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Author Topic: New wire or vertical antenna...  (Read 1929 times)
N7EKU
Member

Posts: 66




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« on: September 11, 2012, 04:57:29 PM »

Hi,

I'm just looking for some general advice on a couple of questions...

First, my goal is to have an antenna for 40M and 20M (other higher freq would be OK too) with fairly low angle of radiation.  I don't have much preference for directionality.  I would choose one that's more quiet if there is any difference.   I will just be running 100W or lower.

Second, probably like many, my lot is not ideal, but I don't have any space issues with installing half wavelength antennas for these bands and can put up two different ones no problem, but getting high I'm not too sure of.  I think I can raise the center up to about 10M from ground level if I put a short tower on my roof.

I've read the ARRL antenna manual, but would like some real-life recommendations from some hams to add to the theory.  So here is what I am thinking for choices:

* Two dipoles 40M and 20M.  Would the radiation angles be pretty low?  From theory looks like 20m would be OK, but 40M?

* One 40M ladder fed dipole with a balun outside my shack and short good coax to my tuner.  Would this have as good a low angle at 20M as the 20M dipole?  If there is recommended software that a beginner at antennas can use to enter in these designs and look at the results I would be very happy for recommendations on what to use for that.  Is the radiation pattern of a ladder fed 40M dipole (I guess this is called a 40 center fed Zepp?) on 20M a lot different than a 20M dipole?

* So if I put up a little tower on my roof, then I could be lazy and just bite the bullet and $ a Butternut vertical.  Would that have gain over the dipoles?  From theory I understand not and that they would be noisier compared to a dipole -- any experience with that?

Thank you so much for any real-life input you can give me on these questions.  I really appreciate it!

73,

Mark/n7eku
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LX2GT
Member

Posts: 23




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« Reply #1 on: September 11, 2012, 11:22:34 PM »

Horizontal Dipole Antennas, it depends on height above ground. If you can manage to get them 3/8 wavelengths above ground, they will equal the vertical likely for DX, higher beat it (broadside to the wire!)

It is not take off angle that matters, but energy radiated/received, at the takeoff angle that the DX signals come from.
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N8CMQ
Member

Posts: 355




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« Reply #2 on: September 12, 2012, 03:51:27 AM »

I have a vertical trap antenna over a large ground plane.
I have tried other antennas, but the simplicity and the fact it works, makes my vertical, the antenna of choice here.
And, being ground mounted, makes it safer for this old guy to work on!
Let me emphasize, it is a quarter wave trap vertical, not an all band stick and tuner.
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N7EKU
Member

Posts: 66




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« Reply #3 on: September 12, 2012, 04:35:30 AM »

I have a vertical trap antenna over a large ground plane.
I have tried other antennas, but the simplicity and the fact it works, makes my vertical, the antenna of choice here.
And, being ground mounted, makes it safer for this old guy to work on!
Let me emphasize, it is a quarter wave trap vertical, not an all band stick and tuner.

Thanks a lot!  Did you make that vertical trap yourself?  What height is it?  I think I've seen some examples in the ARRL Antenna Book, so I'll see if I can find those again.

73,

Mark.

Oh, and I'd heard of the modeling software EZNEC before so I am trying that now and going through the tutorials.  It's pretty fun and seems to be a very very nicely done program.
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N7EKU
Member

Posts: 66




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« Reply #4 on: September 12, 2012, 02:18:31 PM »

Hi,

Well.  I think I have a plan now.

I thought that if I was going to go to the trouble of putting a short tower on my roof, I might as well try something that rotates.  So I think I will try a 20M moxon which looks pretty easy to get done before winter, and then under the rotor just put in a 40M dipole.  At on 1/4 above the ground in the center it won't quite reach 3/8 for lower radiation angles  but if the ground isn't perfect then maybe it will be closer to 3/8 than I think.  If I ladder feed it, then I think I will have the option to use that one on lots of other bands just for fun, and then have the 20M moxon for a quieter directional one.  I will just have to have a little horizontal extension above the steel of the tower to get the center of the dipole and feedline away from the metal.

The price should be pretty low overall I think.  I will get a 3' Rohn tripod for the ridge of the roof and some fiberglass poles for the moxon from dxengineering.

Cheers!

Mark.
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G0VKT
Member

Posts: 64




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« Reply #5 on: September 12, 2012, 03:41:49 PM »

Hi Mark,

You have come up with a very sensible solution. Don't get too hung up with low angle take off.
It is cheap enough to put up and experiment with.

As you go up in frequency you will no longer have the classic dipole radiation pattern. It will split into multiple lobes.
Just see what happens on air. When you are comfortable with it you could put up, for example, a 10m dipole and switch between the two for comparison.

