Solarcon IMAX-2000 CB / Ham radio Antenna Review

Fiberglass omnidirectional base station antenna


A few weeks ago I bought an IMAX-2000 from www.radiosalg.com in Norway.  This is a CB and Ham radio dealer located in Bergen.  After a few days’ shipment in the Norway Mail, the package arrived.  The package says this is a MAX 2000 though it’s marketed as a Solarcon IMAX-2000.
Solarcon IMAX-2000-1
Technical data about this antenna is a follows:

SWR Tunable

Handles 5000 Watts

5/8 Wave over 1/4 λ (though it’s a little longer that the ordinary 5/8 λ CB antenna)

Optimum SWR 1.5 - 1

Covers far above and below the traditional CB channels

5.1 dBi Gain = 2.95 dB at a minimum of ¼ λ above ground *

DC Grounded (there is an impedance match network to resulting in a 50 Ω radio connection)

7,3m tall ( Three 8' / 2,44 m sections with washers between the sections)

Insulated up to 14,500 Volts

Tested to 5000 watts power !

Typically 3MHz bandwidth with 2:1 VSWR

1 to 2db relative gain higher than the best of our competitors

Wind Rating: 100 MPH (= 160 km/hour wind = 44 m/sec wind)

Wavelength: 5/8 Wave (but no, a few cm / 1 inch longer!)

Lightning protected, D.C. grounded. No lightning arrestor or static discharge unit is needed!

Female UHF Coax Connection

Mounting U Bolts (these are not metric and about one-two mm too tight for a 38 mm steel mast or pole).  The mounting plate is sufficient wide to drill two new holes to make it match a 50 mm mast if you buy the proper U-bolts.

Weight 2.72 kg (= 6 lbs.)

http://www.video-observer.com/imax/imax2000.htm has details about the impedance network and more antenna pictures.

Setting up the antenna

Mounting the antenna parts was an easy task and took 5 minutes.  But placing it on a 38 mm steel mast was a bit trickier, I had to use a small hammer to kick down the U-bolts into their proper position.  A remedy is to widen the bolt holes in the mounting plate with a few mm and buy a pair of metric 38 mm U-bolts at your hardware store.
The IMAX antenna is also supplied with a tuning ring at the base of the antenna if you are not satisfied with the SWR ratio.  These two rings are to be turned clockwise or anticlockwise according to the antenna’s manual for the SWR of your liking.

 

After my antenna was installed, I took some SWR measurements:

The solid black graph is the SWR graph. Notice that this antenna goes down from about 4:1 at 14 MHz to 20 MHz without adjustments.  Also note at the SWR is quite flat from 20 to 28 MHz, with a little rise in SWR near 30 MHz.
My aim is to utilize 21m, 14m , 11m and the 10 meter bands.  Of course the 21 meter band needs to be operated with an antenna tuner.
The blue graph is the serial resistance in ohms.  The left axis is the VSWR axis while the right axis is the ohm axis.  I’ll let the graph speak for itself as the antenna is quite broad-banded!

The 10m SWR :


At 28.100 MHz the SWR is about 1.38 without adjustments.


The 21m SWR:

At 14.250 MHz the vSWR is about 3.87:1


The 15m SWR:
At 21m the VSWR is about 1.3:1


The 11m SWR:


At 27 MHz, the antenna’s VSWR is about 1,24:1 !  Very acceptable without any adjustings.


The 10m SWR:


At 28.1 MHz the VSWR is still an amazing 1.38:1

 

Operating the antenna.

I tried to operate the antenna immediately after set-up.  This was in the afternoon and there was a loud and clear traffic on the ham bands on 14 and 21 MHz.  Much more than I was used to with my old and faithful trapped dipole (horizontal) antenna.  I concluded that the elevation (take-off) angle must be quite low compared to my dipole at the same bands.  In addition, the lower take-off angle let me hear stations from other countries that I had never heard from before.  Too bad I was in a hurry to produce the SWR charts, otherwise I would have worked these stations on PSK-31!  Later that evening these bands was partially closed by ionospheric conditions so I only managed to work a few contacts.

Testing performance on the CB band.

With my car CB and a simple car antenna (about 1.5 m tall) I drove to downtown Tromso from where I live.  My wife was at home at the base station connected to the IMAX-2000 antenna.  Now, between my home and downtown Tromso, the Tromso Island is about 100 meters above sea level, so the downtown area is in a radio shadow.  An earlier test showed that it was impossible to communicate over this this distance with a 5/8 λ Aluminum antenna.  However, with the Solarcon IMAX-2000 I was fully able to hear her voice on FM, and she could also hear me.
The manual says on one place that the IMAX-2000 has a 5.1 dBi gain, but on another page it claims to have an 8.2 dBi gain.  The difference is about 3 dB, but if these figures are correct the difference should have been 2.14 dB if the latter is dBi and the former is dB.  Since I had no antenna to compare with nor a radio voltmeter, I couldn’t verify the correct gain.  All I can say is that it should have at least a 2.96 dB gain as it stand near to my house wall today.  This roughly means a double of power, from 4 W delivered to the antenna, and about 8 W radiated.
But anyway, I was surprised that the IMAX-2000 could deliver a signal at all these circumstances considered.  The line of sight distance is about 10 km apart, with the top of the Tromso island between us.

Conclusion.

This must be the very of antennas I have ever tested and owned.  With regards to the above ham bands mentioned, it is also the most broad-banded antenna I have ever had.  Considering a price of NOK 1790 it’s a very good antenna radio-wise and mechanical-wise.


You can also buy a ground plane for this antenna, but I anticipate that this would have made the IMAX-2000 more narrowband, though giving a more flat take-off angle.  So, my next test will incorporate a hove-made ground plane to see what the SWR would be like.

Test equipment:

  1. A standard miniVNA
  2. A Yaesu FT-950 ham radio
  3. Computer program (programmed by myself, and free for you to try) to plot the graphs
 

The road ahead

My next move is to adjustthe antenna a little bit. I want to make the 21 MHz band the lowest possible SWR. This will also shift the upper frequencies (27-30 MHz) to a maginal lower VSWR. First i will try to accomplish this by turning the tuning ring at the base of the antenna. If this doesn't work out well, I have to cut the antenne gradually until this goal is achieved.

09 March 2012