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Mobile Best Mobile antenna coil position

Alexis Mercado

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May 17, 2016
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Just curious and you (OP) don’t have to answer but how much power are you going to be running?? It’s a key off and that usually means crazy big antennas, monster boxes and a zillion alternators.
I am going to run around 1 kw . I am going to use a motor maul with 4 batteries ( no space extra alternators ).
 

WECSOG

Sr. Member
Jan 1, 2020
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I wouldn't use a 102" whip for competition. I would go to the nearest plumbing/building supply store and get a 10 foot stick of hard copper pipe, at least 1/2" diameter. Then mount it and cut it to best resonance. They are readily available up to 1-1/4" diameter; a 10' stick of that is close to the same price as a 102" whip. And far more efficient, higher power handling, and broader bandwidth.
 

AudioShockwav

Extraterrestrial
Staff member
Apr 6, 2005
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Sierras Near Yosemite National Park
I wouldn't use a 102" whip for competition. I would go to the nearest plumbing/building supply store and get a 10 foot stick of hard copper pipe, at least 1/2" diameter. Then mount it and cut it to best resonance. They are readily available up to 1-1/4" diameter; a 10' stick of that is close to the same price as a 102" whip. And far more efficient, higher power handling, and broader bandwidth.
I like ^^^^^^ that idea.

73
Jeff
 

WECSOG

Sr. Member
Jan 1, 2020
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I like ^^^^^^ that idea.

73
Jeff
Great for 6 Meters, too. They also sell 5 foot sticks, which wouldn't even need trimming for 6. And the 10' stick is resonant on 12M without trimming. If you need to add length to one, just pick up some 6 gauge solid copper wire and a couple of hose clamps. There's no current at that end anyway.
 
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Alexis Mercado

Well-Known Member
May 17, 2016
268
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I wouldn't use a 102" whip for competition. I would go to the nearest plumbing/building supply store and get a 10 foot stick of hard copper pipe, at least 1/2" diameter. Then mount it and cut it to best resonance. They are readily available up to 1-1/4" diameter; a 10' stick of that is close to the same price as a 102" whip. And far more efficient, higher power handling, and broader bandwidth.
Thanks for your suggestion. I want a competition antenna as norrowbanded as posible. I’ve read somewhere that a a narrow banded antenna tends to be more efficient than a wide banded one. Pending for your comments if this info is true.
 

The DB

Sr. Member
Aug 14, 2011
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St. Louis, MO
I wouldn't use a 102" whip for competition. I would go to the nearest plumbing/building supply store and get a 10 foot stick of hard copper pipe, at least 1/2" diameter. Then mount it and cut it to best resonance. They are readily available up to 1-1/4" diameter; a 10' stick of that is close to the same price as a 102" whip. And far more efficient, higher power handling, and broader bandwidth.

The problem with both claiming it is "more efficient" while at the same time having a "broader bandwidth" is larger diameter antennas gain their additional bandwidth by sacrificing efficiency. In this case you simply can't have both at once. Its simply the nature of how said antennas work. In fact, most methods of achieving bandwidth sacrifice efficiency. When it comes to 1/4 wavelength antennas, I don't know of any exception.

Also, a 102" whip with a proper mount can handle a significant amount of power. The amount of power that a 102" whip by itself can handle is seriously staggering. Pretty much all mounts, including competition mounts (aka Breedlove's high power puck which is rated at 45 Kw of power), will fail before a 102" whip fails when it comes to power handling.

Can a wider antenna with a proper mount handle more power? Sure, but even when it comes to competition setups, very few people ever get to that point where they need such a thing, and to them money spent on such setups is no object so they can pretty much do what they want, aka the pic Audioshockwav posted above.

The strangest thing to me, though, is that this line of conversation came out of someone not wanting to drill a hole for a 102" whip mount at a competition and wanting to use a magnet mount instead... In that case, the mount will fail long before the 102" whip (and in fact most quality antennas that can't handle nearly as much power), so in that context pretty much anything along this line since said topic was mentioned is actually moot...


