base antenna setup question

[ocean pond]

I am new to anything to do with base units or antennas so please someone help me with this. I got a 20 foot aluminum pole I want to setup with an A-99 antenna and wondering about if I was still in a wave-length with this height? Thanks

[gun runner]

I'm not sure of the heights of wave lengths .I think there are 3 .The 2ND is better for skip its around 50ft . You can talk OK at 20 ft but its A big difference if you can get over about 40ft . and ground ,ground,ground .

[DX_MONKEY]

I don't believe it matters with this antenna. The Antron is isolated from the mast....it will ignore the mast. Use any mast arrangement you want.

[southerntrucker]

thats about how tall iv got may antron 99 and i get out a good ways with my little galaxy

[rev ike]

genaral consensis would indicate height=might so the higher the better 20 is good but if you can get about 35'thats decent.

[linx]

I've ran a IMax in the range of 20 ft all the way up to 50 ft to the bottom of the antenna, and the higher the better, lol.

It will work fine wherever you put it however. Even on the bumper of your car :p

[Circuit Breaker]

When it comes to doing skip/DX, the height above ground will make very little difference on a vertical antenna. Height will only really make a difference on local contacts.

[ocean pond]

People thanks for the help! So what I am gathering(I think) is that height is from the bottom of the antenna to the ground? Or is it from the tip of the antenna to the ground? Also, is it ok to run two lengths of coax? because I want to be able to disconnect my setup from the base of the pole when foul weather calls.

[drdx]

We're talking from the base of the antenna to the ground here. Height above ground does make a difference in the radiation angle and an optimum height is thought to be 1 to 3 wavelengths (35-90 ft) for dx, and locally the advice above applies. Most likeley, the higher the better. On dx height, it is possible to get so high that your main radiation angle lobe is very low and will start to make your signal "watery" on short skip, such as in the USA, but will excell on long path action to europe, australia, etc. I like a base of 34 feet or so for local and moderate dx, and it is a good height for being low maintenance in the support depart That said, I've had luck in the past on in country skip with a ground mounted quarter wave (a butternut) antenna, although it suffered locally. The closer to the ground, the more the ground comes into play, and if you are using a radial system, the more radials are needed. As you move the antenna up, fewer radials are needed, and for 1/2 wavelenght (17 ft or so) and above, 3 or 4 will do fine for groundplanes. Coax wise, you can use as much as needed but quality and length will effect signal loss and you want as few connections as possible. -drdx

[THE WATCHMAN]

MY COLEY ENFORCER IS ONLY 25 FEET OFF THE GROUND AND IT WORKS GREAT. I WOULD LIKE FOR IT TO BE HIGHER BUT FOR NOW 25 FEET IS ALL I CAN DO. IF A 20 FOOT POLE IS ALL YOU HAVE THEN I SAY USE IT. YOU CAN GET IT HIGHER LATER ON DOWN THE ROAD.

[Jester]

Like most people have reiterated, it wont matter with this antenna. If you are doing a chimney mount on the roof, all you need is a chimney strap ratchet mount from Radio Shack and some mast, which it sounds like you have. 20ft may be a little too much but I am not sure, at least in the sense that the mast+antenna will be pretty long. I always used an 8-10 foot mast with the antenna, but you should be just fine. Good luck and may you have plenty of good DX!

73,

Jester #943
Downers Grove, IL

[TwentyTwo-Zero]

I agree with drdx on this one.

True, you can mount your antenna at just about any height you like and it will work. However, for the most efficient performance from your antenna it should be mounted at a height that is a multiple of the frequency (in this case 11m) that you are transmitting on.

You can find some relevant info about antennas and how mounting height affects them [Please login or register to view this link]

[samskip]

genaral consensis would indicate height=might so the higher the better 20 is good but if you can get about 35'thats decent.

True....For local contacts


For skip, your antenna height doesn't matter too much. Just get above near by objects that would block signals. Large buildings, other homes etc.

However, I run my 21' vertical antenna 8 feet off the ground at the feed point and I get 5/9 reports.

Locally speaking take every foot you can get, when it comes to skip, it won't make a massive difference. Run it on the ground with a tripod and I know you'll get out just fine...

[countryboy]

just my two cents but i have my copy stick on a 25' pole, mounted on a 5' pole cemented in the ground. well only 5' is above the ground.... anyway the top of my antenna sticks about 3 feet above the closest tree . i seem to have no problems geting out...

now i would like to get a 40 foot tower and put my antenna up higer...

but thats just my thoughts...

