SIRIO SD-27 Dipole

[W5LZ]

Don't get too wrapped up in that 'gain' thing. That dipole is what all other antennas are compared to, and except for the directional antennas, and the arrays, there are very, very few antennas that have much 'gain' over a dipole anyway.
Most antenna 'gain' figures are either imaginary (isotropic) or a figment of the advertising department's imagination, to put it nicely.
If you want to try a particular 'type' of antenna, do so. Any antenna is only going to work as well as it's environment will allow, no matter which/what kind it is. Sometimes that works out very nicely, some times not. What works well in my backyard may be terrible in yours. What else is new?
If you ever find that absolutely bestest in all cases, gorgeous, miracle antenna, would you let me have one too?
- 'Doc

 

[Lazybones1222]

. Don't get too wrapped up in that 'gain' thing. That dipole is what all other antennas are compared to, and except for the directional antennas, and the arrays, there are very, very few antennas that have much 'gain' over a dipole anyway. What works well in my backyard may be terrible in yours. What else is new? - 'Doc

Doc,

That is so true, but many don't get that. I bet that dipole will be a better antenna than a a99, Imax ect just because of it's design. The rf has two equal lengths to push against. I have read and read and read about the no radial "stick" antennas, and just can't visualize in my mind how they work so well, and if you read the threads - people can't agree on how they work either.

I KNOW and can visualize in my mind how a dipole works, and dipoles work very well. If you don't have the room for a real ground plane antenna with radials like a Maco V58 or I-10k, then I like that dipole.

Now if I only had room for a tower and a beam, then I would get excited about gain.

 

[Mr Clean]

I had two avanti 160 ramrod antennas. Just about the same as the siro but made thiry something years ago. Gave one to my brother in law for his summer home in florida. May take the other one to florida this spring and get it up high on a condo down there. Think I will take it and my 95t with a 35 amp supply and see how it does.

 

[Wire Weasel]

Doc,

That is so true, but many don't get that. I bet that dipole will be a better antenna than a a99, Imax ect just because of it's design.

I'll take that bet....especially against the .64 Imax 2000

A dipole is a dipole....gain wise. Doesn't matter how it's built or if it's made out of solid silver rods. Gain will be the same.


just sayin'

 

[Lazybones1222]

Ok, help me understand then. How does a piece of fiberglass with a loading coil and a piece of wire with no radials get gain? What does the rf ac wave push against (in slang terms)?

I am not trying to be a wise a$$, but I have read the arguments on the stick antennas and I just don't get it. The big stick coaxial sleeve type I understand (it is a dipole), but the A99 and the IMAX, I don't get. Do they operate like a j-pole or an end fed zepp? Me no understand.

 

[Wire Weasel]

They worky SUPER DUPER !! Just ask Robb! Git yer an Imax 2000 and put it up. You'll sell everything else cheap and won't look back.

 

[Lazybones1222]

Are you pulling my leg? Is the IMax a shunt fed dipole?

 

[Robb]

Well, I do use the IMAX presently, but will be getting a 4 element beam up pretty quick. I have talked to every state in the US - except for some of New England (Maine, Mass, VT, NH, & Connecticut). Including Canada, Mexico, Hawaii and Alaska more than a few times. Curacao Islands, Trinidad, New Zealand, Brazil, Argentina, and Australia several times as well. It'a $100 wonder - w/o the ground plane kit and using only 50 watts PEP SSB. I'm pleased with its performance at this point when conditions have been favorable - yes. Local use is superb too...

 

[n9zas]

Read the ARRL amateur radio handbook for starters! You'll learn a great deal about how antenna theory works and the practical applications used for ALL types of antennas. Then you'll understand how the "gain factor" works!
n9zas

 

[Lazybones1222]

Ok - have that - but what kind of antenna is an IMAX? A shunt fed dipole? A zep, a J-pole?

 

[n9zas]

The IMAX is a cb antenna...OR were you referring to the Hi-Def movie theaters?
n9zas

 

[Lazybones1222]

The IMAX is a cb antenna...OR were you referring to the Hi-Def movie theaters?
n9zas

haha - That is funny, and this thread is too. Check this out from:

End-fed Vertical and J-pole

You need to go there to see the pics. Seems the modeling software no likey the Imax.