The DB
 

WECSOG

Sr. Member
Jan 1, 2020
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That's true of shortened antennas. If a short antenna has a high "Q", it has low DC resistance. DC resistance does increase the bandwidth; consider the bandwidth of a dummy load.
But a full length 1/4 wave antenna is not a shortened antenna and does not have a coil.
There are loaded whips that have wider bandwidth than other loaded whips. But even those don't have as much bandwidth as a 102" whip. Does that mean they are more efficient than a 102" whip? Think about it.
 
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The DB

Sr. Member
Aug 14, 2011
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That's true of shortened antennas.

The context of my post was clear, I was referring to 1/4 wavelength antennas, not shortened antennas.

But a full length 1/4 wave antenna is not a shortened antenna and does not have a coil.

When you take a full length 1/4 wavelength antenna of a given diameter, and compare it with a full length 1/4 wavelength of another diameter, the wider diameter full length 1/4 wavelength antenna will be less efficient. This is established fact, and has been for decades.

I'm literally looking at a chart in an ARRL Antenna Book right now that shows the relationship between a full length 1/4 wavelength antenna's diameter vs efficiency, and as the antenna gets wider it clearly gets less efficient. (Unfortunately I don't have a CD drive anymore so I can't easily grab said chart from said accompanied .pdf file, I will look around to see if I can find a copy somewhere that I can use). The change isn't so much that you would notice in the real world (perhaps short of contesting, maybe), but the text is clear.

I have also seen similar data in the past from many different sources, including engineering level texts. Antenna modeling also agrees with this. I have never once seen any source that shows a wider full length 1/4 wavelength antenna being more efficient than a narrower one.

Because of this I would love to get the source of your claim. I want to take a look at it.


The DB
 

WECSOG

Sr. Member
Jan 1, 2020
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The context of my post was clear, I was referring to 1/4 wavelength antennas, not shortened antennas.



When you take a full length 1/4 wavelength antenna of a given diameter, and compare it with a full length 1/4 wavelength of another diameter, the wider diameter full length 1/4 wavelength antenna will be less efficient. This is established fact, and has been for decades.

I'm literally looking at a chart in an ARRL Antenna Book right now that shows the relationship between a full length 1/4 wavelength antenna's diameter vs efficiency, and as the antenna gets wider it clearly gets less efficient. (Unfortunately I don't have a CD drive anymore so I can't easily grab said chart from said accompanied .pdf file, I will look around to see if I can find a copy somewhere that I can use). The change isn't so much that you would notice in the real world (perhaps short of contesting, maybe), but the text is clear.

I have also seen similar data in the past from many different sources, including engineering level texts. Antenna modeling also agrees with this. I have never once seen any source that shows a wider full length 1/4 wavelength antenna being more efficient than a narrower one.

Because of this I would love to get the source of your claim. I want to take a look at it.


The DB
Without going and digging into my ARRL and RSGB radio handbooks and other books by Doug Demaw and others, I'm going on the concept that DC resistance is loss, and more DC resistance equals more loss. Stainless steel has greater DC resistance than copper, and because of skin effect a large diameter tube conducts AC (which radio signals are) better than the same amount of solid copper.
However, I will look in my ARRL Antenna Book for the chart you mention.
 

The DB

Sr. Member
Aug 14, 2011
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St. Louis, MO
I see your logic now. Its a different way of looking at it than I have ever seen anyone use before...

When working with DC, what you are saying makes perfect sense. Further, to some degree, some of that actually translates to what is happening on the antenna itself, even though the signal being transmitted/received is AC instead.

When it comes to metals used in antennas themselves. Every now and then someone brings up the materials used in antennas and tries to make a big deal about one of the other, typically copper, saying something like 'copper will always be the best'. When looking at the numbers, they always seem to disregard some of all of the leading 0's. In the real world, the difference in losses between these materials on an antenna comes down to essentially none to the point of insignificance, and even less. To put another way, so small that you would need specialized equipment just to measure it.

