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PFX Series

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PFX  PFX HRU with extended case.


PFX + PF85   Front view of PF85 (top) and PFX (bottom) with antennas removed.

  Newcomers to the PFX are advised to download and read Section 1 of the Service Manual (TP312).

The PF85 and its successor the PFX are often confused. The PF85 is a 3-channel crystal-controlled handheld, while the PFX is a 16-, 32- or 100-channel handheld with synthesizer control. The letters PF stand for PocketFone, a highly successful series of handhelds designed and marketed by Pye before Philips took over.

The PF85 is hardly worth buying these days because the cost of crystals made to order will almost certainly exceed that of the radio itself.

Like many other PMRs from Philips Telecommunications, the PFX comes in a staggering number of variants, not all of which are of interest to radio amateurs. As always the clues are to be taken from the type label at the back of the radio.

One fault that occurs with many ex-service PFX's is apparent from the fact that the radio indicates Channel 00 on alternate lines of the LCD and effectively works on Channel 1 only. The cure is simply to replace the internal 3-volt Lithium button cells and all will be restored to its former glory.

Type code analysis

The label on the back of the PFX will tell a lot, but not all, about the radio. The codes used largely follow the Philips PMR tradition. Unfortunately, it is difficult to determine the exact band the radio works in, e.g., A1 or A2, because the print on the label will only give 'A'. However the existing PMR channel(s) loaded in the radio will provide a useful clue. The commonly found PFX A(2) band radio will not be pulled down to 2 metres. Another popular model, the PFX U(P), will cover our 70cms band but with a increasing deafness towards 430 MHz. All PFX radios require VCO and RF front-end retuning after any frequency change of more than about 2 MHz.

1st letter



high power (5W) (4W UHF)


low power (1.5W)


2nd letter

channel spacing


12.5 kHz


20 kHz


25 KHz


30 kHz (rare)


3rd letter



E1 68-79 MHz

E2 77-88 MHz


A1 148-162 MHz

A2 160-174 MHz


B1 137-146 MHz

B2 142-156 MHz


TP 405-447 MHz

TL 405-425 MHz

TH 412-447 MHz


UP 440-472 MHz


WP 466-512 MHz

  If you need to be absolutely sure about the band your PFX was designed for, there is no alternative to opening the radio, copy the (hand-pencilled!) production number on a couple of conspicuous modules and then find the matching identifiers in the tables that can be downloaded here.


The PFX takes its frequency information from a PROM (programmable read-only memory) chip type 82S129 (16-channel), 82S131 (32-channel) or 82S185 (100-channel). These 4-bit PROMs are products of the early 1980's which unfortunately means that they are now obsolete and very hard to get. The younger generation may be surprised to learn that a PROM can not be erased and re-programmed. However, if you are lucky, the PROM in your PFX may have unused space to accommodate your channel codes. In a PROM, an empty location reads 0, not F as in an EPROM.

Read this!

The 82S129, 82S131 and 82S185 are 4-bit non-erasable devices, requiring an advanced programmer like the Data I/O 2900.
Most of today's hex editor programs will show 8-bit data format, so a leading '0' will be affixed to every 4-bit word read from these PROMs. New bytes also have to be entered with a leading 0.
A bit set to '1' cannot be reset to '0' by programming.
A bit set to '0' can be set to '1' by programming.
Incorrectly programmed PROMs are goners so think hard before pressing the 'Program' button.
The limited space available inside the PFX makes PROM replacement by a 27C series EPROM a pipe dream.

PFX Programming Software

The algorithm used to build the code words that determine the receive and transmit frequencies in the PFX are interesting in themselves. However you do not need to know them if you have suitable software available that turns the desired TX/RX channel frequencies into codes and then puts them in sequence to build a file that can be blown into a PROM.

  This little program, FPROM for PFX and MX290, does it all. Here are my notes to advanced users.

Run FPROM under DOS on the oldest PC you can get your hands on. Forget about Windows and Pentiums.
If you select Blow PROM you will get an error message saying that the associated programming system can't be found. Ignore it.
Locate the raw binary file built and saved by the program (*.pfr), then use a hex editor (in binary mode) to strip off the customer section (ASCII data) between 0000 and 001Fh. The code words you want to use should start at 0000. This can also be achieved by copying the area 0020-01FF to 0000.
Blow your PROM. Remember to select 4-bit data word width.
You can read PROM files into FPROM, too. Simply read the PROM on your programmer, and rename your file so that it has the extension '.pfr'. Next, read into FPROM. This is very useful because it will not only tell you the reference module frequency (usually 8.4 MHz), but also if selcall extensions were used, etc.
PROMs taken from ex-PMR PFX radios are dead certain to contain code words which are now useless. Either leave the codes intact or overwrite with 'F'. Copy, then paste the new code area behind the old code and remember where 'your' first channel is (e.g., channel 9 for a PFX that used to contain 8 PMR channels).
Have fun!

Here's what FPROM looks like. Impressive menu structure, eh?

PFX Adjustments

to be published...



The Philips Mobile Radio Collection currently has the following PF and PFX radios, accessories and documentation:

PF85   LRA, HRU, LRU, LRA-EX (intrinsically safe version).
PFX    HRU, LRU, LRA (A1), LRA (A2).
Bodyworn adaptor, charger BC21D, high-capacity and low-capacity batteries.
Pocketfone VHF/UHF FM Transceiver Type PFX Service Manual (TP312).
PF85/PFX Test Box SH10047.

PFX Newsgroup

For more information on PFX series PMRs from Philips/Pye, join the newsgroup 'PFX' via www.yahoogroups.com/group/PFX.

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Last modified: February 21, 2002