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Dipole questions

I

IronGuts

Member
Mar 3, 2012
27
0
11
I'm fairly new to radio so thanks for your help. I installed a cb in my pickup last year, and now I'd like to use my second ssb cb as a base station at home. Rather than mounting a vertical antenna, like an Antron or Imax type, I'd first like to experiment with a simple dipole, that I'll either make or buy. Here are my questions:
1. How high for best dx?
2. What configuration for best dx: horizontal, inverted v, vertical, l-shape?
3. How about hang one end as high as I can in a tree and let it hang vertically?
4. Does it need to be grounded for lightning protection. If so, how do I do that? Trying to keep this simple but safe.
5. Is the antenna and coax destined for destruction by squirrels. If so, what other mounting options might I have, maybe the attic?

Thanks a ton!!
 

IronGuts said:
I'm fairly new to radio so thanks for your help. I installed a cb in my pickup last year, and now I'd like to use my second ssb cb as a base station at home. Rather than mounting a vertical antenna, like an Antron or Imax type, I'd first like to experiment with a simple dipole, that I'll either make or buy. Here are my questions:
1. How high for best dx?
At least half a wavelength; more is better (to a point).

2. What configuration for best dx: horizontal, inverted v, vertical, l-shape?
Experiment and see which works best in YOUR location.

3. How about hang one end as high as I can in a tree and let it hang vertically?
I don't recommend this. The feedline has to be run away from the antenna at as near a right angle as possible. Now, if you have two 60-70 foot trees doing nothing but taking up space, use them.

4. Does it need to be grounded for lightning protection. If so, how do I do that? Trying to keep this simple but safe.
A dipole is a balanced antenna, and should NOT be "grounded" if you want it to act as such. Feeding it with coax via a balun (an actual "balun", not just a coil of coax) will allow the unbalanced feedline to work with the balanced antenna properly. For lightning protection, search the forum. There are hundreds (maybe thousands) of posts and instructions to be found.

5. Is the antenna and coax destined for destruction by squirrels. If so, what other mounting options might I have, maybe the attic?
Squirrels have been known to chew on coax; there may be compounds that taste awful to them but don't hurt the jacket. I've never had the problem, though. Keep the antenna outside. Any antenna outside beats the same antenna inside.

Thanks a ton!!
Click to expand...

Reply in red...
 
Thanks, Beetle. I appreciate your help. Looks like i'll have some fun experimenting with setup. I am concerned about the lightning protection for the house, so ill do some digging on the forum as you suggest. Does the radio in the house need to be grounded in any way?
 
I'll add this much...

"1. How high for best dx?"
There is no -set- 'best' height, it changes along with propagation. In general, higher is better till you reach the highest point that's -practical- in your particular situation. When you can't get it any higher without an unreasonable effort, quit. That's the 'best' height for you.
- 'Doc
 
IronGuts said:
I'm fairly new to radio so thanks for your help. I installed a cb in my pickup last year, and now I'd like to use my second ssb cb as a base station at home. Rather than mounting a vertical antenna, like an Antron or Imax type, I'd first like to experiment with a simple dipole, that I'll either make or buy. Here are my questions:
1. How high for best dx?

Depends if you configure it vertical or horizontal polarization.
If you go vertical then it don't need to go that high and will only need one attachment or support point up high instead of three support locations if you go horizontal with it.

2. What configuration for best dx: horizontal, inverted v, vertical, l-shape?

Since appears to me that you have indicated a preference of 'DX' then it does not matter if it is horizontal or vertical except for the mechanics of the support and mounting scheme.
As 'DX' tumbles as it travels then one moment it will be mostly vertical and then the next mement it will be mostly horizontal and in between those moments it will be skewed between vertical and horizontal.
My preferred polarization would be vertical since it will be easier to mount since it won't need to be mounted as far above ground and also it will be more useful for local talking if it is mounted vertically as it will be mostly useless for talking locally if it is mounted horizontally. ( unless you have a plethora of locals with horizontally polarized antennas )

3. How about hang one end as high as I can in a tree and let it hang vertically?

That is agreeable with my recomendations as per the two previous questions.

