Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1] 2 Next   Go Down
  Print  
Author Topic: Combination Vertical Counterpoise and Dipole antenna  (Read 894 times)
WY7CHY
Member

Posts: 638




Ignore
« on: November 09, 2017, 06:13:39 AM »

As some know, I'm still experimenting with a vertical antenna.

I know that when a vertical is elevated; e.g. on the roof of the house; it requires a ground plane. As such, a counterpoise is required. I also understand that as a minimum, at least 2 counterpoise elements are required for each band/frequency I want to tune to.

So, lets say I put up 2 each counterpoise elements for 80m, 40m, and 20m. Supposedly, the center radiates the RF and the counterpoise is the artificial ground plane. And supposedly, if you only put 1 counterpoise radial out, instead of a ground plane, you actually have an "L-Shape" dipole in essence.

So, the question is: What if I put up 3 each counterpoise elements for 20m, 3 each for 40m, and ONLY 1 element for 80m? Would the antenna perform as a vertical on 40m and 20m and act as a dipole on 80m? What sort of propagation would there be? And is an "L Shape" dipole directional in the direction that the horizontal element at the bottom is pointing? But... if the "L-Shape" dipole on 80m is only 15-16 feet off the ground, would most of the propagation be NVIS Cloud Warmer?

I'd like the 20m and 40m to be more for DX; but I almost always use 80m strictly for in-state net control type contacts. About 200-400 miles away.

Thoughts?

Thanks. Mike
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
AC2RY
Member

Posts: 280




Ignore
« Reply #1 on: November 09, 2017, 06:31:14 AM »

As some know, I'm still experimenting with a vertical antenna.

I know that when a vertical is elevated; e.g. on the roof of the house; it requires a ground plane. As such, a counterpoise is required. I also understand that as a minimum, at least 2 counterpoise elements are required for each band/frequency I want to tune to.

So, lets say I put up 2 each counterpoise elements for 80m, 40m, and 20m. Supposedly, the center radiates the RF and the counterpoise is the artificial ground plane. And supposedly, if you only put 1 counterpoise radial out, instead of a ground plane, you actually have an "L-Shape" dipole in essence.

So, the question is: What if I put up 3 each counterpoise elements for 20m, 3 each for 40m, and ONLY 1 element for 80m? Would the antenna perform as a vertical on 40m and 20m and act as a dipole on 80m? What sort of propagation would there be? And is an "L Shape" dipole directional in the direction that the horizontal element at the bottom is pointing? But... if the "L-Shape" dipole on 80m is only 15-16 feet off the ground, would most of the propagation be NVIS Cloud Warmer?

I'd like the 20m and 40m to be more for DX; but I almost always use 80m strictly for in-state net control type contacts. About 200-400 miles away.

Thoughts?

Thanks. Mike

Start with reading something like this http://rudys.typepad.com/files/elevated-ground-systems-article-final-version.pdf
Logged
W1VT
Member

Posts: 2488




Ignore
« Reply #2 on: November 09, 2017, 06:37:10 AM »

http://www.qsl.net/kk4obi/Center-fed%20L-Dipoles%20Horizontal.html
This site has a large collection of antenna patterns for bent antennas.
Logged
WY7CHY
Member

Posts: 638




Ignore
« Reply #3 on: November 09, 2017, 06:52:29 AM »

Thanks for replies. And AC2RY, I've actually seen that link. I have a copy of the pdf downloaded.

I'm familiar with the anomalies with verticals, height, length of radials, etc. I've always said that antennas, especially in the HF world, is 10% Math, 15% Physics, and 85% Experimentation. Electricity may have certain laws, but it doesn't always follow what we think it should.

My question, while probably not really answerable; is dealing more with the interaction of the radials in the counterpoise.

In it's simplest form, Example: if a vertical elevated had 2 horizontal elements each for 80m/40m/20m for the counterpoise; if instead that was changed to  2 each for the 40m and 20m and only 1 for the 80m, would the 80m act as a bent dipole or would there be too much interaction with the 4 other radials and 80m would act as a 80m vertical with an "Untuned" counterpoise?

Likewise, if you took the same vertical; 15-20 feet elevated; and added ONLY 1 Each radial for 80m, 40m, and 20m (3 radials total), would you have a Bent Dipole for 80m, 40m, and 20m or would you have a vertical with untuned counterpoise?

P.S. I should have included that we are assuming the vertical is a multi-band vertical.
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
KM1H
Member

Posts: 2489




Ignore
« Reply #4 on: November 09, 2017, 06:57:30 AM »

Quote
I know that when a vertical is elevated; e.g. on the roof of the house; it requires a ground plane. As such, a counterpoise is required. I also understand that as a minimum, at least 2 counterpoise elements are required for each band/frequency I want to tune to.

