The MICOR Exciter

Explanation of the MICOR VHF Exciter

By Kevin Custer W3KKC

There are basically four types of exciters that are common in the VHF Highband.
An explanation of each follows:

1) Early PM (Phase Modulated). These have 3 channel element interface pins and used the K1007 element only. These exicters have good voice audio characteristics and will do a PL tone pretty well without much distortion. They however will not do DPL (Digital Private Line) or data in any way. These have a DIP type IC (M6702) for the modulator. There were commonly used in the MICOR highband mobile. We commonly refer to these as 3 pin exciters.

2) Mid run PM. These have 4 channel element interface pins and will accept either a K1007 or KXN1019B true FM element. These have a DIP type IC (M6702) for the modulator. The voice modulation is done the same as scenario 1 above, but the unit could be used in DPL systems if a KXN1019B element was used. If the KXN element was used, the PL or DPL was applied to the fourth pin on the exciter and this FM'ed the element, so very good PL or DPL modulation took place. A DPL signal is basically a square wave serial data stream and PM modulation doesn't have good enough low frequency response to be usable. These were used in the MICOR mobile where DPL was necessary. We refer to these as 4 pin phase modulated exciters.

3) Late Model FM. These have 4 channel element interface pins and used a KXN1019B element only. The voice and PL or DPL modulation was applied to the FM element. These exciters didn't have any DIP ICs, but rather only the 5 pin (usually blue) clipper/limiter amplifier and some transistors. The voice audio was processed by the clipper while the PL/DPL was applied after the clipper directly into the channel element. These were used in the MICOR Station. We refer to these as true FM exciters.

4) Unknown Model FM. These have 4 channel element interface pins and used a KXN1019B element only. The voice and PL or DPL modulation was applied to the FM element. These exciters didn't have any DIP IC's, or the 5 pin (usually blue) clipper/limiter amplifier, just some transistors and a big coil looking thingy. The voice audio was processed by the clipper while the PL/DPL was applied after the clipper directly into the channel element. These were used in the MICOR Station. We refer to these as true FM exciters.

Here are some pictures of the popular MICOR Channel Elements

Note: The K1007 and K1005 only have 3 interface pins, while the KXN series have 4.