The Solarcon I-MAX 2000
This antenna is so unique, I thought it deserved talking about. So I decided to do an article to explain why the I-MAX 2000 is the perfect antenna for ham radio use on 17 through 10 meters.
The I-MAX 2000 is the newer big brother to another famous antenna that was originally called the Antron 99. It was made by Antron Antenna Company. Antron sold the design to Solarcon Research who continued to manufacture and sell it as the A99. Same antenna, new name. The A99 is a 1/2 wave over a 1/4 wave antenna for CB (11 meters). CB’ers found the A99 to be a great antenna that performed better than most other antennas in it’s class. And hams found it to work well from 17 through 10 meters as well.
This new big brother antenna was named the I-MAX 2000 for it’s performance values.
(I)=Current, (MAX)=maximum, rated at 2,000 watts. It means that the loading coil design and its wavelength, will radiate the maximum amount of RF possible up to 2,000 watts. Compared to any other antenna. It has a rated gain of 3dB/i, or a 0.8dB/d. Although that figure is actually a bit low. Several (Real time) measurements of the I-MAX 2000 have been made showing a 5 to 5.5dB gain over a dipole. Remember, no other manufacturer uses this design. Some have tried to copy it’s looks and function, but only the Solarcon I-MAX 2000 is designed like a Solarcon I-MAX 2000. Don’t fall for impostors.
The I-MAX 2000 is designed very similarly to the 1/2 wave A99, but longer. It is being advertised as a 5/8 wave for CB. But the actual measurements say differently for use on 10 meters. The antenna comes in 3 fiberglass sections that screw into each other to make a 23 foot tall antenna. Each section has a #14 bare copper wire that runs inside the entire length of the sections.
Near the inside middle of the center section, there is a high power capacitor-coupler (Shown below) approximately 40pf in value, and yes it couples the top half of the antenna. This allows the center section to radiate a larger pattern than most verticals do.
When the copper wire radiator alone is measured, the bottom section is 80 inches, the middle section is 90 inches, and the top section is 90 inches. That is a total of 260 inches.
So that means that the I-MAX 2000 is a 5/8 wave antenna on 11 meters, (27MHz CB band) as advertised.
But on 10 meters, it works out to a sweet .64 wave antenna. This is a very good thing. And it just so happens that the unique length of this antenna turns out to be a virtual nice little 1/2 wave on 15 meters. With 17 meters being close to 15 meters, the I-MAX 2000 will load up nicely there too with an antenna tuner. The antenna is wide banded enough to cover 12 meters very well also.
The .64 wavelength is very important, and a widely kept secret in CB antennas back in the 70’s and 80’s. A .64 wavelength is the maximum length that can be used for an antenna to maintain the largest transmitting RF pattern from the antenna. An antenna any longer than a .64 wavelength will begin to collapse the pattern. For a very detailed explanation on the importance of the secret .64 wavelength.
The I-MAX 2000 is known for blowing away all 5/8 wave antennas, and being equal to many small 3 element beams in gain towards the horizon.
The I-MAX 2000 uses a capacitance-inductance loaded coil in the base.
In the diagram above, the top figure is the schematic diagram of the I-MAX 2000. Notice the location of the letter “B”. It is a capacitance connection that connects the main element to the the coil load.
The diagram on the bottom is a rough drawn cross-section picture of the base coil load. On the left, is the coil that creates the 50 ohm impedance. The 2 solid gray lines represent the tuning rings. The 2 rings are coated with an aluminum paint. As the rings are turned up or down, it changes the resonating frequency of the antenna to adjust the SWR.
On the right, the solid orange area is the brass sleeve that surrounds the nylon core. The brass sleeve is connected to the coil. During transmission, the brass sleeve generates an RF field all throughout the inside.
A few inches of the main radiating element goes down inside the brass sleeve, but does not directly connect to the sleeve. That is where the inductance comes in. The RF field inside the brass sleeve is arched (Inductance) to the main element inside. The main element picks up the RF and radiates it from the entire 22 foot length of the main copper wire element.
The I-MAX 2000 is head and shoulders above the Antron 99 in engineering practice. So much additional inductance coil is needed in the Antron 99 to get the highly capacitive 1/2 wave element tuned. However, in the I-MAX 2000, with the .64 wavelength element, the capacitance is much lower, which requires much less inductance to tune it out. Therefore, much less coil is required to tune the I-MAX 2000 to resonance, which greatly reduces the coil losses. It also helps make this antenna very wide banded.
The I-MAX 2000 on 17, 15, 12, and 10 meters.
One of the reasons I consider this antenna to be a ham operators dream antenna, is it’s ability to load up on 17 through 10 meters. And it does this quite nicely too.
As we have said, the I-MAX 2000 was designed as a CB antenna. With the 10 meter ham band just above the CB band, the I-MAX 2000 will load up and work perfectly as a .64 wave on all of 10 meters with a very low SWR. And 12 meters is just below CB, so it loads up very well there as well. But here is where it gets interesting.
The .64 wavelength at 10 meters makes the I-MAX 2000 a virtual 1/2 wave antenna on 15 meters. And with 17 meters being a small band, and not that far below 15 meters, the I-MAX 2000 will work quite well on 17 meters too with a tuner.
