| Author |
Message |
    
Gonzo
Member
Username: Gonzo
Post Number: 99
Registered: 9-2004
| | Posted on Wednesday, November 10, 2004 - 5:48 pm: | 
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Another in a long line of antenna tests, I conducted, I am sure this will bring numerous responses as well.
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I tested my 5/8 wave Imax2000 vs. a Hygain 5/8 wave Penetrator. Basically this is a test of 2 5/8 wave antennas of different designs. The Imax2000 is rated at 5.1 db gain, which is exactly what Hygain rated the Penetrator when they were making them. I often wondered if The Imax was just rated the same, without anyone doing any testing on it. Being that they were both 5/8 wave antennas.
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Results: same heights, coax, swr.......
Gain: about the same, both are excellent and so far have recieved the same reports and tested the same as far as gain locally. There has been no skip here in the past few days, so I haven't been able to test that. There might be a slight gain difference in favor of the HYgain, but ever so slight, there is slight field strenght difference as well.
Recieve: Here's a big difference. The Hygain has less noise than the Imax and therefore can out hear it. Not to say that the Imax is noisy, it isn't. However there is NO question that the old Hygain Aluminum antenna has better ears, due mostly to less noise and static and electrical garbage that is common here in NY.
I was in disbelief that there could be this much difference, so I switched the antennas on the mounts and noted the same result.
In favor of the Imax: This antenna exhibits a lower SWR than the Hygain over a wider range of frequencys. The Hygain is great 40 channels above and below the CB band, but much more and the SWR starts to go above 2:1
The Imax also wins hands down in the stealth dept. And you can paint it lightly with non-metallic enamel if you wish.
If you area isn't particularly noisy, then the difference between these antennas would be slight indeed.
The Imax2000 can also take more power then the Penetrator for you 1K + freaks.
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So as far as Gain, The Hygain Penetrator was considered the standard by which most all Omni directionals were measured against, back in the day. So for the Imax2000 to come this close in performance to the Hygain,,,is a big compliment.
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The Interceptor 10K appears to be a very expensive copy of the Hygain Penetrator BTW.
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Road_warrior
Intermediate Member
Username: Road_warrior
Post Number: 175
Registered: 7-2004
| | Posted on Friday, November 12, 2004 - 11:44 am: |
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Gonzo,
You are right about the Imax 2000 having more noise. I love the performance & simple design,
but, i live in a noisy neighborhood & mine sure
brings in more noise than other antennas i had up.
JIM/CENTRAL PA/CEF 375 |
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 278
Registered: 6-2003
| | Posted on Friday, November 12, 2004 - 11:02 pm: |
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One guy around here says the gpk reduces the noise for him. If you don't have a gpk then maybe this would help.
mikefromms |
Road_warrior
Intermediate Member
Username: Road_warrior
Post Number: 176
Registered: 7-2004
| | Posted on Saturday, November 13, 2004 - 12:41 pm: |
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Mikefromms,
I tried GPK, didn't help noise in my area. I took
it back off. I just installed a S.E. Lightning 4
Quad beam. Very, Very much quieter now for me.
I'm not sure if i'm going to keep Imax 2000 up or not, since, all my friends that talk on CB all live South of me & i can hear every one great just leaving beam pointed South.
JIM/CENTRAL PA/CEF 375 |
Gonzo
Intermediate Member
Username: Gonzo
Post Number: 107
Registered: 9-2004
| | Posted on Sunday, November 14, 2004 - 6:45 pm: |
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I have the GPK on as well, no noise difference |
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 280
Registered: 6-2003
| | Posted on Sunday, November 14, 2004 - 8:56 pm: |
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Road Warrior, you will have no problem unloading that Imax 2000. Oh, I'm not to big on the extra gpk anyway. Maybe it would help at lower heights. I have a Thunder 8xb. It has great ears and low noise. I should have put it on a tower instead of in the top of a pine tree. Can't keep the limbs out of my wires!
mikefromms |
Road_warrior
Intermediate Member
Username: Road_warrior
Post Number: 178
Registered: 7-2004
| | Posted on Monday, November 15, 2004 - 10:26 pm: |
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Hows it going Mikefromms:
I'll keep Imax 2000. Once in awhile i drive to the
top of Indian Lookout mountain to talk long distances on the radio. I have a 30ft Lowes
telescoping mast i take with me, I'll slap the
Imax 2000 to the mast...LOL
JIM/CENTRAL PA/CEF 375 |
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 282
Registered: 6-2003
| | Posted on Tuesday, November 16, 2004 - 11:28 am: |
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That sounds like fun! That's one of the good things about the Imax 2000 is it is very portable and quick set up. Yeah, keep that thing, I hear new ones are hard to come by or at you have to wait in line.
