Combo PIC-a-STAR build and interconnection pictures

Last updated Dec 7th 2013, RS232 test cable details added.

17th May, 2013, some "{P2" pcb version info added}

These are pictures of the 1st build of a "P1" version PCB, to give builders a better idea of the connections which have to be made. The P2 & P2a version is near identical, just a few of the minor errors of P1 corrected. The pictures show the 1st test of the Combo P1 receiving signals, not the final unit. Basically several cables are needed:-

1) 20 way IDC cable which runs from top to bottom, oriented as per the pictures below.

2) 4 way cable carrying the DSP 15KHz signals from top to bottom, located near the DSP section. See text near last picture.

3) Four co-axial cables under the PCB's connecting the top and bottom boards. There are numbers printed under the PCB's which show what points each of the cables connect to. The best way to run these is to bring them towards the front of the sub-chassis as you can see. Best cable to use is miniature teflon covered co-ax. Often found on eBay in short lengths. eg search "K02252D" which is teflon cable 3mm OD. Even better is the smaller, as more flexible, is (~1.8mm OD) RG178 Teflon cable that is item number 380576703742. (Feb 2013) This vendor is selling 4 x 18" lengths which should be about right, although might be better to get two lots.

Update 17th May 2013:- also check ebay item 150498248282 This seems very cheap for the RG178 cable in a 50 foot length. The ebay link may be invalid now but a search for RG178 should find it.

Your local Ham radio supplier may have some RG178 also. Or, at a pinch, use RG174.

4) Microphone and PTT cables run under the PCB to your chosen Mic. socket. (not shown in these pictures) Use shielded audio cable.

5) Ribbon cables to the LPF (not shown), the TFT display and keypad. The latter come from the Trxavr controller (ATMEGA2560 area)

6) You will also need a test cable for the RS232 jack, for testing using Peter's QBASIC software. The cable will have a male 3.5mm plug on one end and a DB9 socket on the other. Refer to schemacts, "DSP MB" area. If in doubt, email me for more info.

There is also an integration drawing in diagramatic form, here.


BOTTOM view, shows cables (note some ribbon cable here go to the keypad and TFT on the bench !)

Overhead view of above picture. NOTE orientation of the 20way IDC at the top.



More detail of the 20 way IDC to bottom PCB and also the keypad. Lower cable is to TFT. NOTE: additional heatsink on the OCXO regulator here. (there are two back to back heatsinks) Not fitted in picture, are encoder and tuner controls.

This picture shows the other end of the 20 way IDC cable. NOTE the pin 1 end (red stripe) on both ends of the cable should be as shown in the pictures !

This is the 4 way cable to mating connector on the other PCB. It's a 1:1 cable. VK3PE reccomends using two core shielded 'audio' cable and also a single core shielded cable to make the assembly. Make the cable long enough to allow each of the PCB's to be removed if required for testing. Although there is a hole in the PCB for the cable to run through, VK3PE found it better not to use the hole on this side of the radio.


Once completed and all software loaded, a jack with the active pins connected using a 1k leaded resistor should be inserted into the 'serial' socket adjacent to the rear slide switch. This allows the S'meter and other data to be correctly displayed on the TFT display. OR, a resistor may be fitted on the RS232 jack. Refer to schematic for details.

NOTE: the P2 & P2a version has this resistor fitted on the underside of the pcb in the 'RS232' jack area. May 17th 2013

DEC 2013:- The RS232 test cable unfortunately is different to that used by G3XJP on the homebrew PCB's. So, if you built H/B pcb's and made up a cable for the RS232, it is different on 'P' version PCB's. Details are in the Schematic file and also here, in this drawing.


3rd March, 2013:- This is the current state of the VK3PE build with the case, made from extrusions.

This build will be 20W PA only. Although, there is space allocated on the rear, for the 140W PA later. The hombrew PCB in the back is Ian's (G3VPX) PEAKSWR bridge which integrates into the Trxavr & TFT display for on-screen power output and SWR.

As space is tight in this build, the PCB's are mounted on a top "deck" which can be hinged upwards for access to the main "P1" PCB's below. The top cover will just clear the LPF by about 5mm.

Below is the top "deck" hinged upwards. Still not fitted are the front supports for this chassis.

You can also see the four co-ax interconnect cables, wrapping around the central chassis. (the black coax cable on the right is temporary only)






The VK3PE build above does not yet show the fitting of shielding which is highly recommended. The radio will function perfectly well as it is shown here, but for best shielding and reduction of spurs. the shielding should be fitted, once happy with the testing.



This web page created for the Combo version P1 and later, the P2 version, PICASTAR, on Feb 23rd, 2013 by VK3PE

Created on 23rd Feb, 2013,