Radials vs Counterpoise... what am I using?

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AgentCOPP1

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I have a decent understanding of what the two different things are. Radials hug the ground to help provide a low loss return path for the RF that is soaking into the ground. A counterpoise is used to create an artificial ground when an antenna is elevated. However, I'm trying to make my antenna system as efficient as possible with what I've got and I'm really getting confused with what people tell me. If you look on my QRZ page, you'll see the antenna I've got. To my knowledge, I'm using a counterpoise system because my antenna is elevated and the counterpoise wires aren't exactly close enough to the ground to create good capacitive coupling. After reading something on the internet, I was informed that a large portion of the antenna's emitted RF energy is soaked into the ground with a radius of half a wavelength, so they tell me to make radials that are half wavelength. However, I've got other people that tell me that counterpoises only need to be quarter wavelength, but I don't think they were counting on my antenna being only 5 feet off the ground.

In addition, people say that you ideally need 120 radials, but only 4 counterpoises. So basically since my antenna is so close to the ground, I'm having trouble determining whether or not my counterpoise system needs to be half a wavelength long and with 120 radials.

And another question, if you are using a radial system, do you only need 120 radials of half wavelength long on the lowest band that the antenna transmits at (you only need them tuned for the lowest band)?
 

zz0468

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I've looked at your QRZ page, and seen your antenna.

First off, your radials don't look very long in the photo. Do they angle toward the ground for the first 10 feet, then go further on the surface?

I think a main source of your troubles is that with your antenna is so close to the ground, even though your counterpoise is composed of four 1/4 wave radials per band, you're still suffering from ground resistance. At 5 feet off the ground, you would need to be building your counterpoise as if it was a buried radial system. Much of the RF currents will be flowing along the earth itself

As to whether radials should be a half or a quarter wave, the source of ambiguity you're getting in your answers may be due to the difference between being able to achieve resonance, vs. having an efficient antenna system that actually works.

Ground mounted Quarter wave vertical antennas are VERY dependent on ground conductivity. With poor ground conductivity, a good chunk of transmitter power is lost in the ground itself as heat. A few quarter wave radials will allow you to achieve resonance, but help little when it comes to actual radiation efficiency. Extending lots of radials out a half wave on the lowest frequency lowers the effective resistance of the ground itself, making the antenna a lot more efficient.

The reason a quarter wave ground plane can be so effective at VHF is because it's usually several wavelengths above the earth, which is high enough that ground conductivity isn't as much of a factor in determining antenna efficiency.

If you're convinced that your antenna system isn't up to par, you may want to consider using a balanced antenna instead, such as a dipole. Since it's not dependent upon low ground resistance to determine the effectiveness of it's counterpoise, they tend to be easier to make work.
 

AgentCOPP1

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The radials you're looking at are probably the 15 and 17 meters. They are quarter wavelength like the rest but they're still fairly short. The 20 and 40 meter radials are the longest but you can't really see the full extent of where they extend.

I'm not really interested in a dipole at the moment because I have an antenna that works, and I've already invested so much time into it and I don't really want to just give up on it. I mean I've made contacts all over the world with it but I feel as if it's still suffering from poor efficiency because it has to be a really good propagation day for me to get any DX contacts.

So what you'd suggest is that I make the radials extend out half wavelength along the ground instead of angled down? Does the initial antenna height matter at all, because the radials would have to travel a certain distance upwards to get to the base of the antenna so I'm wondering if I just need to measure the radials half wavelength plus the height of the antenna base.
 
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zz0468

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...I mean I've made contacts all over the world with it but I feel as if it's still suffering from poor efficiency because it has to be a really good propagation day for me to get any DX contacts.
I'm not sure I see a problem here, then. That's the way it is with just about ANY antenna. The guys who can work DX when conditions are lousy are running full legal power, and huge antennas 100' or more in the air.

If conditions are lousy, and they frequently are, there's not much you can do at your antenna to change it.

So what you'd suggest is that I make the radials extend out half wavelength along the ground instead of angled down?
What I'm suggesting is that, if your radials are so low to the ground, you need to treat them as if they were buried in the ground, as opposed to a 4 radial (per band) ground plane that's several wavelengths above ground.

