GE Mastr Exec II Combination Numbers
and Crystal Ordering

April, 2010
Ron Wright, N9EE

The following are comments on the GE Mastr Exec II radios for use in Ham Radio and Repeaters.

The combination number (model number) tells what is in the Exec II.  The combination number is found on the front panel just behind the handle.

This is a break down of the combination number:

The combination number will be in the form of RT56AAU88

RT or ST	5N (35-40W) 	XYZ 	31 (30-36 MHz, good for 10 meter)
RT or ST	6N (60/75W)	XYZ	23 (36-42 MHZ, have little use to Ham Radio)
RT or ST	6N (60/75W)	XYZ	33 (46-50 mhZ, good for 6m, but for 53 MHz 	
RT or ST	6N (60/75W)	XYZ	56 (136-150 MHz, good as is for 2m, Gov or 							CANADA)
RT or ST	7N (100W)	XYZ	66 (150-174 MHz, good for 2m)
RT or ST	7N (100W)	XYZ	88 (450-470 MHz, good for 440)

As shown the first digit gives power level (5 - 35/40W, 6 - 60.75W, 7 - 100W) and last 2 digits gives band (31 - 10m, 33 - 6m, 56 or 66 - 2m, 88 - 440 MHz).

The N and XYZ of the comb nr tells things like the number of channels, having Channel Guard (GE's CTCSS or tone), etc.  Normally one is not concerned with these number/letters for a repeater.

Some combinations to be aware of:
V1A04 or the like.  These are Pack/RTs having very low power PAs and uncommon SAS (audio/squelch) boards, but exciter and receivers are same as regular radio and can be used as spare parts.  

Except for 6m (53 MHz) most times radio will tune into Ham Bands as is.  For 6m transmit in the 53 MHz segment it is best to replace 7 capacitors in the exciter chain to make tune (this info is given in another document on this board).

Advise for 10m (31), 2m (66) and 440 (88) use high side injection for receive crystals.  This will have the receiver LO operating in the GE spec'd range of its design.  For 6m low side injection is preferred.

The Exec II uses a crystal holder/module (not ICOM like for the Mastr II) with oscillator located on the main PC boards.  One can simply order the crystal and insert in the crystal holder.  Always use the correct band crystal holder (lo band, VHF hi or UHF).

To order crystals one needs to give to crystal manufacture the following:
1. for GE Mastr Exec II radio
2. frequencies transmit & receive (spec low or high side injection)
3. address to ship to
4. method of payment (most take credit cards)

Crystal manufacture will have info on how to make the crystal, both transmit and receive.

Some popular and good crystal manufactures are:
BOMAR 800-526-3835, Middle Sex, NJ ($50 min, $15 ea, 2 weeks)
International Crystal Manuf (ICM) 800-725-1426, OK City, OK ($25 ea)

There are others.

For mobiles operated as a repeater turn down the PA power to 50-60% max rating.  This is done with pot inside PA.  There is no tuning in any of the PAs.  Some higher powered PAs have SWR network circuits with pot adjustment.  Unless you know what you are doing do not adjust these pots.

The PAs for the Exec II and Mastr II are the same in most.  In the Exec II the lower power, 35-60W (5/6N) the PA is in a smaller chassis.  In higher power radios the PAs are in larger chassis and are same as in Mastr II.

In some Mastr II UHF radios the PA was driven by VHF (150 MHz) exciter and had trippler as first stage in PA.  Normally do not use unless you have complete Mastr II radio.  Exec IIs did not have this configuration for all PAs were driven at the operating output frequency.

One can use external continous duty PA, 19 in rack mount, and all exciters will drive these.

On receive the Exec II draws about 0.5 Amps.
On transmit at 30 W draws about 8 Amps, at 50/60W draws about 15 Amps.  The higher powered PAs are less efficent so current/watt is more.

Typically one can turn down the power levels to at least 30% max rated power.