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Author Topic: Vertical vs beam  (Read 4260 times)
N3ANO
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Posts: 33




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« on: May 02, 2017, 09:30:51 PM »

40 years a ham but new to vhf/uhf base operation. I have a Diamond 510 dual band which has about 6db real gain on 2m. I know a beam will have more gain and thus perhaps allows me to hit a farther repeater. I'm assuming I'll have stronger received strength too
Correct? I feel a little stupid for asking but want to know.
Kind replies only please,thank you. Torry N3ANO
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KB2WIG
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Posts: 344




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« Reply #1 on: May 02, 2017, 09:58:08 PM »


T,

Well, using a  beam may make you pay a premium to hit a vertical fed repeater. Cross-polarization tends to reduce the signal level. Now, a vertically polarized beam, and a "vertical" repeater, you'll be cooking with gas.


klc
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WB6BYU
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« Reply #2 on: May 02, 2017, 10:02:05 PM »

Quote from: N3ANO

...I know a beam will have more gain and thus perhaps allows me to hit a farther repeater...



That depends on what type of beam you put up, of course.

The Diamond isn't quite tall enough to get a full 6 dB gain over a dipole on 2m, and the dualbanding
process probably drops it a bit as well.  A 3-element yagi or a 2-element quad might be slightly stronger,
but not a big difference.  A longer beam will do better than the omni vertical.

The problem with a beam, however, is that you have to point it in the right direction.  If you are trying
to hit multiple distant repeaters, that means the addition of a rotator.  (Or multiple fixed yagis, which
may be more practical, especially when you are building them yourself so they are cheap.)  You probably
can hit the local repeaters regardless of the direction that the beam is pointing.

Are there repeaters that you can currently hear (perhaps in the noise), but can't access due to signal strength?
If so, then a medium-length beam could help you hit them.  The longer the boom, the higher the gain, and
the narrower the radiation pattern, meaning that aiming is more important.

The most important parameter, however, is generally height.  It may be easier to get your current
antenna up higher in the air, which will improve the signal at distant repeaters without requiring a rotator.
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W8JX
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Posts: 12080




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« Reply #3 on: May 03, 2017, 03:18:20 AM »

For FM a good vertical up as high as possible is tuff to beat. I have had a Hustler G6 (5/8 or 5/8) up for over 20 years now. It is about 40 feet up at base and it gives me access to repeaters in Columbus, Cincinnati Richmond IN, Lima and points in between. Works well on FM simplex too. A large 2M beam vertically polarized can extend range and allow you to be more selective if you are bringing up more than one repeater on same frequency. I like the simplicity of the vertical because you never need to turn it, easier to get up higher and it has high survivabilty in extreme weather.  I do prefer the Hustler G6/G7 series for this as they are a lot stiffer than fiberglass antenna and are less effected in coverage in high winds when can bend a tall diamond style antenna and effect its pattern/gain.
« Last Edit: May 03, 2017, 03:21:09 AM by W8JX » Logged

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Ham since 1969....  Old School 20wpm REAL Extra Class..
AA4HA
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Posts: 2375




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« Reply #4 on: May 03, 2017, 09:48:51 AM »

A vertical will usually be vertically polarized; that is pretty standard for FM operation.

Beams may be vertically or horizontally polarized. Elements parallel to the earth indicate that the antenna is horizontally polarized; straight up and down is vertically polarized.

Horizontal polarization is pretty standard for SSB operation.

----------------
Cross polarization (vertical polarization at one site, horizontal polarization at the other) is very inefficient. Often the cross-polarization losses are up around 20 dB. Using a vertically polarized antenna for SSB or a horizontally polarized antenna for FM is going to preform very poorly.

----------------

Vertical antennas are often omni-directional in coverage.. they radiate equally as well in all directions to the horizon. This is popular for repeaters or for operations where you do not want or need to point the antenna to a station or if you are working multiple stations on different azimuths at the same time.

Beams usually require a rotator to point the antenna to where the gain is the highest. Some may be fixed, if you were using a radio to just talk to a single base station 30 miles away or on a point to point link.

-----------------

Depending upon your mode of operation (are you an SSB'er or do you spend all of your time on FM repeaters) should determine what type of antenna you end up with.

