• VHF Low Band: There are 4 "splits" available in this band. The only interesting splits are the "12" split (25-30 MHz, rare!), the "13" split (30-36) and the "33" split (42-50 MHz). The "23" split should be avoided at all costs; it is useless for amateur operation. The 12 & 13 split radios can be tuned into the amateur 10-meter band, and the 33 split radios can be tuned into the amateur 6-meter band.

• VHF High Band: There are 2 splits available in the VHF high band. The "56" split is from 138-155 MHz. These are more desirable for amateur work, and much more difficult to find. (If you find some, get one for me!) The "66" split is from 150.8-174 MHz, and is more commonly available. The high split radios can be re-tuned into the amateur bands, typically without too much difficulty, but care must be taken that the transmitter does not have excessive spurious emissions. The 66 split exciters can be modified to be 56 split exciters by replacing a dozen or so disc capacitors. The 66 split radios are preferred for 222 MHz conversion.

• UHF: There are five different splits for UHF MASTR IIs. Only three are interesting for amateur use: the "77" split (406-420 MHz), the "78" split (420-450 MHz, rare!), and the "88" split (450-470 MHz). The other two splits (89 & 91) are in the so-called "T-band" (UHF television spectrum) and are not useful to amateurs. The 77 split (406-420) radios can be retuned into the bottom segment of the 420-450 MHz U.S. amateur 70cm band, where they are useful for linking repeaters, remote receivers, etc. (See Crossbanding Applications for some ideas...) The 78 split (420-450) radios are already in the U.S. amateur band, but are extremely rare. Radios in the 88 split (450-470) split can be re-tuned into the 440-450 band and used as UHF repeaters.

• 2C ICOMs: These are the 2 PPM oscillators. They are what you want if you are going to build a wide-area coverage repeater that will not be in a climate-controlled environment. The ICOMs themselves are more expensive, as are the crystals that go inside the ICOM.

• 5C ICOMs: These are the 5 PPM oscillators. Most mobile radios will use 5 PPM oscillator stability and will have at least one 5C ICOM. These are reasonably stable, and can be used for repeater operation if the environmental temperature is relatively constant. 5C ICOMs provide "temperature compensation" to EC ICOMs.

• EC ICOMs: These are used in conjunction with 5C ICOMs. DO NOT USE EC ICOMs IN A RADIO WITHOUT A 5C ICOM INSTALLED. The oscillator frequency will not be stable. These ICOMs provide 5 PPM stability when used with a 5C ICOM. They use a "temperature compensation" signal provided by a 5C ICOM. Typically, the receiver has a 5C ICOM and the transmitter a EC ICOM.

You can change the ICOM's frequency by replacing the crystal. However, if you change the crystal yourself, you risk upsetting the temperature compensation of the ICOM, which must be matched to the crystal. If you are going to pay for a 2C ICOM with a 2 PPM crystal, it is well worth the money to get a reputable crystal house (like International Crystal Manufacturing) to compensate the ICOM to match the crystal. This typically costs about $25.00.

There is a true-FM exciter available for UHF MASTR IIs, but it is somewhat rare and the prices reflect that. You can recognize this exciter by the larger ICOM module, the FM ICOMs are about 50% wider and 50% thicker than the usual ones.