Later,
Mikefromms |
Tech808
Moderator
Username: Tech808
Post Number: 4095
Registered: 8-2002
| | Posted on Tuesday, November 16, 2004 - 11:42 am: |
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Mikefromms,
NAWWWWWWWWWWW, they are not hard to find Copper has them on hand for anyone who wants to order one. 
RUMORS are a terrible thing as they tend to spread a lot of false information about products.
As far as I know there has never been a shortage but with Copper selling so many they do have to re-order quite often.
Lon
Tech808
CEF808
N9OSN |
Road_warrior
Intermediate Member
Username: Road_warrior
Post Number: 179
Registered: 7-2004
| | Posted on Tuesday, November 16, 2004 - 12:04 pm: |
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Mikefromms,
The Imax 2000 is a good Antenna and definitely will stay home here with Daddy...LOL...I learned my lesson in the past as i parted with nice equipment that i wish i would of kept. CB's, Mics, meters, Antennas,Amps, still kicking myself in the butt.
JIM/CENTRAL PA/CEF 375 |
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 305
Registered: 6-2003
| | Posted on Tuesday, December 07, 2004 - 3:02 pm: |
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Just saw the last couple of post here. I may have to go ahead and order my Imax. I have a friend here in my hometown who wants me to order one for him later on. The best price in town is here.
mikefromms |
Assaulter
Junior Member
Username: Assaulter
Post Number: 12
Registered: 1-2003
| | Posted on Tuesday, December 07, 2004 - 8:32 pm: |
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Jim, I hear that...I miss my 142 GTL!!!! |
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 374
Registered: 6-2003
| | Posted on Saturday, January 22, 2005 - 10:40 am: |
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Well, I order an imax. The thing looks like it is build solid.
A guy across town says I will be disappointed in the performance if I don't get the Imax. I told him I would be up over 70 feet at the feedpoint and the antenna will be ground good. He insists that he talked to Solorcon and they said (per him) you won't be able to tell in difference in transmitt or receive after you go up past 30 feet unless you have the gd/p kit. I told him this is just the opposite of what the tech say here.
I'm putting the Imax up around the second wave 72 feet +, I say I don't need the kit; he says, you won't be happy unless you have it. State your position (again if necessary) and lead me in the right direction.
Thanks,
Mikefromms |
Tech808
Moderator
Username: Tech808
Post Number: 4596
Registered: 8-2002
| | Posted on Saturday, January 22, 2005 - 10:56 am: |
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Mikefromms,
Sure glad to help with Tech833's REVIEW that is posted on the GPK Kit in the Subscriber (Preview) area of the Forum for the members to read.
Imax 2000 Ground Plane Kit Reviewed
What difference does the ground plane kit make on the Imax 2000 antenna?
After dissecting the Antron 99 and Imax 2000 antennas and discussing the construction and theoretical performance for each, I still wondered what the fiberglass antennas would do on the antenna range. Add to this, the constantly asked question about whether or not the available ground plane kits (GPK) made any difference in the performance of these antennas, and my curiosity peaked.
Copper Electronics has begun to sell a special ground plane kit which easily mounts to the Imax antennas' new mounting plate scheme. The ground plane kit for the Imax 2000 is the model A65-00005 and sells for just over $30. The Imax GPK consists of a nicely chromed metal bracket and four 6-foot fiberglass radials (which strangely resemble the top sections of the A99 antennas). The Imax 2000 is a .64 wave antenna which theory tells us highly benefits from a counterpoise beneath the feedpoint and radiating element. Typically on 5/8 and .64 wave antennas (both are considered the same), the counterpoise (ground plane) is at a 90 degree angle from the radiator. With the Imax GPK, the radials are angled at nearly a 45 degree angle downward from the radiator. Although I did not test the Imax 2000 with the 45 degree and then a 90 degree counterpoise to compare them, the new Imax GPK with 45 degree tilt did produce nearly the same results as theory dictates a 90 degree counterpoise would, so I have temporarily concluded that the difference in effects would be minimal.
