Opinions on height........

[153]

Hey folks! I have a question. i am kinda new to the beam world. I have always run a maco v-5000 but several months ago put up a m-105. Here is my question. Me and a buddy have the same set up as far as beams. I know ther are other factors but the they are both really close when set up by a mfj 259. The only major differenc is his tower is 90 ft, mine is 60 ft, his elevation is 410, mine is 395. That equals 45 ft difference. OK now when we run the same power he is always 1 s unit above me. I have to run twice the power to produce the same signal to a given location of the same distance between us. Does 45 ft make that much difference? I have always heard that for every s unit you have to double the power so i guess thats right. What is opinions do yall have? Seems to me that height makes up more ground that power to a certain height. At what height do you no longer gain anything noticiable. THANKS

[Circuit Breaker]

There's debate on how much you have to increase your power to achieve an increase of 1 s-unit. Generally speaking, doubling your power will only get you an increase of 1/2 and s-unit. You would have to double your power twice to get 1 s-unit. That means if you were hitting your buddy at s-5 with 4 watts you would have to increase your power 6dB (3dB is doubling your power) or 16 watts (2*4=8...8*2=16) to move the s-meter to s-6. However, it isn't an industry standard. Are you both running the same radio? Both of your radios could be calibrated differently if they're by different manufacturers. His radio could be calibrated so that each s-unit is equal to 6dB and yours could be calibrated so that each s-unit is 3dB.

[153]

We are running to another station about 40 miles away.

[Circuit Breaker]

We are running to another station about 40 miles away.

Okay, let me see if I understand...you're talking to a third station not each other? 45 feet could make a difference if it puts some hills or other obstacles between you and the third station. Are you both the same distance away from the third station? What kind of antenna is the third station using? If he has a beam, maybe he has it pointed more towards your friend than towards you.

[153]

ground plane and we are the same distance. Thanks

[Red Warrior]

As I understand antenna theory, the optimum height of an antenna is 1 wavelength above the ground. At that height the antenna will perform at it's "free space" maximum. Going above that height will not improve the characteristics of the antenna but will improve line of sight. Line of sight could account for the difference.

Try this, get an inexpensive field strength meter and check your field strength a few hundred feet in each direction from your antennas. Compare the measurements. If they are similar (and I suspect they will be) then the difference in signal is being caused by line of sight. If your field strength is lower than your friends, then look for losses in your transmission line.

['Doc]

For all practical purposes the difference in height of those two antennas is 30 feet, not 45 feet. that's height above ground (AGL), not sea level (ASL), that makes a difference. That 30 feet would mean that your friend's antenna can see further away than yours. The horizon is further away as you get higher, see where that's going? That by it's self -could- account for the differences in signal strength reports. No idea if that's the only thing affecting it, but it could certainly be part of it.
The 'best' height above ground for any particular band changes as propagation changes. Sometimes lower is better than higher (angle of incidence). On a very rough average, more higher is more better, in general. Some of the variables of how dirt under an antenna affects that antenna sort of taper off at something over 1/2 wave length above ground. That's not a definite height, it varies according to how the dirt under that antenna varies, and on the particular antenna too. Most of that deals with how ground/dirt affect the input impedance of the antenna (and it does). At something like 1/2 wave length, that 'affecting' starts to get less noticeable, which can make tuning easier. After about a 100 yards of height, things start to really taper off. At least, so I'm told. Ain't never had nothing that high. But one'a these days!
- 'Doc

[153]

How tall is 1 wave length?

[Circuit Breaker]

1 wavelength for 27 MHz is approximately 36 feet.

[153]

Thanks all yall.

[153]

I believe I will just go higher and see what happens. Gone go 100 ft plus mast = 110ft I will let yall know the outcome. Man.....I just didn't want to climb that high but oh well.

