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Okay, Here's Your Challenge: A 6mhz Bandwidth 10~11M Vertical
- Thread starter Wire Weasel
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Personally for the money i found this the best damned 6mhz bandwidth 11m antenna i ever used.
its only slightly bettered by the A99/I MAX 2000, but they cost so much more
Ya know... talk about stealth antennas, if you live within 1/2 mile or so of a buddy, maybe more, you can both talk to each other fine on dummy loads and be invisible to everyone else.
First you have to think of the antenna system as a whole and understand how it acts. Basically the antenna and the ground perform as a series circuit with the RF leaving the antenna and some of that RF being returned to the transmitter by the ground. The impedance of the antenna system is comprised of two parts. The radiation resistance of the antenna and the resistance of the ground system.The radiation resistance of the antenna depends on the antenna type but for any given type of antenna it remains constant. The ground resistance however is something that we can change. We can make it lower by adding radials or improving the groundplane under the antenna.Think of each radial as a resistor and the more resistors (radials) we add in parallel the lower the resulting resistance becomes. Suppose we have an antenna that has a radiation resistance of 35 ohms as is the case of a 1/4 wave vertical over a perfect groundplane. Now suppose the ground return losses amount to 15 ohms. We now have 35 ohms plus 15 ohms which equals 50 ohms. Looks good on an SWR meter doesn't it? Now lets look at the efficiency of this system. We find that by dividing the radiation resistance by the total antenna impedance x 100 to get % therefore we have 35 ohms divided by 50 ohms which equals 0.7 x100 which makes this antenna 70% efficient. Now suppose we add a bunch of radials and bring the ground losses down to 5 ohms. Now 35 + 5 = 40 ohms total antenna impedance. The efficiency is now 35/40 x 100 or 87.5% efficient. If we could improve the ground system until we achieved just 1 ohm of ground losses the antenna would be 35/36 x 100 or 97.22% efficient. This is what happens when we add radials. Yes it increases efficiency but it does it by lowering the losses in the ground system. Hope you were able to follow that.
Finally CK got to some of the missing parts of the discussion.
Without getting into it deeper it cannot be fully explained by dancing around the outside of the subject with only small parts of it being used for discussion.
RF theroy never changes no matter what the antenna design is.
No antenna 'has' to be resonant to radiate a signal with reasonable efficiency.
Go back for minute to the non resonant dipole.
50 ohms is not a magic number. It could be 75 ohms or any other number.
This NR antenna does not have a 50 ohm match but uses a lower loss feedline at high SWR with a balun to a tuner. This is one example of an antenna that is not resonant on any band but works just fine.
The major parameter for wide bandwidth is system Q.
Normally you cannot get wide band width with coils involved.
They have a higher Q of there own that becomes the limiting factor for band width no matter where on the radiator they are put.
Going on, making the radiation element a larger area or a better metal surface reduces the Q by reducing the loss resistance therefore the bandwidth gets wider but there is a practical physical limit to that as well.
To work an antenna over a very wide bandwidth, the impedence at the lowest frequency should be known then do an impedence conversion from that value to 50 ohms and be able to vary the tranformation to meet the objective over the total bandwidth.
As the frequency goes higher the radiating element becomes more and more inductive. The tuner needs to counter it with series capacitance to canel out the reactance.
The final impedance * can still be any value at the antenna terminals and does change with frequency.
The radials, ground plane, counterpoise or what you want to call them is the other half of a vertical antenna system.
How you use them in the system makes some differances in final impedance and radiating efficiency.
Always remember the antenna is an oscillating system between the halves.
RF current is involved so you have losses to consider.
*The impedance at any point in the system is still akin to R=E/I plus the effects of phase shift. This is called AC impedance
Again you have to consider all the operating parameters of the system and cannot ignor any of it or it leaves you with unknowns until you catch up with them.
Good luck.
Without getting into it deeper it cannot be fully explained by dancing around the outside of the subject with only small parts of it being used for discussion.
RF theroy never changes no matter what the antenna design is.
No antenna 'has' to be resonant to radiate a signal with reasonable efficiency.
Go back for minute to the non resonant dipole.
50 ohms is not a magic number. It could be 75 ohms or any other number.
This NR antenna does not have a 50 ohm match but uses a lower loss feedline at high SWR with a balun to a tuner. This is one example of an antenna that is not resonant on any band but works just fine.
The major parameter for wide bandwidth is system Q.
Normally you cannot get wide band width with coils involved.
They have a higher Q of there own that becomes the limiting factor for band width no matter where on the radiator they are put.
Going on, making the radiation element a larger area or a better metal surface reduces the Q by reducing the loss resistance therefore the bandwidth gets wider but there is a practical physical limit to that as well.
To work an antenna over a very wide bandwidth, the impedence at the lowest frequency should be known then do an impedence conversion from that value to 50 ohms and be able to vary the tranformation to meet the objective over the total bandwidth.
As the frequency goes higher the radiating element becomes more and more inductive. The tuner needs to counter it with series capacitance to canel out the reactance.
The final impedance * can still be any value at the antenna terminals and does change with frequency.
