G3VMW Star II Transceiver

Here are a few pictures showing my build of the G3XJP Star II Transceiver with the basic rig still on the workbench after doing most of the calibration and set-up routines. I made my first SSB QSOs on the Homebrew Net on 3727 with the rig in this very unfinished state on February 25th. Thanks everyone for the encouraging reports.

Below: Top view of G3VMW Star - first QSO on 21st February 2008 with 5B4AGN on 80m CW

Star Front Top

Below: Another view of the G3VMW Star in a working but raw state. The 100W T/R switch is top right above the 100W LPFs. The Timer Board and MR mixer are above the DSP Brick which is fitted through the aluminium chassis. The aluminium enclosure to the left of the MR is the PnM DDS assembly with the LO fed out via an SMC coax connector to the MR.

Star Under

Below: Side view of Star showing DSP brick with AF amp to the right then the status board. The G6ALU 20W PA is top left, then to the right of the PA is the BPF board and then the PnM DDS with the HEDS-5701 commercial encoder.

Star side view of DSP

Below: View of G3VMW Star from top front - DSP brick on the left with BPFs to right and G6ALU 20W PA behind the BPF assembly, which is similar to the CDG2000 BPF using Lodestone Pacific formers. The 100W PA, which is the Motorola AN-762 design with a pair of MRF-454s, is fixed vertically on the back panel in a screened box and combined heatsink courtesy of an old Plessey 1.5 GHz microwave link.

Star front view

Below: Rear view of G3VMW Star showing 100W PA heatsink, RS-232 connection and DC Powerpole connectors - and also a very cluttered workbench! The chassis is adapted from an old Heathkit 70cms transverter obtained at a junk sale for just £1 UKP. The outer case uses curved wrap-around panels made from perforated steel sheet, similar to that used on Collins and KW Electronics gear to give the finished unit a bit of a retro appearance.

Star back view

Below: The finished Star with the top cover removed

Star

Below: The completed Star in pride of place on the operating bench. The wrap-around case is from an old Heathkit 70cms transverter that was bought for £1 UKP at a radio junk sale. The case has been resprayed in Ford Sea Grey.

Star top

Below:The Star receiving strong signals on the Home Brew Net on 3727.00 kHz

Star operating

 

Below: AN762 100W PA after modifications to switch the amplifier bias supply. An FQP8P10 P-channel MOSFET is switched by the external PA line, i.e. grounded on TX to switch the 13.8v input volts to the input of the PA bias regulator. Also, a pad is fitted on the RF input side of the AN762 to allow the G6ALU PA to drive it to about 100W output with 10W of drive. The pad improves overall system stability. The bias switching line should use shielded cable with a ferrite ring or a ferrite binocular core fitted close the 100W PA.

AN762 100W Amplifier

Below: Underside of the AN762 PA PCB showing the track cuts to isolate the bias supply so it can be switched. A wire link is then added to connect the 20 ohm 5W resistor R12 to the 1K resistor R12. Both resisitors need to be isolated from the outer track round the underside edge of the PCB that carries 13.8v

Track cuts AN762

 

100W T/R Switch suitable for Star II Transceiver

The 100W T/R switch below is derived from the QRP Elecraft K2 T/R switch and has been modified to operate at 100W by the addition of a 140v high voltage supply that is applied to D4 and D5 in the RX path on transmit. The T/R switch is stable in use and has been tested at over 100W on all bands with no problems to date.

100W T/R Switch

100W T/R Switch Bias Supply

 

Earlier pictures during PnM and IF/DSP Construction

Below: PnM on bench being tested with the status board connected

PnM

Below: Completed PnM DDS PCB with AD9951 DDS adapter.

PnM DDS PCB

Below: PnM working with a TS-930S encoder in place of the home made version. The TS-930S encoder needs a small interface board to work with the Star PnM.

PnM with TS-930S encoder

Below: PnM Display board using red 7 segment LEDs. I tried some blue 7 segment LEDs but they had a tendency to display what should have been the extinguished segments quite clearly as well as the wanted segments. The standard red LEDs were used in the event.

PnM Display

Below: Power meter displaying PnM output of +5.7dBm in signal generator mode at 30 MHz

Power Meter

Below: Spectrum analyser display of PnM output at 30 MHz.

Spectrum analyser display

Below: CD4013 latch circuit for TS-930S encoder or Agilent HEDS-5701 encoder that I finally used in PnM DDS.

4013 Latch

Below: Top view of IF/DSP unit

IF/DSP top

Below: Bottom view of IF/DSP unit

IF/DSP Bottom