Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 [2]   Go Down
  Print  
Author Topic: How to squeeze more range out of a 2 meter beam?  (Read 5306 times)
KB1GMX
Member

Posts: 775




Ignore
« Reply #15 on: May 31, 2013, 10:02:09 AM »

First the fiberglass mast was a must (or an offset).

Rg213 is OK to maybe 100FT.  Use better if longer.

Height, higher than trees, higher still.  Your working with the effective radio horizon
and that is mostly about height.

Power, If you hear them but they don't hear you(or well enough) more power.

Yagi antenna effective gain is proportional to the boom length, the longer antenna
has more gain. We are not talking about a foot we are talking in terms of wavelengths
or about 40-80 inches for every major increase in gain.

10 elements on 7ft!?!  Thats a lot for such a short beam and the gain claims are a
tad high for that long.  Also any decently designed beam with a 13-15ft boom will
not sag noticeably.  Reason, your paying for enough metal to not sag.

I assume a rotator.  Its a must unless your only interested in one direction.

Allison
Logged
W4KVW
Member

Posts: 491




Ignore
« Reply #16 on: May 31, 2013, 11:43:30 AM »

Well it would depend on the amount of hills,mountains,& other obstructions that you have between you & who you are attempting to talk with.I run about 140 watts into a 13 element 2 meter yagi at 53 ft here in North Florida & can talk into the repeaters usually 100 plus miles away in the middle of the day.At night when condition improve I have worked repeaters & some simplex over 300 miles many times.I have sometimes worked repeaters in Virginia & the Carolina's but that's not every night.A good amplifier with a good preamp is the only way I see that you will improve with your current antenna but a larger yagi would for sure help your transmit & receive & M2 makes some AWESOME antennas for both VHF & UHF FM.I think that most any FM yagi designed for 2 meters should be just fine for a TV rotor since wind load is very low on these antennas.  Grin

Clayton
W4KVW 
Logged
WB2WIK
Member

Posts: 20603




Ignore
« Reply #17 on: May 31, 2013, 03:39:35 PM »

M2 antennas is the premier provider of high performance VHF-UHF beams in the U.S.

Their website seems to be down today, not sure why...I suspect they had a server crash or maybe just updating the site.

Anyway, their 9L 2m beam is 14.5' long and handles legal-limit (1500W) power, and works very well.  But it costs quite a lot more than $100. Wink

They are distributed by HRO, Texas Towers, and others: http://www.hamradio.com/detail.cfm?pid=H0-000716

If the beam has elements on both sides of a supporting mast, the coax should not run down the mast; that defeats the purpose of using a non-conductive mast. Smiley
Logged
AA4HA
Member

Posts: 1451




Ignore
« Reply #18 on: May 31, 2013, 05:10:02 PM »

I assume you are working on FM where antenna polarization is vertical (elements pointing up and down, not side to side). If you have a mismatched polarization it will take your signal down ~20 dB.

Use the best feedline you can afford. Minimize losses here and you improve receiver and transmitter performance so you are less of an alligator. If the power is the same at both ends (example, 50 watts) and receiver performance is the same (-100 dBm) you should experience "reciprocity" across a link. Here are some examples of feedline losses;

RG-58U   6.1 dB/100'
RG-8X   4.7 dB/100'
LMR-240   2.94 dB/100'
RG-213/U   2.5 dB/100'
LMR-400   1.47 dB/100'
LMR-600   .94 dB/100'
LDF4-50A   .83 dB/100'
LDF5-50A   .45 dB/100'

At the bottom end you may be paying .20/foot, at the top end as much as $7.00/foot. Keep it as short as possible.

Height, Line of Sight is pretty easy to determine if the world is flat in all directions. It is a simple calculation to convert height into milage distance. There are some propagation effects that can make that +/- 15%. This is known as "the k factor", it can be from 4/3 to 1 to 2/3 of earth. +15% assumes that  the weather is perfect, life is perfect. -15% is ugly weather or thermal effects/inversions where the earth may appear to be smaller than it actually is (making the radio horizon much closer).

In reality, unless you live on a boat in the middle of the ocean and only talk to other boats you will always see some terrain obstructions. Also, depending upon frequency you will see different sized Fresnel zones (imagine the path between two places is shaped like a lens, lower frequencies have thicker lenses and the Fresnel zone can be eaten up with ground interference or subject to more reflective losses or gains (picket-fencing)).

Now this sounds perverse but it is true, you can get some antenna gains too high. If you do not have a direct line-of-sight you might of been working the other station off of beneficial reflections from objects or terrain. On an omni antenna you can create a null under the antenna if you are mounted up really high with a high gain antenna. I have had systems where I benefited more by taking out a 10 dBi Yagi and putting in a 3 dBi omni. It improved my signal levels by up to 10 dBm.

