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Lou's Questions and Answers

Question 1
Can I use 450 Ohm ladder line on my multiband antenna.
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Question 2
Can I use your Balanced Self Matching Feed Line System on my multiband antenna.
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Question 3
Can I use A Common-Mode Choke Balun made from Coax on my multiband or mono band antenna.
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Question 4
Can I you use your dual polarity 80 meter or 160 meter antenna designed for multiband use.
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Question 5
Why do you not recommend vertical antennas above 80 meters.
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Question 6
I have a one wavelength loop antenna that is perpendicular to the ground and I want to feed it for horizontal polarity should I feed it at the top of the loop or at the bottom.
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Question 7
What is the optimum height above ground for a one wavelength Loop that is perpendicular to the ground.
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Question 8
Can you recommend to me a simple antenna system that will give me a killer signal on 40 meters. .
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Question 9
Can you recommend a high performance antenna for my R.V..
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Question 10
Can you tell me the secret to having a consistently loud signal on 40 meters. .
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Answer 1 Yes you can if you meet the minimum requirements. For a high-performance multiband antenna the antenna must be one half wavelength long or more on its lowest band of operation, there is a measurable amount of reduced performance when the antenna is only one quarter wavelength long.

The other mandatory requirement is that the 450 Ohm ladder line be one-quarter wavelength long on its lowest band of operation. When this requirement is not met you will have very high amounts of reactance on the feedline and this typically will cause radiation from the feedline.

When you cannot meet this minimum requirement the best alternative type of feedline to use is two pieces of RG-8X coax you solder the braided shields of each coax together at the antenna end and at the radio end, then connect the braided shields to ground at the radio end.

This will make a balance shielded feedline that is 100 ohms. This balance shielded feedline should eliminate or at least greatly reduce your RFI- TV I problems The center conductors of the coaxs connect to the input of the antenna, at the radio end connect to the balanced input of your antenna tuner. If your antenna tuner does not have balanced input here is what you do. Connect your balanced feedline to the input of a 1 to 1 current balun and the balun goes to the unbalanced antenna tuner input. This is a superior multiband feedline system compared to a single piece of coax this will give you the ability to easily tune from 160 m through 10 m with no feedline radiation. The two cables are side-by-side with little or no gap between them . To keep the cables manageable you take electrical tape and tape them together approximately every 12 to 18 inches. I highly recommend this type of feedline.


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Answer 2 No my balanced self matching feedline system will only work properly when used on single band operation.

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Answer 3 I do not recommend using a Common-Mode Choke Balun made from Coax. The reason I do not recommend it, is because the coax has a measurable amount of capacitance per foot and the inductance per foot you get from coiling it usually is not enough to give adequate isolation, specially at 160m's.

What I recommend is to buy a 1 to 1 current balun from Radio Works Model-B1-2K (B1-2K Plus) 10-80 meters $24.95 it's Power Rating @ 3.5 MHz is 1.5 KW of course you will not be able to use this Balun on 160 meters, for that band I recommend the B1-5k (B1-5k Plus) $35.95 it's Power Rating @ 3.5 MHz is 5 KW either one of these Baluns is an excellent investment. In my opinion this is one of the finest manufacturers of current Baluns on the market today. You will see at least 35 db isolation compared to 3 to 10db from the coax balun.

A Common-Mode Choke Balun made from Coax, has about 10db of feedline isolation that is 100 watts into the antenna and 10 watts radiating off of the coax. A quality commercial made 1to1 current Balun has about 35db of feedline isolation that is 100 watts into the antenna and 0.028 watts radiating off of the coax that is a whopping differs. Not all commercial made 1to1 current Baluns will work on 160 meters so make sure that they clearly state that it will.

On 160 meters a Common-Mode Choke Balun made from Coax has only about 3db of feedline isolation that is 100 watts into the antenna and 50 watts radiating off of the coax. The reason why this occurs is because when you wind the coax into a coil you get very little inductance because you have such a small fraction of a wavelength of coax making up that coil it takes a lot of inductance to get good isolation.


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Answer 4 I would not recommend doing this for multiband operation you will be better off using traditional designs. One of the main reasons is because of the dual polarity. For example if you were to use this antenna on 40 meters it would become a voltage fed antenna, and this would cause the current to be maximum at the bottom of the vertical element and not at the top. Not to mention the fact that there would be a large amount of reactance on the feedline. This would of course make it more difficult to transfer the power to the antenna.

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Answer 5 You know a lot of people are not aware of this, but a half wavelength horizontally polarized antenna. At one half wavelength above the ground, has a minimum of 7 db gain over a monopoll vertical at 30 degrees take off angle even at 15 degrees take off angle it still has 5db more gain. Interestingly enough if it was even a quarter of a wavelength above the ground, It would still have 4db gain over the vertical at 30 degrees take off angle and at 15 degrees take off angle it still has 1db more gain. So to put things into perspective, if you had a horizontal dipole for 40 m at 33 feet in the air which is a quarter of a wavelength you can still outperform the very best verticals that anyone can build. Now on 20m you would be one-half wavelength and you can easily outperform a pair of verticals. On 17 meters backup to 10 m it only gets better.

The reason why this happens is due to the fact that horizontally polarized antennas are not all that dependent on the ground beneath them for propagation unlike vertical antennas. That one fact alone is the reason why I do not recommend vertical antennas above 80 meters.

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Answer 6 It makes no difference rather it is a Delta, Square, rectangle, or Round Loop they can all be used as either vertically polarized, horizontally polarized or even duel polarity antennas, provided that the Loop is perpendicular to the ground. A one wavelength Loop antenna has two high current points one at the feedpoint and the second one half way around the Loop, so 50 watts out of 100 watts will be at the feedpoint and the other 50 watts will be halfway around the loop.

