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Real World Vertical Bandwidth

K

kt4ye

Member
Aug 18, 2012
27
2
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83
Matthews, NC
I am involved in an experiment on what appears to be a new type of vertical antenna. I can't tell you what it is at this time

What I'm interested in is MEASURED 2.0:1 VSWR bandwidth from 1/4 wave verticals that have enought radials attached to all-but-eliminate ground losses from the data. And/Or similar data from elevated verticals with radials.

I'm most interested in 10M and 15 M but any information will be useful.

Please note I am NOT interested in techniques to improve vertical efficiency, info on qty of radials vs efficiency, elevated vs ground radials etc. ONLY bandwidth of real 1/4 wave antennas.

Several prototypes of my new design are showing what appear to be unusually large bandwidths that are NOT due to matching network losses nor to ground losses. So I want to learn "how good is it?" when compared with a standard 1/4 wave antenna. And I can't find any info in the literature that I have, nor online, on bandwidth.

Thanks es 73!

Bill
 

kt4ye said:
I am involved in an experiment on what appears to be a new type of vertical antenna. I can't tell you what it is at this time

What I'm interested in is MEASURED 2.0:1 VSWR bandwidth from 1/4 wave verticals that have enought radials attached to all-but-eliminate ground losses from the data. And/Or similar data from elevated verticals with radials.

I'm most interested in 10M and 15 M but any information will be useful.

Please note I am NOT interested in techniques to improve vertical efficiency, info on qty of radials vs efficiency, elevated vs ground radials etc. ONLY bandwidth of real 1/4 wave antennas.

Several prototypes of my new design are showing what appear to be unusually large bandwidths that are NOT due to matching network losses nor to ground losses. So I want to learn "how good is it?" when compared with a standard 1/4 wave antenna. And I can't find any info in the literature that I have, nor online, on bandwidth.

Thanks es 73!

Bill
Click to expand...

A new type of vertical antenna? Hmm... I would love to see what is being called a new type of vertical antenna.

It largely depends on how the antenna is built and (if necessary) matched. Without knowing the details of the antenna itself it is difficult to predict, and thus answer this question.


The DB
 
Even for 10m that can be used from 28mhz to 29.6mhz, I don't see why there is a need to have more than 2mhz bandwidth. Which a vertical with proper radials would do anyway. 15m doesn't have a a large frequency allocation either, from 21.0mhz to just 21.450mhz. Gee; even a slightly re-tuned Imax 2000 can do all of that.

I don't understand your request nor your urgency; I'm sorry . . .
 
if it is a real 1/4 wl vertical with proper ground plane direct feed it should have around a 35 ohm impedance. The radials/ground plane/counterpoise will need to be angled down at a 30 to 45 degree angle to get a 50 ohm impedance match.

If you get a very broad bandwidth it will have a low Q and this will be very poor in efficiency for radiating RF.

The laws of physics do not change, the broader the bandwidth the lower the Q of the antenna. IMAX2000 is fine example of that.

Use an 8' section of ROHN25 isolate it from earth ground, lay a few 1/4 wl ground radials under it. Direct connect the coax to the rohn, shield to the ground radials, it will be broad banded as heck, but will it radiate rf?
 
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Non Responsive Answers

All the tutorials were 100% accurate as it relates to current technology and designs. Unfortunately, none of the replys came close to answering the simple question that I asked (with NO urgency.)

I was hoping for some BANDWIDTH measurements from folks that have actually built 1/4 wave verticals and measured their bandwidth. If nobody has such information, or chooses not to pass it on... so be it.

73

Bill
KT4YE
 
kt4ye said:
All the tutorials were 100% accurate as it relates to current technology and designs. Unfortunately, none of the replys came close to answering the simple question that I asked (with NO urgency.)

I was hoping for some BANDWIDTH measurements from folks that have actually built 1/4 wave verticals and measured their bandwidth. If nobody has such information, or chooses not to pass it on... so be it.

73

Bill
KT4YE
Click to expand...