You get what you pay for with antennas. A $50 antenna is probably not going to be really clear about their gain calculations and they may be based off of ideal installations or perfect SWR. More expensive antennas (commercial grade) will usually be tested on an antenna range to validate the modeling and will include antenna patterns in the V and H profiles (looking from the side, looking from the top).
Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
WALTERB
Member

Posts: 528




Ignore
« Reply #19 on: June 02, 2013, 08:46:28 AM »

M2 antennas is the premier provider of high performance VHF-UHF beams in the U.S.

Their website seems to be down today, not sure why...I suspect they had a server crash or maybe just updating the site.

Anyway, their 9L 2m beam is 14.5' long and handles legal-limit (1500W) power, and works very well.  But it costs quite a lot more than $100. Wink

They are distributed by HRO, Texas Towers, and others: http://www.hamradio.com/detail.cfm?pid=H0-000716

If the beam has elements on both sides of a supporting mast, the coax should not run down the mast; that defeats the purpose of using a non-conductive mast. Smiley

thanks, if I ever get off my butt and get my tower up I'll put it on it (provided I can figure out a way to get it to live with a hexbeam. )   Grin
Logged
WB2WIK
Member

Posts: 20603




Ignore
« Reply #20 on: June 02, 2013, 06:41:31 PM »

thanks, if I ever get off my butt and get my tower up I'll put it on it (provided I can figure out a way to get it to live with a hexbeam. )   Grin
Not so easily done, actually, and that's a good point.

Vertically polarized beams are way more critical to install than horizontally polarized ones.
Logged
AD4U
Member

Posts: 2167




Ignore
« Reply #21 on: June 03, 2013, 06:41:17 AM »

Walterb - You have been given some good advice.

However assuming that you do not live on a tall hill, that your antenna is "stuck" at 25 feet, and that you cannot put it any higher, IMO you can spend $100,000 for a 300 element yagi on a 600 foot long boom with 50dB gain and still not increase your range very much. 

In fact given your location as you stated previously, a simple 1/4 wavelength homebrew ground plane made out of brass brazing rod at 70 feet in a pine tree would PROBABLY out perform a yagi at 25 feet.

At VHF and UHF heighth is everything.

Dick  AD4U
Logged
WALTERB
Member

Posts: 528




Ignore
« Reply #22 on: June 05, 2013, 08:34:02 AM »

Walterb - You have been given some good advice.

However assuming that you do not live on a tall hill, that your antenna is "stuck" at 25 feet, and that you cannot put it any higher, IMO you can spend $100,000 for a 300 element yagi on a 600 foot long boom with 50dB gain and still not increase your range very much. 

In fact given your location as you stated previously, a simple 1/4 wavelength homebrew ground plane made out of brass brazing rod at 70 feet in a pine tree would PROBABLY out perform a yagi at 25 feet.

At VHF and UHF heighth is everything.

Dick  AD4U

interesting.  I might try that that. Would some sort of ground plane or better mast grounding help my current situation?

thanks.
Logged
AD4U
Member

Posts: 2167




Ignore
« Reply #23 on: June 05, 2013, 12:26:21 PM »



interesting.  I might try that that. Would some sort of ground plane or better mast grounding help my current situation?

thanks.
[/quote]

NO.  The only thing that will help you is more heighth.  The 1/4 ground plane or a similar omni antenna hauled up in the top of a tall tree won't be noticed by anybody.

Dick  AD4U
Logged
WALTERB
Member

Posts: 528




Ignore
« Reply #24 on: June 05, 2013, 01:31:19 PM »



interesting.  I might try that that. Would some sort of ground plane or better mast grounding help my current situation?

thanks.

NO.  The only thing that will help you is more heighth.  The 1/4 ground plane or a similar omni antenna hauled up in the top of a tall tree won't be noticed by anybody.

Dick  AD4U
[/quote]

thanks.  not worried about the appearance. my back yard already looks like a bunch of kids have been flying kites all over the place.  Grin

I assume its coax up to the top of the tree then the brazing rod cut to 1/4 wave for 2 meters, then keep it from making contact with the tree?  does it have to be oriented vertically, or does it matter?

thanks
Logged
K1CJS
Member

Posts: 6034




Ignore
« Reply #25 on: June 06, 2013, 03:22:12 PM »

Its just like trying to squeeze more juice out of an orange.  You might get a little bit, but not much.
Logged
Pages: Prev 1 [2]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!