For horizontal polarity

(For a Delta Loop you feed it at the top apex or at the bottom center)

(For a Square Loop you feed it halfway between the top right corner and top left corner or halfway between the bottom right corner and the bottom left corner)

(For a Diamond shaped Loop) "I call it A Square on edge all four corners equal 90 degrees". Feed it at the top corner or the bottom corner)

(For a Rectangle Loop you feed it halfway between the top right corner and top left corner or halfway between the bottom right corner and the bottom left corner)

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Answer 7 To obtain optimum performance from a one wavelength Loop that is perpendicular to the ground, the height above ground of the bottom of the Loop should be 1/2 wavelength above the ground. But when the bottom is very close to the ground in terms of wavelength, you will have half of your power radiating at extremely high angles. When you have a one wavelength Loop antenna that is perpendicular to the ground and horizontally polarized, with the bottom of the Loop one-half wavelength high, you will have even radiation from 7 1/2 degrees take off angle all the way up to 55 degrees take off angle + or - 2db. So you can work short medium and long propagation paths simultaneously. Unfortunately for most people it is not possible on 40 meters due to the extreme height of the top of the antenna, approximately 100 feet.

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Answer 8 Yes if you put up two horizontal dipoles end to end with 1/2 wavelength spacing between them, as parallel to the ground as possible and oriented in your two most favored directions, the optimum height above ground is one-half wavelength 66Ft. minimum height 35Ft. I guarantee you will have a killer signal on 40 m.

If you take two pieces of RG-8X 50 ohm coax 82 feet 3 inches long which is three-quarters of a wavelength on 40 m and connect one end of each cable to the feed point of each dipole and then connect both of the other ends together and connect that to a 75 ohm coax cable going back to the radio you'll have less than a 1.2 to 1 S.W.R. match at the radio. Each dipole is approximately 73 ohms when you put them in parallel you get 36 1/2 ohms.

So if you multiply 36 1/2 ohms two dipoles in parallel x 75 ohm feedline to radio =2737.5 The square root will be 52.3 ohms. So 50 ohm coax cable is a near perfect match for the phasing lines at 1.2 to 1 S.W.R. you are losing just 2 watts out of 100.



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Answer 9 I would be lying to you if I said I invented this antenna. But I have built quite a few of them for ham radio friends of mine. It is a very simple antenna to install. All you have to do is to take, some PVC flanges, that will except a 3/4" PVC pipe about 6" long. Attach the flange's to the top perimeter of the roof with liquid nails space them about every three to four feet apart. Then you will use the PVC pipe like a tall insulator. You will drill holes near the top of the pipe, and lace the wire through the hole's. When you have finished you will have a loop antenna on the roof of your R.V.

The length of this loop is not important. So long as the loop is at least 1/2 wavelength long , the antenna will work very efficiently. Even if it is only a quarter of a wavelength it will still work good. The best way to feed the antenna is to use two pieces of RG-8X coax cable. This will make a balance shielded feedline that is 100 ohms.

Connect the braided shields of the coax's to gather both at the antenna and at the radio, then connect the braided shields to ground at the radio end. You use the center conductors of each coax for the transmission line. At the radio end connect the two Center conductors to the balance input of your antenna tuner. If your antenna tuner does not have balanced input here is what you do. Connect your balanced feedline to the input of a 1 to 1 current balun and the balun goes to the unbalanced antenna tuner input. Depending on the size of your R.V. you could have from 52 feet to as much as 90 feet of wire in the air.

There are a lot of ham radio operators that do not have antennas at their homes as good as this.

Comparing this loop to a screwdriver antenna, is like comparing a Ugo to a Mercedes. The efficiency of an antenna, is directly proportional to the physical length of the antenna. An antenna that is physically one half wavelength long, operates at 98 percent efficiency. A screwdriver antenna that is 13 feet long is a quarter of a wavelength on 17 meters, and operates at 50 percent efficiency. The same antenna is less than 1/8 wavelength long at 40 m and is operating at less than 25 percent efficiency. You could easily operate at more than 80 percent efficiency on 40m if the loop is 52 feet long, and 95 percent efficiency on 20m an up.


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Answer 10 For 40 meters the secret is getting all of your current as high above ground as possible and of course you want the antenna to be resonant this will guarantee the highest efficiency, there is a measurable difference in performance between a horizontal dipole at 50 feet and a inverted V at 50 feet, the same is true for a loop the reason is even though the high current point of the inverted V is at 50 feet there is still measurable amounts of current half way down each leg, and for the loop you have a second high current point at the bottom of the antenna, in fact it makes absolutely no difference rather you feed the loop at the top or feed the loop at the bottom .

To obtain optimum performance from a one wavelength Loop that is perpendicular to the ground, the height above ground of the bottom of the Loop should be 1/2 wavelength above the ground. When the bottom is very close to the ground in terms of wavelength, you will have half of your power radiating at extremely high angles.

When you have a one wavelength Loop antenna that is perpendicular to the ground and horizontally polarized, with the bottom of the Loop one-half wavelength high, you will have even radiation from 7 1/2 degrees take off angle all the way up to 55 degrees take off angle + or - 2db. So you can work short medium and long propagation paths simultaneously. Unfortunately for most people it is not possible on 40 meters due to the extreme height of the top of the antenna, approximately 100 feet.


A true resonant 40 meter horizontal dipole (flat top) at 50 feet will definitely outperform a 40 meter Loop with a top high of 60 feet.

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