If you are working DX and going for distance and/or weak signal then you probably want a beam. Beams (or miniflectors, paraflectors, etc..) can have gains of 14-16 dBi. Omni's (whips, co-linears, folded dipoles) become fairly large when you get beyond 3-6 dBi (depending upon the band).

Many beams can be vertically polarized or horizontally polarized, depending on if you set the elements parallel to Earth (horizontal) or up and down (vertical).
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
Free space loss (dB) = 32.4 + 20 × log10d + 20 × log10 f
N3ANO
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Posts: 33




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« Reply #5 on: May 03, 2017, 04:58:00 PM »

We'll thank you all for the replies. I am aware of polarization issues and the need for a rotator. I don't have funds or means to install a beam at this time. My vertical is only up 8 foot on a concreted mast. Best I can do for now. I'm at 1180 feet on a hill in the clear. I can hit all nearby repeaters, with farthest so far 72 miles away. These sites are all at higher elevations I'm sure. So I'm happy for now. I do full duplex crossband repeat so all are within reach using a half watt with my ht. Thanks again.
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ONAIR
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« Reply #6 on: May 03, 2017, 05:39:31 PM »

I use an ELK 2m/440 beam, and it greatly outperforms verticals!  It even works well indoors!!   Smiley
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G8YMW
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Posts: 651




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« Reply #7 on: May 03, 2017, 05:47:35 PM »

With your setup, I would suggest getting the mast up higher.
Clear of the house would be as good as you could get height wise and of course, decent coax
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73 de Tony
Windows 10:  Making me profane since March 2017
W8JX
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Posts: 12080




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« Reply #8 on: May 04, 2017, 03:26:51 AM »

With your setup, I would suggest getting the mast up higher.
Clear of the house would be as good as you could get height wise and of course, decent coax

Height of ground is a big factor in range/coverage. The first 40 or 50 feet making the biggest difference.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
AA4HA
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Posts: 2375




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« Reply #9 on: May 04, 2017, 07:34:31 AM »

It is interesting in what happens to an antenna's radiation pattern when it is too close to the ground (or ground plane).

I had mounted a 10 dBi 900 MHz Yagi antenna on a water tower in Shreveport Louisiana for a 1 watt transmitter (902-928 MHz ISM band, spread spectrum frequency hopping radio, 5 watt EIRP). It had to go the distance of 5 miles to a 6 dBi omni that was 40 feet off the ground.

Clear path, no terrain, buildings or vegetation.. feedlines were all 1/2" Heliax, after losses the EIRP was right at 36 dB (legal limit for that band).

I could not get a received signal of better than -97 dBm, completely perplexing; It should of been around -74 dBm after all of the antenna patterns, elevation differences, up/down tilts were all taken in to consideration. Losing 23 dB of receiver signal was totally unacceptable; I was convinced I had a bad antenna or a bad coax connector, I sent crews up the water tower twice to redo things and the results never got better.

So I climbed the water tower myself; The Yagi antenna was mounted approximately 4 feet above the steel roof of the tank. Due to the curvature of the tank I could not see this from the ground.

I had them put up a 10' mast on the roof and mounted the Yagi to that. Suddenly the signal level jumped up to -77 dBm. I recovered 20 dB of received signal.

The height alone was not the issue, the water tower was more than 100' above the ground.

Being so close to the steel roof the take-off angle for the Yagi was severely affected. Instead of shooting straight off of the end of the antenna it was deflected upwards by about 30 degrees. The line-of-sight path was in a 20 dB null of the modified antenna radiation pattern. I verified this with another antenna setup on the steel roof of our building and using a test receiving antenna about 100 feet away on a mast where I could raise and lower the height.

So I again learned just how much influence nearby objects have on antennas. You can have a great looking SWR but if the gain of the antenna is not going in a useful direction you might as well try transmitting in to a 50 ohm resistor.
« Last Edit: May 04, 2017, 07:38:08 AM by AA4HA » Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
Free space loss (dB) = 32.4 + 20 × log10d + 20 × log10 f
K0RGR
Member

Posts: 138




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« Reply #10 on: May 04, 2017, 01:24:12 PM »

A beam can turn a marginal signal into a good one, or allow you marginal access to distant repeaters you can't reach with a vertical.