In other words, in terms of antenna efficiency, it doesn't matter if your radials are a few feet above ground, or 12" below ground - if you don't have enough of them, poor ground conductivity is going to absorb much of your transmitter power. Raise those four radials up a few wavelengths, and the ground conductivity is no longer as important a factor, which is why VHF ground plane antennas actually work so well.

Does the initial antenna height matter at all, because the radials would have to travel a certain distance upwards to get to the base of the antenna so I'm wondering if I just need to measure the radials half wavelength plus the height of the antenna base.
I don't think it would matter if the antenna base is at 5 feet, or 5 inches, if that's what you mean.

You really need to locate an article that was published in either QST or QEX magazine within the last several years. The author did quite a bit of experimentation on radial systems for vertical antennas and came to some interesting conclusions. If I recall correctly, one of the conclusions was that it was less important that the the radials be a half wave or even a quarter wave, in terms of antenna efficiency. What was important was that there be LOTS of radials, as long as you could make them*. The magic number (again, going on my somewhat sketchy memory here) was 30 radials. Once you reached 30 radials, additional radials helped, but not enough to be worth the effort and expense, when dealing with an amateur project.

*Residential lots are not round, and they usually have houses plopped down somewhere in the middle of them. If your antenna is mounted in some place in the yard where you can run 20 radials for 50 feet in some directions, but only 25 feet for the other 10, put in what you can, and don't sweat it - it is what it is. The key being, put in LOTS of radials, and the point of diminishing returns starts at about 30 radials.

Find and read the article yourself, and correct the numbers as necessary.
 

AgentCOPP1

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I'm not sure I see a problem here, then. That's the way it is with just about ANY antenna. The guys who can work DX when conditions are lousy are running full legal power, and huge antennas 100' or more in the air.
Well, there is a problem. My neighbor ham has a vertical as well and he can get DX contacts on just about any day he pleases with the same amount of power as me, save for the really bad propagation days . So I know my antenna isn't performing optimally because I can compare it to another that's very similar to mine.

I read that article I think you were talking about. Pretty interesting and the graphs it gave were very helpful to see how much of a difference different variables make. I think it's helped me answer a lot of my questions.

As you can see from my picture, you're right I can't really put down 20 meter radials towards the left because there's a lake there (which also isn't ideal but it's what I've got). I'll be putting some more down like you've said and see how it works. Also, if there are more radials on one side of the antenna, would it bias the radiation lobe in any particular direction? I'm sure there's a QST article on that somewhere haha.

I'll be experimenting a little bit and update the thread with what I find out. I'll probably get most of the work done over the Thanksgiving weekend.
 

N5TWB

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You really need to locate an article that was published in either QST or QEX magazine within the last several years. The author did quite a bit of experimentation on radial systems for vertical antennas and came to some interesting conclusions. If I recall correctly, one of the conclusions was that it was less important that the the radials be a half wave or even a quarter wave, in terms of antenna efficiency. What was important was that there be LOTS of radials, as long as you could make them*. The magic number (again, going on my somewhat sketchy memory here) was 30 radials. Once you reached 30 radials, additional radials helped, but not enough to be worth the effort and expense, when dealing with an amateur project.

*Residential lots are not round, and they usually have houses plopped down somewhere in the middle of them. If your antenna is mounted in some place in the yard where you can run 20 radials for 50 feet in some directions, but only 25 feet for the other 10, put in what you can, and don't sweat it - it is what it is. The key being, put in LOTS of radials, and the point of diminishing returns starts at about 30 radials.

Find and read the article yourself, and correct the numbers as necessary.
If you're not an ARRL member with the ability to search those publications, go to the DX Engineering website and read the install manual for the Hustler 4/5/6-BTV vertical antenna system. It's free and tells the same type of information on the ground radial system recommended for that installation.
 

zz0468

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Well, there is a problem. My neighbor ham has a vertical as well and he can get DX contacts on just about any day he pleases with the same amount of power as me...
Ok, so there 's something to directly compare to. Fair enough.


I read that article I think you were talking about. Pretty interesting and the graphs it gave were very helpful to see how much of a difference different variables make. I think it's helped me answer a lot of my questions.