The radials, ground plane, counterpoise or what you want to call them is the other half of a vertical antenna system.
How you use them in the system makes some differances in final impedance and radiating efficiency.
Always remember the antenna is an oscillating system between the halves.
RF current is involved so you have losses to consider.
*The impedance at any point in the system is still akin to R=E/I plus the effects of phase shift. This is called AC impedance
Again you have to consider all the operating parameters of the system and cannot ignor any of it or it leaves you with unknowns until you catch up with them.
Good luck.
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Someone asked, "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?"
Here are a few:
1. At this bandwidth, you have both an 11M and 10M antenna. Saves money for the manufacturer AND for those ops that operate in both bands.
2. With this bandwidth, it is likely that no re-tuning would be needed. It would work "right out of the box." That saves the recipient time/money. It saves the manufacturer service time trying to help a customer set up the antenna.
3. What you learn in making a 6 MHz antenna for 10M should be directly transferrable to, say an 80 M antenna where a 20% bandwidth allows ONE antenna to be used on low end CW and all the way up to the Nets near 4.0 MHz without needing a tuner. Super easy QSY.
4. If the 6 MHz 10M antenna is of reasonable size, then a "shrunk" version with reduced bandwidth might allow full operation on 10M in physical environments where a "standard" antenna won't fit.
Of course, conventional wisdom says the above is not possible.
Conventional wisdom is sometimes not completely accurate.
73
Bill
Here are a few:
1. At this bandwidth, you have both an 11M and 10M antenna. Saves money for the manufacturer AND for those ops that operate in both bands.
2. With this bandwidth, it is likely that no re-tuning would be needed. It would work "right out of the box." That saves the recipient time/money. It saves the manufacturer service time trying to help a customer set up the antenna.
3. What you learn in making a 6 MHz antenna for 10M should be directly transferrable to, say an 80 M antenna where a 20% bandwidth allows ONE antenna to be used on low end CW and all the way up to the Nets near 4.0 MHz without needing a tuner. Super easy QSY.
4. If the 6 MHz 10M antenna is of reasonable size, then a "shrunk" version with reduced bandwidth might allow full operation on 10M in physical environments where a "standard" antenna won't fit.
Of course, conventional wisdom says the above is not possible.
Conventional wisdom is sometimes not completely accurate.
73
Bill
Someone asked, "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?"
Here are a few:
1. At this bandwidth, you have both an 11M and 10M antenna. Saves money for the manufacturer AND for those ops that operate in both bands.
2. With this bandwidth, it is likely that no re-tuning would be needed. It would work "right out of the box." That saves the recipient time/money. It saves the manufacturer service time trying to help a customer set up the antenna.
3. What you learn in making a 6 MHz antenna for 10M should be directly transferrable to, say an 80 M antenna where a 20% bandwidth allows ONE antenna to be used on low end CW and all the way up to the Nets near 4.0 MHz without needing a tuner. Super easy QSY.
4. If the 6 MHz 10M antenna is of reasonable size, then a "shrunk" version with reduced bandwidth might allow full operation on 10M in physical environments where a "standard" antenna won't fit.
Of course, conventional wisdom says the above is not possible.
Conventional wisdom is sometimes not completely accurate.
73
Bill
OK, not necessarily bad answers. One more question.
Is such a benefit really worth the sacrifices that have to be made in order to achieve it? Of course only the individual who has the need can truly answer that one. Just remember everything is a tradeoff, including extreme bandwidth.
The DB
See attached photos...
Height above ground approx 20'.
Based on a LDG S9 telescoping 18' (actually 17'8") standard fiberglass antenna with included 1:1 balun. Telescoped to about 14.5 ft. Mounted on a Radio Shack tripod with a 5' Home Depot wooden shovel handle.
Added cost: 3 additional clamp-on ferrite beads, 2 sheet metal screws, 1 "U" mounting bracket. 1 adaptation of S9 (Details not yet available...
) but modification does not use any inductors, capacitors, gamma match, resistors or other passive or active devices. No adjustments. Additional cost: Approx 500 hours of NEC modeling and device prototyping.
EZNEC Modeled gain: approx 1 dBi. Takeoff angle at 5 ft above avg ground: 18 degrees.
Best DX so far UK to Brasil.
73
Bill
Attachments
1DBI gain modeled in free space.?????
Negative gain in the real world.
All the information you are asking/seeking is in any antenna handbook.
Look at the Cushcraft R8000 antenna. Single vertical radiating element in the center with one trap if I remember correctly, the rest is just basically parasitic rods mutually coupling off the radiating element. 6 meters to 40 meters.
What you are attempting is nothing new, it has been R&D and distributed.
Now if you can get a vertical with 1.5DBD gain that covers 6mhz in the upper HF region then you will have something. Collinear 5/8 wl vertical?
The IMAX2000 will work 21mhz to 29 mhz with acceptable VSWR on the ham/cb bands. Cost of this vertical dummy load shipped to the door is around $100 plus or minus a few $$.
DX? I have worked Japan from Florida with this IMAX2000 vertical on 15 meters. DX does not mean nothing when it comes to antennas.
Negative gain in the real world.
