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Author Topic: Resonant vs. Non-Resonant Verticals  (Read 7363 times)
KD2CJJ
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Posts: 369




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« on: August 13, 2012, 11:41:05 AM »

Im interested in adding a vertical.  Right now I have a dipole in a compromised situation - I intend to keep it and improve it over time (as much as I can).... But I would like to see how a vertical polarization can help with DXing and increasing my contact counts...

I have been a slew of research but have yet to find a definative answer being which has more efficiency - resonant vs non-resonant vertical. 

Now I want to compare something like a

Resonant  Vertical - Gap Titan/CrushCraft R8 (no traps with resonant rails) or Hustler 5BTV (with traps)
to
Non-Resonant Zero Five 29 Foot  6 - 80 Meter with 4:1 unun
OR DX Engineering MBVE-2 HF Multi-Band Vertical Antennas MBVE-2

My situation is I can not ground mount this and I would elevate it roughly 10 feet up and put elevated radials (2 at the most 180 degrees)..

Keep cost out of the factor - which do you guys think is most effective based on the setup I describe... I know its not ideal setup but it is what it is - unless I sell my house and move to an antenna friendly area - so I am looking for which setup and why....

Everything I have found has an argument for one or the other.. of course the non resonant is easiest to setup - but Im ok with doing some work.. I just want the best bang for efficiency - the little that I will have...

Thanks again for your feedback!
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73

Mike
KD2CJJ
N4UM
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« Reply #1 on: August 13, 2012, 12:10:49 PM »

I don't think there's any magic in resonance provided you're able to match the antenna input impedance to the the line impedance (particularly when using coax).  A non-resonant antenna is simply one where either inductive or capacitive reactance is involved.

A major consideration would be the antenna's vertical radiation pattern which is a function of the length of the vertical in terms of wavelengths.  Make it more than 5/8 wavelengths and much of your radiation will be at high angles - usually unsuitable for DX.

In my case I use a 23 foot nonresonant vertical with a semi-decent radial system under it and match it by means of a remote antenna tuner.  The antenna works well on 40 thru 10 meters even though it is perhaps a bit too long on 10 and the efficiency on 40 is reduced somewhat.

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AA4PB
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« Reply #2 on: August 13, 2012, 12:26:27 PM »

I'd say that neither is going to work very well with only two radials.
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KD2CJJ
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Posts: 369




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« Reply #3 on: August 13, 2012, 12:28:44 PM »

My understanding is that a non-resonant antenna has greater losses due to the need of UNUNs and Tuners to bring the antenna into resonance...

Also as you stated without the use of traps, etc. the entire length is used for that band thus affecting (more or less) depending on the band you intend to use it for the take off angle - or am I mistaken on this point and would be the same for a resonant antenna at the same length (height).
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73

Mike
KD2CJJ
N4CR
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« Reply #4 on: August 13, 2012, 12:54:59 PM »

The resonant antennas you mention are 1/2 wavelength antennas and require no radial field since the counterpoise is self contained.

Since the radial field is EVERYTHING on a 1/4 wave vertical I'd say not being able to supply one pretty much finishes that conversation.

My R-8 is a great antenna. I highly recommend it or the HyGain AV-640 which is a nearly identical knockoff of the R-8.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
KD2CJJ
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« Reply #5 on: August 13, 2012, 01:01:48 PM »

You make a great point that I suspected but didnt take seriously enough..

It sounds like to me due to my lack of space for radials one of the resonant antennas such as you described would be better -

How would the GAP titan compare?

Could there be a large effect if it is put near (15 or so) to a house?



The resonant antennas you mention are 1/2 wavelength antennas and require no radial field since the counterpoise is self contained.

Since the radial field is EVERYTHING on a 1/4 wave vertical I'd say not being able to supply one pretty much finishes that conversation.

My R-8 is a great antenna. I highly recommend it or the HyGain AV-640 which is a nearly identical knockoff of the R-8.
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73

Mike
KD2CJJ
N4CR
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« Reply #6 on: August 13, 2012, 01:29:11 PM »

I'm not sure anyone can answer that without doing some investigation. Is it a wood frame house? Metal studs? Stucco? Aluminum siding? I suspect the effect will be some but minimal without any more information.

I have mine at 12' and out in the open but I have a big yard to put it in so I don't have experience with putting it close to the house other than having it on my roof and it got into all of my electronics. Now that it's way away from the house not a peep from anything.