...if there are more radials on one side of the antenna, would it bias the radiation lobe in any particular direction?
Yes, having non-symmetrical radials will cause the main lobe of the antenna to be something other than omni-directional. All you can do is the best you can do, and you get what you get. Search the web for every resource on vertical antennas and their counterpoise/ground systems that you can find. There's a TON of excellent material out there. The build the best you can within your available resources, and don't worry about what you can't afford, or don't have room for.

I'll be experimenting a little bit and update the thread with what I find out. I'll probably get most of the work done over the Thanksgiving weekend.
Have fun! :)
 

ab3a

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Landon, I noticed that your coax looked a bit small, perhaps RG-58-ish. How long is it?

If you're on 15 or 17 meters, and your coax is over 100 feet long, you might want to try upgrading it, especially if the SWR at your antenna is greater than 3:1. Also, make sure you have a very clean, bright, low loss connection to the coax. The feed point is a current node. Even small amounts of resistance matters there.
 

AgentCOPP1

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zz0468, you are a genius. I put a bunch of 1/2 wave 20 meter radials down and it's working wonders. I don't have it done yet because I ran out of wire, but with what I've got it's working great. I decided not to go with 40 meter radials because where I am, it's just not feasible. Consequently, the SWR bandwidth on 40 is disappointingly small (and if you have any suggestions for that I'd appreciate it), but it's still doing good. SWR bandwidth on 20 is superb however it hovers around 1.5-1.7. Before it was around 1.2 but hey it's still good.

AB3A, the coax is LMR-400. It's 250 feet long (wow, right?) but the attenuation for that length is around 1.5dB so it's not unusable. Thanks for reminding me about the feed point too. I'll have to take a wire brush or something to it to clean it up and then use some coax seal.
 

zz0468

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zz0468, you are a genius. I put a bunch of 1/2 wave 20 meter radials down and it's working wonders. I don't have it done yet because I ran out of wire, but with what I've got it's working great.
Glad it's working better. A couple of things below to be concerned about, though...

I decided not to go with 40 meter radials because where I am, it's just not feasible. Consequently, the SWR bandwidth on 40 is disappointingly small (and if you have any suggestions for that I'd appreciate it)
Do you have any 40 meter radials at all? If not, it's more likely that you have capacitive coupling to ground. My suggestion would be to put as many radials as you can for the lowest frequency you intend to operate on. If it's 20 meters, so be it. You could probably use a tuner and make the transmitter happier over a wider frequency range, but antenna efficiency will be low.

...but it's still doing good. SWR bandwidth on 20 is superb however it hovers around 1.5-1.7. Before it was around 1.2 but hey it's still good.

AB3A, the coax is LMR-400. It's 250 feet long (wow, right?) but the attenuation for that length is around 1.5dB so it's not unusable.
This is the part that raises my eyebrows. That's a pretty long run of coax. Are you measuring VSWR at the antenna end, or the radio end? If at the radio end, your VSWR, and therefor your losses, could be MUCH higher than what you think it is. Put the SWR meter at the antenna, and have someone key the transmitter for you, and then measure. If your VSWR is 1.7:1 at the end of 250 feet of coax, you could have serious problems at the other end.
 

prcguy

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Elevated ground radials are usually 1/4 wavelength long to provide a low impedance at the feedpoint where 1/2 wave radials or random lengths may not provide the same low impedance. Another thing to consider is a lot of short radials can be more effective than a few long ones because at some point the distance between the ends of the radials becomes as or more important than the length.

Obviously a solid sheet metal ground plane extending 1/4 wavelength out from the feedpoint would be ideal and you can mimic that with wires if you keep the spacing a minimum of a certain fraction of a wavelength between the ends and I forget the recommended spacing at the moment but 120 1/4 wavelength radials easily meets that. AM broadcast antennas are usually required to have 120 1/4 wavelength radials to meet certain performance specifications under all conditions and its probably overkill for amateur use.

If your ground radials are on the ground or too close, they are detuned, no longer resonant and at that point its better to stick to the formula of enough radials of any length to meet the minimum spacing between the ends of the radials to approximate a solid sheet of metal. Here is a good article on the optimum number of radials based on soil type, available space and wire: http://www.ncjweb.com/k3lcmaxgainradials.pdf

Or consider using wide, long lengths of chicken wire or hardware cloth to reduce ground loss and here is an excellent article on that: http://www.sherweng.com/documents/GroundScreen-sm.pdf

The last vertical I installed was a DX Engineering 43ft with supplied 4:1 balun at the feedpoint and fed with 125ft of LMR400 but the mfr recommends 150ft of RG-213 to provide some loss so most radios with internal tuners will work on the lower bands where the match is not so good.

