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Author Topic: Vertical antenna-how is this possible?  (Read 5959 times)
W8JI
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« Reply #15 on: March 14, 2014, 07:29:25 PM »

I had the 4BTV vertical mounted above my 20 meter 5 element Yagi, at about 150 feet, using the 20 Yagi and a full size 40 Yagi below that as a ground.

It worked very well for a vertical with no radials and no ground rod.
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WX7G
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« Reply #16 on: March 15, 2014, 04:37:54 AM »

Some hams with ground mounted verticals having only a ground rod report a VSWR of 1.5:1. This tells us the input resistance is 75 ohms and with their 1/4 wavelength vertical being 36 ohms the ground loss is 39 ohms. The (near field) radiation efficiency is then 48% putting it 3 dB down from a vertical having an extensive radial system.

The next time I install a vertical in a new location I'll see what just a ground rod yields before adding radials.
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NK7Z
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« Reply #17 on: March 15, 2014, 05:51:34 AM »

Some hams with ground mounted verticals having only a ground rod report a VSWR of 1.5:1. This tells us the input resistance is 75 ohms and with their 1/4 wavelength vertical being 36 ohms the ground loss is 39 ohms. The (near field) radiation efficiency is then 48% putting it 3 dB down from a vertical having an extensive radial system.

The next time I install a vertical in a new location I'll see what just a ground rod yields before adding radials.
I have a phased array on 40 I am putting in, and my intent is to add radials until I stop seeing a change in R for Antenna 1, I have done this sort of install for decades on verticals...  Saves copper and time...  Once you hit the point of diminishing returns there is no real need for more radials.
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
G8HQP
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« Reply #18 on: March 15, 2014, 09:03:29 AM »

Quote from: ZENKI
Having said that many of the so called "no radial/ground/ verticals like the Hygain AV640 etc if place high like 30ft or more above the ground can be  very good performers.
An elevated vertical with no radials etc. is definitely using the coax outer as at least a counterpoise, and possibly a radiator too. Putting a balun at the feedpoint often kills such an antenna; people then blame the balun for poor performance when in fact this is clear evidence that the balun is doing precisely what a balun is supposed to do!
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AD5X
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« Reply #19 on: March 15, 2014, 04:04:23 PM »

A recent QEX article showed an average gain difference of about 6dB between a 1/4-wave vertical with an extensive ground system and an 8-foot ground rod (including both ground losses and differences in take-off angle).  One S-unit loss is not necessarily that bad unless you're close to the noise floor of the station you're trying to talk too.  So you can still have a lot of fun. 

When I was first licensed (9th grade) I put in a 14AVQ vertical with an 8-foot ground rod.  I had years of fun with that antenna being driven with a Knight T60 transmitter. 

Phil - AD5X
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KH6DC
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« Reply #20 on: March 15, 2014, 05:29:32 PM »

That's a Mosley paragraph, I saw it on their website and I'm tempted to try it.  Anyone has it or used it before, what's your take on it?
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73 and Aloha,
de Delwyn, KH6DC
N5GZH
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« Reply #21 on: March 17, 2014, 06:53:54 AM »

I was on an antenna manufacturer's website today (not MFJ or one of their associated companies) and here is what they had to say about their quarter wave vertical antennas:

" These verticals require only a modest earth ground system.  Complex ground and radial systems are optional, but extensive installation experience has proven that outstanding performance is achieve with only a simple mounting post which doubles as the ground rod."


The only credible part of this claim may be the part about the mounting post doubling as a ground rod.  Maybe.

In a sense, ground radial systems are  optional. As in not wasting 90 percent of your RF output heating soil is optional.  I've worked from central Texas to Canada QRP using 30 feet of sloping end fed wire and a ground rod. Was this a "good" antenna?  No.  And you can likewise work quite a few stations using 1/4 wave verticals that keep the earthworms warm and cozy instead of radiating efficiently, when conditions are right.

A very readable article from Butternut antennas about the importance of ground systems for monopole antennas:

http://www.bencher.com/pdfs/00361ZZV.pdf

Jim
N5GZH
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N6DGY
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« Reply #22 on: March 17, 2014, 03:02:31 PM »

The Mosley vertical, without any radials, is still better than a CHA250 Comet with 100 radials or an Isotron antenna. Look at the eHam reviews for those things!

People think anything that makes contacts is great!