If you're involved in designing "what appears to be a new type of vertical antenna" then why are you asking for this data from forum members instead of doing it yourself? Is this you're concept of R&D? Seems that collecting anectodal data from a radio forum is not the best way to go about this. Or maybe you just needed totell someone about your "new type of vertical ntenna". :confused:
 
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RatsoW8 said:
If you're involved in designing "what appears to be a new type of vertical antenna" then why are you asking for this data from forum members instead of doing it yourself? "
Click to expand...

Because I want to learn from others that have built and tested plain vanilla 1/4 wave antennas in a variety of different environments, soil conditions, etc.

After about 40 years in engineering, I believe that I know how to do R/D. But I don't have access to multiple sites and multiple locations. The ham community has that info.

73

Bill
KT4YE
 
I see more people are gaining interest in a wide band vertical at the top of the HF spectrum. I would suggest you not expect miracles from a simple 1/4 wave ground plane. You'll never see 4 Mhz. of bandwidth with any efficiency in a simple 1/4 wave at HF. Even over a perfect ground, it's not close to that bandwidth.

To accomplish your goal usually requires several elements that are stager tuned across the desired bandwidth. Radio Shack use to sell a Scanner antenna that was a 1/4 wave ground plane with 3 vertical elements of different length, evenly spaced apart and all driven in parallel at the base. No gain but this is one way to make a 1/4 wave cover lots of bandwidth.

Sirio has already built us a 4 Mhz. bandwidth vertical 5/8 wave for this spectrum called the Gain-Master. From what I can tell it has four areas that affect it's bandwidth. Top radiator length, bottom radiator length, coax stub length, and matching capacitor value. Using the antenna analyzer reveals more then one overlapping resonant point.
 
Shockwave said:
I see more people are gaining interest in a wide band vertical at the top of the HF spectrum. I would suggest you not expect miracles from a simple 1/4 wave ground plane. You'll never see 4 Mhz. of bandwidth with any efficiency in a simple 1/4 wave at HF. Even over a perfect ground, it's not close to that bandwidth.
Click to expand...

That's why I'm asking the question. I want to know what the benchmark is. 4 MHz 2:1 bandwidth at, say, 28 MHz is about 14%. But if that same technique is applied to, say 3.725 MHz, then that's 520 KHz... and THAT is enough to cover the entire 80M band!

Shockwave said:
To accomplish your goal usually requires several elements that are stager tuned across the desired bandwidth. Radio Shack use to sell a Scanner antenna that was a 1/4 wave ground plane with 3 vertical elements of different length, evenly spaced apart and all driven in parallel at the base. No gain but this is one way to make a 1/4 wave cover lots of bandwidth.
Click to expand...

Yep. Complex and also requires a very large "footprint," IOW lots of radials (and real estate) at HF. An ideal design would have a much smaller

Shockwave said:
Sirio has already built us a 4 Mhz. bandwidth vertical 5/8 wave for this spectrum called the Gain-Master. From what I can tell it has four areas that affect it's bandwidth. Top radiator length, bottom radiator length, coax stub length, and matching capacitor value. Using the antenna analyzer reveals more then one overlapping resonant point.
Click to expand...

Yep, multiple tuned elements can provide extra bandwidth at the expense of higher mfg/sale price. There is also an issue of power loss in the phasing coil. Glad to see they incorporate a Common Mode choke, but a 1:1 current balun might have been a better technical choice.

It's interesting that they chose to show free-space radiation patterns. TakeOff angle is heavily influenced by height above ground. So is power distribution vs angle.

Too bad it's so tall, and so narrowband! :D

73

Bill KT4YE
 
I think you'll find the typical 1/4 wave ground plane on 10 or 11 meters is going to struggle to provide a 1 Mhz. bandwidth at a reasonable VSWR.
 
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ummm you don't need coils and junk to run multiple elements on the same feed line.

I built a ground feed vertical, 1/4 wave, 3 elements, 1 for 160m, 1 for 80m, and another for 40m, and it works quite well. all on the same feedline, it just works.
 
~~

Shockwave said:
I think you'll find the typical 1/4 wave ground plane on 10 or 11 meters is going to struggle to provide a 1 Mhz. bandwidth at a reasonable VSWR.
Click to expand...

Actually the "Starduster" type 1/4 GP delivers 2mhz bandwidth. 1/4~ radiator with 4 radials at 45 degree angle.
 

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