But that's going to be an issue with any antenna where the house is being bombarded with near field RF. It's called primary overload.

I have no opinion on the Gap Titan but it probably gets about the same reports as other half wave self contained verticals. A half wave vertical is a half wave vertical. There won't be a lot of differences other than which bands are covered.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
W8JI
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« Reply #7 on: August 13, 2012, 01:30:14 PM »

Im interested in adding a vertical.  Right now I have a dipole in a compromised situation - I intend to keep it and improve it over time (as much as I can).... But I would like to see how a vertical polarization can help with DXing and increasing my contact counts...

I have been a slew of research but have yet to find a definative answer being which has more efficiency - resonant vs non-resonant vertical. 

Forget about "resonant" and "non-resonant". That, by itself, is a non-issue for radiation. It confuses people when thinking about performance.

Matching is important, but not exclusively important. A good match to feedline does not mean anything in and by itself, but it is a consideration.

If an antenna is **not matched** to a feedline of significant length, it increases losses in that feedline. How much it increases losses depends on the feedline length and type, but match can be VERY important or not important at all.

Non-resonant verticals have significant mismatch on almost all bands, and they become particularly bad on frequencies below 3/16th wave long. That means a 43 foot vertical will be poor on 80 meters with any significant length of coax,  and horrible on 160 meters with almost any feeder length. SWR is over 100:1 on 160, and it takes many thousands of volts applied to radiate just a few hundred watts! They have other sweet and sour spots up in frequency.

Overall, you would be far better off with a regular trap vertical like a 6BTV or 4BTV, so long as they all use the same basic ground system.

There is no magic in any of this. No-radial verticals compromise performance for ease of installation. The Gap isn't magic either. The Gap is a terrible antenna on 80 meters or the lowest bands, and not significantly better than a regular trap vertical on the best bands for the Gap. As a general rule, a regular trap vertical with a reasonable ground system will beat a Gap.

The no-radial resonant antennas mentioned are **NOT** 1/2 wave verticals. They are all off-center-fed Marconi antennas with a very small counterpoise system. They are sometimes falsely called "1/2 wave antennas" in advertisements or talk, but they are not half waves. I have not ever seen a multiband half-wave vertical manufactured for HF, although I have seen antennas that were NOT half waves called half waves just to sell antennas.

(If anyone knows of a **real** half-wave multiband antenna, please point it out.)

There are a few single-band half wave antennas, but even half-wave end-fed or base-fed antennas require a ground or counterpoise. Without a ground or counterpoise, they will have all sorts of common mode current and radiation on the feeder.

There is so much confusing and misleading stuff about antennas, it is shameful. Advertising and some articles totally confuse people and makes them misunderstand how antennas really work.

If I were installing a multband antenna and gave a hoot about efficiency, I'd either buy a 6BTV or similar for higher bands and price...or a Hygain Hytower for all bands including lower bands. I would always use a grounded vertical, and just do the best I could with a multiple-wire radial ground.

73 Tom
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N4CR
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Posts: 1694




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« Reply #8 on: August 13, 2012, 01:35:16 PM »

When you say they are not half wave, do you mean they are not center fed half wave?

Yes, they are off center fed. I don't think that makes them not half wave.

What wavelength are they?
« Last Edit: August 13, 2012, 01:55:29 PM by N4CR » Logged

73 de N4CR, Phil

Never believe an atom. They make up everything.
WB6BYU
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Posts: 13482




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« Reply #9 on: August 13, 2012, 01:42:03 PM »

Resonance doesn't really make any difference with regards to efficiency.  What matters
more is the radiation resistance and losses, some of which are a function of the antenna
design and some are due to the local environment (ground characteristics, nearby
buildings, etc.)  So you really need to take antenna on its own merits:  both the theoretical
performance and how well it is implemented.

It will help to specify what bands you are most interested in.  Two elevated radials at 10'
will interact differently with the ground on 10m than on 160m.  A 29' vertical will behave
differently on 10m, 20m or 80m.

Generally, antenna efficiency drops off significantly for lengths less than about 1/8 wavelength
or so.  The 29' vertical will work well on 40m (and can be brought to resonance with a bit of
base loading inductance) and on 20m (though with a higher feedpoint impedance).  Above 15m
performance falls off because the radiator is too long, but it is still usable on 10m.  80m isn't
as efficient (too short) and the vertical pattern isn't as useful on 6m (too long).  But if your
primary interests are on 40, 20 and 17m, this can work very well.

