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Author Topic: HF Vertical: Ground Mounted or Elevated. Will it matter with this antenna?  (Read 5514 times)
N4NOO
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« on: June 27, 2012, 11:06:33 PM »

Just as an experiment, I am thinking of using my mobile HF antenna as a "base station" antenna.  I have a spare mounting fixture for the antenna and a junk box full of "stuff" but I wonder if the antenna will work better mounted just inches above the ground or some distance above the ground.  I will use a Hi-Q 6-160 remote tune antenna in the middle of my back yard.  I have a steel plate to attach about 25 radial wires to and the antenna will be centered in that plate at either an inch or so above it or 10' - 20' directly above it.  Which location do you think will work better if there even is any difference?
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KB3FFH
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« Reply #1 on: June 28, 2012, 04:15:34 AM »

Look at the base station pictures on the Tarheel antenna web site.
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K5LXP
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« Reply #2 on: June 28, 2012, 10:30:23 AM »

If you're going to mount the antenna above ground, the radials will have to be with it.  So in your example, the radial plate and radials  would be at the base of the antenna, 10' - 20' up off the ground.


Mark K5LXP
Albuquerque, NM
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K3VAT
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« Reply #3 on: June 28, 2012, 10:50:49 AM »

Just as an experiment, I am thinking of using my mobile HF antenna as a "base station" antenna.  I have a spare mounting fixture for the antenna and a junk box full of "stuff" but I wonder if the antenna will work better mounted just inches above the ground or some distance above the ground.  I will use a Hi-Q 6-160 remote tune antenna in the middle of my back yard.  I have a steel plate to attach about 25 radial wires to and the antenna will be centered in that plate at either an inch or so above it or 10' - 20' directly above it.  Which location do you think will work better if there even is any difference?

Rick,

If you elevate (both antenna and radial ground system as Mark said), then the radials will need to be tuned.  That means that for each band that you operate on, you can use 4 tuned radials (all at right angles if possible) and that will provide you with 6 bands (since you have about 25 radials).  If you ground mount, then you don't need to do this.  25 ground mounted radials are a good number, especially if they are around 30 feet (always list the length of your radials on the posting).

Elevated mounting has benefit that it gets the antenna system up away from lossy ground and nearby obstacles, but laying out 6 sets of 4 tuned radials can be a real pain.

Performance-wise, IMHO, it's a toss-up.  The compromise Hi-Q whether it is ground- or elevated-mounted won't reap you tons of DX (especially on the lower bands) - although DXCC on some of the higher bands is a good possibility given some decent sunspots.

GL, 73, Rich, K3VAT


« Last Edit: June 28, 2012, 10:58:24 AM by K3VAT » Logged
WX7G
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« Reply #4 on: June 28, 2012, 12:06:01 PM »

Grounded mounted with twenty 20' radials will be quite good. I have measured the base-referred ground loss resistance of such a ground (and a Tarheel antenna) to be about 10 ohms.

I regularly work Europe from Utah on 80 meter CW running 600 watts and a long whip using the Tarheel. With the standard 6' whip I've worked Europe but it's not a regular occurance.
« Last Edit: June 28, 2012, 12:07:53 PM by WX7G » Logged
N4NOO
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« Reply #5 on: June 28, 2012, 12:57:25 PM »

Thank you all for you insights.  I will try close to the ground first.  This should be fun!
 
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K5LXP
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« Reply #6 on: June 28, 2012, 01:32:19 PM »

I've done it at ground level with a lesser screwdriver and it "works", basically about as well as it does on the car.  Better than nothing, with "convenient" being the operative word.


Mark K5LXP
Albuquerque, NM

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KB5UBI
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« Reply #7 on: June 28, 2012, 05:22:41 PM »

I would use it ground mounted over a bed of 12 to 20 radials. The bed of radials can be used on any vertical if you change antennas at a later date.

KB5UBI
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STAYVERTICAL
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« Reply #8 on: June 29, 2012, 01:16:47 AM »

I have done this experiment many times, and can give you some practical insights.

First - my setup:
A 15 foot vertical, no loading coils, tuned with an FC40 remote ATU at the base.

Radials do not need to be tuned if you are using a remote ATU.
Tuning is mainly for direct coax fed systems where you are trying to get close to 36 ohms for matching to a 50 ohm feedline.
Keep in mind, with a short antenna your theoretical radiation resistance is going to go down, so any losses will have a greater effect.
So keep the losses low - which means use elevated radials - two are as good as more in my experience.
If your remote ATU can tune the antenna, you are good to go.

Do NOT use ground mounted radials unless you can put down a good radial field.
Even two elevated radials per band (roughly cut, 3 feet off the ground) will far outperform a few ground laying radials.
The difference will be very noticeable on transmit, but not on receive.

