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Message |
    
Charliebrown
Member
Username: Charliebrown
Post Number: 80
Registered: 10-2002
| | Posted on Thursday, August 05, 2010 - 9:30 am: | 
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I have seen a web site that offers to take the i max apart and put bigger coils in it (to take more power ) and to change the copper wire out to a much bigger wire. I have several questions about this. The first question is what would it help in changing the copper wire out to bigger wire? The last question is how would you get the fyberglass apart from this antenna without harming the antenna? I know that if you have bigger coils that would help it handle more power, perhaps even less power loss. I hope some of the techs can help me with these questions. Be a myth buster and let us know if this is true or not true. I know I can count on you guys.. |
Tech833
Moderator
Username: Tech833
Post Number: 1836
Registered: 8-2002
| | Posted on Thursday, August 05, 2010 - 12:58 pm: |
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I have viewed that website in which you refer. That website isn't exactly modifying Imax 2000's, they are building their own versions of them. The purpose for using larger coils is so they will handle more power (as if 1,000 watts isn't enough).
You cannot put bigger coils in an Imax and seal the fiberglass shell again. Once you cut it open, it is ruined.
As it is, the Imax 2000 has tremendous bandwidth and good gain. Why mess it up? If you want to run monster power, select a different antenna like the Maco V-5000 or similar.
Your radio 'Mythbuster' since 1998
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Charliebrown
Member
Username: Charliebrown
Post Number: 81
Registered: 10-2002
| | Posted on Thursday, August 05, 2010 - 6:07 pm: |
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Thanks Tech 833, I thought they were doing an upgrade. I found it interesting on the claims they had made and I knew that one of the techs could set me straight on their claims. Always nice to hear from you all and I do thank you all for the information. Have a nice day and God bless. |
Starface
Senior Member
Username: Starface
Post Number: 2875
Registered: 1-2005
| | Posted on Friday, August 06, 2010 - 1:51 am: |
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Charlie Brown, Don't believe what they say...
Lucy isn't going to hold that football so you can kick it ....hehehe
Life is a mirror and will reflect back to the thinker what he thinks into it.
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Funtimebob
Intermediate Member
Username: Funtimebob
Post Number: 260
Registered: 5-2002
| | Posted on Sunday, August 08, 2010 - 3:33 pm: |
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If you look in some of the antenna books (ARRL) etc you will see that the diameter of the antenna VS frequency (K factor) has an effect on antenna length AND bandwidth.
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Charliebrown
Member
Username: Charliebrown
Post Number: 82
Registered: 10-2002
| | Posted on Monday, August 09, 2010 - 2:32 pm: |
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Funtimebob, I remember reading a little about the diameter but I did not pursue looking into the data on the specs for the difference it will make for the antenna. I have friends that swear that the metal antennas (because of diameter and the material it is made of ) will receive better. I can not confirm what they say but, they do seem to hear more than I can. I am aware that some of this is due to their antenna being located in a different place and that will make a dfference as well. What experience do you or anyone have with this? I have been in radio as hobby for over 42 years and all I have ever owned is the fyberglass antennas. I am always looking to learn something new. |
Tech833
Moderator
Username: Tech833
Post Number: 1839
Registered: 8-2002
| | Posted on Tuesday, August 10, 2010 - 12:48 pm: |
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At 27 MHz., diameter has to change drastically to make any noticeable difference to the characteristics of the antenna.
Assume your antenna is a #10 copper wire. The length is x. Now, change the diameter of the copper wire to 12 inches, circumference is now over 37.6 inches. You subtract this circumference from the overall length, so length becomes x - (37.6 / 2). If your #10 copper wire half wave was 17.5 feet long using a #10 copper wire, it will now be just over 15.9 feet long using 12 inch diameter copper 'wire'.
Since diameter/circumference vs. wavelength is a tracking factor, as frequency goes higher and higher, the effect is more dramatic. At low frequencies, like the AM broadcast band, a large diameter free-standing tower can be used as the antenna element and diameter effect is less of a factor on overall length.