I-Max 2000 Solarcon A-99 Antenna

The following model is an I-Max 2000 5/8th wave vertical with a vertical feedline or mast connected to the antenna base, and no radials. In this case I picked the worse case multiple of feedline or mast length:

Feedline current is 100% of antenna current. This illustrates why so many people complain about SWR problems and RF in the shack with end-fed verticals like the I-MAX 2000! Other people do not complain and seem to love the antenna. This is because some people pick a lucky mast height or feedline length, while others are not so lucky. They chose a mast height, feedline length, or grounding system length that enhances common mode.

Here is the pattern of an antenna that copies the I-MAX dimensions and feed system:

This is a NEGATIVE gain antenna at low angles. A 1/4wl groundplane would seriously out-talk the I-MAX 2000 or any other 1/2 or 5/8th wl antenna that does not have a large groundplane.

Even if we use the optimum feedline and mast length, here is the very best the end-fed antenna will do:

In this case we now have 2.67 dBi, which is actually a little less than a 1/4wl groundplane will do! The severe common-mode mast and feedline currents make "no-radial" verticals extremely sensitive to mounting height, mounting structure, feedline length, and grounding. This is NOT normal for antennas, it is a sign of a design problem.

 

[Wire Weasel]

haha - That is funny, and this thread is too. Check this out from:

End-fed Vertical and J-pole

You need to go there to see the pics. Seems the modeling software no likey the Imax.

I-Max 2000 Solarcon A-99 Antenna

The following model is an I-Max 2000 5/8th wave vertical with a vertical feedline or mast connected to the antenna base, and no radials. In this case I picked the worse case multiple of feedline or mast length:

Feedline current is 100% of antenna current. This illustrates why so many people complain about SWR problems and RF in the shack with end-fed verticals like the I-MAX 2000! Other people do not complain and seem to love the antenna. This is because some people pick a lucky mast height or feedline length, while others are not so lucky. They chose a mast height, feedline length, or grounding system length that enhances common mode.

Here is the pattern of an antenna that copies the I-MAX dimensions and feed system:

This is a NEGATIVE gain antenna at low angles. A 1/4wl groundplane would seriously out-talk the I-MAX 2000 or any other 1/2 or 5/8th wl antenna that does not have a large groundplane.

Even if we use the optimum feedline and mast length, here is the very best the end-fed antenna will do:

In this case we now have 2.67 dBi, which is actually a little less than a 1/4wl groundplane will do! The severe common-mode mast and feedline currents make "no-radial" verticals extremely sensitive to mounting height, mounting structure, feedline length, and grounding. This is NOT normal for antennas, it is a sign of a design problem.

Whatever. They work and work wonky great. Everybody I know who has one, uses one, is a longer antenna then what they were using before....LOVES THEM and testifies to increased signal on both ends.

I don't care how they work or if they are made from monkey guts...they work....and NO...I won't sell you mine. Get your own

 

[Lazybones1222]

Now that is funny.

 

[Lazybones1222]

Well, I do use the IMAX presently, but will be getting a 4 element beam up pretty quick. I have talked to every state in the US - except for some of New England (Maine, Mass, VT, NH, & Connecticut). Including Canada, Mexico, Hawaii and Alaska more than a few times. Curacao Islands, Trinidad, New Zealand, Brazil, Argentina, and Australia several times as well. It'a $100 wonder - w/o the ground plane kit and using only 50 watts PEP SSB. I'm pleased with its performance at this point when conditions have been favorable - yes. Local use is superb too...

Here is one for you Robb, thought it appropriate.

from : Antenna Myths

The DX Myth

No doubt, the single, most often used reference (past the point of triteness) is the number of DX stations said antenna installation garnered. How or why this practice got started is an unsolvable mystery. As condescending as it may sound, amateurs who use their DX contacts as a reference, typically have the poorest of installations, and the worst of operating skills. If your intent is to be a LID (very poor operator), then visit this web page.

Just for the record, the number of DX stations worked has no correlation to any antenna parameter.


Just for fun:

How to sound like a LID