| Author |
Message |
    
Junior
| | Posted on Thursday, August 08, 2002 - 11:24 am: | 
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what is the difference besides length
and what are the advantages?
(seen some at a cb shop that said 1 1/2 wave quad wave etc...) |
bruce
| | Posted on Friday, August 09, 2002 - 7:19 am: |
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junior
the rule of vertical antenas gain is this
a 1/2 wave will give you a nice clean lobe with 2db gain a 5/8 wave distorts the lobe but in a way that you have about 3 db gain now if you go to 3/4 wave you start to get SEVERAL lobes it will show gain but some what less than a 5/8 wave and if you go to a 1 wave ( 36 foot ) antenna you have lots of lobes and even less gain. Bottom line its a toss up between a 1/2 and a 5/8 wave both will give you gain with a slight edge going to the 5/8. AND DO NOT EVER BELEVE YOU WILL GET OVER 3DB REAL GAIN NO MATTER WHAT THE SELLER SAYS! |
Junior
| | Posted on Friday, August 09, 2002 - 12:05 pm: |
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hmm very ineresting
thanks bruce |
Marconi
| | Posted on Friday, August 09, 2002 - 1:05 pm: |
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Junior, to a point I agree with Bruce on this one. I like the way he makes his point, "...clean lobe...." I am not sure if he is referring to an end fed 1/2 wave or a center fed 1/2 wave dipole, but either way, in principle, I agree his point has merit.
As a mater of choice, I prefer a ground plane with a 1/4 wave radiator where the radials hang down at an angle. This configuration produces a natural match that is almost purely resistive at 50 ohms. Very little loss there due to matching. Regardless of the take off angle, that some will tell you is too high, it works local and DX right up there with the big boys when I get the tip up there as high.
BTW, that business of 1-1/2 wave quad is just window dressing if you consider exactly what Bruce described to you earlier.
If you just want something big, which is in style, then build yourself a very long random long-wire and use a tuner. You will have all kinds of high gain lobes, and nulls to work with. The lobes probably won't be in the direction you might think however. Remember as you reduce (concentrate) the volume of an RF lobe to increase gain you will likely generate an adjacent null, at some other angle, which is similar in loss in the far field as the major lobe produces in gain at its own angle in the far field.
Because the 1/4 wave probably covers the far field with more consistency, with its modest lobe pattern, is why I believe it produces such good results.
What do you think?
Marconi |
bruce
| | Posted on Friday, August 09, 2002 - 2:23 pm: |
|
Marconi
I know what your getting at with the very long wire is the same as a rombic. If correctly feed with a antenna tunner will produce good results and I aggree it could be a good choice. When i answered him my thought was he was more intrested in a simple vertical for cb. As you also point out a 1/4 wave groundplane with drooping radals also will produce a very nice pattern and with almost no matching devices at all a very good match.
SADLY too many cb antennas are junk made to look like something from NASA but produce little in return in real gain. Sometimes simple is better.
Bruce |
Junior
| | Posted on Friday, August 09, 2002 - 10:24 pm: |
|
bruce and marconi
yes simple vertical for cb
but i am always willing to listen because i learn and when i learn i am enjoying it
people with curious minds are fascinated by anything technical. you know?
i definately agree with the 1/4 and 5/8 wave don't fully understand but makes sense |
Marconi
| | Posted on Friday, August 09, 2002 - 11:33 pm: |
|
You are correct, that is my point, "Sometimes simple is better." another very meaningful comment.
To me the big deal hear is the losses often associated with and the matching required for some of these longer antennas including the complicate patterns they may produce. They may show a big signal at some points but that is not always the true test of an antenna.
My old Starduster talks just about as far as anything else I have and it hears everything I can hear on the big-uns when conditions are noisy. I can often hear a lot better on the SD'r when conditions are very quite. The only problem, if it is a problem, is that the SD'r seems to have a very heavy vertical polarization factor and this is evident with heavy horizontal signals are rolling. I like to work that long distance no signal ground wave kind of stuff. Just my thing.
Bruce, your points and a little common sense attest to why I hold these opinions about simpler antennas.
Marconi |
Junior
| | Posted on Saturday, August 10, 2002 - 1:04 pm: |
|
bruce and marconi
i was thinking vertical cb
and just wondered other than length if there was any merit to the "quad wave" etc....
so much bull to sort through sometimes it can be confusing for a newbie
thanks for the great info.. |
bruce
| | Posted on Saturday, August 10, 2002 - 8:55 pm: |
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Marconi Im tinkering with a mulitiband dypole and this is realy strange i added 17, 10 meters and it killed resonance. IT dosnt seem to have ANY 50 ohm point just a slight drop and rise as you move from 7 - 29 mhz. Humm now the only thing i can figure is 20,15,17 are too close and the imp is going bonkers YET as seperat dypole elements there fine what you think ???? |
Marconi
| | Posted on Saturday, August 10, 2002 - 11:34 pm: |
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Bruce, are you feeding this with one line into an inverted V configuration? I don't think they are too close, I just don't think you can succeed trying to cover a very large area with one direct feed. Maybe 20,17,15 or 10,11,12.
I have a bud that built one as I describe, but he was never happy with performance either. I seem to recall that he even trapped some of the bands and that did not seem to work well either. I do not know the technique or problems involved but generally I consider him to be very sharp along these lines. Let me know if your design fits the basic design I noted above and I will call him and ask him what his opinion on this one is.
I have tried several homebrew designed, wire type antennas and beams, and have never been impressed. Either the author's left something important out, or I just plain missed something. I am a resonant antenna nut you see. I like to see old mother nature work, I don't enjoy trying to fool her with tricks.
Marconi |
bruce
| | Posted on Sunday, August 11, 2002 - 4:50 am: |
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Yes feeding with a W2AU balum and its a flat 3:1 across a wide range going up under 10 mhz and above 24 my only thought was interaction between them but i got 2 emails this morning saying what you said they had little luck too.... so much for a good idea!
bruce |
Marconi
| | Posted on Sunday, August 11, 2002 - 3:15 pm: |
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Junior, that is why common sense and self-reliance are wonderful things to pursue.
Marconi |
bruce
| | Posted on Sunday, August 11, 2002 - 9:13 pm: |
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O the BOOK SAID " THERE WILL BE A LITTLE INTERACTION BETWEEN DYPOLES " HA HA HA |
Nightshift221
New member
Username: Nightshift221
Post Number: 1
Registered: 2-2005
| | Posted on Monday, February 07, 2005 - 10:50 pm: |
|
what is the best roof antenna for 11 meter.
i have a skylab it performs well but the top element does not like wind.it has broke off 3 times. i've replaced it with a maco 5/8 top section and tuned it to 1.1 swr as well as putting the tristar that the original top section had on. but people tell me i dont do as well as before. i,m considering a replacement but dunno what to use maco 5/8 or cte's spectrum 1600 . help |
Tech291
Moderator
Username: Tech291
Post Number: 70
Registered: 11-2004
| | Posted on Tuesday, February 08, 2005 - 6:45 pm: |
|
Nightshift221,
Maco V5/8
http://www.copperelectronics.com/cgi-bin/checkitout/checkitout.cgi?catalogSTORE:CKIE:prodM00-05140+
tech291
CEF#291
kc8zpj |
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