If you can get more height, this will help you mainly on the lower bands, but for 20m and up, having the vertical base around 3 feet
off the ground will be good.
Mount the radials at the same height off the base plate at 3 feet.

I would not put the vertical base less than 3 feet off the ground otherwise it may just as well be ground mounted.

These are my experiences over many experiments both on air and with analysers, and I keep coming back to this configuration.

73 - Rob
 
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K1WJ
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« Reply #9 on: June 29, 2012, 08:42:33 AM »

Last summer I used a 20m MFJ Hamtenna ( Mobile Antenna ) Mounted 2 ft off the ground - then had single 1/4wave 20m counterpoise also 2ft off the ground held up on end by camera tripod - can see general set up on QRZ  pic on upper Right under call K1WJ.
Made hundreds of contacts - had set up in back yard of Arizona HOA for 8 months.
Now at new house going to set up a MFJ 2286 - 6m-40m vertical - has 17 foot whip - telescoping. Should be interesting, may try ground mounted - for multi band use - or elevated with single counterpoise maybe elevated 4-6 ft this time, for single band use, most likely 20m.

73 K1WJ David Cool
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N4NOO
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« Reply #10 on: June 29, 2012, 02:56:23 PM »

So after rethinking, I am going to try elevated.  If I have 4 tuned radials per band and if I try several bands can I run the tuned radials somewhat parallel like one does with a multi-band fan dipole?  The radials in a "fan" configuration with the shorter ones under the longest one?
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KC4MOP
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« Reply #11 on: June 30, 2012, 03:48:04 AM »

I hope your favorite bands are 40 and up. That would untangle the mess of radial wires that you are going to have there. You would need almost an acre of property to set up for tuned radials and elevated for 160 and 80. Elevated radials make a very potent vertical, but at a price of having them above ground and not a danger to you as you mow the grass. Or a choking hazard to you or any wild animals running around.
I'm gonna be struggling to get a 10M 5/8 wave vertical up 20 feet to make it happy.
Fred
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K3VAT
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« Reply #12 on: June 30, 2012, 07:14:54 AM »

So after rethinking, I am going to try elevated.  If I have 4 tuned radials per band and if I try several bands can I run the tuned radials somewhat parallel like one does with a multi-band fan dipole?  The radials in a "fan" configuration with the shorter ones under the longest one?

It is sometimes difficult to decide whether to go 'ground-mount' or 'elevated-mount'.  If you're going elevated and running ~100 watts, then you might want to follow the recommendation of STAYVERTICAL (above) and try the auto-tuner (also referred to as autocoupler).  This is a fairly common practice (maybe more so with ground-mounted verticals) and folks don't have to worry about constantly fiddling with their radials.

I guess that you could configure lower radials underneath the longer ones - don't think that it would hamper the performance. 

The important thing to keep in mind with elevated radials is that you might find yourself spending lots of time pruning this radial or re-positioning that radial in order to get a decent SWR because these elevated interact with one another.  I always had difficulty getting a SWR < 1.5:1 on both 40M and 15M; even parts of the same band would sometimes act strangely.

If it were me, then I would first go with ground mounted system.  Yes, it is a pain laying out 2 or 3 dozen radials and either pinning them to earth or burying them within earth, but maintenance-wise it is far better in the long-run.  You also don't have the concern about pruning radials nor the safety hazards with using elevated radials.

If you first go with ground-mount and then decide that you want to try elevated mount, you don't have to remove the ground radial field.  Just leave it in place (don't connect it to the elevated radial system) and it will help (albeit minor) with system performance.

GL, 73, Rich, K3VAT
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K7MH
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« Reply #13 on: June 30, 2012, 07:42:38 AM »

Elevated a couple feet or a few feet performance wise it probably won't matter much.
If you can get it up high like rooftop height, 20ft up or more, it will have much better performance especially on 20 meters and higher frequencies if set up properly. Just no way around that.
When I moved a Hustler 4BTV from the ground to a rooftop it was like night and day.
Any antenna is better than no antenna however.

Play with it both ways if you can. It would be a good experience and you will learn a few things along the way.
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K5KNE
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« Reply #14 on: July 06, 2012, 08:33:38 PM »

Vertical antennas radiate equally poorly in all directions.

A mobile antenna mounted on a good ground plane (radials) should work as good or better than it does on a car. You are also going to pick up some local noise around you neighborhood that you can drive away from in the car.

It is worth a try. Just hook it up and see how you like it. I would not bury the radials until I was happy with the way it worked.

Good Luck,  Walter K5KNE
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