore seems to indicate a benefit of roof top
verticals with their "elevated" radials over ground mounted verticals
with elevated radials/or in ground radials.

73 de Brian/K3KO

On 7/13/2016 8:49 AM, David Gilbert wrote:

>
> Agree on the coax losses, but totally disagree on both of your other
> comments:
>
> 1. Elevated radials will ONLY help reduce near field ground losses ...
> they will do nothing to help radiation pattern. The effects of ground
> conductivity determine far field pattern (given a particular profile) no
> matter what kind of radials he uses.
>
> 2. If there is any gain benefit from the terrain profile at all, it
> will be much more than 1 db.
>
> Dave AB7E
>
>
> On 7/12/2016 3:49 PM, Craig Smith wrote:
>> Ted …
>>
>> I think you are overstating the coax losses. Even stock RG-11 should
>> be perhaps 0.3 dB/100ft on 80 meters - around 1.5 dB for the 500 ft. run.
>>
>> Even so, I would probably gravitate toward the closer location. With
>> the elevated radials, the effects of the ground conductivity should be
>> minimal. Not sure if ON4UNs data assume elevated radials or many
>> on-ground radials. It could be that his estimate of the sloping
>> ground advantage is for the later. With the closer location, you
>> will have perhaps 1 dB stronger signal in all directions because of
>> the lower feedline loss.
>>
>> 73 Craig AC0DS
>
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Wes Stewart-2

Re: Sloping Terrain vs Feedline Losses

In reply to this post by David Gilbert

I hope you meant much less than 1 dB.

On 7/13/2016 1:49 AM, David Gilbert wrote:

>
> Agree on the coax losses, but totally disagree on both of your other comments:
>
> 1. Elevated radials will ONLY help reduce near field ground losses ... they
> will do nothing to help radiation pattern. The effects of ground conductivity
> determine far field pattern (given a particular profile) no matter what kind
> of radials he uses.
>
> 2. If there is any gain benefit from the terrain profile at all, it will be
> much more than 1 db.
>
> Dave AB7E
>

David Gilbert

Re: Sloping Terrain vs Feedline Losses

In reply to this post by briancom

Hi, Brian.

I have no idea how or to what extent terrain affects a vertically
polarized signal. I am, however, pretty certain that if it does at all
it would be worth more than 1 db. That's just the nature of proximity
effects in general. I suspect that one possible effect of sloping
ground for a vertical antenna might be to move the lossy environment to
where it has less effect on the signal (i.e., lower), and that might be
more significant with poor soil conductivity than with good
conductivity. It seems reasonable to me to imagine that the pattern for
sloping ground would shift at least to some minor extent toward that of
a free space pattern, but I'm pretty sure that ON4UN and others have far
more insight into this than I do.

I've always wished we had a version of HFTA that handled vertically
polarized antennas ... that would probably be enlightening. I've also
tried on occasion to use EZNEC+ for the same purpose since it allows you
to specify at least two different zones around the antenna, but I didn't
have much success with that.

I'm one of those who had quite good luck with roof mounted verticals,
but it's hard to say whether any improvement (if there was one) was the
result of distance from lossy ground or simply the ability to shoot over
lossy surrounding structures like trees and houses. I do think it is
more than "folklore" that elevated radials have benefits over in-ground
radials unless the in-ground radial system is reasonably extensive.
There have been some pretty decent studies on that.

But again, it is important to keep separate the effect of radials on
feedpoint return loss from the effect of ground on radiation pattern.
Radials reduce feedpoint loss but have minimal effect on radiation
pattern unless you are able to go out several wavelengths. On the other
hand, the conductivity of the ground has much less effect on return loss
than a decent radial system, but it is the ONLY determinant of far field
radiation pattern (other than whatever effect the terrain profile itself
may have).

