Combo PICaSTAR build by VK3ATC

Pages last updated on April 7, 2011

Peter is making excellent progress on his Combo version.

Nov 2010, Peter has had a chnage of plans and has now re-housed his Combo build into a new case. Peter has used a 19" rack mounting case available in VK in 3ru size. (ie 3x3.75" high). This (Jaycar™) case is pre finished in black and comes with spare front and rear panels and internal brackets.

Peter also fitted a Tft display and reports he is very happy with the overall build. PA's and LPF yet to be fitted.



April 7th, 2011, UPDATE:- Peter has built two Combo Stars with 100W PA in separate case. All cases are off the shelf rack types that are already powder coated and make excellent cases for the rigs. These cases are available in VK and possibly other countries also or a near equivalent. These have internal brackets provided and a simple internal plate is all that's required to mount PCB's etc. <vk3pe>


VK3ATC's Combo-Stars

The various pictures attached demonstrate the 2 Combo-star units which I have constructed in 3U Rack-mount cabinets, including my 13.0 Volt 20 Amp DC Power Supply and 30 Watt RF amplifier unit, also housed in a matching rack-mount cabinet, located at the bottom of the stack.
Pictures demonstrate the individual Combo1 and Combo2 units and upper and lower compartment views of Combo No.2 unit.

The 2 combo-stars run as transceiver exciter units, which interface with the Power supply-RF Amplifier unit.

Each of the combo-star transceiver-exciter units also contain an additional transmit RF driver amplifer, installed after the main bandpass filter, as a separate PC board assembly, to provide approximately 0.5 watts RF output for each exciter, which is then capable of providing adequate power to drive the 30 Watt amplifier to its full output. The transmit driver amplifier is shown closest to the rear wall on the underside view of the Combo 2 unit.

The power supply-RFamplifier unit is constructed with the transformer, rectifier, filter and regulator components and heat sinks mounted on the floor of the cabinet on stand-offs to allow air flow.

The RF amplifier and heatsink is mounted on a tray directly bolted to the rails which traverse the cabinet about halfway up, again allowing airflow to be directed forwards from the fan at the rear of the cabinet. Extra space has been included in the power supply-amplifier unit(seen to the right of the unit viewed from the front) to enable installation of a 100 Watt amplifier unit and subsequent band-pass filter assembly, these two items thus completing the system.

The pictures of the stack demonstrate the PSU-amplifier unit, the meters, and the switching for power control relays and the SWR metering facilty for the 3rd meter.

Metering on the front panel of the PSU-Amplifier unit comprise a 0 to 20 Volts DC, 0 to 20 Amps DC and finally a multimeter for montoring various voltages, including forward and reflected SWR and power output.

So far, my combo-star units have been tested on air using the 30 watt amplifier, the output of which has been passed directly through to my link-coupled ATU and then onto my dipole antenna via open wire feedline, with no significant RF feedback problems encountered.

I have also built and installed an SWR metering facility in the power supply-amplifier unit to directly monitor power output and SWR, although this information will be also displayed on the 5" LCD of both combostars.

On one of the Combostar units, I have installed a stepper-motor rotary encoder system, whilst the other utilises a switched up-down frequency control system, and in both cases, extra logic circuitry has been designed to interface with the frequency control input of the TrxAVRB-At2560 MCU-AVR.

Both Combostars utilise the 5" Colour LCD and TFTA controller in conjunction with 8 rotary encoders, 4 arranged on either side of the LCD, providing a good level of flexibility in adjustment of various transceiver parameters. A separate menu encoder, and Pots A & B (AF and manual IF Gain controls) complete the control features.

One Combostar runs an analogue S-meter, but this was omitted in the second unit due to space restrictions on the front panel, after having decided to install the rotary encoder for frequency tuning control. The 5" LCD provides a very adequate graphical S-Meter, making the decision to use an analogue meter not necessary in the second unit.

Peter VK3ATC

Above, power supply and power amp.





This is Peter's previous case.

Hi Glenn,

OK, Please find attached some pictures of my Combo-star HF transceiver.
The receive input I have wired to the rear RF connector in preparation for getting the receive side of things operational to begin with.
I have decided to use a stepper motor rotary encoder, with some logic circuitry to produce the same output, as what an optical encoder would do, as per the actual project design requirements.
The logic circuit for the stepper motor encoder unit is constructed on a small PC board which is not visible in the pictures I have sent you, because it resides under the chassis, but really is very simple, using a twin OP amp, followed by a quad NOR gate and a simple flip flop, thus providing tach pulse train and dir. up down logic signals.
My problem now is to decide how to best use the software subroutines which I have for my project requirements.
I have downloaded the source code files to my computer...just need to figure out which ones I need to call up in the "make" program to get my radio running....any help here will be much appreciated.
Let me know what you think.
Peter VK3ATC


Page created on 22nd July 2010 by vk3pe