The thing is, the diameter of an antenna's element also has an effect on an antenna's efficiency and bandwidth. This has nothing to do with the resistance you are talking about, and is directly related to how the AC signal interacts with the diameter of the element. Even using the same material, just changing the diameter of the antenna is enough to have an effect on the antenna's feed point impedance, its resonant length, its efficiency, and the R and X curves (and by extension the SWR curve). Ever see antenna instructions that says to start with a length given by a formula and cut to resonance? This is one of the reasons that something like that is necessary.


The DB
 

WECSOG

Sr. Member
Jan 1, 2020
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Interesting that you've never seen anyone else use that logic.
Ever notice how in hardline, the feedline used in commercial installations, the center conductor is made of either copper tubing or (in less expensive hardline) aluminum tubing with a copper plating? Ever notice how antenna wire is copper plated steel, instead of just galvanized like guy wire?
Ever notice how professional repeater antennas are made of aluminum tubing, instead of steel rod?
I'm not interested in continuing this. I'm pretty sure the OP has been answered.
 

The DB

Sr. Member
Aug 14, 2011
1,997
1,490
193
St. Louis, MO
Interesting that you've never seen anyone else use that logic.

The logic I've never seen anyone use is the logic based on DC resistance.

You seemed to think that all of my argument was based on materials, yet you actually missed the important part. Strangely my statements on materials was more of a side story yet you seem to think it is the end all and be all of what I was saying, and nothing after that matters. Perhaps you should read my post to the end...

As I stated above, the main point actually, and something you apparently missed. The diameter of the antenna itself matters. This, alone, regardless of the material it is made of, has an effect, even if you use a theoretical perfect conductor in an antenna model. This effect is well known and being completely ignored by you.

I also see why you can't present the source I asked for, it clearly doesn't exist. All you have is a list of circumstantial evidence, noting more.

I love how you look down on someone while clearly not understanding the main point of their argument...

When it comes to materials, I don't think you are entirely wrong, it is more a question of scale than anything, and you are overestimating said effects, which is actually a common thing. I have antenna models experimenting with with different materials used for the antenna, and there is a difference, and it is very small, to the point that even going from stainless steel to a theoretical perfect conductor, you will never notice it. Also, I have worked with literally hundreds of antennas, both CB and ham radio, including the repeater antennas you mentioned. The views where some of our local ones are installed are amazing... If material mattered anywhere near as much as you seem to think, they would all be copper (or copper clad something else) because nothing else would matter, yet somehow they are not... Strange that.

We do agree on one thing, the ops question has been answered long ago. I would say long before any of this part of the discussion came up.


The DB
 

WECSOG

Sr. Member
Jan 1, 2020
757
1,346
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No, I'm not focusing on materials alone; I'm focusing on resistive loss which is affected by both material and diameter. I was attempting to point out that if a thinner conductor were better, commercial hardline would use thin conductors and commercial antennas would use thin elements, yet they don't.
I'm sorry though; I assumed you understood that I was using the term DC resistance to differentiate from radiation resistance. Apparently not, so let's just say resistive loss. It does indeed affect both DC and AC. It resists current, and converts power to heat.

I don't see you presenting evidence. I'm not going to try to prove to you that resistive loss exists; if you think it doesn't or is irrelevant, good luck with that.
The ARRL Handbook says that if the diameter of the antenna conductor is increased, the capacitance per unit length increases and the inductance decreases. Since the radiation resistance is affected relatively little,the decreased L/C ratio causes the Q to decrease so that the resonance curve becomes less sharp with change in frequency. Both my 1959 Handbook (page 358) and my 1997 Handbook (ch.20, page 2) say exactly the same thing. Neither say that efficiency is decreased.
Antenna-theary.com says: "The Q of an antenna is a measure of the bandwidth of an antenna relative to the center frequency of the bandwidth." It also doesn't say that the wider bandwidth results in less efficiency.
 

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