Currently I am experimenting with single band verticals and I am comparing them to a 102' doublet fed with ladder line.
It is sort of an inverted V, one leg goes over the house and one end is bent to fit. Radiation patttern? Who knows or cares.
It is an antenna I know at my QTH and gives me reference for testing.

Paul.
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N7EKU
Member

Posts: 66




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« Reply #6 on: September 12, 2012, 04:48:14 PM »

Thank you Paul,

Yeah I mostly want to get the little tower up so I can start hanging/mounting stuff on it.  Like you say just to get going.  I will have my XYL belay me on my roof as I'm not keen on walking around up there unprotected.

I started on a pac-12 for travels a couple years ago, but never got around to finishing it.  Now that I am getting going on my antennas, maybe I will finish that before the moxon.  I have the hard parts done already (coil mounts) I just need to get the rods and put threads on them.

It would be interesting to hear about your comparison results when you get done!

73,

Mark.
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KB5UBI
Member

Posts: 97




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« Reply #7 on: September 13, 2012, 12:09:04 AM »

I have a vertical trap antenna over a large ground plane.
I have tried other antennas, but the simplicity and the fact it works, makes my vertical, the antenna of choice here.
And, being ground mounted, makes it safer for this old guy to work on!
Let me emphasize, it is a quarter wave trap vertical, not an all band stick and tuner.

Pretty much makes my point. I have a ground mounted Butternut HF6V over several radials and all I can say is it works well. I can bypass my tuner with the Butternut which routinely out does my 80 meter ladder line fed doublet.

Don't skimp on the radials and you'll be pleased with a Butternut or the Hustler 5btv.

KB5UBI   
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N7EKU
Member

Posts: 66




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« Reply #8 on: September 13, 2012, 08:28:10 AM »

...I have a ground mounted Butternut HF6V over several radials and all I can say is it works well. I can bypass my tuner with the Butternut which routinely out does my 80 meter ladder line fed doublet.

Don't skimp on the radials and you'll be pleased with a Butternut or the Hustler 5btv.

KB5UBI   

Thank you for the input :-) !

How long are your radials?  My lot is a bit of a postage stamp -  a 15M square spot in the backyard is all I have to work with, so my radials could only be about 7.5M each.  That doesn't seem long enough for even 40M?

73,

Mark
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KB5UBI
Member

Posts: 97




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« Reply #9 on: September 13, 2012, 09:12:06 PM »

Well, that gives you 10 meters in each corner. Install 18 to 24 radials in the space you have. They tend to de-tune when under the dirt a few inches so exact length isn't a worry. In my hard Texas soil, I used an edger attachment for my lawn trimmer to cut the slots for the radials. I pushed the radial wires into the slots, watered the area and they disappeared. If you have a good turf, you don't need to bury them as they will disappear in a few months on their own.

KB5UBI   
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KC4MOP
Member

Posts: 732




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« Reply #10 on: September 16, 2012, 04:03:23 AM »

Hi Mark,
with your small property going up is the solution. I think you mentioned a couple of posts ago that a small tower and a Moxon 20M antenna. You do whatever it takes to get on the air. The majority of us are in the same situation.
Maintain the vertical for the low bands 160-40. The present sunspot cycle has a short life span according to the predictors.

Fred
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K3VAT
Member

Posts: 709




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« Reply #11 on: September 16, 2012, 03:53:33 PM »

..  The present sunspot cycle has a short life span according to the predictors.  Fred

Hey Fred,
Present solar cycle is about the same span (duration) as previous ones, but what makes this cycle notable is that it's intensity is weak.  See http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif
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N8CMQ
Member

Posts: 355




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« Reply #12 on: September 16, 2012, 04:13:21 PM »

...I have a ground mounted Butternut HF6V over several radials and all I can say is it works well. I can bypass my tuner with the Butternut which routinely out does my 80 meter ladder line fed doublet.

Don't skimp on the radials and you'll be pleased with a Butternut or the Hustler 5btv.

KB5UBI   

Thank you for the input :-) !

How long are your radials?  My lot is a bit of a postage stamp -  a 15M square spot in the backyard is all I have to work with, so my radials could only be about 7.5M each.  That doesn't seem long enough for even 40M?

73,

Mark


My antenna is on a 60 foot square, and I have 125 radials around the antenna mast.
I used copper coated steel wire for the radials, but I am going to use stainless wire for my next project.
Ground mounted antennas don't have to have full quarter wave length radials, but, make them as long as practical.
I have a 4 band trap vertical, but I don't remember who made it, and I have rebuilt it twice now.
I thought it was the AVQ, but it could be a BTV, both are similar.
I also added an 80 meter resonator, and it works very well too.
So the antenna is able to be used on 5 bands, and if you add the WARC bands, you could have 7 bands.
I am sure you can find them reasonable used, but they will need work.
Get the plain quarter wave antenna, not the half wave 'radial free' antennas...
Good luck, and have fun!
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