I got to experiment with radials and due to the surrounding trees and foliage and a creek I could only run the wires about 30ft from the antenna. I started with four radials 30ft long and tested the internal antenna tuner in the radio and made contacts on most bands. The internal tuner worked fine on all bands 160 through 10m.

Then I added four more radials and could tell the antenna was working a little better as verified by contacts and a very slight increase in receive noise. Then I went from 8 to 16 radials and could tell a very slight improvement again. Then I went to 30 or 33, I forget but it used up my 1000ft spool of 16ga wire and could not perceive any further improvement. This amount and length of radials agrees with the first article link I provided, at least for 40m.

However, the built in antenna tuner would no longer tune 160m reliably due to ground losses being reduced and the LMR400 coax not providing the loss to cover up the difficult match for the radios tuner.

Anyway, the 43ft vertical with 30 something radials about 30ft long each works surprisingly well and outperforms a 94ft flat top dipole (ZS6BKW) at about 25-30ft on 40 through 20m DX, which is quite an accomplishment. On 80m the dipole is better than the 43ft vertical, probably due to the mismatch and losses in the 4:1 balun and feed but on 160m the vertical hears stations all over the place that do not exist on the dipole, which is way too short for 160.

In the past most dipoles outperformed any vertical I played with for DX except for a Butternut HV6 mounted on a 100ft X 100ft solid copper sheet metal roof which is not something you run across very often. It worked really well on all bands. That same antenna was later moved to a different location on the same property with a chain link fence as a counterpoise and it was like a dummy load in comparison.
prcguy


zz0468, you are a genius. I put a bunch of 1/2 wave 20 meter radials down and it's working wonders. I don't have it done yet because I ran out of wire, but with what I've got it's working great. I decided not to go with 40 meter radials because where I am, it's just not feasible. Consequently, the SWR bandwidth on 40 is disappointingly small (and if you have any suggestions for that I'd appreciate it), but it's still doing good. SWR bandwidth on 20 is superb however it hovers around 1.5-1.7. Before it was around 1.2 but hey it's still good.

AB3A, the coax is LMR-400. It's 250 feet long (wow, right?) but the attenuation for that length is around 1.5dB so it's not unusable. Thanks for reminding me about the feed point too. I'll have to take a wire brush or something to it to clean it up and then use some coax seal.
 

AgentCOPP1

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Do you have any 40 meter radials at all? If not, it's more likely that you have capacitive coupling to ground. My suggestion would be to put as many radials as you can for the lowest frequency you intend to operate on. If it's 20 meters, so be it. You could probably use a tuner and make the transmitter happier over a wider frequency range, but antenna efficiency will be low.
Based on calculations for 40 and 20 meters, half wave 20 meter radials are actually very close in length for quarter wave 40 meter radials, only off by about 20cm. It may be enough to skew results a little bit but it surely is better than no radials at all. However, as much as I'd like to put down 40 meter radials, the space of where my antenna is just doesn't allow it. The radials would have to extend very far out into the lawn, but I suppose I could try some lawn staples and see how concealed I can make them. That would have to wait until spring.
This is the part that raises my eyebrows. That's a pretty long run of coax. Are you measuring VSWR at the antenna end, or the radio end? If at the radio end, your VSWR, and therefor your losses, could be MUCH higher than what you think it is. Put the SWR meter at the antenna, and have someone key the transmitter for you, and then measure. If your VSWR is 1.7:1 at the end of 250 feet of coax, you could have serious problems at the other end.
No I've been measuring it at the antenna end because it's pretty obvious that the SWR at the radio end doesn't mean that much. I don't have all of my radials in yet so I'm not exactly sure if the SWR will go down once I finish it, but hopefully it'll go down a tad bit more. I've heard that 1.4 is optimal because that means the antenna feedpoint impedance is 36 ohm, right where it should be.
 