Getting the Imax 2000 out to the antenna test range near Sacramento, CA was much more difficult than expected due to the unusual rains and winds the area experienced in early April. Once the range dried out and some commercial work was completed, I assembled and tuned the Imax 2000 for 27.200 MHz. This was the center frequency used for all testing as performed here. Measurments were taken at 10 degree intervals which is common practice with low band antennas. Ground effects were minimized with software compensation. The raw data is below the diagrams and text relating to the plots.
 | | Imax 2000 in free space without GPK. To explain what it means to plot an antenna 'in free space', that means that the plot does not consider ground reflection, absorption, capacitance, refraction, etc. So if there were no Earth, as in free space, this is the radiated pattern of an Imax 2000. Viewing this plot chart, the tip of the antenna would be at the top of the chart, the feedpoint (and mounting point) is at the bottom. Each mark about the perimeter is 10 degrees. As you can see here, there is considerable radiation about the base of the antenna. In a situation where an Imax 2000 owner is susceptible to causing disturbance to consumer electronics by his transmissions, the Imax 2000 would blanket equipment located beneath its feedpoint with signal levels only slightly below the level on the horizon. Also note that the signal level at the horizon is the same as signal levels up to 30 degrees above the horizon. For sky-wave transmissions, this would be the ideal scenario. However, as we discuss below, ground effect distorts this pattern greatly which cancels out any benefits that would be achieved by a radiator with this pattern. |
 | | Imax 2000 in free space with GPK. Once the Imax GPK was added in our test, the pattern changed drastically. Besides a small amount of added efficiency, there are some other effects worth mentioning. First of all, notice that signal level on the horizon did not change. In free space, adding the Imax GPK to the Imax 2000 will not 'improve the range' of a system. The gain on the horizon is precisely the same with or without the Imax GPK installed. Second, and most worthy of note, the amount of radiation directly below and up to 45 degrees away from the area directly below the feedpoint experiences drastically reduced RF levels. In installations near consumer electronics (such as Imax 2000 with GPK installed in residential neighborhood), this could greatly reduce interference potential by an average of 10 dB. Second, note the reduced radiation in the area of 20 to 50 degrees above the horizon. Absent of ground effects, this would reduce sky-wave interference by as much as 10 dB. Since ground does effect the pattern greatly, this man-made interference reduction does not actually occur over real ground (as we will see below). However, there is still some benefit from this sky-wave reduction over ground, although at a higher angle than the free space values. |
 | | Imax 2000 without GPK installed with feedpoint mounted 1/2 wave over ground. Using software modeling and the free space information gathered from the range, we can determine what the actual radiation pattern would be over average ground. With the feedpoint located 1/2 wavelength over ground (18 feet in this case), the pattern varies from free space values drastically. Here, in this computer generated theoretical radiation pattern, you will notice the 'angle of radiation' (also called the 'take-off angle) is at approximately 7 degrees above the horizon. As you move further from the signal source, the signal would become weaker at ground level by an amount not proportional to the levels experienced above ground. The further you travel from the source, the higher you would have to be above ground for the signal levels to approach free space values. The Imax 2000 without the GPK has nearly an isotropic pattern when mounted 1/2 wave over average ground. As you increase the feedpoint mounting height over ground, the angle of radiation does decrease slightly. Until the feedpoint reaches over 1 wavelength above average ground, very little change was made. Heights considerably over 2 wavelengths above average ground (1 mile or more) bring the pattern slightly closer to free space values. However, since the FCC limits CB antenna height to 60 feet above ground (or 20 feet above mounting structure such as a building), I did not present that information here. |
