Okay, Here's Your Challenge: A 6mhz Bandwidth 10~11M Vertical

[Wire Weasel]

Look at the Hustler G6 144B. 2M Vertical. I've had 3 of these over the years and will get another (station components come and go).

Advertise and deliver a 6mhz bandwidth. Assemble per instructions and they deliver 143~149mhz (+) flat 1:1 SWR perfect resonance.

Now take this design and build us a 6mhz bandwidth similar vertical for 10~11 meters.

 

[Captain Kilowatt]

There are several ways to broadband an antenna but every one of them causes a lowering of the efficiency. Load up a 50 ohm resistor with a whip attached to one end and ground the other end. Great bandwidth around the resonant freq of the whip but the eff. is not so great.

 

[Wire Weasel]

But the G6 also has 6db gain. Not shabby at all.

 

[dxhound]

Somthing to think about in this discusion and why this is more challenging, is the physical wave itself. The dimmensions of a wavelength from 140 Mhz to 146 Mhz means less of a change than from say 26 Mhz to 32Mhz.

 

[W5LZ]

Looks/sounds like a three element vertical array. Roughly, multiply that antennas length by 5 (or 6) and you'd have something very close in performance but on 10 - 11 meters. Wish I could do that, but just don't have the room. Challenge declined, sorry.
- 'Doc

 

[Shockwave]

As DX hound points out, the 6 Mhz. bandwidth is a much larger percentage of the overall frequency at 26 Mhz. than it is at 144 Mhz. and that limits the possible bandwidth of a given antenna. About the best you're going to see at 26 Mhz. would be the Gain-Master that provides coverage from 25.7 to 29.7 Mhz. at a VSWR below 1.5:1 at the edges. Getting even 4 Mhz. coverage with any gain was a significant accomplishment.

 

[Captain Kilowatt]

But the G6 also has 6db gain. Not shabby at all.

6 dB as referenced to what? I haven't looked at it yet. The above posts regarding bandwidth are right on the money. When you scale an antenna from one freq to another everything changes in % however the bandwidth remains a constant % and therefore the freq range gets narrower as the wavelength is lowered. Getting 6 MHz is easy on VHF,my Comet CA-2x4SR mobile antenna is dual band and has at least that on 2m and damn near 20 MHz on 70cm but the same design for 10/11m would be hard pressed to provide more than 2 Mhz.

 

[The DB]

Just a quick rough estimate, but wouldn't 6Mhz bandwidth at 2 meters be equivalent to somewhere between 1 and 1.5Mhz on 10 or 11 meters?

If you scale antennas from one frequency to another the bandwidth in Mhz also scales, however bandwidth scales with frequency and not the size of the antenna, so the lower in frequency you go the less bandwidth the same antenna will appear to have. Its all in the math.

I also noted that you put 10 and 11 meters in there. I can see the use for 10 meters, but what would be the need on 11 meters? A properly tuned antenna can easily cover the 1/2Mhz bandwidth that is needed here in the US, and even if you freeband a quarter wave whip will be widebanded enough to cover everything between the 10 and 12 meter HAM bands and even into those bands with a descent SWR.

That being said if the only requirement is 6Mhz of bandwidth on the HF bands that is easy, a 50 ohm resistor will easily meet those needs and far beyond... Oh did you want to actually talk to someone??


The DB

 

[Captain Kilowatt]

Just a quick rough estimate, but wouldn't 6Mhz bandwidth at 2 meters be equivalent to somewhere between 1 and 1.5Mhz on 10 or 11 meters?

If you scale antennas from one frequency to another the bandwidth in Mhz also scales, however bandwidth scales with frequency and not the size of the antenna, so the lower in frequency you go the less bandwidth the same antenna will appear to have. Its all in the math.

I also noted that you put 10 and 11 meters in there. I can see the use for 10 meters, but what would be the need on 11 meters? A properly tuned antenna can easily cover the 1/2Mhz bandwidth that is needed here in the US, and even if you freeband a quarter wave whip will be widebanded enough to cover everything between the 10 and 12 meter HAM bands and even into those bands with a descent SWR.