By contrast, the 6BTV is electrically 1/4 wavelength on all bands, due to the use of traps (which
aren't as bad as some advertisers make them out to be.)   That allows enough length to make it
reasonably efficient on 40m without having the pattern break up on 10m.  You would need a pair
of resonant radials for each band you plan to operate.  Some such as the R8 are actually
designed to be 1/2 wave antennas that don't require radials (other than the bottom "hat"),
but because these have a high impedance at the bottom they sometimes can be detuned
by nearby structures.  Some of the GAP antennas have been measured to have several dB more
lower signals than other comparable antennas, but I don't know what it is about the design
that affects that.

If you put the tuner at the base of an antenna, or a design that has a low SWR at the feedpoint,
it keeps the feedline losses low.  If you are using a non-resonant antenna with a tuner in the shack,
you need to determine the losses on each band based on the input impedance of the antenna and
the type and length of the coax.  In some cases the loses are tolerable, but not always.


So it isn't as simple as just comparing "resonant' to "non-resonant" antennas.  An antenna can be
resonant and still have a high SWR.  A non-resonant antenna can be matched with a tuner, but
still have high coax losses and/or an unfavorable vertical radiation pattern on some bands.
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KD2CJJ
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Posts: 369




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« Reply #10 on: August 13, 2012, 02:37:25 PM »

The issue I am facing is that I can only elevate mount a vertical as my back yard is covered with paverstone and pool with the other end of the yard full of power lines.

With that said I can only get 2 radials elevated 180 degrees if radials are needed...

 I want to see how a vertical polarization can change my situation (have a dipole inverted V 24 feet up but against my house)... but I have some constraints..

I know its not ideal situation but I would like the best of a bad situation.. 

Thanks
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73

Mike
KD2CJJ
W8JI
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« Reply #11 on: August 13, 2012, 02:41:49 PM »

When you say they are not half wave, do you mean they are not center fed half wave?

Yes, they are off center fed. I don't think that makes them not half wave.

What wavelength are they?

Wavelength varies with band. On some bands they are around 1/4 wave long, on some bands less than 1/4 wave for some antennas, on other bands about 3/8th wave. There isn't any band where they are 1/2 wave long.

They behave as off-center feed antennas, and there isn't any band where any multiband HF antennas I'm aware of are functioning as ground independent half-waves. If you can think of one, let me know!!

73 Tom
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N4CR
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Posts: 1694




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« Reply #12 on: August 13, 2012, 03:38:14 PM »

Wavelength varies with band. On some bands they are around 1/4 wave long, on some bands less than 1/4 wave for some antennas, on other bands about 3/8th wave. There isn't any band where they are 1/2 wave long.

They behave as off-center feed antennas, and there isn't any band where any multiband HF antennas I'm aware of are functioning as ground independent half-waves. If you can think of one, let me know!!

73 Tom

Thanks. for the education. Again. You are a wealth of knowledge.

I did look up the definition of a Marconi and yup, it's that.

Just out of curiosity, do they not recommend adding radials because it would necessitate the need for further tuning away from the specifications they provide? It would violate the 'design package' and documentation?
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73 de N4CR, Phil

Never believe an atom. They make up everything.
W5DXP
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« Reply #13 on: August 13, 2012, 06:26:00 PM »

I have been a slew of research but have yet to find a definative answer being which has more efficiency - resonant vs non-resonant vertical.

Here's a data point for you based on EZNEC.

A resonant 33' 1/4WL vertical over mininec ground has a maximum gain of -0.05 dBi at a take-off-angle of 26 degrees.

A non-resonant 33' 5/8WL vertical over mininec ground has a maximum gain of 2.19 dBi at a take-off-angle of 16 degrees.

Which is better?

Yes, they are off center fed. I don't think that makes them not half wave.

By definition, a half-wave antenna cannot be a multi-band antenna because it is a half-wavelength on only one frequency.Smiley
« Last Edit: August 13, 2012, 06:31:49 PM by W5DXP » Logged
N4CR
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Posts: 1694




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« Reply #14 on: August 13, 2012, 06:46:08 PM »

By definition, a half-wave antenna cannot be a multi-band antenna because it is a half-wavelength on only one frequency.Smiley

So a fan dipole is not a half wave?

These antennas have multiple elements.

A Hy Gain hytower is not a quarter wave vertical on 5 bands? If a half wave antenna can't be a multi-band antenna, then neither can a quarter wave antenna.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
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