73,

Dave AB7E

On 7/13/2016 3:46 AM, brian wrote:

> Hi Dave.
>
> Care to comment on how much benefit vertically polarized antennas
> might gain from terrain sloping away from vertical?
>
> For horizontally polarized antennas, where ground reflection gain is
> up to 6 dB, the sloping terrain can lower the effective take off angle
> a lot- 10's of degrees. There was a program called YTAD that
> estimated this effect in one dimension. It's results were quite
> enlightening.
>
> Vertical antennas have no ground reflection gain. Would one then
> expect sloping terrain NOT to alter their already low take off angle
> much? On the other hand, folklore seems to indicate a benefit of roof
> top verticals with their "elevated" radials over ground mounted
> verticals with elevated radials/or in ground radials.
>
> 73 de Brian/K3KO
>
>
>
> On 7/13/2016 8:49 AM, David Gilbert wrote:
>>
>> Agree on the coax losses, but totally disagree on both of your other
>> comments:
>>
>> 1. Elevated radials will ONLY help reduce near field ground losses ...
>> they will do nothing to help radiation pattern. The effects of ground
>> conductivity determine far field pattern (given a particular profile) no
>> matter what kind of radials he uses.
>>
>> 2. If there is any gain benefit from the terrain profile at all, it
>> will be much more than 1 db.
>>
>> Dave AB7E
>>
>>
>> On 7/12/2016 3:49 PM, Craig Smith wrote:
>>> Ted …
>>>
>>> I think you are overstating the coax losses. Even stock RG-11 should
>>> be perhaps 0.3 dB/100ft on 80 meters - around 1.5 dB for the 500 ft.
>>> run.
>>>
>>> Even so, I would probably gravitate toward the closer location. With
>>> the elevated radials, the effects of the ground conductivity should be
>>> minimal. Not sure if ON4UNs data assume elevated radials or many
>>> on-ground radials. It could be that his estimate of the sloping
>>> ground advantage is for the later. With the closer location, you
>>> will have perhaps 1 dB stronger signal in all directions because of
>>> the lower feedline loss.
>>>
>>> 73 Craig AC0DS
>>
>> _

a
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David Gilbert

Re: Sloping Terrain vs Feedline Losses

In reply to this post by Wes Stewart-2

No, I didn't mean that.

If sloping ground improves radiation pattern, it's going to be worth
more than 1 db. Pattern changes of any sort typically have significant
effect, whereas one db is almost trivial (notwithstanding my own
experiments on that on my website). I'm not saying that sloping ground
actually has a significant effect ... only that if it has any effect at
all it is likely to be greater than 1 db.

Dave AB7E

On 7/13/2016 10:06 AM, Wes Stewart wrote:

> I hope you meant much less than 1 dB.
>
> On 7/13/2016 1:49 AM, David Gilbert wrote:
>>
>> Agree on the coax losses, but totally disagree on both of your other
>> comments:
>>
>> 1. Elevated radials will ONLY help reduce near field ground losses
>> ... they will do nothing to help radiation pattern. The effects of
>> ground conductivity determine far field pattern (given a particular
>> profile) no matter what kind of radials he uses.
>>
>> 2. If there is any gain benefit from the terrain profile at all, it
>> will be much more than 1 db.
>>
>> Dave AB7E
>>
>
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Jim Brown-10

Re: Sloping Terrain vs Feedline Losses

In reply to this post by David Gilbert

On Wed,7/13/2016 10:29 AM, David Gilbert wrote:
> I have no idea how or to what extent terrain affects a vertically
> polarized signal. I am, however, pretty certain that if it does at
> all it would be worth more than 1 db.

N6BT presented excellent experimental work on the effect of terrain on
vertically polarized antennas as his contribution to the Pacificon
Antenna forum last fall. He's been working on vertical dipoles for
several years now. This experiment included setting one up at various
locations on a broad knoll with drop-offs in most directions. He made
some measurements of vertical pattern using a drone, and also used the
antennas at those various locations to make contacts on the air. As I
recall, he was operating on 20M, but I could be wrong about that.

The antenna location near a dropoff in the direction of SA yielded QSOs
with SA, but none with JA. A location near a dropoff in the direction of
JA yielded JA QSOs but no SA. And a setup in the center of the knoll,
relatively far from the dropoffs yielded no QSOs with SA or JA. And his
measurements with the drone showed vertical radiation increasing below 0
degrees in the direction of the dropoff.

> I've always wished we had a version of HFTA that handled vertically
> polarized antennas ... that would probably be enlightening. I've also
> tried on occasion to use EZNEC+ for the same purpose since it allows
> you to specify at least two different zones around the antenna, but I
> didn't have much success with that.

The interaction of vertically and horizontally polarized signals with
ground is quite different, so the math is quite different. Among other
things, a primary determinant of ground interaction with vertical
antennas is soil conductivity in the far field (that is, at the point of
interaction). Height is also a factor. With horizontal antennas, soil
conductivity is essentially insignificant, and the primary determinants
are height and the elevation profile.

