imax vs i10k

[Moleculo]

If you want something scientific to study for a while, go research in the ARRL Antenna book and the ARRL Handbook how an end fed entenna without any ground plane radials achieves counterpoise. To save some trouble digging through it (the books can be a little tough to find details sometimes), it uses the coax braid. I know that in this example the Imax in question had the ground plane kit, but I believe if you research the topic thoroughly in the books, you'll find that the Imax ground plane radials are the wrong dimensions (if I'm wrong about this, someone help me out).

Another technical (read scientific, if you like) problem with the Imax is the design of the matching section. This has been pointed out a few times but dismissed as hear-say. If you study the circuit, it's easy to see that it is designed such that if the antenna comes in contact with electrical lines, it will blow the matching section to isolate the antenna from the feedline and any equipment down the line. Basically it acts like a big fuse. Unfortunately, the side effect is that it limits the amount of power the antenna can handle (which isn't really what we're discussing), but also is a fairly inefficient method for matching. The result will definately be some loss delivered to the radiating element over a better matching system. How much? I don't know, but there will be some. I'm not positive, but I believe this is also why the groundplane kit has the radials at 45 degree angles. Lowering the angle of the radials on an antenna really only serves one purpose, which is to raise the impedence of the antenna. However, one would think that if the matching system was effective, you wouldn't need to do this. I realize that changing the radial angles will probably also change the radiation angle, but that is not why it is usually done.

Anyway, I say use whatever antenna makes you happy. But if you're really interested, there is plenty of documented material on what makes for good antenna design. Start with the ARRL books I mentioned. But also remember, that a lot of this stuff is theory and the guys that write these books also typically work for antenna companies. If they work for antenna companies, they're not going to divulge all their companies research and secrets. Something to think about...

 

[Michael Bravo]

That's why they have so many different antennas available, some people like one, other people like another. Not only that, but I can see situations where someone wants short range communications, and a simple A99 is perfect... it's easy to set up, match and mount on the supporting structure.

so by the I10-k having a lower angle of radiation it is actually at a disadvantage compared to the Imax 2000 in short range transmissions and still had the same S-unit reading on 194's radio which would make it better than the Imax in that respect?

Thanks for proving the I10-k is superior 194.

 

[W5LZ]

Something to keep in mind is that whatever an antenna's highest(lowest) radiation angle, it also uses all of them up to that maximum(minimum) angle. How well it 'hears' just depends on propagation to a large extent. (It will 'talk' as well as it 'hears' by the way.)
As to which is 'best'... I ain't getting into that can of worms. Far as I'm concerned, there ain't no such thing as the 'best' antenna.
- 'Doc

 

[Unit 194]

I have been using my chimney mounted Imax 2000 with the GPK for approximately 6 years. Over the course of the past 6 years this antenna has survived the rain, snow, hail (golf ball sized), wind storms (75 MPH gusts) and temperatures as high as 103 and as low as 5 degrees. This antenna currently shows NO visible signs of wear and tear (cracks, etc.).

As far as the performance of my Imax is concerned, it has very good RX and TX and I also have low SWR's (1.2) in my current application. I have had no problems with TVI as long as I am not running excessive power. The antenna is still performing as well today as it did 6 years ago.

I am very satisfied with my Imax 2000.

 

[Marconi]

I tend to agree with 'Doc here. I have found over a long time span that all of these 11 meter antennas seem to work about the same if the overall height is within a 60' limit. The next factor I find important is how an antenna handles the noise level when conditions are generally quiet. Sometimes this makes a big difference and I find that generally my Imax is always heavy on the noise level compared to some others.

My I-10K works fine except when it rains. It is build stronger that any other ground plane antenna I know of. I am currently working an A99 at 35' and a .64 Wolf Radio Ground Plane at about 30' and I can hardly tell a difference. Depending on the TX'ings station's location often determines the signal strength noted. Sometime the audio level of the TX'ing station is louder on the .64 and I noted that also when comparing it to the I-10K a while back.

Biggest problem I had with my Imax was and is feed line radiation, common mode currents (CMC). It is the worst among the whole bunch in that regard. I have also had A99's that exhibited the same problem. However the A99 I am working right now, a very old one, does not show the same bad nature.

The install factor and cost of both the Solarcon products cannot be equaled and they both transmit very well, CMC or no CMC.

 

[Switch Kit]

Something to keep in mind is that whatever an antenna's highest(lowest) radiation angle, it also uses all of them up to that maximum(minimum) angle. How well it 'hears' just depends on propagation to a large extent. (It will 'talk' as well as it 'hears' by the way.)
As to which is 'best'... I ain't getting into that can of worms. Far as I'm concerned, there ain't no such thing as the 'best' antenna.
- 'Doc

I really don't know who this dude is ? But 99.9% of the time , he always seems to have all the right things to say. Think I've might have even learned a few things from this dude "The Antenna Wizard" Thanks Doc !! You Rock !!

 

[Master Chief]

So I guess it would be a bad time to bring up that fact that the Sigma IV is only a 1/2 wave.....

 

[Michael Bravo]

So I guess it would be a bad time to bring up that fact that the Sigma IV is only a 1/2 wave.....

:shock:

 

[W5LZ]

'Chief,
Sometimes, you just ain't right.
- 'Doc

 

[bob85]

half wave hahahahhahahhahahhahahhahahhahahhahhahah :roll:

 

[Marconi]

Well MC, maybe you should start a thread about this vision you have with the Sigma IV. We talked about this once before sometime back, but I believe the thread is long gone. If not, then maybe you could find it and give us a link and we could use it as a reference to get up to speed.