I would suggest calling them radials as has been the norm for many decades. A counterpoise is generally related to a horizontal long wire.

If you extend the upper part of the 80M element horizontally you will get the necessary NVIS pattern. This can also be done with commercial multiband verticals.

Carl
Logged
W1VT
Member

Posts: 2488




Ignore
« Reply #5 on: November 09, 2017, 07:02:33 AM »

The best way to see the interaction would be to conduct measurements.  Build single band antennas and measure the radial currents with an RF ammeter. Take down the unused wires so you don't have unwanted interactions.  Remove any nearby antennas that would upset your measurements. Measure the current in the radiating element in case someone is willing to model your antennas on a computer. Then build the whole thing and see how the radial currents compare.  

The last step, if you don't like what you get, is to experiment to see what you can do to get the currents to be more like what you want them to be.

Zack W1VT
« Last Edit: November 09, 2017, 07:05:27 AM by W1VT » Logged
KM1H
Member

Posts: 2489




Ignore
« Reply #6 on: November 09, 2017, 07:21:59 AM »

For the new 160/80/75 full size sloping vertical Im building, the 1/4 wave elevated radials are 15' high.

While trimming the 160M radials to length as two fan dipoles, one for 1840 and the other for 1950 kHz, I got the bright idea to allow them to be relay switched as radials or NVIS dipoles. The trimming is finished and today I start on the 80/75 pairs, unreeling wire, cutting, and running thru the woods and open spaces.

Carl
Logged
WY7CHY
Member

Posts: 638




Ignore
« Reply #7 on: November 09, 2017, 08:35:03 AM »

KM1H; it is mostly semantics; but a counterpoise is an elevated substitute for earth ground. It's a ground plane elevated. And it's made of numerous wires cut to resonance; vs radials laying on the ground or slightly buried and can be random length. The radials augment poor earth ground; and a counterpoise substitutes NO Earth Ground.

As for what my intentions are with this antenna:

My main antenna is my 80m loop. It's not the best, but it does quite well. Europe, Russia, Central and South america, hawaii, and all of the USA. It only averages 10-12 feet off the ground with a couple of high spots at 15-16 feet. But I'd like to replace it with a 40m loop. Main reason is because I know I can make the 40m a better and more efficient antenna. I can make the 40m more square and significantly higher; averaging about 20 feet. Plus, there's the aesthetics part of it to make it look better and "Please the Wife".

Unfortunately, I do have some need for 80m. Only for in-state net control stuff. But putting up a traditional 80m dipole isn't an option. I have a vertical multi-band antenna that was given to me by a friend. Obviously because of the take-off angle, the vertical isn't the best for NVIS 200-400 miles contacts. But, being a vertical, I thought i could also use it as an alternate DX antenna on 20m and 40m when conditions were better for a vertical antenna vs my loop.

I've tried the vertical with multiple elements for the counterpoise. Currently I have 2 for the 80m, 2 for 20m and 2 for 40m. I have been able to make contacts on the 80m in-state net control; but it requires me to use my amp. Barefoot, the loop is exponentially better than the vertical for 80m in state contacts. I'm trying to see if there's a way to have my cake and eat it to. A vertical for 20m and 40m low angle DX; and at the same time an 80m pseudo dipole that will do NVIS type of propagation.

If not, I can always use the vertical as a bent "L-Shape" dipole for 80m and forget about using it as an alternate 40/20m DX low angle antenna.
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
AC2RY
Member

Posts: 280




Ignore
« Reply #8 on: November 09, 2017, 08:41:47 AM »

Thanks for replies. And AC2RY, I've actually seen that link. I have a copy of the pdf downloaded.

I'm familiar with the anomalies with verticals, height, length of radials, etc. I've always said that antennas, especially in the HF world, is 10% Math, 15% Physics, and 85% Experimentation. Electricity may have certain laws, but it doesn't always follow what we think it should.

My question, while probably not really answerable; is dealing more with the interaction of the radials in the counterpoise.

In it's simplest form, Example: if a vertical elevated had 2 horizontal elements each for 80m/40m/20m for the counterpoise; if instead that was changed to  2 each for the 40m and 20m and only 1 for the 80m, would the 80m act as a bent dipole or would there be too much interaction with the 4 other radials and 80m would act as a 80m vertical with an "Untuned" counterpoise?

