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imax 2000 with maco gpk kit or homebrew

Hey Guys, I am no antenna expert but a ground plane ( Counterpoise ) kit on this type of antenna in my opinion is snake oil. It will not make a difference since this antenna has its own matching device. Maybe it makes the antenna look better ( cosmetic Value ) but will not increase efficiency. I would like some feedback.

I wouldn't call it snake oil.
I have/use the IMAX. I run it presently w/o the 'ground plane kit' - but I will be putting it on before Winter gets here. The IMAX will work off of the coax and masting to get a counterpoise. But it is better to use the 'gpk' to minimize the common-mode current as well as improve the radiation pattern.

On of the guys on the forum has modified the IMAX using a ground plane kit from the Maco 5/8 and added a 102 inch steel whip to the top section.

This antenna has proven to be remarkable modded or stock - able to use between 10 to 12m w/o using a tuner - and is also able to use 15m and 17m in addition with a tuner. For $100, I consider it a marvel of cheap engineering. Many people that own and use them can and have compared them to their 5/8 wave stand-by antenna. So much so, that even Sirio has figured this out and has made an IMAX copy - just to cash into the IMAX market. They ('Sirio') obviously have realized the virtues of this design and can see that enough people buy them because they just flat out work well enough. . .
:whistle:
 
I wouldn't call it snake oil.
I have/use the IMAX. I run it presently w/o the 'ground plane kit' - but I will be putting it on before Winter gets here. The IMAX will work off of the coax and masting to get a counterpoise. But it is better to use the 'gpk' to minimize the common-mode current as well as improve the radiation pattern.

On of the guys on the forum has modified the IMAX using a ground plane kit from the Maco 5/8 and added a 102 inch steel whip to the top section.

This antenna has proven to be remarkable modded or stock - able to use between 10 to 12m w/o using a tuner - and is also able to use 15m and 17m in addition with a tuner. For $100, I consider it a marvel of cheap engineering. Many people that own and use them can and have compared them to their 5/8 wave stand-by antenna. So much so, that even Sirio has figured this out and has made an IMAX copy - just to cash into the IMAX market. They ('Sirio') obviously have realized the virtues of this design and can see that enough people buy them because they just flat out work well enough. . .
:whistle:

Sirio's gain master is far from an "i max copy",it is a completely different type of antenna altogether,if anything its a copy of a shakespeare bigstick (centre fed halfwave dipole,mountable from the base for ease of mounting and also to get it clear of surrounding objects) with a little refinement added in the shape of an rf choke,

whereas the i max is a .64 wave end fed vertical,with a dummy load style matching circuit.
 
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Sirio's gain master is far from an "i max copy",it is a completely different type of antenna altogether,if anything its a copy of a shakespeare bigstick (centre fed halfwave dipole,mountable from the base for ease of mounting and also to get it clea of surrounding objects) with a little refinement added in the shape of an rf choke,

whereas the i max is a .64 wave end fed vertical,with a dummy load style matching circuit.
I don't doubt you - as there is little info on it that I can find.
However, why would they need a matching network with a 1/2 center-fed vertical dipole? A dipole doesn't necessarily need a matching network - right? Since it uses four interlocking sections; the marvel would be just how they could build it that way - if in fact it is a center-fed dipole...

Explain please . . .
? ? ?
 
theres probably more info about the gainmaster on their website than any other cb antenna out there, the internal layout is shown in the user manual,

http://www.gain-master.it/Id-406 Gain master.pdf

it claims to be a centerfed 5/8wave dipole which does need the matching stub it uses or some other form of matching,
its nothing at all like an imax, more like a supercharged big-stick,
sirio know how to make great performing antennas,
when they hit the market we can test the veracity of their low angle gain claims;).
 
theres probably more info about the gainmaster on their website than any other cb antenna out there, the internal layout is shown in the user manual,

http://www.gain-master.it/Id-406%20Gain%20master.pdf

it claims to be a centerfed 5/8wave dipole which does need the matching stub it uses or some other form of matching,
its nothing at all like an imax, more like a supercharged big-stick,
sirio know how to make great performing antennas,
when they hit the market we can test the veracity of their low angle gain claims;).

Hmm,

i think its a centre fed halfwave dipole,

as shockwave has posted about the i max in the better antenna thread,the i max has a capacitor in series with the radiator which electrically shortens it,therefore you need to make the radiator longer to compensate,which begs the question is the i max a 5/8 wave with a longer than normal radiator to compensate for the series capacitance rather than a .64 wave like some people claim?

anyway getting back to the sirio,now we find it also has a capacitor in series with the radiator,now if the right value capacitance was chosen you could make the radiator to appear like the top half of a centre fed 5/8 wave,very shrewd or very cunning ? i'll let others judge that,i have my own opinion.

they say a picture says more than a thousand words,in this case two pictures may well tell a lot more truth than sirios hype,for me the givaway in the gain master pdf is the current distribution and the radiation pattern.

the radiation pattern is typical half wave dipole mounted in free space when the antenna is balanced,funnily enough the rf current distribution is also typical of a 1/2 wave dipole,how can that be if its a 5/8 wave centre fed dipole?

have sirio rewrote physics ? or just cunningly bettered on shakespeares design (the same way they did on avanti's sigma 4 design) by including a choke to ensure balance,cut down on common mode current and no doubt give a much cleaner radiation pattern than a bigstick.at the same time giving the impression that it is a 5/8 wave centrefed dipole,with the keyword being 5/8 wave,everyone knows 5/8 waves are ultimately more desireable than halfwaves.