acyddrop

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There are so many things that can go wrong with this setup. First of all, counterpoise is incredibly inefficient to begin with, so you lose power right away even in an idea setup. Second, you're using a trap antenna which incurres losses as well. So right away you lose power before you even begin. Nextly if you're using RG-58 (I can't tell and I didn't bother reading all the posts, oh well) you will be losing some (probably 1 to 1.5db) you can increase your performance there by going to RG-213 or LMR-400 (or 400MAX from DXE). That would decrease your losses to sub 1db over a short run (~100ft or so). Also if you've not tuned your traps it's possible that they might be inefficient for the frequencies you use them on. That would hold true for the Hustler BTV series or any other tuned/tunable trap multiband antenna. Lastly you can increase your efficiency by using a remote antenna tuner, but this would be less effective with a tuned trap antenna system like the one you have (at least it looks tuned)/

Your radial/counterpoise setup looks very bad and I know other have said this and if that IS a Hustler BTV type antenna it's not meant to be operated in the manner you have it at present anyway. I don't know how your mate has his antenna, but I can also tell you those trees will suck up your signal like a sponge, especially during rain/snow but really all the time. But they will 100% effect your signal and your ability to transmit over great distances. This would apply to any antenna not just verticals, it's why people elevate antennas (trees, buildings, cars, any multipathing effects, etc).

20cm (7inches) is not going to make a huge difference one way or another, if it were an antenna you're band edges would change but that's about all, and more or less the same holds true for your radial field.

Hope some of this is useful..
 

AgentCOPP1

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There are so many things that can go wrong with this setup. First of all, counterpoise is incredibly inefficient to begin with, so you lose power right away even in an idea setup. Second, you're using a trap antenna which incurres losses as well. So right away you lose power before you even begin. Nextly if you're using RG-58 (I can't tell and I didn't bother reading all the posts, oh well) you will be losing some (probably 1 to 1.5db) you can increase your performance there by going to RG-213 or LMR-400 (or 400MAX from DXE). That would decrease your losses to sub 1db over a short run (~100ft or so). Also if you've not tuned your traps it's possible that they might be inefficient for the frequencies you use them on. That would hold true for the Hustler BTV series or any other tuned/tunable trap multiband antenna. Lastly you can increase your efficiency by using a remote antenna tuner, but this would be less effective with a tuned trap antenna system like the one you have (at least it looks tuned)/
Firstly, thank you very much for the input. I am quite aware of all the things you've stated. As you might know, sometimes with ham radio things aren't going to be the best they possibly could because circumstances aren't always ideal. I'm using LMR-400 but the length of it is long enough to lose 1.5dB, but there's really not much I can do about it. A remote tuner is an interesting idea though. I never really gave that any thought before so I might need to look into it especially since my coax is really long.

Your radial/counterpoise setup looks very bad and I know other have said this and if that IS a Hustler BTV type antenna it's not meant to be operated in the manner you have it at present anyway. I don't know how your mate has his antenna, but I can also tell you those trees will suck up your signal like a sponge, especially during rain/snow but really all the time. But they will 100% effect your signal and your ability to transmit over great distances. This would apply to any antenna not just verticals, it's why people elevate antennas (trees, buildings, cars, any multipathing effects, etc).

20cm (7inches) is not going to make a huge difference one way or another, if it were an antenna you're band edges would change but that's about all, and more or less the same holds true for your radial field.

Hope some of this is useful..
The picture you see is of an incomplete radial set up. I was actually in the process of constructing it when I took the picture but I suppose it leads to some confusion lol. When I'm completely done with it (still waiting for the last rounds of wire to come in the mail), I'll update the picture. It's a Cushcraft AV-4, and I honestly don't know how well-tuned the traps are. But I got it for free so I can't complain too much! How would I go about tuning the traps anyway?

I probably sound like a broken record but the placement of the antenna is really the only place I could put it (save for a few other spots but really there are trees everywhere on my property. Can't avoid them.). I'm just trying to make the set up as efficient as possible.
 

acyddrop

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Tuning traps is relatively easy, just open them up and tune them. I've also heard that the traps on the Cushcraft go bad at a high rate, if you're having troubles they might be "blown" (for lack of a better word) and need replacing/maintenance. I've not used a Cushcraft vertical so I don't know the exact procedures but I'm sure if you spend some time with Google you can find the answers and possibly gather enough information to determin if a faulty trap/mistuned trap is to blame for any of your problems.