Remember Gotham?  Consider them as a baseline for performance.  :-)

Joe, N6DGY
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K1DA
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« Reply #23 on: March 24, 2014, 09:04:16 AM »

When I installed my HyTower  some years ago, as I added radials the SWR went UP, the bandwidth DOWN and the antenna bgan to play very well.  Though I live on an island, local ground is dry sand.  I have about half a mile of wire under it now.  In a swamp, your mpg  may vary.
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NK7Z
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« Reply #24 on: March 24, 2014, 09:32:12 AM »

I was on an antenna manufacturer's website today (not MFJ or one of their associated companies) and here is what they had to say about their quarter wave vertical antennas:

" These verticals require only a modest earth ground system.  Complex ground and radial systems are optional, but extensive installation experience has proven that outstanding performance is achieve with only a simple mounting post which doubles as the ground rod."

Now how is this possible?  Seems they have violated the laws of physics, unless the simple mounting post is in the middle of the ocean. 
Guess it depends on how you define outstanding performance.

John AF5CC
Elevated radials...  Much less loss...  Rudy Severn did an extensive study of this at:
http://rudys.typepad.com/files/qex-mar-apr-2012.pdf
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
NK7Z
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« Reply #25 on: March 24, 2014, 09:35:22 AM »

When I installed my HyTower  some years ago, as I added radials the SWR went UP, the bandwidth DOWN and the antenna bgan to play very well.  Though I live on an island, local ground is dry sand.  I have about half a mile of wire under it now.  In a swamp, your mpg  may vary.
Not surprising, the antenna wants to be over good ground, and it is then 36 ohms...  Was probably closer to 50 ohms with no radials, as you add them, the moves towards 36.
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
K2GWK
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« Reply #26 on: March 26, 2014, 11:39:55 AM »

Counterpoise?Huh? Maybe??
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WA9CFK
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« Reply #27 on: March 28, 2014, 02:17:07 PM »

I suppose if you had a vertically mounted dipole, elevated radials or a counterpoise you would not need a radial system. So yes you can have good results with no radials.

No magic here; since how good is good is relative.   Wink
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ZENKI
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« Reply #28 on: March 28, 2014, 08:23:29 PM »

Yes, the feedline is always part of the antenna if you dont have a common mode choke. I do acknowledge this point. For portable ops  regardless of the rights or wrongs of this issue it can result in a convenient antenna. Getting any  vertical away from lossy earth is good practice even if your  current return is your feedline! In the perfect world we use common mode chokes and an extensive ground system and we all realize you not going to get something for nothing. If you dont have exceptional ground conductivity in most cases a fan dipole or a resonant monoband dipole will beat the pants off the average  vertical or one of these verticals in the box with no radials. The lazy in many hams make these  "no ground" antennas attractive even if it is am technically incorrect statement. All vertical antennas need a current return and  I suppose if that means the feedline or what it is attached to is the current return so be it.

Quote from: ZENKI
Having said that many of the so called "no radial/ground/ verticals like the Hygain AV640 etc if place high like 30ft or more above the ground can be  very good performers.
An elevated vertical with no radials etc. is definitely using the coax outer as at least a counterpoise, and possibly a radiator too. Putting a balun at the feedpoint often kills such an antenna; people then blame the balun for poor performance when in fact this is clear evidence that the balun is doing precisely what a balun is supposed to do!
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KF7VXA
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« Reply #29 on: April 01, 2014, 05:46:15 PM »

The only vertical antenna I know that really works with a bare minimum of radials is the Gap antennas. They require three radials on top of the ground. The reason is that they are a Vertical Dipole. Anyone who says a vertical won't work with 3 radials knows nothing about how the gap works. It's true for a regular vertical, but the gap being a vertical dipole is far different and much quieter. It also will have less than a 2 to 1 SWR on every band and does not need an antenna tuner..Another big plus. At about $350.00, they are the best vertical multi band antenna going.
All of that said, they work excellent, not anything like the two others mentioned.
Look at the 5 pages of reviews on this site under Gap Challenger, people who have them, love them. I know I sure do. just look at the contacts I made Sunday on QRZ.com. See my log. I used about 450 watts on these contacts, all of the others and I log little were made with 100 watts from a lousy QTH for radio...Idaho.
The Gap's are fantastic.

73's John KF7VXA
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