[drdx]

Depending on your operating goal, you can go too high. It is entirely possible to get too high and make your domestic skip more watery and not as solid and when the conditions pick up, make the europeans stronger. If you like talking to other states, be aware that the extra height may hurt your effort. As doc mentioned, conditions vary. Among all of my reading, the only real general consensus is that 3 wavelengths is thought to be too high, and about 1.5 is good to be at, which is in the 50 foot range, but terrain will vary and effect it. For a better result, forget about just getting that one antenna way up. Get 2, one high and one low. Together they will increase gain, and apart one will offer better results than the other depending on conditions. They will need to be separated a good distance and that distance will vary depending on the antenna's gain and capture area, but think in terms of 36 foot separation. Use what is called a BLU switch setup, for Both, Lower, and Upper, to take most advantage of your setup by switching to the antenna with the best height for a given situation.

If you're sticking with a single antenna, instead of height considering you're already high, I'd go with a bigger antenna, maybe an 8 or 10 element, or a gizmotchi or something that is expandable for some real brute force. We had a local here once that did a 60 foot deal and was the laughing stock of the area. Up close his junk was too high to hurt us. Soon he figured it out. He had a crank up tower and ran it down to about 40 feet and killed us.

So this other guy has an s-unit on you to another station. Is this the case to all other stations or this one? There are many factors that effect it.

Something else to think about: All antennas differ. Sure, you may both have 4 element beams. But....what about the hardware, element diameter, taper schedule, reflector and director spacing, boom length, coax run, coax size, coax age, other antenna proximity, guy wire configuration, ground system, connections, ????? It all matters. No 2 setups are identical.

-drdx

[Circuit Breaker]

Is it THAT important that your signal is the same as your friend's? 1 s-unit isn't going to make much of a difference. There are going to be cases where your signal is stronger than his. You're never going to have the same signal strength to all the people you'll be talking to.

[153]

we just play around. We both have m105's set up the identical way only difference I forgot to mention is I have a 5k gamma and his is 10k. That may make some difference but I dont know. We just enjoy ourselves. I am currently having to run a 16 pill worldwide to keep up with his 2X4. So yea its that important.

[lonesome 500]

gamma makes no diff

height = might.......esp vert polarized

hey drdx...you ever hear watchamadoodle in uncertian tx?

m108 vert at 198'
m108 horz at 183'

[153]

I'm gone try going 100ft and thats it. No taller. If that don't work I'll just go fishing!!!!!!!!!!!1

[highdrive]

If you gotta run a 16 pill to keep up with a 2x4(4pill)...something else is wrong. Or either your friend is'nt playin fair and puttin more power out. Also, if your antenna is closer than 36' to the house or another antenna...it will detune and distort the pattern of the beam

[Circuit Breaker]

gamma makes no diff

height = might.......esp vert polarized

That's hard to say. I know height above ground will affect horizontal radiation patterns...which is why the big amateur radio contest stations have antennas at varying elevations. The lower antennas get them contacts closer to their location and the higher antennas get them the long haul stuff. It might work in reverse on vertically polarized antennas. A vertical mounted on the ground with 60 or so radials will have a very low angle of radiation which is great for DX...but not so great for local communications.

['Doc]

I really don't think I'd worry much about the radiation patterns of vertical/horizontal polarization. If the antenna is the same, then the pattern is gong to be basically the same. There can be some differences but those differences are very seldom noticeable at all. That's the pattern of radiation, not the polarization of it, there can be sort of big differences there, which is typical/normal.
As far as how far away from the house, etc, also not worth spending too much worry on. Everything around that antenna is going to affect it's radiation pattern, and there are always going to be something that sort of 'deforms' that pattern to some extent. If you measure that pattern to see what it looks like, don't expect the 'classical', pretty shaped thing shown in most diagrams. The only time you ever see those is on paper, none are absolutely symmetrical. That's one reason why the same antenna produces differing results for different people. As long as that 'deformation' doesn't get really, really weird, the typical user will never know it.
- 'Doc