The remote tuner will not compensate for your 1.5db loss, but it will allow you to tune out issues caused by the feedline, in general, and more specifically for non-resonant verticals a remote tuner is the ideal way to go. You will probably gain some from using one, but I'm not sure if the gains in this case would justify the $300+ on a remote tuner. You would probably want to address the trap issue first, just to either confirm or eliminate it, and continue with your efforts on radials before trying the remote tuner. But I think you would find they do improve things somewhat.

Unfortunately, I think the trees are a large enough portion of your problem that you will continue to have issues. I have the tree problem at our property on Kau'i in Hawaii, worse you can't erect a humungus tower. What I did in that case was find the two tallest trees for an East/West dipole and string up fan dipole setup between them for 20 and 40 meters.
 

prcguy

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I have not encountered tunable traps in a commercially made vertical yet and the only ones I've seen are the individual traps made for dipoles, etc by Reyco/Unadilla.

Usually you tune a trap vertical by changing the length of tubing below each trap and you start with the highest band which would be the lowest trap.
prcguy


Tuning traps is relatively easy, just open them up and tune them. I've also heard that the traps on the Cushcraft go bad at a high rate, if you're having troubles they might be "blown" (for lack of a better word) and need replacing/maintenance. I've not used a Cushcraft vertical so I don't know the exact procedures but I'm sure if you spend some time with Google you can find the answers and possibly gather enough information to determin if a faulty trap/mistuned trap is to blame for any of your problems.

The remote tuner will not compensate for your 1.5db loss, but it will allow you to tune out issues caused by the feedline, in general, and more specifically for non-resonant verticals a remote tuner is the ideal way to go. You will probably gain some from using one, but I'm not sure if the gains in this case would justify the $300+ on a remote tuner. You would probably want to address the trap issue first, just to either confirm or eliminate it, and continue with your efforts on radials before trying the remote tuner. But I think you would find they do improve things somewhat.

Unfortunately, I think the trees are a large enough portion of your problem that you will continue to have issues. I have the tree problem at our property on Kau'i in Hawaii, worse you can't erect a humungus tower. What I did in that case was find the two tallest trees for an East/West dipole and string up fan dipole setup between them for 20 and 40 meters.
 

acyddrop

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Well if you've never encountered them than there you go, they probably don't exist. I guess you're the expert on the subject, and defer to you. I've never used any trapped vertical personally so I have no first hand knowledge, but clearly you've used a lot of them. I've only gone by what I've read about them online and in forums (not this one though). But I did suggest google, it knows everything.

I have not encountered tunable traps in a commercially made vertical yet and the only ones I've seen are the individual traps made for dipoles, etc by Reyco/Unadilla.

Usually you tune a trap vertical by changing the length of tubing below each trap and you start with the highest band which would be the lowest trap.
prcguy
 

LtDoc

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The only good reason to use a trapped or loaded antenna of any sort is that you can't afford or don't have room for a full sized one. If a trapped or loaded antenna fulfills your needs then do it. If such a thing doesn't fulfill your needs then you're just out of luck, sorry 'bout that.
Any trapped or loaded antenna isn't going to do as well as a 'real live' full-sized antenna. That's just the way it is. So, if that 'real live' antenna isn't a reasonable possibility, then do that trapped/loaded antenna thingy! Hey, it's better than nothing, right?
There will be times when an 'almost' antenna will do as well as a 'real live' one. The difference is in the realistic possibilities. Can't get something for nothing no matter how hard you try.
Have fun.
- 'Doc
 

W9BU

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Folks, if you have something useful to contribute to the thread, feel free to post it. Snarky responses, however, are really not called for.
 

ab3a

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I don't have all of my radials in yet so I'm not exactly sure if the SWR will go down once I finish it, but hopefully it'll go down a tad bit more. I've heard that 1.4 is optimal because that means the antenna feedpoint impedance is 36 ohm, right where it should be.
You should have several dozens of radials in place to get that impedance anywhere near 36 ohms. Two radials is nowhere near enough. Consider using at least 8 to 16 evenly spaced radials. That might get you just below 50 ohms. I suggest using (or borrowing) a noise bridge or an antenna analyzer to get the straight scoop on what impedance you're seeing.
 
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