Photo 1
Photo 1 | In photo 1 I have the antenna laid out with the insides alongside the fiberglass shell it was once housed in. Removing the insides from the 2 lower sections was accomplished with a Dremel tool and a cutting wheel. Removing the insides of the upper section required a planer and systematically shaving away fiberglass until I got down to the copper wire inside. I had to determine if there were any coils or anything inside the top section. Instead, it's just a length of stranded copper wire. However, with a .64 wavelength element, adding coils would distort the otherwise clean pattern, so I was glad to find just the wire. The only thing that could improve this antenna would be a counterpoise (ground planes). More on this later. |
 Photo 2 | In photo 2, you see what is inside the lower section and how the tuning rings affect the coil's tuning. Except for the lower 2 feet of the Imax 2000, all the rest of the antenna contains nothing more than a straight piece of #14 bare copper wire. An upgrade from the A99, the Imax 2000 uses RG-213 coaxial cable which connects to the SO-239 connector in the bottom of the mounting pipe and to the coils of the matching section. Just to the right the outer coil is the brass outer 'plate' of the coupling capacitor. The 'twin ring' match works by moving the metal rings closer or further away from the outer coil which changes the inductance and therefore, the resonant frequency of the radiating element. |
 Photo 3 | In photo 3, you can see how the coaxial cable connects to the Imax 2000 feedpoint at the bottom of the coils. There was a small plastic spacer that I removed for the clarity of the photo. Here, you can see that the soldering job was excellent and very electrically secure. Using the brass crimp sleeve seen here helps add a mechanical strength to the solder joint which will help the antenna maintain it's electrical integrity through vibration and temperature fluctuations. The inductance tuning coil in the Imax 2000 is much smaller (and less lossy) than the Antron 99 antenna. The Imax 2000 uses 10 turns of #14 enameled copper wire. |
 Photo 4 | Photo 4 gives you a good view of how the inner impedance matching coil fits inside the outer tuning coil. With the radiator length being .64 wave, the impedance at this point is extremely high. The inner coil provides a 50 ohm tap on the driven element, while the outer coil cancels out the capacitive reactance created by the coupling capacitor and the capacitance at the fed end of the radiator. One of the big secrets to getting a wideband antenna, which many other antenna makers apparently ignore, is completely canceling out the reactance. Even a few ohms of reactance at the feedpoint will greatly reduce the bandwidth. By tuning the reactance to zero, the SWR will be very low over a wide frequency range. |
 Photo 5 | Photo 5 provides a look inside the coupling capacitor viewed from the radiating element end. If you look carefully, you will be able to see the excellent soldering job from the copper wire to the brass inner 'plate' of the capacitor. Here, as in the Antron 99, you also see another brass crimp sleeve used to strengthen the capacitor plate stub to radiator element solder joint. The Imax 2000 is built much better than the Antron 99 reviewed in an earlier article. The attention to solder joints was much better in the Imax 2000, and I was very pleased to see this attention to detail. It makes for a much 'quieter' antenna. |
 Photo 6 | In photo 6, you get a look at the nylon spacer which forms the 'dielectric' of the coupling capacitor. I had to use a great deal of heat to remove the press fit brass sleeve, so some melting of the nylon is evident. There is NO WAY this would come apart by accident! Like the Antron 99 coupling capacitor, when measured with a capacitance meter, I measured a value of 4pF for each end. That's measured radiator-to-sleeve and again from ground-to- sleeve. The Imax 2000 radiating element is capacitively coupled rather than connected directly to the coax to isolate the antenna base from high voltages in case the installer happens to drop it across power lines and the radiator happens to make contact with high voltage. |
 Photo 7 | Photo 7 shows the inside of the capacitor coupling unit with the components alongside each other for spacing reference. A brass cylinder inside the nylon forms the inner conductor or 'plate' of each end of the coupling capacitor. The brass cylinders do not touch each other end to end, there is a small space left which acts like a spark gap in the case of lightning strike to take the charge straight to ground. For a more detailed idea of how this works, check out the schematic diagram below. |
 Schematic 1 |