i think its a very clever manipulation by sirio to improve sales on what looks like a very well thought out centre fed halfwave dipole,i may be wrong but those radiation pattern/rf current distribution pics tell a story.if it truly was a centrefed 5/8 wave dipole,current maxima would not be in the centre.
 
the imax exposed article fails to take the slowing effect of the radome into account so who knows what it is electrically, solarcon say its a .625wave, it would be the first time a cb antenna manufacturer created an advantage and kept it a secret, its usually the other way round,

look again at the rf current plot at 90 degrees, compare it to sirio's depiction of the rf currents in the upper 1/2wave of the 5/8wave antenna,
the gainmaster shows a dip in the center and current maxima some point away from the centre unlike a regular dipole but shows a dipole like pattern which according to what i have read it should have,

sirio claim the effective radiator is 6.9mtrs between the choke that defines the end of the lower leg and the tip with near uniform dipole like radiation along that length, if its just a 1/2wave dipole they are been very deceptive,

it looks to me like a .625wave dipole as claimed with a parallel none radiating matching stub placed the right distance from the feedpoint to cancel the reflection from the higher than 50ohm feedpoint impedance of a .625wave dipole,
i have no idea if that setup will outperform a 1/2wave dipole,

my tutors never sounded like this, they had beards and a pipe(y)


YouTube - ECE3300 Lecture 13b-8 Impedance Matching stub match parallel
 
Seems like on this forum and every other one, ALOT of people confuse the following:

1. CENTER FED Half Wave Dipole
2. END FED Half Wave Radiator

The two are NOTHING alike.
 
Seems like on this forum and every other one, ALOT of people confuse the following:

1. CENTER FED Half Wave Dipole
2. END FED Half Wave Radiator

The two are NOTHING alike.

Closer examination will reveal we are talking about a vertical antenna that is indeed center fed like a dipole but has it's RF connector at the base. I know the concept is different but many of the people commenting here do understand the effects of feeding the radiator at different places and how it changes the radiation pattern or TOA.
 
Seems like on this forum and every other one, ALOT of people confuse the following:

1. CENTER FED Half Wave Dipole
2. END FED Half Wave Radiator

The two are NOTHING alike.

Care to elaborate ? If you know more than those who have posted it would be nice to hear your thoughts.
 
so is the gain-master essentially a sleeved dipole with a coax choke built in at the bottom ?
 
so is the gain-master essentially a sleeved dipole with a coax choke built in at the bottom ?

The Gain-Master is a true 5/8 wave radiator that is center fed. The bottom radiator element is formed from the very coax that feeds the antenna. It is choked off at the base so the radiation stops at that point and tuned with a coax stub to correct impedance. The design is simple and well thought out. It is supported with the latest computer modeling and field testing. It has me curious enough that I've ordered one of the first sample units for testing from the Factory.
 
so should the gain-master perform just as well as a old school penetrator or a currently made interceptor 10k ?

ill be looking forward to your comments on you experience with the G-M shockwave . what omni(s) are you currently using/have access to for a comparison ?
 
so should the gain-master perform just as well as a old school penetrator or a currently made interceptor 10k ?

ill be looking forward to your comments on you experience with the G-M shockwave . what omni(s) are you currently using/have access to for a comparison ?

Sirio is claiming the Gain-Master will have at least 1db more apparent gain then those types of 5/8 waves. Not because the field is stronger but because the center feed lowers the take off angle. I would love to report that I will have the time to spend testing the Gain-Master against several antennas at a wavelength above ground. The reality is I'm juggling several projects as it is to complete them before winter and can only spend perhaps an afternoon field testing the antenna at only 15 to 20 feet.

I do have several antennas in stock that I can assemble to test against. I have a few old model Vector 4000's, a S-827 5/8 wave and a S-2016 5/8 wave. The S-827 is buried in a box behind lots of stuff but the other two are easy for me to put together. When the Gain-Master arrives next month, I'll test it against a Vector and the S-2016. One thing I'll add is that Sirio has taken the time to thoroughly test their antennas and they report some of the most accurate results you'll see in this market. The construction quality of the Gain-Master also seems to have been a focal point in it's design.
 
thats not mine hotrod but this one is!this is the end result.top section 102 stainless making the radiator 23 feet and the overall antenna 24 1/2 feet.the maco ground planes are stretched out to 104 inches each,that was stretching.as for the match it was not affected at all.i dont have an antenna analyzer or tuner so i am going to have to go by ears and reports.ears may have gotten a little better or might have just reduced noise a little not to sure yet.i did get one report so far at 55 miles that said he usually has no s units on me but had 1-2 on me last night.

Nice work! And (especially), if you increased 1-2 S units on ground wave (or LOS), then you've GOT IT!... don't touch a thing.... enjoy the results!

As long as you can effectively couple power to the antenna and as long as it survives your local weather, you've improved your station's performance DRAMATICALLY!

Looks like you've made yourself a 'knock-off' version of the old (can't remember the mfg) either Hustler, Hygain, Antenna Specialists, or Avanti: Collinears..... they were the absolute BOMB in the 70's!!!
 
Nice work! And (especially), if you increased 1-2 S units on ground wave (or LOS), then you've GOT IT!... don't touch a thing.... enjoy the results!

As long as you can effectively couple power to the antenna and as long as it survives your local weather, you've improved your station's performance DRAMATICALLY!

Looks like you've made yourself a 'knock-off' version of the old (can't remember the mfg) either Hustler, Hygain, Antenna Specialists, or Avanti: Collinears..... they were the absolute BOMB in the 70's!!!
thanks ct i have no problems talking 100 miles with 25 watts at 40 feet and the band width is under 2.5 from 25 to 28.5.so unless that baby snaps the mast again she is going to stay right there lol.
 

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