Antenna element diameter has more of an effect on Q and bandwidth than element length.
Your radio 'Mythbuster' since 1998
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Funtimebob
Intermediate Member
Username: Funtimebob
Post Number: 261
Registered: 5-2002
| | Posted on Tuesday, August 10, 2010 - 8:29 pm: |
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I didn't say that it made a major change in bandwidth just that it was affected 
as far as metal VS fiberglass. just think, there is Metal (wire) inside a fiberglass "antenna". They didn't come out because they were superior, They were introduced because of too many people electrocuting themselves trying to install aluminum ones!!
The wire inside may be coiled which would shorten the antenna (same principle as used in a mobile whip) BUT it is still a "metal" antenna and still follows the same engineering principles as any other transmitting antenna.
Being enclosed in fiberglass I don't know if any capacitance comes into play or not as it would if you built something like a 2 meter J-pole inside some PVC which would shorten the needed length a tad.
The only noticeable difference between a "Metal" or "Fiberglass" antenna would then be attributed to the method used to feed the antenna (some better than others).
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Tech833
Moderator
Username: Tech833
Post Number: 1841
Registered: 8-2002
| | Posted on Wednesday, August 11, 2010 - 2:41 am: |
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A fiberglass antenna does have a wire inside. The fiberglass shell does not change any capacitance or anything, it does have a minimal effect on the velocity factor of the wire inside though. As you encase the wire with dilectric (fiberglass in this case), it lowers the velocity factor of the wire, making it appear longer to the RF traveling over its surface.
I'm confused about your last line. You can feed a metal antenna or a fiberglass encased wire antenna exactly the same way.
Your radio 'Mythbuster' since 1998
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Charliebrown
Member
Username: Charliebrown
Post Number: 83
Registered: 10-2002
| | Posted on Wednesday, August 11, 2010 - 11:27 am: |
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Tech 833 and Funtimebob, My friends theory between the wire in the fyberglass and the metal antenna on receive is they believe that the bigger diameter metal antenna has more surface to catch the signal waves. And the small wire in the fyberglass antennas has a smaller diameter wire so, they believe it will receive less signal. Now what they say sounds logical to me but, not having the proper equipment to check their theory out is the reason I had asked this question. The good thing I have found in making dipoles is that when you put pvc pipe over them they seem to pick up a little less electrical interference. Perhaps this helps fyberglass antennas as well. |
Tech833
Moderator
Username: Tech833
Post Number: 1842
Registered: 8-2002
| | Posted on Thursday, August 12, 2010 - 1:33 am: |
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Using a dilectric material to 'shield' the metal antenna element does reduce wind and moisture related static. That one is true.
As for an aluminum antenna receiving better than a wire inside fiberglass antenna, yes and no.
Bigger metal does make a slightly better receive antenna (read the "Giant Coil Antennas" article in the latest Copper Electronics subscriber magazine). However, for the frequencies we are talking about, 27 MHz., the effect is minimal. If you want to compare a copper wire to aluminum tubing, the copper wire slightly edges out the aluminum, even though it is slightly larger in diameter. Why? Clean copper wire makes a better conductor for RF than aluminum tubing.
The slight disadvantage of the fiberglass shell is more than made up by using a clean copper conductor.
Where the actual difference is will be found in the feedpoint and matching scheme. The A99 and Imax 2000 have lossier matching networks than a Penetrator P500 or Maco V-5/8.
Do a search through the forums here, and you will find a post I made not long ago showing the polar plots of fiberglass antennas and a P500. There, you will see a slight gain (I mean a fraction of a dB) of a P500 (Penetrator) over an Imax 2000. Literally, the miniscule difference is about the same as adding another 20 feet of RG-8 coax to your feedline.
In favor of the Imax, it has WAY better bandwidth that any aluminum CB antenna.
