better antenna

[Radio75]

But how on earth can the thing be efficient and broad banded at the same time?
That pretty much goes against everything I have ever learned about antennas.

 

[W5LZ]

It isn't the size of wire doing the radiating I'd worry about. The size of the conductors in the matching device, and the insulation all through that antenna would be the things to worry about. the size of the conductors making up that coil, and the turns spacing of that coil, determine it's voltage break down point, when it will start arcing. There is quite a voltage build up in any matching device. To some ridiculous point, bigger is better.
For most typical use, it ought'a work just fine with proper tuning. How many people do you know who are ever going to really run huge amounts of power? And if they've already spent the kind of money to produce that power, why would they use a cheap-axed Imax antenna? I don't think that's very smart, do you?
- 'Doc

 

[Shockwave]

But how on earth can the thing be efficient and broad banded at the same time?
That pretty much goes against everything I have ever learned about antennas.

I too have been amazed at the bandwidth on some of the newer antenna designs that feed the radiator through a capacitor like the Imax or Sirio Gain-Master. Sirio has improved the design of the Imax so that it very well could exceed the performance of a standard 5/8 wave where the Imax does not. This is accomplished by effectively center feeding the radiator even though the connector is at the base. This lowers the angle of radiation placing more power on the horizon.

The Imax and Gain-Master use the capacitor in series with the RF feeding the radiator and this has a lot to do with the wide bandwidth. I suspect a method of stagger tuning is being used where different parts of the antenna are tuned to favor different frequencies. For example the radiator is tuned near the center. The capacitor tends to extend the high frequency spectrum. While adding some inductance to the matching network could extend the low frequency coverage.

 

[443]

I. Sirio has improved the design of the Imax so that it very well could exceed the performance of a standard 5/8 wave where the Imax does not

Where did you see those results? Personal tests? Link to field experiment on web? I don't see why the Imax would not perform AS GOOD as a standard 5/8 wave. That is IF the GPK actually works.

Links to Sirio info? So the Sirio has a piece of coax running half way up the radiator to center feed it? Wow. I thought about making a home dipole like that, but have the coax connector on the bottom of the antenna, but it would just be a junction to pass the signal to another piece of coax running up the inside of the tubing/pipe/whatever of the bottom half of the dipole and then have it's actual attachement to the elements in the center, but you wouldn't "see" it from the outside of the antenna.

This Sirio stuff is new to me. I think they were just getting started back when I got out of radio 5 years ago. Maybe not, but don't remember their name being popular back then.

My IMAX-2000 coming UPS today. Will try to get it in the air tonight to start playing with it. I hope it at least performs as good as my old Maco V 5/8 did. I am expecting slightly better.

And to the OP, no you will NOT melt down the IMAX-2000 with anything less than a 10-16 pill.. Even then... not all that likely. Any base linear amplifier would have to be one of the "big boy" tube types to be in danger of melting it or making it arc inside. In other words, a 3-500Z box is NOT a big boy amplifier. A 3CX25000 or something maybe.

 

[W5LZ]

Broadbandedness, what contributes to that?
Several things.
The diameter of the conductor for one thing, but that isn't a 'small' change sort of thing, it's a 'large' change sort of thing, and is directly related to wave length of the frequency in use. The lower in frequency you go, the 'smaller' that broadbandedness get's when measured in inches. Or another way of saying it is the lower in frequency the larger the change in diameter to make any significant difference. At HF, figure 'feet'. At VHF/UHF, figure inches.
Another factor that definitely plays a part in that broadbandedness is reactances present in any impedance matching devices used (and impedance matching devices are used with any antenna required to have a 50 ohm input, none of them have that 'naturally').
It depends on how you are determining that broadbandedness! If you are only using an SWR meter, you are only measuring possible impedance matches over a frequency range. That can tell you absolutely nothing about the efficiency of the antenna being measured, how resonant it is, meaning how well it's radiating. A broad SWR match is a bad way of doing that efficiency thingy! Dummy loads have a tremendously good SWR range! They make terrible antennas though.
The higher the 'Q' of an antenna the smaller it's bandwidth range is. 'Q' is a measure of efficiency. The higher the 'Q' the more efficient the antenna. The lower the 'Q' the less efficient the antenna is. So, a really broadbandedness means an inefficient antenna.