Use Quality Coax ONLY
I use LMR-400 coax on my I-MAX 2000. It is important to use a good quality double shielded
RG-8 type of coax like LMR-400, when using this antenna for 17 through 10 meters. Any coax will do if you are only using the I-MAX 2000 for just 11 meters, or 11 and 10 meters. But when using the antenna to cover such a wide range of frequencies like 17 through 10 meters, only a quality double shielded coax can deliver the most power to the antenna with the lowest SWR possible. Using a cheaper RG-8 or RG-8X (mini) or worse yet, RG-58U coax will cause SWR problems on 17, 15 and possibly 12 meters.
Using LMR-400 coax, I measured the SWR on each band with an MFJ-269 Antenna Analyzer, at the radio insertion point.
- 10 meters = 1.2:1 at 28MHz, to 1.6:1 at 29.700MHz.
- 11 meters = 1.2 to flat 1.1 across 1MHz
- 12 meters = 1.5:1 entire band.
- 15 meters = 1.7:1 at 21.450MHz to 1.9:1 at 21.200MHz.
- 17 meters = 2.9:1 entire band. Built in auto tuner brings it down to flat.
I have worked all continents on 17 and 15M with the I-MAX 2000 and had great strong signals TX and Rec. QSO’s on 10 and 12 meters to all of No. & So. America, and Europe are fantastic with very strong signals TX and Rec. All with just 100 watts.
The Ground Plane Kit
The I-MAX 2000 has a ground plane radial kit available. It consists of 4 fiberglass radials at 70 inches each. They screw into a bracket that mounts onto the antenna mounting bracket. The kit is fine if you just want to use the antenna for 10 and 11 meters. But on 12, 15, and 17 meters, the radial kit will detune the antenna for these bands, and raise the SWR.
Instead, I left the radial kit off, and made an open air wound choke coil with the LMR-400 at the antenna feed point. The choke keeps the RF from coming back down the coax, and allows the full power to radiate from the antenna. But it does not have any effect on the SWR on any band from 10 to 17 meters. No counterpoise wires are necessary. The I-MAX 2000 antenna is made for these bands, and is widely known to out perform dipoles cut for the same bands. And it’s the best ground plane antenna for 11 meters hands down.
(An RF choke coil is easy to make. I created a great article on the myths about chokes and how to build the one I use. It is so simple and only takes a few minutes.)
The Tuning Rings
For ham radio operators only. Leave the rings set in the center factory position. Do not move them ever. The rings only have a 3MHz bandwidth and covers roughly 26MHz through 29MHz. So they will have very little to no effect on 17, 15 and 12 meters. The I-MAX 2000 is already a 5/8 wave on 11 meters and a .64 wave on 10 meters. Changing the tuning rings will alter the wavelength on these 2 bands and slightly detune the antenna. It will actually be “Electrically” too long or too short to be a .64 wave on 10 meters.
For CB operators… The rings should be already set from the factory to CB channel 20, (27.205MHz). This setting should provide an even SWR rise to the highest and lowest frequency of 11 meters. But if you use one specific channel most of the time, and wish to tune the antenna to that frequency, you can raise or lower the tuning rings for the lowest SWR on the channel of your choice. Raise the rings higher, for better SWR on the higher end of the 11 meter band. Or tune the rings lower for lower SWR on the lower end of the 11 meter band. When retuning the rings, move the rings only 1 full turn, then check the SWR. Keep moving the rings 1 full turn and checking the SWR until the SWR is as low as it can be.
You may be wondering about the vertical polarization on HF ham bands. Yes the I-MAX 2000 is vertically polarized, but vertical polarization sends a greater amount of signal towards the horizon than a horizontal polarized antenna. And once the signal reaches the curve of the earth and hits the ionosphere, there is no real polarization left to the signal. It becomes scattered or circular. It no longer makes any difference.
Replacing Top Whip??? NOOOOOO….!
There have been a few people that say they replaced the top whip of the I-MAX 2000 with a steel whip, and got improved signals. But they were mistaken. The top whip of the I-MAX is an 8 foot whip. A steel whip is usually 9 feet. The added 12 inches would lower the resonance of the I-MAX 2000 considerably, and it would no longer be a .64 wave on 10M, or a 5/8 wave on 11M, or a 1/2 wave on 15M. In fact, it would be too long to work well on any CB or ham band. The signal pattern would begin to collapse on those bands because of the incorrect length. You could correct this mismatch by cutting the steel whip down to 8 feet like the original fiberglass whip. But then it would be the same as the original fiberglass whip, and there would be no difference in performance. So why bother? Just leave it as it comes from the factory. It can not be modified to improve performance.
What this means to you is, don’t waste your time by replacing the fiberglass whip with a steel whip. It does not add to the performance of the already perfect I-MAX 2000.
One extra little bonus. Anyone who needs a great general coverage antenna for short wave listening, the I-MAX 2000 works very well indeed. I would not use it for transmit on 20 meters and below. The SWR at 20M is at least 10.0:1 or worse, but it receives those bands great.
The I-MAX 2000 retails for around $75 to $90. For a 5 band HF vertical, that’s not too shabby. I would not give up or trade mine for any other antenna. I did not include a link to Solarcon because they do not have a website that shows or details the I-MAX 2000.
A Thank You
Some of the text and research used in this article was from an original article titled, “The I-MAX 2000 Exposed”, By Paul Shinn aka.. Tech 833. Thanks Paul for your wonderful research.
By Dave – K3DAV (11/29/2010)