 | | Imax 2000 with GPK installed with feedpoint mounted 1/2 wave over ground. When the Imax GPK was installed, the main lobe was directed more downward and less radiation about the base of the antenna was created. When modeled over average ground, these two things help to lower the 'angle of radiation' (take-off angle). Let's discuss this first. Since the angle of radiation is lowered, this means that as you travel further from the signal source, the received signal level will be slightly higher at a fixed far field distance from the source over the Imax 2000 without the GPK installed. Near field values are almost unchanged. What this means is that for communications close to the Imax 2000, there will be little (if any) noticed difference in signal strength to another station from the Imax 2000. However, far field transmissions would likely experience signals perhaps 2 dBm stronger from a GPK equipped Imax 2000. Once the receiving station is far enough away from the Imax 2000 signal source that curvature effect begins, the signal from a GPK equipped Imax 2000 over a non- GPK equipped Imax 2000 may have little more strength. Second point to consider in this over-ground plot is the reduced signal (and sensitivity) at angles of 60 degrees above horizon. Since most man-made interference received during the day is sky-wave, and usually high angle sky-wave, an Imax 2000 with the GPK installed will likely experience the 'noise floor' reduced by as much as 12 dB. This is quite significant if you are trying to carry on local communications when sky-wave noise is very high. |
Conclusion: In both cases, it should be noted that the gain in the major lobe of the Imax 2000 was unchanged when the Imax GPK was added. Therefore, advertising claims of 'added gain' are arguably untrue. The net effect on the major lobe to sky-wave transmission and reception would be identical either way. However, sky-wave interference in the receiver would be reduced quite noticeably with the addition of the Imax GPK to the Imax 2000 while not affecting far field sky-wave performance at all. Also, since the angle of radiation is lowered when the Imax GPK is installed, Imax 2000 owners whose antennas are mounted less than 1 wavelegth above ground level should notice slightly greater useable ground wave range and a reduction in sky-wave interference during those communications. Both Imax 2000 owners with their antennas mounted either low or high above ground level should notice reduced 'TVI' and other non-intentional interference. For this reason alone, Imax 2000 owners would be advised to add the Imax GPK to their installation in either case.
Raw data:
Imax 2000 sweep
Degrees from
vertical | Measured dBm
with GPK | Measured dBm
without GPK | | 0 | -67 | -68 | | 10 | -66 | -68 | | 20 | -66 | -69 | | 30 | -66 | -72 | | 40 | -70.5 | -72 | | 50 | -70 | -68 | | 60 | -68 | -66 | | 70 | -67 | -66 | | 80 | -66 | -66 | | 90 | -66 | -66 | | 100 | -66 | -67 | | 110 | -67 | -70 | | 120 | -68 | -72 | | 130 | -72 | -70 | | 140 | -82 | -69 | | 150 | -75 | -69 | | 160 | -76 | -70 | | 170 | -73 | -70 | | 180 | -73 | -70 |
by Tech833
About the author:
The author is a professional broadcast engineer with over 20 years experience in the design, maintenance, and construction of broadcast transmitter and studio facilities. He has experience with high power antenna installations and has been involved with simple single antenna installations to complex phasing and directional arrays. The author is currently a successful contract engineer in California and has become highly respected and well known in the industry.
But to see the Pictures in the Review you will actually have to click on it and read it in the:
Subscriber (Preview)
» Product Reviews
» Imax 2000 Ground Plane Kit Reviewed
» Review
And it will answer all of your questions for you. 
Hope this helps,
Lon
Tech808
CEF808
N9OSN |
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 384
Registered: 6-2003
| | Posted on Sunday, January 23, 2005 - 10:04 pm: |
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Lon, You've sold me. This Imax is going up right. I will have new LMR-400 coax with factory installed PL-259's, a short run of mini 8x, the gd/p kit. My losses should be pretty minimal. I should be up around 70 to 75 ft at the base of the Imax 2000. I want trouble-free operation. The Imax will have no wires for the limbs to blow into and pull.
mikefromms |
Tech808
Moderator
Username: Tech808
Post Number: 4609
Registered: 8-2002
| | Posted on Sunday, January 23, 2005 - 11:24 pm: |
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Mikefromms,
Well thanks I guess, But the one you REALLY need to thank is Tech833 for donating all of his spare time to do the Reviews and Articles for the Copper Forum Members to read.
All I did was re-post his Review that he did to help the Copper Forum Members.
There is a LOT of very helpful information here on the Copper Forum and all a person needs to do is CLICK on it and READ it.
Lon
Tech808
CEF808
N9OSN
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Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 387
Registered: 6-2003
| | Posted on Monday, January 24, 2005 - 8:22 pm: |
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You've got that right. Anything you want to know can be found here. I really enjoy searching the sight and reading other opinions and comments.
mikefromms |
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