Don't like the idea of any of that? Don't bother yelling at me, I didn't make it that way. Yell at 'Momma Nature', she did it! (Then you'd better run like hell, 'She' get's even! )
- 'Doc

 

[bluestallion]

i cant decide if wanna get a imax with gpk or the maco 5/8. anyone done any testing to see which is better?

 

[BOOTY MONSTER]

SIRIO S-827 WEB SPECIAL-H&Y Electronics
the sirio 827 could be a good ....... does anyone knoe if the fixed the issue with the coil going open circuit with the radiator ?

 

[Robb]

SIRIO S-827 WEB SPECIAL-H&Y Electronics
the sirio 827 could be a good ....... does anyone knoe if the fixed the issue with the coil going open circuit with the radiator ?

I think bob85 once said that these can easily come apart with too much wind. Something about the hub was funky. But if the fix is in - and for that price - it doesn't look half bad.

 

[443]

If this antenna really is just like the Maco V58 then it would be a great buy:

W-58 High Performance Base Antenna-H&Y Electronics

 

[bluestallion]

I saw one of those on ebay, and was wondering the same thing.

 

[Shockwave]

An Imax can be blown up with much less then 220 volts at 50 amps but you don't have to worry much about 2 KW PEP or less. RF can certainly burn up a thin wire. It's called the corona arc. Put a real 5 KW into a Francis 96 inch whip and watch the fire at the tip begin. With the Imax it's the hidden capacitor formed with two metal tubes insulated by a plastic one that will fail first.

The Imax and the V-58 are very close in performance but most people who have tested this will admit the Imax does not outperform the V-58. It's just easier to put up. One thing is for sure, if you run power the V-58 is going the be more desirable in terms of RFI. The full sized ground radials and matching network that depends on the radials is very effective at reducing RFI. If you run 10 and 11 meters you'll need the Imax for the bandwidth.

 

[bluestallion]

Think i may just go with the imax. Cuz i can get some higher winds, and may do 10 meter in the future

 

[BOOTY MONSTER]

there is always the option of home brewing a base antenna .

 

[1342]

An Imax can be blown up with much less then 220 volts at 50 amps but you don't have to worry much about 2 KW PEP or less. RF can certainly burn up a thin wire. It's called the corona arc. Put a real 5 KW into a Francis 96 inch whip and watch the fire at the tip begin. With the Imax it's the hidden capacitor formed with two metal tubes insulated by a plastic one that will fail first.

The Imax and the V-58 are very close in performance but most people who have tested this will admit the Imax does not outperform the V-58. It's just easier to put up. One thing is for sure, if you run power the V-58 is going the be more desirable in terms of RFI. The full sized ground radials and matching network that depends on the radials is very effective at reducing RFI. If you run 10 and 11 meters you'll need the Imax for the bandwidth.

actually the funny part about that is several people on this forum myself also have owned the maco and the imax and the imax performed better but this guy is still lost.the 19 foot maco did not perform as well as my 24 foot imax sorry shock.maybe its the added length??????????????????

 

[Shockwave]

Yes of course it's the capture area again. The longer the antenna the better. So what if the extra length hits the point where it's now out of phase. Replace the top section on the Imax with a longer whip and claim even more gain. Lets assume you were right and the Imax had noticeably more gain simply because it's longer. Go to Home Depot and buy an extra length of 3/8 tubing to make your Maco V58 into a "super .64 wave". You can't get more gain in these types of antennas beyond .64 wave and there is little gain change from the 5/8 electrical length.

It's much more likely something has skewed your one test then the Imax having a noticeable gain increase. You're not understanding the difference between electrical length and how the construction of the antenna can alter the physical length. The advantage in the Imax is bandwidth not far field gain. The disadvantage of the Imax is RFI. There is no comparison in the reduction of RFI the classic 5/8 wave groundplane offers over the Imax. That alone can make the difference in being able to use your station or not. Naturally I already know your Imax doesn't even get into your computer speakers. Lucky you.