| Author |
Message |
    
Twentynineva
New member
Username: Twentynineva
Post Number: 1
Registered: 5-2010
| | Posted on Tuesday, May 11, 2010 - 5:15 pm: | 
|
I have a m103 "flatside" at 22 foot.Used for dx only.Seems to do a great job.My budget will allow one of two things.I can stay at 22foot and go with a 5 element,or keep the m103 and put it up on a 40 foot tower.What should i do? |
Tech833
Intermediate Member
Username: Tech833
Post Number: 178
Registered: 12-2001
| | Posted on Wednesday, May 12, 2010 - 1:20 am: |
|
Put the M103 on the 40 foot tower. WAY better of the two options.
Your radio 'Mythbuster' since 1998
|
N8fgb
Member
Username: N8fgb
Post Number: 89
Registered: 5-2002
| | Posted on Wednesday, May 12, 2010 - 5:50 pm: |
|
It will depend upon what kind of a shot you have to the horizon at the height. If there are no obstructions at that height, then add the 2 elements. If you have obstructions, than go higher.
Rich |
Twentynineva
New member
Username: Twentynineva
Post Number: 3
Registered: 5-2010
| | Posted on Wednesday, May 12, 2010 - 9:00 pm: |
|
thanks for the advice! |
Tech237
Moderator
Username: Tech237
Post Number: 1338
Registered: 4-2004
| | Posted on Thursday, May 13, 2010 - 10:59 am: |
|
I agree with Tech 833.
Tech237
N7AUS
God only made some many perfect head, on the rest he put hair.
|
Tech833
Intermediate Member
Username: Tech833
Post Number: 180
Registered: 12-2001
| | Posted on Friday, May 14, 2010 - 8:43 am: |
|
Rich,
The horizon isn't nearly as important as the overall takeoff angle. Adding 2 elements to a 3 element yagi will only increase the 'free-space' gain by a few dB (this disregards ground effects). At 22 feet AGL, the takeoff angle is already way above optimum, so by adding forward gain, which narrows the gain lobe width, the gain at optimum is even LESS with the narrower gain lobe beamwidth. Doubling the height above ground with the 3 element antenna lowers the takeoff angle, and even with the broader major lobe beamwidth, gain at optimum is increased over 4 dB. You actually end up with about 6 dB MORE gain at optimum with the 3 el at 40 feet over a 5 el at 22 feet.
This kind of thing is easy to play with using even the simplest software like EZNEC.
73, 833.
Your radio 'Mythbuster' since 1998
|
Dale
Senior Member
Username: Dale
Post Number: 1589
Registered: 12-2002
| | Posted on Friday, May 14, 2010 - 2:08 pm: |
|
i agree with tech 833.height is might.why niot just mount the 5 element at 40 ft though
dale/a.k.a.hotrod
cef426
cvc#64
|
Twentynineva
New member
Username: Twentynineva
Post Number: 5
Registered: 5-2010
| | Posted on Friday, May 14, 2010 - 3:04 pm: |
|
my money is to 'funny'.I can either do one or the other,so im going with the tower.Thanks for all the input! |
Spiderleggs
Junior Member
Username: Spiderleggs
Post Number: 48
Registered: 5-2002
| | Posted on Friday, May 14, 2010 - 6:07 pm: |
|
Couple of years back there was a cb'er who was about 50 miles away. He had some moonraker 4's on a 40 ft tower but had some 107's at around 15 to 20 ft that he was going to put on the tower. I could hear the 107's barefoot but could not hear the moonraker 4's. |
Tech833
Intermediate Member
Username: Tech833
Post Number: 182
Registered: 12-2001
| | Posted on Friday, May 14, 2010 - 11:14 pm: |
|
That doesn't mean anything.
What about coax loss? What about tuning? What about phasing? What about etc., etc. etc.
Fact is fact. Speculation is speculation. Go with what is proven to work.
Your radio 'Mythbuster' since 1998
|