>
> I'm one of those who had quite good luck with roof mounted verticals,
> but it's hard to say whether any improvement (if there was one) was
> the result of distance from lossy ground or simply the ability to
> shoot over lossy surrounding structures like trees and houses.

See my NEC study on this, which is in line with your observations. When
I presented this material to an NCCC meeting a few years ago, the OT
hams with solid engineering background were nodding their heads in
agreement.

http://k9yc.com/AntennaPlanning.pdf
http://k9yc.com/VerticalHeight.pdf

> I do think it is more than "folklore" that elevated radials have
> benefits over in-ground radials unless the in-ground radial system is
> reasonably extensive. There have been some pretty decent studies on
> that.

Yep. N6LF has done lots of excellent work, which is on his website.

http://www.antennasbyn6lf.com/

I've used part of his work in my applications note/tutorial on antennas
for 160M.

http://k9yc.com/160MPacificon.pdf

73, Jim K9YC

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Wes Stewart-2

Re: Sloping Terrain vs Feedline Losses

In reply to this post by David Gilbert

Ok, but I'm unclear about what "improves radiation pattern" means. To paraphrase
your other premise, "I'm not sure if it does or doesn't but if it does, I'm sure
it's big" has me wondering. But I wonder about a lot of things...

On 7/13/2016 10:38 AM, David Gilbert wrote:

>
> No, I didn't mean that.
>
> If sloping ground improves radiation pattern, it's going to be worth more than
> 1 db. Pattern changes of any sort typically have significant effect, whereas
> one db is almost trivial (notwithstanding my own experiments on that on my
> website). I'm not saying that sloping ground actually has a significant
> effect ... only that if it has any effect at all it is likely to be greater
> than 1 db.
>
> Dave AB7E
>
>
>
> On 7/13/2016 10:06 AM, Wes Stewart wrote:
>> I hope you meant much less than 1 dB.
>>
>> On 7/13/2016 1:49 AM, David Gilbert wrote:
>>>
>>> Agree on the coax losses, but totally disagree on both of your other comments:
>>>
>>> 1. Elevated radials will ONLY help reduce near field ground losses ... they
>>> will do nothing to help radiation pattern. The effects of ground
>>> conductivity determine far field pattern (given a particular profile) no
>>> matter what kind of radials he uses.
>>>
>>> 2. If there is any gain benefit from the terrain profile at all, it will be
>>> much more than 1 db.
>>>
>>> Dave AB7E

David Gilbert

Re: Sloping Terrain vs Feedline Losses

Lowering takeoff angle.

Regarding the other part, I've stated it as clearly as I can about three
times now. If you disagree or can't follow the point, I don't think
anything else I might say will change that.

73,

Dave AB7E

On 7/13/2016 12:03 PM, Wes Stewart wrote:

> Ok, but I'm unclear about what "improves radiation pattern" means. To
> paraphrase your other premise, "I'm not sure if it does or doesn't but
> if it does, I'm sure it's big" has me wondering. But I wonder about a
> lot of things...
>
>
> On 7/13/2016 10:38 AM, David Gilbert wrote:
>>
>> No, I didn't mean that.
>>
>> If sloping ground improves radiation pattern, it's going to be worth
>> more than 1 db. Pattern changes of any sort typically have
>> significant effect, whereas one db is almost trivial (notwithstanding
>> my own experiments on that on my website). I'm not saying that
>> sloping ground actually has a significant effect ... only that if it
>> has any effect at all it is likely to be greater than 1 db.
>>
>> Dave AB7E
>>
>>
>>
>> On 7/13/2016 10:06 AM, Wes Stewart wrote:
>>> I hope you meant much less than 1 dB.
>>>
>>> On 7/13/2016 1:49 AM, David Gilbert wrote:
>>>>
>>>> Agree on the coax losses, but totally disagree on both of your
>>>> other comments:
>>>>
>>>> 1. Elevated radials will ONLY help reduce near field ground losses
>>>> ... they will do nothing to help radiation pattern. The effects of
>>>> ground conductivity determine far field pattern (given a particular
>>>> profile) no matter what kind of radials he uses.
>>>>
>>>> 2. If there is any gain benefit from the terrain profile at all,
>>>> it will be much more than 1 db.
>>>>
>>>> Dave AB7E
>
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Re: Sloping Terrain vs Feedline Losses

On a slightly different take, controlling the vertical pattern, ie minimizing the minor lobes, will have a significant effect on gain as the major lobe now gets all of the energy. Elevated radials have more to do in establishing the actual TOA above ground. This is not easy. Try modelling the vertical with radials in free space and see the TOA move around and the minor lobes move with the angle of the radials away for 90 degrees. When you have the TOA where you want it, move the antenna to somewhere AGL and watch the pattern. The ground losses will now start to absorb the lower portion of the major lobe. The result will always be a higher TOA unless over VERY conductive ground.

