Subject: Modifying the Azden PCS-4000

From: dave


Modifying the Azden PCS-4000



The Azden PCS-4000, popular some years ago, is a 25W mobile FM

transceiver.  Functions such as frequency selection etc are performed

by a matrix of buttons on the front panel (and auxiliary buttons

on the microphone); there is no "VFO" control as such.  The control

microprocessor continually scans this matrix; this scanning also

applies to the frequency display and other functions.



Many preset functions, such as band limits and step, are also under

the control of the matrix, and these are readily modifiable by the

user.  NB:it is likely that other adjustments may have to be done

if the band edges are changed.



Call the scan lines K0 - K3 and R0 - R6 (using Azden's nomenclature);

refer to the circuit diagram for their location.  Lines K0-K3 take

part in most operations, R0-R3 scan the keyboard, R4 scans the

"M-Mode" switch, R5 selects the step, and R6 the band edge.  The

following are under control of these lines:



[ O - Open, S - Short (diode) ]



STEP

                                 R5

      5K     10K    12.5K    15K     20K     25K    40K     50K



K3     O      O       O       O       S       S      S       S



K2     O      O       S       S       O       O      S       S



K1     O      S       O       S       O       S      O       S



By default, the rig is shipped (in Australia anyway) with steps of

5 and 10 KHz; to change to 5 and 25 KHz it can be seen that all

that is required is the addition of a diode at K3/R5.  This can be

done anywhere, but I installed mine on the small PCB holding the

STEP switch behind the front panel; I prefer my mods to look as

though they were original.





BAND (2m version only)



          R6

      US    JP    EU

                                    US:142.000 - 149.995, 5 kHz

K3     O     O     O

                                    JP:144.000 - 145.995, 5 kHz

K2     O     O     S

                                    EU:144.000 - 145.995, 12.5 kHz

K1     O     S     O



This is of limited use, unless you were contemplating modifying

an imported set, in which case a realignment is probably necessary.



--

Dave Horsfall (VK2KFU) | dave
Opinions expressed are mine. | E7 FE 97 88 E5 02 3C AE  9C 8C 54 5B 9A D4 A0 CD