72 miles sounds like you are already pushing the limits for most FM work.

Now, if you were doing SSB, a horizontal yagi would make a huge difference. Horizontal antennas actually work better for DX than verticals do. We only use verticals for convenience. Even low to the ground, a horizontal beam works better for SSB, but pretty much not at all for distant FM.

I have a big vertical at about 50 feet up. With that, I can usually hit repeaters out to a 35-40 mile radius. On SSB, with a horizontal 10 element beam, I can usually work out to similarly equipped stations 2-300 miles away. If we used horizontals on FM, you'd see a big improvement, but we don't.
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KC2MMI
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« Reply #11 on: May 05, 2017, 04:44:31 PM »

Bear in mind that one antenna is only one half of a pair, and as they say 'it takes two to tango".

If you have a great +50db antenna, and the other guy just has a 6db stick...You may find that he can hear you but you still won't hear him, his signal is still going to be weak and the s/n level is not going to change, so you'll pick up "more" noise as well as the weak signals.

Your money would be better spent trying to get your antenna up higher, since VHF/UHF range is very dependent on line-of-sight. If you look online there are line-of-sight range calculators, and you can see just how much greater your range will be for every couple of feet higher that either (or both) antennas are.

And you won't have to play with rotors and trying to direction find the other stations.

Not to say that a directional antenna and rotor aren't good things, but unless you are trying to work other stations that will have similar equipment, I think plain antenna height (and low-loss coax, etc.) will be the better bet.
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AA4HA
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Posts: 2375




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« Reply #12 on: May 05, 2017, 06:26:20 PM »

If you have a great +50db antenna, and the other guy just has a 6db stick...You may find that he can hear you but you still won't hear him, his signal is still going to be weak and the s/n level is not going to change, so you'll pick up "more" noise as well as the weak signals.

I think you are confusing transmitter power output Txo with antenna gain. Usually if you are both operating at the same transmitter power outputs and have the same receiver sensitivities the gains are reciprocal (the link budget numbers work out to be roughly the same).

Now if you have a higher power transmitter than the other station; Then indeed it will be different as the link budget calculates differently in one direction than it does in the other.

I qualify that with a "usually" because there are times where you do get one-way path behaviors.

Also what gets messy is when you run high gain antennas, the antenna gain pattern becomes much more compressed. "You don't get somethin' for nothin'" and antenna gain is always traded off for all of the different directions an antenna can work. A good example is an idealized antenna (that does not exist) known as an isotropic radiator; It sends signals out the same in every direction (a perfect ball). Isotropic numbers are only useful as a comparison to a dipole antenna (dBi vs. dBd where dBd has 2.14 dB more gain than an isotropic radiator because it is a dimpled ball).

Outside of upper millimeter wave frequencies with some really crazy antennas you would never see any antenna have more than around 30 dBi of gain. Getting higher gains at any amateur frequency would be crazy-large (like a radio telescope).
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
Free space loss (dB) = 32.4 + 20 × log10d + 20 × log10 f
AA4PB
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Posts: 14300




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« Reply #13 on: May 05, 2017, 07:02:10 PM »

A 50dB gain antenna is going to add 50dB to both the transmit and the receive signal. In addition, the narrow pattern of the 50dB antenna will reduce noise picked up in directions outside the main lobe and may actually reduce the total noise at the same time it adds many dB to the signal.

When I was active in MARS I had a need to copy RTTY signals being sent from a VHF repeater about 80 miles away. With a gain Omni antenna I couldn't get any copy on many days and very marginal on the best days. I replace the Omni with a pair of phased, vertically polarized 11 element Yagis pointed at the repeater. The signals were then solid copy every day.
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N8EKT
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Posts: 580




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« Reply #14 on: May 23, 2017, 04:27:46 PM »

those high gain omni antennas  have only about a 7 degree beamwidth on UHF which causes large signal fluctuations when the wind moves them around so they are a very poor choice on 440 and they only have about 16 degrees of beamwidth on 2 meters

A typical 5 element yagi will produce about 11dbi gain
and will have a vertical beamwidth of 47degrees

A massive improvement over the High gain fiberglass omni antennas

so yes, beam antennas are the only way to go
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