| Author |
Message |
    
Radiopat
New member
Username: Radiopat
Post Number: 5
Registered: 9-2003
| | Posted on Monday, May 10, 2004 - 5:49 am: | 
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Which type of mobile antenna performs better, base or center loaded ones?
Thanks.
Patrick |
Tech237
Moderator
Username: Tech237
Post Number: 17
Registered: 4-2004
| | Posted on Monday, May 10, 2004 - 8:55 am: |
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From memeory - the higher up the antenna the loading is the better the antenna SHOULD work. So a center loaded is better than a base loaded and a top loaded is better again. Of course a full size unloaded antenna is better still. |
Pig040
Intermediate Member
Username: Pig040
Post Number: 406
Registered: 7-2003
| | Posted on Monday, May 10, 2004 - 10:44 am: |
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In My personal experience the higher the load the better, one thing to remember if you are using a mag mount it may not hold the antenna with the higher load due to wind resistance. |
Davesmeg
New member
Username: Davesmeg
Post Number: 9
Registered: 3-2004
| | Posted on Monday, May 10, 2004 - 4:32 pm: |
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I had a twin coiled modulator and a base coil whip.
The base loaded out performed the twin coil by around 2 S points even though the twin was 5/8 wave and the base was 1/2 wave. |
Tech833
Moderator
Username: Tech833
Post Number: 682
Registered: 8-2002
| | Posted on Monday, May 10, 2004 - 4:35 pm: |
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SAhakespeare used to make a 4 foot fiberglass antenna that was top loaded with a simple metal whip making up the bottom 3.5 feet of the antenna. The Shakespeare 4 footer put out nearly the same gain as a full 9 foot whip. Much higher gain than any other loaded antenna we had on the range. The Firestik is top loaded, but it is also partially loaded all the way up to the top coil which reduces the efficiency.
Radio Shack used to sell the Shakespeare whip with their name on it. Look for the skinny fiberglass 4 foot antenna that is thicker on top than the bottom 3 feet. That would be the next best thing to a full 9 foot whip.
Does Copper sell anything like this?
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Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 162
Registered: 6-2003
| | Posted on Monday, May 10, 2004 - 5:23 pm: |
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Unless it is a Wilson 1000.
mikefromms |
Tech548
Moderator
Username: Tech548
Post Number: 32
Registered: 5-2004
| | Posted on Tuesday, May 11, 2004 - 4:17 am: |
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Yes, a coil does radiate but, it does not radiate the same RF pattern as the whip does-or as far as the whip does.
Personally, I'd rather have more whip in the air than coil. If you can figure what the impedence of a particular whip is, build a dummyload of the same impedence and mount it to your coil. Then transmit on it and lets see just how far that coil will be received.
I guarentee it won't be heard very far for two reasons. #1, its radiation pattern will be very narrow and completely different than that of a whip. #2, having them radiate in the first place wasn't on the minds of its designers.
All a coil does is replace the loss (shortness) of the radiator. "Radiator"!! Radiator is the key word here boys and girls. Look at it this way. If having the coil radiate is such a great thing, why don't the designers build them so we don't need a whip at all? Yes, the coil DOES radiate some, BUT, nowhere near the same radiation pattern as the whip does. And nowhere near as far as the radiator. A few blocks maybe. The coil is nothing more than a load. Thickness of the wire, diameter of the coil, number of windings and length of the radiator will determine the wavelength of a given antenna.
Firestiks' way of thinking is, since the coil also radiates, lets put it on top of the radiator instead of the bottom. Like other companys, they do this "ONLY" because the coil radiates some. But what they don't tell you is, at what wavelength and how far that coil actually radiates. In my opinion, the only decent antennas that Firestik makes are their 6 and 7 footers. Why? Because they use far less coil than their 3, 4 and 5 footers use.
Lets look at it this way. Take 36 feet of thin wire and hang it up somewhere where it's off the ground. Wow. 36 feet (full wavelength) of antenna is a LOT of antenna. Now take that same 36 foot piece of thin wire, wrap it around a pencel and hang it up at the same height. Doesn't look so impressive any more does it. Now tell me which one you think will radiate the farthest.