Mel, K6KBE

From: David Gilbert <[hidden email]>
To: [hidden email]
Sent: Wednesday, July 13, 2016 1:24 PM
Subject: Re: [Elecraft] Sloping Terrain vs Feedline Losses

Lowering takeoff angle.

Regarding the other part, I've stated it as clearly as I can about three
times now. If you disagree or can't follow the point, I don't think
anything else I might say will change that.

73,

Dave AB7E

On 7/13/2016 12:03 PM, Wes Stewart wrote:

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Jim Brown-10

Re: Sloping Terrain vs Feedline Losses

In reply to this post by Wes Stewart-2

On Wed,7/13/2016 12:03 PM, Wes Stewart wrote:
> Ok, but I'm unclear about what "improves radiation pattern" means.

Wes,

Take a look at the links I posted to my NEC studies. There can be no
doubt as to the meaning of "improves radiation pattern."

BTW -- I do NOT agree that elevated radials have much to do with
establishing the take-off angle. AND, more to the point, I view take-off
angle as absolutely the wrong way to look at the vertical pattern of an
antenna. A FAR better approach is the one I used in those antenna
planning applications notes, for which I posted links a few hours ago.

73, Jim K9YC

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Wes Stewart-2

Re: Sloping Terrain vs Feedline Losses

Jim, I've looked at your stuff in the past.

But, "improvement" is in the eye of the beholder. The ionosphere determines the
optimum TOA, not the antenna. Taking heroic measures to get the max TOA down to
10 degrees (a near impossibility over dirt) when the signals are arriving at 45
degrees is hardly optimum.

Anecdotal evidence is mostly worthless but for what it's worth, I have 48
entities worked on 160 meters from here in the desert using no more than 500
watts into an inverted-V, apex at 45' ends at 6'. Everyone "knows" that this
can't possibly work because it radiates straight up. (Except that it doesn't)

Wes

On 7/13/2016 3:07 PM, Jim Brown wrote:

> On Wed,7/13/2016 12:03 PM, Wes Stewart wrote:
>> Ok, but I'm unclear about what "improves radiation pattern" means.
>
> Wes,
>
> Take a look at the links I posted to my NEC studies. There can be no doubt as
> to the meaning of "improves radiation pattern."
>
>
> BTW -- I do NOT agree that elevated radials have much to do with establishing
> the take-off angle. AND, more to the point, I view take-off angle as
> absolutely the wrong way to look at the vertical pattern of an antenna. A FAR
> better approach is the one I used in those antenna planning applications
> notes, for which I posted links a few hours ago.
>
> 73, Jim K9YC

David Gilbert

Re: Sloping Terrain vs Feedline Losses

I've played around with VOACAP a lot in the past. Possibly you want to
argue with it's validity, but I can tell you that the percentage of time
it shows signals optimally arriving at 45 degrees is much less than the
percentage of time they arrive closer to 10 degrees ... certainly for
any kind of DX work and most of the time for domestic work here in the
U.S. That depends upon the band, of course, and also the time of the
opening (optimum angles are lower at openings and closings versus
mid-opening), but in general the best TOA's area lot lower than most
hams assume.

If low takeoff angles weren't generally desirable our hobby has several
generations of very misguided members who have squandered millions of
dollars.

