Mastr II Conversion Page

The first thing I did was to change out the RF sections with UHF ones. I took the modules from my original repeater which was a converted Mastr II mobile. The biggest challenge was coming up with a continuous duty UHF PA. The original station PA was only an intermittent duty PA so it was nothing more than a mobile PA mounted on a bracket. After some searching and bidding on eBay, I finally came up with a 75 Watt, continuous duty UHF PA.

Next, came converting the station to full duplex and interfacing the controller. Since this is a station, it wasn't really a big deal. The only thing I had to do was locate the receiver mute line on the connector that plugs into the backplane and pull it out of the connector.

I also had to add a jumper from pin 1 to pin 3 on the 10 volt regulator card to get the PTT to work.

I left the GE audio card in the shelf because I like the GE audio. To interface the controller, I used a "wild-card" in the furtherest slot to the left in the station shelf. I used a DB-9 computer cable to go from the wild-card to the controller. This particular slot doesn't have connections for audio or COS, so I had to find them on the backplane and get them to J1216.

On the backplane, I located the audio line after it passes through the audio card. This point provides de-emphasized audio. The easiest place to get this was on connector J1203 pin 9. I pulled the pin out of the connector and extended the wire so it reached J1216 Pin 10 which goes to J1213C Pin 14, which is the connector that feeds the controller audio in. I then fabricated another wire to go from J1216 Pin 12 to the pin that was removed from J1203. J1216 Pin 12 goes to J1213C pin 13 This feeds controller audio to the exciter.

I connected the PTT line from the controller to the solder pad on the wild card that mates up with J1213D Pin 3. With the station door open, look at the far left slot. J1213D is the bottom connector on the backplane. Pin 3 is the 3rd pin from the top on the left side. J1213D Pin 8 is used for ground.

For COS/COR, I used a GE squelch operated relay card and used the relay contacts to take the controller COR line to ground. This required a jumper from J1216 (the wild-card connector) pin 8 to J1214 (for the Squelch operated relay) pin 12. On the wild card, J1216 Pin 8 corresponds to J1213C Pin 12. This goes to the controller COR line. The controler is set for COS low so I just came off of J1214 pin 5 and tied it to the ground on the backplane. As an alternative, you could build a transistor COR circuit on the wild card and eliminate the Squelch Operated Relay (SOR). You could also take one of the cards you pulled from the shelf, like DC Control, and strip all of the components off of it and build the COR circuit on the card and use it in the SOR slot since the signals are already there. For CTCSS I connected the controller's CTCSS detect line to J1213 pin 7 which is CG Monitor.

The good thing about this configuration is that if the controller dies, I plug in the Mastr II repeater card and flip a switch that jumpers the audio and I'm back on the air in a hurry.

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