That being said if the only requirement is 6Mhz of bandwidth on the HF bands that is easy, a 50 ohm resistor will easily meet those needs and far beyond... Oh did you want to actually talk to someone??


The DB

With 12m starting at 24.890 and 10m ending at 29.7 (or even 29.0 MHz ) that means a bandwidth of either 4.11 MHz or as much as 4.81 MHz which a properly installed quarter wave whip would be hard pressed to provide a decent SWR across. Been there and tried that. Then again maybe your idea of acceptable SWR is different than mine. I mean less than 2:1 without any form of tuner inline. If ground losses are high the SWR can appear to be low over a W-I-D-E bandwidth but the radiation efficiency is low. It will work but just not as effectively.

 

[wavrider]

Three element STEPPIR yagi, cover any freq you want in HF at 6DB gain, but is the price worth it?

Or the STEPPIR vertical? Doubt you would get 6DB gain from the vert.

Yagi Antennas | Steppir, Inc – Antennas for Amateur Radio and Industry

You could use a remote tuner at the base of a 26' vertical and tune it from 10 meters to 15 meters, that will work decent also.

 

[The DB]

With 12m starting at 24.890 and 10m ending at 29.7 (or even 29.0 MHz ) that means a bandwidth of either 4.11 MHz or as much as 4.81 MHz which a properly installed quarter wave whip would be hard pressed to provide a decent SWR across. Been there and tried that. Then again maybe your idea of acceptable SWR is different than mine. I mean less than 2:1 without any form of tuner inline. If ground losses are high the SWR can appear to be low over a W-I-D-E bandwidth but the radiation efficiency is low. It will work but just not as effectively.

For one I said to not through, that is 3Mhz give or take. 2:1 is my limit in SWR as well. Where I see this type of bandwidth is on a vehicle mount. Most are also using a chromed spring and perhaps a chromed stud or even chromed quick releases. Chrome means more bandwidth at the cost of efficiency.

That being said, a quarter wave whip with no chrome on a fully bonded SUV covers the conditions I listed above. In that vehicle cycling through the frequencies with an analyzer you see the center point of the bandwidth move down to 25 ohm impedance, then rises from there. 25 Ohms of impedance is still 2:1 so the SWR curve goes down to a match, (50 ohm point) then up to 2:1, then it curves back down to another match, then goes up from there.

The quarter wave antenna is a wide banded antenna as it is, and with that vehicle's ground plane giving the antenna a 25 ohm low impedance point just increases that bandwidth more. That one, for the record does cover both the 10 meter and 12 meter bands and everything in between with 2:1 or better SWR. I suppose I could upgrade my SUV to a larger one to see if I can make it more efficient...


The DB

 

[Captain Kilowatt]

For one I said to not through, that is 3Mhz give or take. 2:1 is my limit in SWR as well. Where I see this type of bandwidth is on a vehicle mount. Most are also using a chromed spring and perhaps a chromed stud or even chromed quick releases. Chrome means more bandwidth at the cost of efficiency.

That being said, a quarter wave whip with no chrome on a fully bonded SUV covers the conditions I listed above. In that vehicle cycling through the frequencies with an analyzer you see the center point of the bandwidth move down to 25 ohm impedance, then rises from there. 25 Ohms of impedance is still 2:1 so the SWR curve goes down to a match, (50 ohm point) then up to 2:1, then it curves back down to another match, then goes up from there.

The quarter wave antenna is a wide banded antenna as it is, and with that vehicle's ground plane giving the antenna a 25 ohm low impedance point just increases that bandwidth more. That one, for the record does cover both the 10 meter and 12 meter bands and everything in between with 2:1 or better SWR. I suppose I could upgrade my SUV to a larger one to see if I can make it more efficient...