4. Does it need to be grounded for lightning protection. If so, how do I do that? Trying to keep this simple but safe.

The best lightning protection, and the one I practice, is to unhook your coax from the radio and short the shell to the center pin and then hook the other end of the large guage wire to the mains ground or a cold water pipe.
Keep this large guage wire to the shortest possible distance as what is needed to reach the point of grounding attachment.

5. Is the antenna and coax destined for destruction by squirrels. If so, what other mounting options might I have, maybe the attic?

I would not be too concerned about this.
But if you find that the animals are damaging the antenna/coax then you can take measures as needed to minimize or stop their efforts.

Thanks a ton!!
Click to expand...


Radiooman
 
IronGuts said:
2. What configuration for best dx: horizontal, inverted v, vertical, l-shape?
Click to expand...

Most questions have been answered well, but the best answer to this question is "yes", and by "yes" I mean all of the options you listed and more. Another, better answer is "it depends".

Some people like one type of antenna over another. Others use multiple different types, from verticals to horizontal beams. Sometimes conditions favor one over the other, sometimes it ends up being the other way around, and sometimes conditions can change from one to the other as you are using them. There is no one best antenna that will always be the best antenna in every circumstance. There are advantages and disadvantages to each type of setup to consider. For example, a horizontal antenna has an advantage of lessening the impact of local cb traffic on your attempts to dx, an usually has less noise to boot. However, if you want to talk to that local on a base with a vertical antenna 50 miles away it also isn't going to happen, especially if that base is on the axis of the horizontal antenna.

The best thing to do to determine which antenna is right for you is ask questions, then more questions. Ask people who have used not only multiple antennas, but multiple types of antennas to compare them for you. Find out what they liked and didn't like from each one.


The DB
 
The DB said:
Most questions have been answered well, but the best answer to this question is "yes", and by "yes" I mean all of the options you listed and more. Another, better answer is "it depends".

For example, a horizontal antenna has an advantage of lessening the impact of local cb traffic on your attempts to dx, an usually has less noise to boot.

The DB
Click to expand...

Point well taken.
I had not considered this in my previous posting.

Radiooman
 
A horizontally polarised dipole will have significantly more gain than when vertical, now that's a freebie I like ;)
 
No popcorn needed, here's a photo that might help, guess which is the horizontal dipole:

V-against-H-dipole_zps76249d3b.jpg
 
I haven't used Makoto Mori's program so can't say anything specific about it's results. I can say that the radiation pattern shown for a 1/2 wave dipole at 1/2 wave above ground ('real' or not) is not as directional as shown. The shown plot is a 'classic' directional pattern at much more than 1/2 wave length above ground, probably something greater than 1 or 2 wave lengths.
I'm also not going to do the work in duplicating plots for a 1/2 wave horizontal dipole at a 1/2 wave above ground, I'm too lazy and don't know what I did with the program, lost the @#$ thing somewhere. Marconi is familiar with all that, ask him to do it with his preferred modeling program. I know that sounds like a 'cop-out', but it's a fact, I can't find the @#$ thing!
Very simply, the cited results are just too 'good' to be true, you know? Mori is a very accomplished programmer and his program does work, but you gotta use the correct 'input's to get it to produce 'real life' (Isotropic results really, never 'real life') results.
- 'Doc
 
W5LZ said:
I haven't used Makoto Mori's program so can't say anything specific about it's results. I can say that the radiation pattern shown for a 1/2 wave dipole at 1/2 wave above ground ('real' or not) is not as directional as shown. The shown plot is a 'classic' directional pattern at much more than 1/2 wave length above ground, probably something greater than 1 or 2 wave lengths.
I'm also not going to do the work in duplicating plots for a 1/2 wave horizontal dipole at a 1/2 wave above ground, I'm too lazy and don't know what I did with the program, lost the @#$ thing somewhere. Marconi is familiar with all that, ask him to do it with his preferred modeling program. I know that sounds like a 'cop-out', but it's a fact, I can't find the @#$ thing!
Very simply, the cited results are just too 'good' to be true, you know? Mori is a very accomplished programmer and his program does work, but you gotta use the correct 'input's to get it to produce 'real life' (Isotropic results really, never 'real life') results.
- 'Doc
Click to expand...

If you look at the details under the comparison, you'll notice both these antennas are at 10m agl, that's plus the original model height of 1m agl, a total of 11m high, a not too unrealistic height for many people ;)
 

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