Your radio 'Mythbuster' since 1998
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Charliebrown
Member
Username: Charliebrown
Post Number: 84
Registered: 10-2002
| | Posted on Thursday, August 12, 2010 - 10:06 am: |
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TECH 833. Thanks for facts on this subject. The last question I have on this is, with the I MAX and the A 99 ( and I like both antennas ) having a little bit more loss on the coils and the copper wire could be a litte bit bigger to help as well. Do you think the manufacture could or would give us in the future an improved antenna ( even if it is just a little improvement on gain or receive) and do you think in doing this it would help them compete better with other manufactures? I would be willing to pay more for the I MAX if they improved it. When you live in an area where you live in the valley and you have to run the antenna far away up to the hill top to perform better, even a little improvement helps. I have done all I could afford at this time on getting better line for less line loss and about the only thing I believe could help next is trying to improve on the antenna. Thanks TECH 833 for your time and the great advice you have given me over the years. I consider you as a friend and I wish you a great day and may GOD bless you. |
Tech833
Moderator
Username: Tech833
Post Number: 1843
Registered: 8-2002
| | Posted on Thursday, August 12, 2010 - 10:40 am: |
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The Imax 2000 is about as improved as it gets. Add the GPK and bend the ground planes up to about 25-30 degrees from horizontal for that extra little oomph.
If you want to improve the Imax 2000 performance significantly, get a beam.
Your radio 'Mythbuster' since 1998
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Funtimebob
Intermediate Member
Username: Funtimebob
Post Number: 263
Registered: 5-2002
| | Posted on Thursday, August 12, 2010 - 5:25 pm: |
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883-Already answered your own question
"Where the actual difference is will be found in the feedpoint and matching scheme. The A99 and Imax 2000 have lossier matching networks than a Penetrator P500 or Maco V-5/8"
Yes you can feed both types of antennas the same way BUT that doesn't necessarily mean that they did. just think of a Ringo Vs an end fed vs....
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Charliebrown
Member
Username: Charliebrown
Post Number: 85
Registered: 10-2002
| | Posted on Thursday, August 12, 2010 - 9:48 pm: |
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Funtimebob, In my questions that were last asked it was about diameter and difference in how the two metals would conduct the waves and which would perform better if any. Now TECH 833 had answered my question in great detail with some added information in detail about the coils and how it cannot be made any better. Now in the past TECH 833 has told me about the ground GPK being the only way to improve the I MAX. He most likely wanted to make sure that I and all others remember this fact. I do not feel tht my question was asked twice because there were more in the question that needed to be inquired of. However thank you very much Funtimebob for your interest and help. I wish you as well a great day and May GOD bless you. HEY TECH 833, JUST CALL ME CB IF YOU WANT. |
Tech833
Moderator
Username: Tech833
Post Number: 1845
Registered: 8-2002
| | Posted on Thursday, August 12, 2010 - 11:11 pm: |
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OK. "Hey, CB!" May God bless you too. Glad to help.
Your radio 'Mythbuster' since 1998
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Charliebrown
Member
Username: Charliebrown
Post Number: 86
Registered: 10-2002
| | Posted on Friday, August 13, 2010 - 12:44 am: |
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TECH833, You pull some very long hours. I do not know if I had told you but I have had radios as a hobby for over 42 years. I started with my dad on a three channel radio that if you wanted to talk on more than three frequencies you had to change the crystals. I do not remember the name of the radio. Things has changed a lot over the years and I feel that with eveyones help we will always have something new to learn. I can not thank eveyone and especialy the TECHS here enough for their time and patience for all the questions you all have answered. This is one of the best places to get help on products and to grow in wisdom for this hobby. Some of my questions are because of friends that put me to thinking and some are because of false information on the web. Thanks to this forum, this is truely where the MYTHBUSTING THRIVES. Good night friends and thanks again for everyones help. Till next time, have a great day and may GOD BLESS ALL. YOUR FRIEND,CB |