All the information you are asking/seeking is in any antenna handbook.
Look at the Cushcraft R8000 antenna. Single vertical radiating element in the center with one trap if I remember correctly, the rest is just basically parasitic rods mutually coupling off the radiating element. 6 meters to 40 meters.
What you are attempting is nothing new, it has been R&D and distributed.
Now if you can get a vertical with 1.5DBD gain that covers 6mhz in the upper HF region then you will have something. Collinear 5/8 wl vertical?
The IMAX2000 will work 21mhz to 29 mhz with acceptable VSWR on the ham/cb bands. Cost of this vertical dummy load shipped to the door is around $100 plus or minus a few $$.
DX? I have worked Japan from Florida with this IMAX2000 vertical on 15 meters. DX does not mean nothing when it comes to antennas.
I love it when someone uses DX contacts to try and justify, well, anything really. I'm happy you are getting great DX to some spot on the planet, but that doesn't really tell me much. If the conditions are right an ERP of 1 watt will talk around the world.
I also stand by this statement.
Remember there is always a tradeoff, anything that moves the antenna away from its most efficient setup has a consequence. Adjustments to increase bandwidth are no exception.
Yes it would cost more, but I think you would get more out of a single properly set up antenna with an antenna tuner.
The DB
Well not necessarily. The Hustler G6 144B / 2 meter Base antenna offered in the original example presents 6 mhz bandwidth AND 6 db gain. This heavy duty repeater grade antenna has been around for decades. Are you sneezing at 6 db gain? Here we have "extreme bandwidth" and excellent gain.
Nope. See EZNEC plots.
See the last diagram. It's for 1/4 wave monopole over std ground with 8 radials. Gain -0.31dBi at about 26 degrees.
See the first diagram for my design over std ground. No radials. Gain = 1.13 dBi at about 18 degrees. (lower is better)
I own quite a few. Would you like to quote from any of them? Otherwise, this is an incorrect statement.
I just searched for it on the MFJ site. No such part number. Are you suggesting that what appears to be a trap multiband antenna (with all the claptrap and adjustments that are implied) should be compared to a ultra wideband monoband antenna? Mine or anybodys?
Let's please stick to the same subject, OK?
By whom? When? Where. If you cannot answer these simple questions, then please stick to factual data.
First, it is important to understand, as I am sure you do, that gain all by itself is meaningless. Many antennas, especially in the CB realm, have incredible gain figures (A99 = 9.9 dB for example) and many designs send this "high gain" radiation UP at a dramatic angle. Great if you wnat to talk to planes, but useless for DX. In a real environment, Height Above Ground (HAG) plays a major role in gain.
See the middle plot showing a 5+ dBi gain with my antenna at 70 feet. Great gain at a very low angle (But a ridiculous height for most of us.) It's "only" around 3 dB at half the height.
No disagreement here. I entered my DX reference for two reasons. First as anecdotal information showing that it actually does radiate. Second, since I'm in NC, this shows that at least one other operator has replicated my findings."
All the best,
Bill
Attachments
So you are using the 2 Meter band to compare bandwidth to 10/11 Meters? OK, lets do some simple math...
Middle frequency of the 2 meter HAM band: 146Mhz
Bandwidth: 6Mhz
To calculate the bandwidth % of the frequency in question you take 100%, multiply it by the bandwidth, then you divide the frequency. You get about 4%.
Now you take the middle frequency of the 10 meter ham band (low frequency plus high frequency, then divide that sum by 2) which is 28.85, and multiply that by the 4% bandwidth mentioned above and get 1.154Mhz. The 10 Meter ham band is 1.7Mhz wide. Hmm problem...
When scaled, the example antenna you are referencing won't even cover the full 10 Meter ham band. I have no quarrel with your statement that it is a great antenna for 2 Meter radio, but if bandwidth is what you want scaling it to HF kills that bandwidth.
For comparrison purposes, if you had 6Mhz bandwidth in 10 meters that would scale to almost 30Mhz in the 2 Meters band.
Long story short, the referenced antenna that is likely a very good 2 Meter antenna. However after scaling it to HF we find it isn't the miracle in bandwidth you seem to think it is, not even close.
Also, find out what that 6db is in relation to. Not including what it is in relation to doesn't tell me much. Unless I am told otherwise I like to assume that that it is being compared to a dummy load.
The DB
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So you are using the 2 Meter band to compare bandwidth to 10/11 Meters? OK, lets do some simple math...
You point has already been covered by discussion in this thread. No need to repeat yourself. I am not disputing this.
I have no quarrel with your statement that it is a great antenna for 2 Meter radio.
Well that's good. Because that's what it is.
Long story short, the referenced antenna that is likely a very good 2 Meter antenna. However after scaling it to HF we find it isn't the miracle in bandwidth you seem to think it is, not even close.
Never said it was. That is apples and oranges.
Also, find out what that 6db is in relation to. Not including what it is in relation to doesn't tell me much. Unless I am told otherwise I like to assume that that it is being compared to a dummy load.
No, YOU find out what that is referenced to if it bothers you. Your argument may be with the Hustler Company and not me.
The DB
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