GE MASTER II Information

Where to Get the Signals from a MASTR II

The following is the pin out of the front radio connector looking from outside the radio

J901 Pin Out

Important Pins

Pin	Wire Color	Description / Function
3	Yellow/Blue	RX-Mute
5	Yellow/Gray	Spare
7	Yellow/Red	Spare
2	(sheild)	Mic-Low
4	Brown	Mic-Hi
24	Red	A+
25	White	PTT (active low)
16	Violet	CAS (active high)
29	Yellow	A+ (RX/TX/10vReg)
30	Black	A- (RX/TX/10vReg)
27	Brown	Speaker-Low
28	Green	Speaker-Hi
6	White/Green	PL/CG board disable

The following picture is not the front side of the radio!

j901.gif (8537 bytes)

The above picture is inside down on the system board

not the front side of the radio!

Pin 4 is the audio input connection point (Mic Hi), Pin 2 is the audio input ground (Mic low). Pin 4 has a +10V bias applied which powered the microphone preamp. Depending on your repeater controller, you may need to insert a DC blocking capacitor. If you are going to use a mic on the control head, you should insert a resistor in series with the controller's audio output to prevent the controller from loading down the microphone's output, a 5K resister should do it.

Pin 20 is the un-squelched (and is not de-emphasized) audio output and offers around 1 V peek to peek RMS. You may have to add a decoupling CAP to this line depending on your repeater controller’s audio input circuit. You may also have to add a resistor in series to reduce the loading on the discriminator. My advise is to add a RC circuit to de-emphasize the audio if your repeater controller does not rc.gif (660 bytes) have it built in, this will eliminate the tinny sound. Wire one side of the 15K resistor to pin 20, and the other side to one side of a .22µF capacitor. Ground the other leg of the capacitor. Take the receiver audio from the capacitor-resistor junction. Pin 18 is the audio output ground. Optionally you can tap audio out from Pin 19 which is the volume control arm. The down fall of this source is that the audio level tracks with the volume control.

Pin 25 is the PTT line, take this line to ground to force the transmitter to on. You will need a circuit which can sink 75 ma of current.

Pin 16 is the CAS (carrier active sensor). It will go to around 10 volts (active high) when the receiver is un-squelched.

Pin 21 is A- and a good place to tap for you signal ground.

Want to add PL encode and/or decode? P908 is the place to do it. Pin 1 is the same as Pin 20 and a ideal place to feed your PL decoder’s input. Pin 4 offers 10 VDC+ and Pin 9 is A-, nice place to take power for your encoder/decoder. Pin 7 is the PL injection point, you can set the PL deviation level by a pot on the exciter board.

I mounted a DB9 female to the front left side of the radio in a small open space and brought out all of the signals on the DB9.

Modifying the MASTR II System Board for Full Duplex

Sysmod.gif (43833 bytes)

In my conversions, I used the MASTR II control head and control cable. I found that it was nice to have a control point at the repeater site. If you choose not to use the control head, you will need to build the volume and squelch circuits for the radio.

Above is the solder side of the system board which is located at the front of the radio. P901 is the control/power cable connector.

The H6-H73 jumper assures that channel one is always selected.

H89-H90 applies A+ to the radio circuits.

H79-H81 forces the RX oscillator to always be on.

Cut the trace between H95-H96, this prevents muting of the receiver during transmit.

That is it, your done. Your MASTR II is now fully duplexed. If you have any questions please drop me an Email.

MASTR II Volume and Squelch Circuit

Volsql.gif (3141 bytes)

VOL LOW can be connected to J901-18 or J904-12

VOL HI can be connected to J901-20 or J904-11

VOL ARM can be connected to J901-19 or J904-13

SQUELCH ARM can be connected to J901-17 or J904-10

J904 is the connector on the right side of the system board. J901 is the connector on the front of the radio which connects to the control cable.

Also add an 8 ohm 5 watt resistor across the speaker output pins J904-18 and J904-19.

A special thanks to Warren, VE7DPG for pointing out that fact that a .68 cap was needed to keep the pots from acting as a voltage divider.

Here's the exciter board mods...

This assumes you remove the board from the Master II and use it standalone with a 10v source

MASTR II VHF Exciter Re-Alignment

exciter.jpg (51376 bytes) The exciter metering jack is located just below T108. As with the receiver, use an analog meter (VTVM). All measurements are from the metering jack ground pin 8 or 9 to the pin called out in the alignment steps.

Tune T101 for maximum meter reading on pin 2.

Tune T102 and then T103 for the maximum meter reading on pin 1.

Tune T104 for a dip in meter reading on pin 3.