The DB

Please explain to me how chrome plating yields more bandwidth while driving the efficiency down? :blink:

As for my experience I was using a straight whip without any spring, chrome plated or not, bonded vehicle panels for an excellent groundplane, and the bandwidth was still not wide enough to cover all of 12m up to the top of 10m and stay below 2:1 on a mid-sized SUV or a small pick-up (Ford Ranger). The coax terminated into a 1.5:1 Rf transformer (unun) placed between the feedline and the antenna for proper matching. This is what I was referring to when I mentioned a PROPERLY installed antenna due to the the fact that a PROPERLY installed 1/4 wave antenna over a good groundplane should NOT show 50 ohms but rather something in the order of 35 ohms +/- j0 for reactance plus maybe a few ohms of ground losses.Additional losses in the ground system (or elsewhere) will add to that 35 ohms and approach 50 ohms which may look good on a meter but the efficiency actually goes down. It has been proven that the resonant impedance of a 1/4 wave over an excellent groundplane is around 35 ohms and we know that maximum power is radiated from the antenna when it is resonant. The minor 1.5:1 SWR is more than offset by this improved efficiency. For ground mounted verticals many hams make the mistake of adding radials until the impedance is 50 ohms for what they think is a perfect match. If they keep adding radials until they see around 35 ohms the efficiency of the antenna will improve greatly as they eliminate an additional 15 ohms of ground losses which is like improving the efficiency about 50%. An SWR of 1.5:1 represents only about a loss of 11%. There are different ways to look at this I suppose but I am taking the far too detailed and analytical way of doing it compared to what the other 99% of folks do. Then again my system is/was probably a bit better than about 99% of the others out there. At least that's what the field strength meters said.

 

[The DB]

Please explain to me how chrome plating yields more bandwidth while driving the efficiency down? :blink:

I'm assuming you have heard of this little thing called skin effect. And chrome is such a great conductor isn't it? Yep its conductive properties are right up there with silver... Odd how my experience shows otherwise. What was that cb antenna that had that large chrome plated coil in it? Very wide banded but transmitted and received about as well as a dummy load...

As for my experience I was using a straight whip without any spring, chrome plated or not, bonded vehicle panels for an excellent groundplane, and the bandwidth was still not wide enough to cover all of 12m up to the top of 10m and stay below 2:1 on a mid-sized SUV or a small pick-up (Ford Ranger). The coax terminated into a 1.5:1 Rf transformer (unun) placed between the feedline and the antenna for proper matching. This is what I was referring to when I mentioned a PROPERLY installed antenna due to the the fact that a PROPERLY installed 1/4 wave antenna over a good groundplane should NOT show 50 ohms but rather something in the order of 35 ohms +/- j0 for reactance plus maybe a few ohms of ground losses.Additional losses in the ground system (or elsewhere) will add to that 35 ohms and approach 50 ohms which may look good on a meter but the efficiency actually goes down. It has been proven that the resonant impedance of a 1/4 wave over an excellent groundplane is around 35 ohms and we know that maximum power is radiated from the antenna when it is resonant. The minor 1.5:1 SWR is more than offset by this improved efficiency. For ground mounted verticals many hams make the mistake of adding radials until the impedance is 50 ohms for what they think is a perfect match. If they keep adding radials until they see around 35 ohms the efficiency of the antenna will improve greatly as they eliminate an additional 15 ohms of ground losses which is like improving the efficiency about 50%. An SWR of 1.5:1 represents only about a loss of 11%. There are different ways to look at this I suppose but I am taking the far too detailed and analytical way of doing it compared to what the other 99% of folks do. Then again my system is/was probably a bit better than about 99% of the others out there. At least that's what the field strength meters said.

You obviously take your mobile antennas far more seriously than most anyone else, including most hams. Unfortunately I was referring to the real world where not everyone takes the time to understand and learn what is actually happening, or has the need for every last ounce of perfection in there setup. I know I don't have a perfect setup on my vehicle, does that make the ever expanding pool of knowledge that I have based on experience and actual experience irrelevant? I offered an opinion based on what I experienced in the real world, nothing more. I do think you mistook one or two things that I said but thats ok, unless of course you want to get into a pissing match over it...

As for the ground mounted monopole you referred to, there are certain circumstances where more radials is better, but none of them are for SWR tuning purposes. And I personally don't think there are many 10 to 11 meter ground mounted monopoles.