The ONLY purpose a coil serves is to make up for the shortness of the radiator. The longer the radiator, the less coil is needed. And also, the longer the radiator, the farther you are going to throw a RF signal.
Jeff. |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 188
Registered: 2-2003
| | Posted on Tuesday, May 11, 2004 - 5:41 am: |
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Or, can Copper obtain that antenna? Does that shakespeare 4 footer "Out gain" an Anttron 1700, or Wilson? Inquiring mind would like to know!
Wolverine. |
Pig040
Intermediate Member
Username: Pig040
Post Number: 409
Registered: 7-2003
| | Posted on Tuesday, May 11, 2004 - 9:29 am: |
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Jeff,
Are you answering the same question? We all know the best mobile antenna is the whip, but what works best base, center or top load was the question. I had a radio shack top load once, best mobile I had, they dont offer them any more unless they have them in the catalogue.
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Tech548
Moderator
Username: Tech548
Post Number: 36
Registered: 5-2004
| | Posted on Wednesday, May 12, 2004 - 2:08 am: |
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Pig040
You guys were discussing coils and where you think they should be located on a antenna. I was only sharing my thoughts on antenna coils. Hope I didn't upset anyone.
Jeff. |
Pig040
Intermediate Member
Username: Pig040
Post Number: 413
Registered: 7-2003
| | Posted on Wednesday, May 12, 2004 - 9:10 am: |
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Of course you didnt upset anyone Jeff, just kind of led me to wonder what the heck it is like inside your head, a view inside would probably make a good made for tv movie, haha. (That is what my xyl tells me!) |
Tech548
Moderator
Username: Tech548
Post Number: 38
Registered: 5-2004
| | Posted on Wednesday, May 12, 2004 - 1:27 pm: |
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Pig040
A movie huh?
OK. Lets do it! It will be interesting to see what kind of rating will be put on it before it goes public.
Jeff. |
Tech833
Moderator
Username: Tech833
Post Number: 685
Registered: 8-2002
| | Posted on Wednesday, May 12, 2004 - 2:45 pm: |
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Jeff,
A Firestik will outperform a 36 foot piece of wire. Why? The Firestick will have more gain on the horizon than a full wave radiator. A full wave has a null on the horizon, it puts out a butterfly shaped pattern in free space. Almost like an X shape.
Wolverine,
Yes, I believe the Shakespeare 4 footer will "out gain" an Anttron 1700, or Wilson. Since the Shakespeare had nearly the same gain as the 1/4 wave whip and the Wilson and Anttron have noticeably less gain than a 1/4 wave whip, I feel comfortable making this statement. |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 189
Registered: 2-2003
| | Posted on Thursday, May 13, 2004 - 3:23 am: |
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I checked the Shakespeare website, and they just specialize in marine cb antennas. Does anyone out there have a clue to where this 4 footer can be purchased?? I want one!!!
Wolverine. |
Tech833
Moderator
Username: Tech833
Post Number: 693
Registered: 8-2002
| | Posted on Thursday, May 13, 2004 - 10:48 am: |
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I am sorry I failed to mention these antennas are no longer made. Shakespeare got out of the CB market. That is why the 'Army Big Stick' disappeared. |
Applejack
Intermediate Member
Username: Applejack
Post Number: 172
Registered: 8-2003
| | Posted on Sunday, May 16, 2004 - 1:54 pm: |
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so apparently an fgt wilson should do better than a workman b50, and a 102 whip the best? i tried all 3 last week and had a terrible swr with the whip. a poor swr with the wilson,even tuned the best i could. and about a 1.7 swr with the b50 without the bottom shaft. all were mounted on a 4'' spring which i have to use because of trees. the swr meter was the stock 3900 meter. not good i suppose, but all 3 used the same meter. a little off topic maybe but what tunes best should work best right? |
Pig040
Intermediate Member
Username: Pig040
Post Number: 423
Registered: 7-2003
| | Posted on Monday, May 17, 2004 - 9:36 am: |
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AJ, with those lousy swrs it sounds like you have another problem, are you using a box? If so try varying the length of jumpers. My wilson is at a 1.2 goes to 1.4 with the heat on. And usually a 102 inch whip falls in with no tuning necessary at all.Just a thought.
Rich |
