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Goat373
Intermediate Member
Username: Goat373
Post Number: 176
Registered: 3-2005
| | Posted on Thursday, February 09, 2006 - 8:28 pm: | 
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log periodic beams cover massive amounts of band with out retuning, but show low gain...regular beams are comparably narrow banded, but show higher gain with less elements...BUT!!!.
A 5 element log periodic on a 6 foot boom shows 7.5 DbI
A 3 element beam on a 6 foot boom shows 6 DbI
ive never really seen a lot of LP antennas around (besides TV antennas) and im sure there is a reason not alot of people transmit on LP's...but i dont know why, seems to be a better alternative, a LP beam centered on 6 meters also show decent gain on 2 meters...so, whats the deal, why dosent every one use this antenna? |
Georgeodjungle
Junior Member
Username: Georgeodjungle
Post Number: 25
Registered: 1-2006
| | Posted on Thursday, February 09, 2006 - 11:47 pm: |
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i don't know about them gain #s.
but a "log periodic" gives up gain for band with.
same as with any other antenna.
i have played with a 6 lp.
it had realy low swr on 11 meter & lower free band.
almost flat.a lil long.
but didn't out perform the moonraker 4 @ 40' on local or dx.
p.s. with higher swr to, like 1.5.
try it you might get better results.
also the lp would probably be have higher manufacturing cost,ya know like 10 cents each.
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Rldrake
Member
Username: Rldrake
Post Number: 60
Registered: 1-2006
| | Posted on Friday, February 10, 2006 - 2:53 am: |
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You can't go by those "gain" figures on the cheap antennas. The better manufacurers will use dbd (gain over dipole/unity). Many manufacturers/sellers just throw out a high gain figure to top the others. Boom length determines the gain of directional "beam" antennas...side and rear rejection also figures in...more so than the number of elements. Log periodics have their place, but never are as effecient as an antenna designed specifically for a small bandwidth.
As you said...if they equalled, or out performed, yagis...everybody would have them. |
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