Tune T105 for maximum meter reading and re-adjust T104 for maximum meter reading. Then tune T106 for a dip in meter reading on pin 4.

Tune T107 for maximum meter reading and re-adjust T106 for maximum meter reading. Then tune T108 for a dip in meter reading and T109 for maximum meter reading on pin 7.

Tune T110 for maximum meter reading, and then re-adjust T108 and T109 for maximum meter reading on pin 5.

Note: These are GE’s alignment instructions. I could not get the exciter to drive the PA following the rest of their steps. I connected a watt meter and dummy load to the transmitter, my VTVM to pin 4 on the PA’s metering jack and adjusted T108 -T112 for maximum meter reading. You may have to play a bit with T108, T109 and T110 to get the exciter to drive the PA so keep an eye on your watt meter.

Move the black metering plug to the Power Amplifier metering jack (pin 8 is ground) and tune T111 and then T112 for maximum meter reading on pin 4 of the PA metering jack.

Move the black metering plug back to the exciter metering jack and re-adjust T108, T109 and T110 for maximum meter reading on pin 5.

Move the black metering plug back to the Power Amplifier metering jack and re-adjust T111 and T112 for maximum meter reading on pin 4 of the PA metering jack.

With the battery voltage at 13.4 Volts or the PA collector voltage at 12.4 Volts, set Power Adjust potentiometer R223 on the PA board for the desired power output (35 to 110 Watts) depending on your PA deck’s model.

The exciter puts out about 250 mw of RF power, adjust the ICOM frequency to the frequency of interest using a frequency counter properly connected to the exciters output. Remember to factor in the temperature curve chart when adjusting the transmitter ICOM.

temp.jpg (55182 bytes)

MASTR II VHF Receiver Re-Alignment

ICOM Adjustment

freq.gif (8460 bytes) Before you align the receiver, you need to net you receiver ICOM. ICOM frequency adjustments are made by attaching a frequency counter at the junction of C417 and C415 (shown in the picture to the right, top right corner) which is located to the right of L403. In a VHF receiver the frequency you want to adjust the ICOM to is your receive frequency less 11.2 MHz which should be 9 times the crystal frequency.

An example, if you wished to receive on 147.99 MHz, subtract 11.2 MHz (the IF frequency) which yields 136.79 MHz. Adjust the ICOM for a frequency reading measured at the indicated test point. The crystal frequency should be the receive frequency less 11.2 divided by 9. For a receive frequency of 147.99 MHz the crystal frequency should be 15.19888 MHz.

To properly adjust the ICOM frequency, you need to factor in the room temperature and be sure the receiver is at room temperature.

receiver.jpg (89647 bytes)

All measurements are against ground (pin 8 of J-601. Use an analog meter or VTVM for all measurements.

Adjust L401 for maximum meter reading at J601-3.
Preset L402 and L403 to a position similar to L401, then preset C306 and C307 fully counter-clockwise.
Adjust L402 and L403 for maximum meter reading on J601-4, then re-tune L401, L402 and L403.
Carefully adjust C306 for minimum then adjust C307 for maximum.
Attach your meter to J601-1 and apply an on frequency signal to the antenna jack. Adjust the signal strength as needed during the alignment.
Adjust C501, C301, C302, C303, C304, C305 (and T2301 if present) for maximum meter reading. Reduce your signal strength and re-tune slightly.
C306 and C307 may be adjusted no more than a quarter turn for best quieting.

MASTR II VHF Receiver Re-Alignment

ICOM Adjustment

To properly adjust the ICOM frequency, you need to factor in the room temperature and be sure the receiver is at room temperature.

receiver.jpg (89647 bytes)

All measurements are against ground (pin 8 of J-601. Use an analog meter or VTVM for all measurements.

Adjust L401 for maximum meter reading at J601-3.
Preset L402 and L403 to a position similar to L401, then preset C306 and C307 fully counter-clockwise.
Adjust L402 and L403 for maximum meter reading on J601-4, then re-tune L401, L402 and L403.
Carefully adjust C306 for minimum then adjust C307 for maximum.
Attach your meter to J601-1 and apply an on frequency signal to the antenna jack. Adjust the signal strength as needed during the alignment.
Adjust C501, C301, C302, C303, C304, C305 (and T2301 if present) for maximum meter reading. Reduce your signal strength and re-tune slightly.
C306 and C307 may be adjusted no more than a quarter turn for best quieting.