I am actually curious as to the goals the op is attempting to achieve with this thread. Why do we need a 6Mhz bandwidth at HF frequencies? I guess it would be neat if you only talked on, say, 10 and 12 meters, but where does that leave the rest of the HF bands? If you talked on any more than 2 neighboring bands you would still need a tuner to tune the rest of the bands in, or perhaps multiple antennas. Also, its efficiency would be shot to hell, and I fear that in the end it would be far more trouble than it was worth. I'm thinking dummy load territory here...


The DB

 

[AudioShockwav]

I'm assuming you have heard of this little thing called skin effect. And chrome is such a great conductor isn't it? Yep its conductive properties are right up there with silver... Odd how my experience shows otherwise. What was that cb antenna that had that large chrome plated coil in it? Very wide banded but transmitted and received about as well as a dummy load...

While I agree with a lot of your postings re antennas, I have to disagree with the above statement.
At 27MHz the skin effect of a mobile antenna is so trivial that I doubt you will find a way to measure it.
I think you are talking about the "Truck Spec" coil antenna ( also sold under different names) with a Chrome coil attached to the shafts with "pot metal" stand offs and Allen head screws, I have used them in the past, and although the suffered from mechanical defects as far as antennas go, they radiated just fine.
IMHO


73
Jeff

 

[Captain Kilowatt]

I'm assuming you have heard of this little thing called skin effect. And chrome is such a great conductor isn't it? Yep its conductive properties are right up there with silver... Odd how my experience shows otherwise. What was that cb antenna that had that large chrome plated coil in it? Very wide banded but transmitted and received about as well as a dummy load...

No need to be a sarcastic ass about it.I am much more informed about skin effect than you may realize having worked with commercial gear from AM broadcast frequencies right up to 1.7GHz systems during my 22 years in commercial broadcasting. Over this range range the skin effect varies greatly however this is all completely irrelevant since a spring base has a COPPER braid inside it which effectively jumpers out the CHROME plated coil. If it didn't then dirt/rust build up between turns would turn the spring coil into a base loading coil of varying inductance which would really screw things up.

You obviously take your mobile antennas far more seriously than most anyone else, including most hams. Unfortunately I was referring to the real world where not everyone takes the time to understand and learn what is actually happening, or has the need for every last ounce of perfection in there setup. I know I don't have a perfect setup on my vehicle, does that make the ever expanding pool of knowledge that I have based on experience and actual experience irrelevant? I offered an opinion based on what I experienced in the real world, nothing more. I do think you mistook one or two things that I said but thats ok, unless of course you want to get into a pissing match over it...

Not looking for a pissing match here, in fact it appears it is YOU that has taken exception to MY opinions based on real world experience. Please do not berate my findings simply because I spent more time and effort finding out WHY things occur as they do. There are a great deal of misconceptions out there regarding antennas and I refuse to believe false information simply because it is the popular way to think. It goes along with the "proper length of coax going to the antenna" thing.

As for the ground mounted monopole you referred to, there are certain circumstances where more radials is better, but none of them are for SWR tuning purposes. And I personally don't think there are many 10 to 11 meter ground mounted monopoles.

I never said it had anything to do with tuning SWR purposes. I did say that many people install radials until they see 50 ohms and then leave it.Again, part of that "it's the popular way so it must be the right way" kind of thinking. I also said that was the wrong way to do it when something in the order of 35 ohms was more the target based on what the proper resonant impedance should be. As for the popularity of ground mounted 10/11m monopoles, you are correct however the antenna does not know whether the groundplane under it is ground radials, an elevated radial system, or a vehicle body. All it knows is the effectiveness of whatever is under it.

I am actually curious as to the goals the op is attempting to achieve with this thread. Why do we need a 6Mhz bandwidth at HF frequencies? I guess it would be neat if you only talked on, say, 10 and 12 meters, but where does that leave the rest of the HF bands? If you talked on any more than 2 neighboring bands you would still need a tuner to tune the rest of the bands in, or perhaps multiple antennas. Also, its efficiency would be shot to hell, and I fear that in the end it would be far more trouble than it was worth. I'm thinking dummy load territory here...


The DB

We are both 100% in agreement with this part.