If you read the patent, and I know that you have, you will note that fully 1/3 of the begining text is devoted to tell the reader how the Sigma IV compares to the .25, .50, and the .625 in all respects. It goes into quite some detail in the first sentence and specifically notes that the radiating element is 3/4 wavelength long.

Personally I take a different a different approach to all of these antennas that are a bit longer, <> an inch or two either way, than a 1/2 wavelength in physical length. So my arguments will take a different view than simply using a tape measure to make a claim.

I can see our friend Bob, across the way, takes jaundice view of your claim already.

Can we believe what is said in the patent? There are other examples of this one being 3/4 wave throughout the body of the balance of the patent as well. What is your argument?

For those that don't have the patent, here is the very first page.
Sigma IV Patent

If this works like I expect, then you might have to click on the view icon at the bottom right edge of the image to read the text.

 

[freecell]

"radiating element is 3/4 wavelength long"

and that fact is echoed several times throughout the entire patent document. his argument (repeatedly) has been that the bottom 1/4 wave doesn't radiate and that it is simply a stub or some such other nonsense.

the "FEEDPOINT" of the antenna is the POINT at which the TRANSMISSION LINE is CONNECTED to the ANTENNA STRUCTURE. this is where the shorting strap of the GAMMA MATCH is located. if this point was actually the ENDFEED point of a 1/2 wave radiator the impedance there would be theoretically infinite but practically speaking on the order of 1000 - 5000 ohms. furthermore, the input impedance of the antenna prior to the addition of the gamma match IS NOT 0 OHMS as was stated earlier but it is well below the required 50 ohms, making the gamma match a necessity as it transforms loads of less than 50 ohms to the required value.

http://forum.worldwidedx.com/viewtopic.php?p=28830&highlight=sigma++++wave#28830

as to the question of the radials: the electrical length of the diverging elements is one-quarter wavelength which is about 9 feet for antennas designed for use in the CB Band. since the diverging elements in the Sigma IV are only 89" in length and in order to broaden the bandwidth of the antenna in terms of maintaining a low standing-wave ratio (S.W.R.) as a function of frequency, a conductive loop or ring is affixed to the free ends of the elements via suitable mechanical connectors. the use of the ring not only broadens the bandwidth of the antenna but also effectively reduces the physical length of the elements to maintain (while maintaining) their one-quarter wave electrical length.

note: as the diverging elements (radials) are positioned anywhere from 5 - 30 degrees away from the main 3/4 wave vertical radiator the gain of the antenna when compared to a half wave dipole varies anywhere from 2.2 (5 deg) - 2.7 (30 deg) db., respectively. gain figures are 4.34 db. - 4.84.db. when referenced to the isotropic source. now those are some believable numbers.

also, interestingly enough for those who subscribe to the "3/4 wave produces less gain" line of thought, as the radials exceed the 30 degree mark and move further away from the 3/4 wave radiating element the gain reverses and begins to drop as they move towards the horizontal plane. but then again, this isn't your every day 3/4 wave antenna. this design causes us to re-think the line of thought mentioned previously and should at the very least be reason enough for us to allow some room for exception to the rule.

in closing, the Sigma IV never has been, isn't now and never will be a 1/2 wave antenna.

i believe this also creates some problems with some of your claimed similarities between the Sigma IV and the J-Pole.

i also suspect and have reason to believe that Avanti's janitor may have been or is currently moonlighting as an engineer in his off time and / or has reservations occasionally at a Holiday Inn Express somewhere nearby.

 

[Marconi]

Well MC, do you believe the Avanti guys when they speak? I would bet that when the patent was being discussed, they were the guys talking to the patnet attorney and not the utility guy.

There is a claim in the patent itself that states to the affect, that the base angle design is a compromise towards keeping the foot print smaller on this antenna and that there are other configurations, being wider in design, that will provide the antenna with more effective gain. This does not prove a point, regarding your claim, but it is directed to your last remark in the linked thread that 228 provided, where we discussed this before. There it states that, as currently designed, the gain is 2.2 dbd over a 1/2 wave dipole and that if the angle is widened out a bit, making the foot print larger, the antenna may show 2.7 dbd over a 1/2 wave dipole.

Furthermore in the details the radiating element #12 is described as:

"The radiating element 12 has an electrical lenght of about three-quarters wave length at the frequency at which the antenna is tuned, e.g., approximately 27 feet for an antenna designed for use in the CB band."

This sounds very reasonable for the Sigma IV, being a longer than half wave antenna to me. Unless I choose to believe that Mr. Blaese and Martino are talking CB BS. Since you conclude that it is a 1/2 wave antenna, is this your position: them old boys are just full of it?

 

[freecell]

Justin,

please feel free at any time to make a deposit.

 

[bob85]

hey guys i am just winding chief up a little :twisted: , i have no idea what wavelength they are other than what it said on the box and instructions i got, what i do know is the only antenna i ever owned that may have equalled or beaten it at this or my last location was the ham big mac which was another 32ft antenna and definately not another halfwave in disguise, thats just an observation not a scientific test

i would love to meet up with chief and marconi to do battle in a large field with our antenna of choice, maybe if i win the lottery i will be on my way to chiefs place with my slightly bent pieces of aluminum or is that aluminium, the winner can buy the beer :idea: ,,, what do you guys like to drink