MASTR II UHF Receiver Re-Alignment

ICOM Adjustment

freq.gif (8460 bytes) Before you align the receiver, you need to net you receiver ICOM. ICOM frequency adjustments are made by attaching a frequency counter at the junction of C417 and C415 (shown in the picture to the right, top right corner) which is located to the right of L403. In a UHF receiver the frequency you want to adjust the ICOM to is the receive frequency less 11.2 MHz divided by 3.

An example, if you wished to receive on 447.275 MHz, subtract 11.2 MHz (the IF frequency) and divide by 3. This results in the frequency you will tune the ICOM, in this case, 145.358333 MHz.

To properly adjust the ICOM frequency, you need to factor in the room temperature and be sure the receiver is at room temperature.

UHF Receiver Re-Alignment

All measurements are against ground (pin 9 of J-601. Use an analog meter or VTVM for all measurements.

Adjust C406 for maximum reading at J601-3.

uhfrec.gif (21550 bytes) Pre-set C411 and C416 in a similar position as C406 then pre-set C306, C307, and C308 fully counterclockwise.

Adjust C411 and C416 for maximum meter reading, then re-tune C406, C411, and C416 for maximum meter reading at J601-4.

Tune C307 and C306 for maximum meter reading at P601-7, then repeat this process. Next tune C308 for minimum meter reading and re-tune C306 for maximum meter reading. Do not re-adjust C307 or C308.

Move you meter to J601-1 and apply an on frequency signal to the antenna jack and tune C301 through C305 and A303 for maximum meter reading. You can also re-adjust C306, C307 and C308 but not more that 1/4 turn. Reduce the signal level being feed in to the receiver and repeat as many time as required, reducing the injected signal until no further sensitivity can be obtained.

Converting a GE Master II mobile to a repeater

Here's the exciter board mods...
- This assumes you remove the board from the Master II and use it standalone with a 10v source
GE Master II 150.8-174MHz conversion to 220MHZ

Front Panel

Back to Main Page

Dave is putting all his repeaters in base station cabinets that have pull out drawers. The following schematic is a standard method Dave used to modify a mobile GE Master II into a repeater when he was using a mobile housing to hold the repeater. The front panel is shown of the previous page.

Back to Main Page

De-emp Board

Back to Main Page

1	100 ohm	R1	1	39K ohm	R6
2	180 ohm	R8.R13	1	.001µf disk cernatuc	C5
1	1K ohm	R9	4	.22µf polyester	C1,C3,C4,C6
2	5.1K ohm	R3,R7	1	22µf tantalum	C7
2	15K ohm	R4.R10	1	22µf electrolytic	C8
1	20K ohm	R11	1	100µf electrolytic	C2
1	2.5k pot	R14

Back to Main Page

Receiver RF Assembly

	No Turns After Modification
L301/311/C301 (silver)	5
L302/312/C302 (silver)	5
L303/313/C303 (silver)	5
L304/314/C304 (silver)	5
L305/315/C305 (silver with coax attached)	4 1/2
L306/316/C306 (bronze)	5 1/3
L307/317/C307 (bronze)	5 1/3

More information on modifying RF Assembly

The RF Assembly has 2 enamel coils and 5 silver coils. Coils L301/311/C301 and L305/315/C305 have taps on the bottom turns. Both taps were originally placed directly across from the solder ends of the coils. Dave replaced both taps 1/8 turn closer to the soldered end of the coil

This is the modified L301/L311/C301 coil

The coils are very difficult to de-solder, Dave places the assembly on and electric kitchen stove at the lowest heat setting. He does not get it hot enough to melt the solder but uses his solder gun to remove and replace the coils. I use a butane torch.

After removing the turns, pull on the top and bottom of the coils until they are at the original length. When you replace the coils, the bottom should be just touching.

Back to Main Page

Transmitter Exciter Board

On the exciter shorten the following coils: L301/L311, L302/L312, L303/L313, L304/L314, L305/L315, L306/L316 and L307/L317. The older models have paper coils and are somewhat easier to modify but tend to slip and require Teflon inserted between the slug and coil sleeve. The later models use plastic coils and are preferred because you don't have the slippage. The plastic and paper have different number of terms.

Paper Coil - 19D416859G4

Plastic Coils - 19D430230G4

To calculate the number of turns to remove

(174-150.8)/2+150.8 = 162.4
162.4/224.6 = 0.723
0.723 times the original No of turns gives the calculated turns to remove
For example T101 has 33.5 turns and .723 times 33.5 equals 9.28

Coil No.	Original Turns Paper Coils	Calculated Turns to Remove	Original Turns Plastic Coils	Calculated Turns to remove	Actual turns removed.
T101,T102,T103	33.5	9.28	33.5	9.277	9
T104, T105	11.75	3.25	14.5	4.016	4
T106	7.5	2.08	7.5	2.077	2
T107	7.5	2.08	7.5	2.077	2
T108,T109,T110	4.75	1.32	4.5	1.246	2
T111	5.25	1.45	5.5	1.523	2
T112	5.5	1.52	5.5	1.523	2

More information on coil modification.

