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Message |
    
747
Intermediate Member
Username: 747
Post Number: 187
Registered: 8-2002
| | Posted on Tuesday, October 17, 2006 - 9:23 pm: | 
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Other than the obvious (naming) , what benefits/draw backs are there to based loaded/center loaded/top loaded antennas? |
Tech237
Moderator
Username: Tech237
Post Number: 574
Registered: 4-2004
| | Posted on Wednesday, October 18, 2006 - 10:23 am: |
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Belive it or not several things are different.
1)The size of the loading coil needed changes with it's location. I'd have to check in my books (as yet unpacked)to tell which one needs more turn or bigger diameter coil.
2) Efficiency of the antenna changes with the coil location and again off the top of the head I cannot recall which is which.
3) You can use a slimmer whip if the antenna base loaded than if center or top loaded. This because the whip is not supporting the loading coil. In turn this can effect the bandwidth of the antenna. Larger wire can have a greater bandwidth than a small diameter wire. This can also affect the whip length. Have you noted that a wire antenna needs to be slightly longer than one made from tubing for the ame frequency?
If no one ele does I'll try to locate my antenna books in the next couple of days and fill in the gaps I left. |
747
Intermediate Member
Username: 747
Post Number: 188
Registered: 8-2002
| | Posted on Wednesday, October 18, 2006 - 1:38 pm: |
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Thank you! Any more info you or anyone else can provide is helpful! |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1911
Registered: 1-2005
| | Posted on Wednesday, October 18, 2006 - 2:04 pm: |
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Efficiency
The full length 102 inch steel and 96 inch fiberglass whips are the most efficient. Once loads are added on to reduce length efficiency lessens.
Of the coil antennas, being the same length
Top loaded antennas (helically wound) are the most effecient
Center loaded are less efficient than top loaded
Base loaded antennas are the least efficient of the 3.
Length plays an important part in the antennas performance. A 6 foot base loaded antenna is better than a 2 foot top loaded antenna. Top loaded make better short antennas for like mirror brackets on big rigs and similar installs where not all the antenna go go above the groundplane. Base loaded make a better roof top antenna where height is not as important and all the antenna can be above the groundplane. Center loaded is somewhere between the other 2 install types. Seems to be a lot of center loaded antennas on the market and there sure is many many killer center loaded antennas.
This is the best I can explain without blowing your mind! kidding
Kenny |
Pogo12
Member
Username: Pogo12
Post Number: 85
Registered: 3-2005
| | Posted on Saturday, October 21, 2006 - 5:05 pm: |
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The higher its loaded(fed) the less ground loss.I have a eagle DX6 that is center fed to decrease ground loss. |
