Subject: Modifying the Azden PCS-4000 From: dave@eram.esi.com.au (Dave Horsfall) 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@esi.com.au | VK2KFU @ VK2AAB.NSW.AUS.OC | PGP 2.6 Opinions expressed are mine. | E7 FE 97 88 E5 02 3C AE 9C 8C 54 5B 9A D4 A0 CD