01/02/07

"W4XE Repeater Tech page ©"
 

I've been using the GE Phoenix SX radio for remote base and backup repeater use. There are many variants, but the Phoenix-S and -SX models are the ones most people use. The older plain Phoenix (non -S or -SX) radio is crystal controlled. These radios can be picked up for $20-$75 range depending on model. They make excellent packet radios and remote base repeater radios. The audio quality is typical GE and sounds great on RX and TX. The radios can not be full duplexed for a portable or backup repeater. So if you want to build a repeater use one as a receiver and one as a transmitter. Make sure to idle down the TX power and use a external fan for cooling. Be careful turning down the power < 50 %. It has been reported to get unstable below this point.

The one's I've used are synthesized radios in the 40W to 25W range covering VHF and UHF frequencies. They come in 2, 8, 16 and up to 32 channel  scanning versions. Even a few special 128 channel models are floating around. The older versions have a light tan case. The newer versions have a dark gray case. I've seen no preferences between the two.

Below is a comparison of the various models.

The memory channels are programmed via an Exar 2212 EEPROM. Inexpensive programmer kits are available in the $50 range. You simply remove the EEPROM IC, insert the IC into the programmer, use the provided software and reinsert the EEPROM into the radio. Be careful, as replacement EEPROMS are scarce running about $20-$25 each! You can program PL encode and/or decode per channel as well.

There is one website that shows how to replace the EEPROM with an inexpensive 2716 type EPROM and gain 'banks' of 32 channels! http://members.shaw.ca/swstuff/phoenix.html

Note, the Phoenix PSX-200 was a latter two channel only model and uses a smaller EEPROM different than the 2212. Make sure you have a programmer capable of programming these if you look at a purchasing a PSX version radio.

Another thing to be aware of is that there are a lot of Phoenix radios on ebay being sold without the CPU or EEPROM installed. Steer clear of those deals! The radio is useless without them. Make sure the seller guarantees they are in the radio you are buying.

I highly recommend the KG4LNE programming package solution:

http://www.rtzaudio.com/kg4lne/

As a side benefit, the programmer and software can also handle the GE DELTA-S series of synthesized trunk mount radios. They use the same 2212 EEPROM.

The Phoenix SX VHF units can be reprogrammed to the ham band without retuning the radio. The UHF units need a little tuning to arrive at the ham bands since you are usually going from 46X commercial range to 44X MHz ham band range. There are also some low split UHF versions floating around if you need a  430 MHz UHF link radio. I've found most 460 versions tune down to to the low 441 MHz range. However, I've had a few that don't lock easily in the 441/442 area even after retuning of the VCO. (New note- I've found the error in my ways and can now get the radios to reliably lock at 441.xxx range on TX with retuning of the VCO). The good news is the low 430 version radios tune up to the normal 440 ham band as well.

Below are top, bottom and rear views of the GE Phoenix radio:

All of the signals needed are located on two Molex connectors on the rear of the radio, including COS or PL detect. This makes it a plug and play radio with no modifications inside the radio. There is a muted high pass filtered (PL tone removed) receiver audio at the rear. I added some more de-emphasis with an R/C combination. In my controller application (ACC RC-85) an inline resistor was needed on the COS detect pin, else the controller loaded down the signal inside the radio. See my hints PDF below.

Shown above is a little interface box I built. It allows the RC85 controller to bump the channel up by one for a semi-agile frequency control. As with most mike up button implementations, the controller's output pulse is usually not not wide enough. So I implemented a one-shot to stretch the signal. If you stretch it too far (> 1/2 second) the radio will go into scan mode. I also included a relay to remotely control power to the radio (as suggested on another website). This allows me to reset the radio to a known starting memory channel position. The radio always powers up in the channel 1 position. Below is a PDF of the circuit. (If you are using at CAT controller, its 200 ms pulse works perfectly without any additional circuitry!)

Here are some PDF documents I created for interfacing the radios to a repeater:

RC85 to Phoenix SX schematic in PDF format

Schematic in PDF format of ARC RC210 controller to phoenix sx remote base

PDF of  GE PHOENIX SX REAR PANEL CONNECTORS and hookup tips

Note - A friend told me the other day that the old PC ATX power supply connector fits the back of the GE Phoenix. I haven't tried this yet, but those old bone pile ATX supplies may provide at least one good part before going to the dump.

Below is a little portable repeater I built up for an emergency deployment with a 40' military portable mast setup. It consist of two GE Phoenix SX UHF radios. One is used for TX and one for RX for a UHF repeater. Another Phoenix VHF radio (on the top) is used as a 2 meter remote base. The repeater is controlled by a NHRC4 controller which fits perfectly in GE's desktop power supply. A diode was added to allow switching to external power such as from a battery. Note, this is an intermittent repeater, not meant for 100% duty cycle. The power supply will only handle the UHF repeater by derating the PA output power. The power supply does not have enough current to run everything at full power. You probably want to run the remote base radio from another power source. Just supply a small UHF mobile duplexer and a dual band antenna with diplexer. The nice thing is that you can substitute two VHF radios and one UHF radio 'plug-n-play' and have a 2 meter repeater with UHF remote base in a matter of minutes. Of course lugging a 2 meter duplexer around is another matter...

There are many excellent sites that discuss this radio for conversion to ham radio use.

A good starting point are the links below:

http://www.engr.mun.ca/~gmarsh/phoenix/

http://www.ccdx.org/zedyx/mods/ab_mod.htm

http://www.nhrc.net/nhrc-pxp/

http://www.lmrgroup.com/ke3ht/gephoenix.html

http://www.rayvaughan.com/kpc3oto.htm

Note: click on thumbnails for enlarged photos!

73's Ralph W4XE

01/02/2007