Dave AB7E

On 7/13/2016 5:02 PM, Wes Stewart wrote:

> Jim, I've looked at your stuff in the past.
>
> But, "improvement" is in the eye of the beholder. The ionosphere
> determines the optimum TOA, not the antenna. Taking heroic measures to
> get the max TOA down to 10 degrees (a near impossibility over dirt)
> when the signals are arriving at 45 degrees is hardly optimum.
>
> Anecdotal evidence is mostly worthless but for what it's worth, I have
> 48 entities worked on 160 meters from here in the desert using no more
> than 500 watts into an inverted-V, apex at 45' ends at 6'. Everyone
> "knows" that this can't possibly work because it radiates straight
> up. (Except that it doesn't)
>
> Wes
>
> On 7/13/2016 3:07 PM, Jim Brown wrote:
>> On Wed,7/13/2016 12:03 PM, Wes Stewart wrote:
>>> Ok, but I'm unclear about what "improves radiation pattern" means.
>>
>> Wes,
>>
>> Take a look at the links I posted to my NEC studies. There can be no
>> doubt as to the meaning of "improves radiation pattern."
>>
>>
>> BTW -- I do NOT agree that elevated radials have much to do with
>> establishing the take-off angle. AND, more to the point, I view
>> take-off angle as absolutely the wrong way to look at the vertical
>> pattern of an antenna. A FAR better approach is the one I used in
>> those antenna planning applications notes, for which I posted links a
>> few hours ago.
>>
>> 73, Jim K9YC
>
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Phil Wheeler-2

Re: Sloping Terrain vs Feedline Losses

Dave,

Aside from the issue at hand, and perhaps sans the
"misguided", I'm certain this "our hobby has
several generations of very misguided members who
have squandered millions of dollars." is true ;-)

73, Phil W7OX

On 7/13/16 5:48 PM, David Gilbert wrote:

>
> I've played around with VOACAP a lot in the
> past. Possibly you want to argue with it's
> validity, but I can tell you that the percentage
> of time it shows signals optimally arriving at
> 45 degrees is much less than the percentage of
> time they arrive closer to 10 degrees ...
> certainly for any kind of DX work and most of
> the time for domestic work here in the U.S.
> That depends upon the band, of course, and also
> the time of the opening (optimum angles are
> lower at openings and closings versus
> mid-opening), but in general the best TOA's area
> lot lower than most hams assume.
>
> If low takeoff angles weren't generally
> desirable our hobby has several generations of
> very misguided members who have squandered
> millions of dollars.
>
> Dave AB7E
>
>
> On 7/13/2016 5:02 PM, Wes Stewart wrote:
>> Jim, I've looked at your stuff in the past.
>>
>> But, "improvement" is in the eye of the
>> beholder. The ionosphere determines the
>> optimum TOA, not the antenna. Taking heroic
>> measures to get the max TOA down to 10 degrees
>> (a near impossibility over dirt) when the
>> signals are arriving at 45 degrees is hardly
>> optimum.
>>
>> Anecdotal evidence is mostly worthless but for
>> what it's worth, I have 48 entities worked on
>> 160 meters from here in the desert using no
>> more than 500 watts into an inverted-V, apex at
>> 45' ends at 6'. Everyone "knows" that this
>> can't possibly work because it radiates
>> straight up. (Except that it doesn't)
>>
>> Wes
>>
>> On 7/13/2016 3:07 PM, Jim Brown wrote:
>>> On Wed,7/13/2016 12:03 PM, Wes Stewart wrote:
>>>> Ok, but I'm unclear about what "improves
>>>> radiation pattern" means.
>>>
>>> Wes,
>>>
>>> Take a look at the links I posted to my NEC
>>> studies. There can be no doubt as to the
>>> meaning of "improves radiation pattern."
>>>
>>>
>>> BTW -- I do NOT agree that elevated radials
>>> have much to do with establishing the take-off
>>> angle. AND, more to the point, I view take-off
>>> angle as absolutely the wrong way to look at
>>> the vertical pattern of an antenna. A FAR
>>> better approach is the one I used in those
>>> antenna planning applications notes, for which
>>> I posted links a few hours ago.
>>>
>>> 73, Jim K9YC

Jim Brown-10

Re: Sloping Terrain vs Feedline Losses

In reply to this post by Wes Stewart-2

That exactly proves my point about takeoff angle being an inappropriate
measure. If you study the plots of my NEC models, it becomes clear that
raising the antenna does much more than moving the peak of radiation
lower -- it also increases the field strength at most angles below
that. See my family of plots of field strength vs height of horizontal
antennas.

73, Jim K9YC

On Wed,7/13/2016 5:02 PM, Wes Stewart wrote:
> Everyone "knows" that this can't possibly work because it radiates
> straight up. (Except that it doesn't)

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