The taps are left unchanged

If L102 is 27 micro henry, it should work fine, if is is 38 micro henry, replace it with a .22 micro henry

Tuning Excitor

Using DC Volt Meter with High Impedance	Tuning Coils	Readings from Dave's 1997 conversion taken with Fluke DVM
Pin 2 & Ground	Peak T101	2.42
Pin 1 & Ground	Peak T102,T103	2.01
Pin 3 & Ground	Dip T104 Peak T105	1.13
Pin 4 & Ground	Peak T104,T105 Dip T106 Peak T107	1.61
Pin 7 & Ground	Peak T106,T107 Dip T108 Peak T109 Dip T110	2.08
Pin 5 & Pin 6	Peak T105,T106,T107,T108,T109, T110	0.63
Using watt meter	Peak T111 & T112	330mwatts@235mamp

You can increase the power output 40mw by removing the resistor between T112 and RF Jack and replacing R147 (the resistor satnding on it end across from T111) a 36 ohm resistor with a 1/4 watt 10 ohm resistor

Receiver Oscillator Mulitipler Board

I know of at least three version of the Oscillator Multiplier Board .I have only use the later model oscillator boards. The earlier boards have 3 tuning coils and the middle model has a C406 capacitor in place of L6. The components of the middle model board are number using three digits and the later model uses one or two digits. I have used both numbering systems on the drawing.

On Coil L1 short out 1.5 turns form Center of coil. On coil L2 short out 1 turn from outside. On L403 short out 1 turn from outside. No. 30 solid wire works well for shorts.

Remove and discard the following capacitor C12

The oscillator may work but the get maximum performance you can:

Replace Q1 with a 2N2857
Replace Q2 with aMRF517

The picture below shows an easier modification the work equally well. Short the three coils as described above and remove capacitor C7. L1 and L2 have two points on the 360 degree tuning radius that seem the tune equally but you have to keep trying different combinations to get the mixer to tune to specifications. If you don't get the combinations correct, it will only tune to 2.5 MV. If you get the combination correct it should tune to .25 MV.

Back to Main Page

Receiver RF Assembly Mixer IF Board

On the RF assembly mixer if board PL19C331099 Group 1 / PL19C320153 Group 1. Short 1/2 turn on L502. Raise one end if R503 so you can ground to shortest path 1/2 turn from ground end. I broke the original resistor and replaced it with a resistor of the same value.

Back to Main Page

PA Modification Mobile

Back to Main Page

Mount the power module to the heat sink as shown below. The little circuit board was etched with a Radio Shack PC board kit 276-1576. Be sure the apply the heat sink grease. The picture below shows the circuit board before connections are attached.

See the schematic below for filter parts list. The schematic is for the entire PA circuit, the filter is only the last part of the circuit. The red arrow points to the one coil you do not have to remove. You must solder a strip across the back of the board where the relay was removed. Pull the same size strip off the board and solder it across the relay. Be sure to use the same size strip to maintain 50 ohms to the RF plug that was left on the board (upper right corner).You must remove the filter shield (see last picture on this page) to access the filter circuit board.

An enlarged view of the picture above

R1	1k - 2 watt Pot
Q1	NPN TO-220 transistor (use transistor on front edge of heat sink)
C3,C4	33 µFD@35vdc tantalum Cap Digi-Key Part No.P2102
Dev2	Power Module RF Parts # M57774
C5,C6	Cap 4700PF 50v Der Disc Digi-Key part No P4057A
C1,C2	Cap 40PF Part No. J101-40
L1	Two turn coil (Strip everything off the filter board except one RF plug, use one of the coils you removed to make the coil)

Back to Main Page

Repeater Mods

The following pictures show the modification made to the system board to make the mobile GE Master II into a repeater. The www has an abundance of information on this subject.

On the solder side of the system board, cut the board traces at the 7 points denoted by the red markings. Add the two white jumpers. This complete the mods on the solder side.

Back to Main Page

Connecting A CAT 1000 to the GE Master II Repeater

The following is a close up of the modifications made to the GE Master was made by W4UWH. The numbers on the Back panel are the DB 9 numbers on the right, and I do not use Pins 1 or 2. I sometimes use pin 4 for power control, it requires the addition of a reed relay and pot. I use the Computer Automated Technology (CAT) Output 1 to close the relay to switch between two power settings.

Back to Main Page