[crazytruker]

DRDX is exactly correct. The antenna will "see" the ground around it and the angle of radiation will be affected. If you live on a hill where the terrain is lower then antenna height can be shortened with good results. If the terrain is higher as in living in a valley then the antenna height must be higher. Terrain height around you will affect the angle of radiation as the antenna, as it is said in layman's terms, will see the terrain. Generally, higher angles of radiation benefit local talking and close skip. Close skip can be defined as 500 - 1000 miles. Now if you are wanting to talk around the world, such as Hams do, then you want a lower angle of radiation. Imagine in your mind that you are looking at your antenna and mast from the side. Or simply draw a straight vertical line on paper. If you draw a line out from the antenna at say an 18 degree angle it will travel further and further away as it increases in distance from the antenna and in angle to the ground. The earth curves so the lower angle of radiation goes further and as the signal bounces it bounces around the earth. A higher angle of take off from the antenna, say 25 degrees, will go higher faster and bounce back down closer than a lower take off angle, thus giving you a stronger signal locally and for close skip. There will be experimenting to be done on your part with lowering and raising the antenna height to achieve best the best angle of radiation that works best for what you are trying to achieve. But that can be done as "the fun" part of the hobby. An antron 99 is not a 5/8 wave antenna. I don't know if they claim it to be or not. If it is claimed to be there is a web site that proves this fact wrong. An Imax 2000 however, is marketed as a 5/8 wave antenna but it is actually a 0.64 wave antenna. That is even better. It is said that the Imax 2000 antenna is the only antenna to be made in a very long time that is a 0.64 wave antenna and that a 0.64 wave antenna is a "little known secret" in antenna design for achieving very low angles of radiation and maximizing skip conditions and success. IMHO, I would go with an Imax 2000 over an A99 any day of the week. The A99 was and still is a decent antenna but IMHO again, it is the K40 of base antennas. It had its day in the sun and did it's thing at one time but over time designs and build quality have left it in the dark for performance.

[ocean pond]

Back to the forum, was unfortunately off the PC for a week&half on some work I was doing. I'm absorbing all the great info(thanks guys) and got some more questions. First off I originally had (3) 10 ft. sections of threaded aluminum conduit that I was going to cement in the ground 4,5 ft. deep. Now I was wanting to add another 10 ft section to that and was wondering what position(height) up the mast I need to add guy wires and how would I insulate them from the mast? Getting back to the sections they are 10 ft of 2 in. diameter, 10 ft. of 1.5 in., and (2) 10 ft. sections of 1 1/4 in. that would be connected with coupling(note the 10 ft. of 2in. conduit wont have to be lifted, lol).

[Rico]

People thanks for the help! So what I am gathering(I think) is that height is from the bottom of the antenna to the ground? Or is it from the tip of the antenna to the ground? Also, is it ok to run two lengths of coax? because I want to be able to disconnect my setup from the base of the pole when foul weather calls.

Why would you want to do that? Invest in a lightening arrestor thingamijig.

[TwentyTwo-Zero]

If you haven't yet, go back and read the info (as I suspect crazytrucker did) in the link I provided in my previous post. It contains detailed info regarding the height of your antenna. The height of your antenna will determine where it does it's best "talking". Keep in mind the height referred to is at the base (bottom) of the antenna. As far as guy wires go, you can use either metal or plastic (parachute) rope. The plastic variety is preferred by most since it will not resonate your signal. The plastic rope does not need to be insulated from the mast. If you use metal, you will need to break up the length of it using porcelain egg insulators. Install an egg at the guy wire ring on the mast, one or more (depending on length) to break the guy wire into shorter lengths and one more where the guy wire terminates to the tension adjuster. This will insulate the guy wire from the mast. I think it was drdx that once posted that he made the upper length of his guy wires into a ground plane. Perhaps he will jump in with further detail. A lightning arrestor (as previously mentioned) is highly recommended.

[Pocono Redneck]

If you do not have or plan on acquiring a lightning arrestor you can always do what folks have done for years....power down and disconnect the coax from the back of your radio (not at the antenna end) when T-storms are approaching. Some folks toss the end of the coax out the window and some drop it into a ceramic or glass container. Personally I disconnect mine and stick the end in a heavy ceramic beer stein right outside my sliding door (which is next to my desk)

When I re-do my shack this spring I will add a *real* lightning arrestor, but until then at least it won't toast my equipment if I have a strike here.

[drdx]

Hey, on the guy wire radial deal, I have, in the past made a ground plane from the guy wires by having the guy wires come down 1/4 wavelength, or about 8 1/2 feet, to form radials. When the slope downward, they radiate. I've tried this with 2 antron 99's side by side, and the one with the radials had exactly 1 full needlewidth increase on reception, using same lengths and types of coax on a switch comparing signals, and the one with the guys was a little lower by about 15 feet. If you have the length, you could even triple that length for 3/4 length radials to help lower radiation angle, but be careful as you might invite TVI. Play with it. You're guying it anyway, might as well have them work for you. I read in an orr publication that the sloping radials on a 1/4 wave groundplane can add as much as .3 db, and on a longer (1/2 or 5/8, or .64) may help more, but on a 5/8 you may benefit more from the 3/4 length variety. I have read that the longer 5/8 and .64 are more difficult in the ground plane department, and using horizontal radials, it is often necessary to do the 3/4 deal if you have the room, so I would think in a sloping configuration the same may apply, but experimentation will tell you. It's free to try, and if you don't like the outcome, just bust them up with insulators. I see a lot of talk of the .64 vs. 5/8 wave, and there is only a few inches difference, so I question any performance difference. If you're homebrewing a vertical, 5/8 is fine, it is basically 3/4 wave that is 5/8 high with the rest in the form of base loading. Don't go with a full 3/4, or wave/radiation angle is thought to be too high yielding diminishing returns. I have often wondered if a 3/4 will have a radiation angle high enough to benefit in the short skip department. -drdx