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Modifications for GE Phoenix-SX 2 Channel Radio to allow Remote control of all 16 channels.

Mods By:

Joel Huntley - WA1ZYX
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Almost ALL GE Phoenix-SX synthesized radios are built on the same chassis. The major difference is, aside from being on another band, is how many "Modes" or channels are available from the front panel or if it has scan capabilities.

The following Modifications when performed on a Phoenix SX Programmable radio, in particular the two-channel model, will allow access to all 16 channels that were normally inaccessible in the standard configuration. Also, these modifications are the same for the two or sixteen channel, except the two-channel radio won't "show" you what channel it's currently on.

When you are switching channels on the two-channel model, removing the power will reset it, to channel 1 if you get lost or need to start from the beginning.

The nomenclature of the radio I used to perform these mods was: N5UU2W25BA
These modifications will also allow the radio to switch through all 16 channels via remote control using only three control lines from almost any repeater controller, making this a very inexpensive and semi frequency agile remote base for repeater linking.

The three control lines are used to:
A Select frequencies
B Toggle between Mode A/B
C Momentarily power down the radio so you can begin changing channels from a "KNOWN" channel.


First, make sure you have a fully working radio, and have the EEPROM programmed for the frequencies you want access to. If you're going to use this radio for a repeater link radio, or remote base, you'll need to leave it in "Mode-B". (After the mods, the radio will default to Channel-1, Mode-B, so make this channel your primary or most frequently used frequency.)

Remove both top and bottom covers of the Phoenix-SX. Locate PIN 2 of P912 on the under side of Radio. This should be the 2nd pin toward the rear of the radio of the 4 contact nylon connector in close proximity of the volume control.

Now on the top side of the radio, locate the corresponding pin of J912, this solder connection is actually the end of the pin that protrudes through the radio to make contact with P912.

Solder wick this connection and while using needle nose pliers, heat the pin, and pull it back through to the top side so there is a minimum of of an inch of the pin showing. This will ensure that you have broken the contact with P912. (It probably isn't a bad idea to power up the radio at this point and confirm that the MODE A/B switch DOES NOT work now.)

Position the radio with the front panel facing you, flop it over and locate the A/B Mode switch (S601) on the underside of the radio.

Using a 1K 1/4w resistor, solder one end to the center tab of the A/B switch (S601), on the row of tabs closest to the Monitor pushbutton. (The other row isn't used, so if you make a mistake, it just won't work, you won't hurt anything.)

Solder one end of a short jumper to the other end of the 1k resistor and route it to the top side of the radio so you can solder the remaining end of the jumper to the Pin at J912. (The one you pulled through).

If you power up the radio now, the Mode A/B switch should be working normally again. What the above mod does is make it possible to leave the A/B switch in the "B" position (which actually supplies 8v to the microprocessor) and pull the microprocessor line to ground (at J912) without shorting the 8v supply - thereby gaining access to the "A" mode. The A/B switch is really nothing more than an on/off switch for 8v to one of the microprocessors logic lines.

What I did next will allow, with the addition of a few pins in the power and mic connector plugs, access via the rear panel to remotely change channels.

If you need pins or connectors, you can get them from DigiKey.

The 11 circuit terminal housing, .156 for J910 is Digi-Key P/N WM-2109-ND
The 8 circuit terminal housing, .156 for J911 is Digi-Key P/N WM-2106-ND
And the Pins for housings are Digi-Key P/N WM2300-ND

Or you can get them from Mouser Electronics.

The 11 circuit terminal housing, .156 for J910 is Mouser P/N 538-09-50-3111
The 8 circuit terminal housing, .156 for J911 is Mouser P/N 538-09-50-3081
And the Pins for housings are Mouser P/N 538-08-50-0106

Now use another jumper and connect one end again to J912 and back to pin 5 of J910 (the 11 pin systems jack on rear panel.) Pin 5 is an extra pin and there are no traces or other connections to it. IMPORTANT, The rear panel jacks are labeled looking from the front of the radio down at them. The 11-pin jack (J910) should be on the left, the Mic connector (J911) to the right of that and the antenna jack on the extreme right. Also the pin numbers are from Left to Right.

Now by pulling Pin-5 of J910 Lo, you can remotely toggle the electrical position of the Mode A/B switch.


To change the frequencies, all you have to do is momentarily pull Pin-7 of J911 to ground. By pulsing Pin-7 of J911 (Mic connector) to ground gives you access to 8 channels, and by changing the condition of the A/B line gives you the other bank of 8 for 16 total.

In order for this to work remotely, you need to leave the radio A/B switch in the "B" position, and now externally pull pin 5 of J910 LO to put the radio in Mode A.


As looking at pins from front of radio w/11 pin connector on LEFT

Pin 1 +12VDC Pin 1 Ground
Pin 3 Ext Spkr HI Pin 4 Mic HI
Pin 4 Filtered Vol/Squ HI Pin 7 Ch Select
Pin 5 A/B Select Pull LO for A (After Mod)  
Pins 6,7 & 8 Ground  
Pin 9 CG Disable  
Pin 11 +12VDC  

This configuration has been successfully interfaced to an S-Com 7K repeater controller. It did require a considerable amount of macro writing, but after doing it, has worked flawlessly for quite a while now.

The macros allow the Phoenix SX, which I am using as a remote base, to be off, Receive only and of course Transmit. They also provide all audio and logic configurations, voice announcements of frequencies and, "Remote" access to establish a link.

The radio audio levels, in my case anyway, were virtually Plug & Play. I didn't have to make any audio adjustments either to the controller or the radio, and the audio quality is fantastic. I've had numerous compliments on it in fact.

If you would like some Scom controller programming help, go to the Scom controller resource page.

Modifications made to any equipment based on the information contained on this or any ZedYX pages are AT YOUR OWN RISK!





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