Likewise, if you took the same vertical; 15-20 feet elevated; and added ONLY 1 Each radial for 80m, 40m, and 20m (3 radials total), would you have a Bent Dipole for 80m, 40m, and 20m or would you have a vertical with untuned counterpoise?

P.S. I should have included that we are assuming the vertical is a multi-band vertical.

From what I can understand from many simulations done so far - you do not necessary need resonant radials when antenna is elevated.  There is some limit of radials length under which they become ineffective for specific band. This limit is the lower, the higher they are from earth. Also pole/mast on which antenna is installed is important too - it is preferable to be non-conductive, otherwise it interacts with main radiator. At the same time some used metal pole and connected it to radial. But this is more like vertical dipole arrangement than GP. In all these cases it is very recommended to have tunable coupler device to be used at antenna feed point to match antenna to coax feed line if work on multiple bands is desired.
Logged
W1VT
Member

Posts: 2488




Ignore
« Reply #9 on: November 09, 2017, 09:25:03 AM »

NVIS typically assume "good enough" signal strengths.  For instance, if someone from a rare state like North Dakota or Delaware shows up on the digital mode FT8, it isn't going to make that much difference how strong he is as long as the people who need him get decodes on their computer.  It doesn't matter whether he is -20 or -10, all the people who need that state will call him.

Zack W1VT
Logged
WY7CHY
Member

Posts: 638




Ignore
« Reply #10 on: November 09, 2017, 09:42:22 AM »

I only do voice / SSB. NVIS is only done with horizontally polarized antennas. A vertical's take off angle is such it wouldn't do NVIS. I was hoping that a single element along with the vertical would be a bent / L-Shape dipole and would do NVIS for in state Voice contacts. At the same time; hoping the additional elements, 3 each for 40m and 3 each for 20m, would be a good vertical DX low take off angle. The counterpoise elements are 1/4 wavelength. My vertical is totally insulated. It's not attached to an electrical ground. The coax has a 1:1 current balun isolator.
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
WB6BYU
Member

Posts: 17053




Ignore
« Reply #11 on: November 09, 2017, 10:01:06 AM »

Quote from: WY7CHY

...I was hoping that a single element along with the vertical would be a bent / L-Shape dipole and would do NVIS for in state Voice contacts...



The "L" antenna acts like a tilted dipole.  The ground reflections are different for the vertical
and horizontal components, but (at least according to EZNEC) the radiation from the radial
wire should provide reasonable NVIS coverage in the direction of the wire.  In the
opposite direction there is a null for NVIS coverage in the reverse direction (what would be
off the end of the equivalent sloping dipole.)  It's pretty omnidirectional out to 50 miles or
so, and should be useable over 270 degrees of beamwidth at longer distances, but if you
are trying to work a particular target at 200 - 300 miles then it will work best when the radial
wire is pointing in that direction.
Logged
WY7CHY
Member

Posts: 638




Ignore
« Reply #12 on: November 09, 2017, 10:48:06 AM »

Fortunately, I live in the bottom corner of the state, so I could have it pointed towards the rest of the state.

Just not sure how the other 6 elements (Counterpoise for the vertical) for 40m/20m may interact with the single element being used for the 80m "Tilted Dipole".

Thanks. Mike
Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
KM1H
Member

Posts: 2489




Ignore
« Reply #13 on: November 09, 2017, 10:57:47 AM »

Quote
KM1H; it is mostly semantics; but a counterpoise is an elevated substitute for earth ground.


No semantics at all as a counterpoise has long been described in literature.

Quote
It's a ground plane elevated. And it's made of numerous wires cut to resonance;

Resonance has nothing to do with it and can actually be a hindrance. A ground plane is always elevated at least 1/4 wave or more.

Quote
vs radials laying on the ground or slightly buried and can be random length. The radials augment poor earth ground; and a counterpoise substitutes NO Earth Ground.

Quote
On/in ground radials are not part of the discussion so why add to your confusion?

As ive said before a counterpoise is historically for a random length wire at some distance above it.

For your continuing education I suggest you read this until you understand it:

https://www.w8ji.com/counterpoise_systems.htm
Logged
WB6BYU
Member

Posts: 17053




Ignore
« Reply #14 on: November 09, 2017, 11:09:17 AM »

Quote from: WY7CHY

Just not sure how the other 6 elements (Counterpoise for the vertical) for 40m/20m may interact with the single element being used for the 80m "Tilted Dipole".




My model included that - I started with a model having 8 radials, deleted one,
and shortened 3 each for 40m and 20m.  They didn't appear to make any
significant difference.
Logged
Pages: [1] 2 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!