Transceiver Enclosure, Front & Rear Panels

The transceiver enclosure is a HP-436A Power Meter chassis.

Blank HP-436A Chassis

I was first introduced to the idea of using these chassis from an article by Scott Roleson, KC7CJ in QEX January/February 2017.

HP-436A Power Meters “for parts only” are available in the US on eBay for $40 – $50 including shipping.

The HP-436A is stripped down to the chassis as shown above plus the top and bottom covers. Single screws secure the top and bottom covers on the chassis. The chassis has plenty of holes for securing 1/2″x1/2″ or 1/2″x3/4″ angle aluminum for mounting front and back panels, shelves, & etc. The chassis measures 8 3/4″W x 5″H x 10 1/2″D.

The Express Transmitter, MRF101 Amplifier, and combination LPF / Power Meter are also built into these chassis.

As with the Express Receiver, after selecting a chassis, the next step was to design the Front Panel. I decided to use two 20×4 white on blue character LCDs for display functions, leaving enough room for a single row of controls.

2020 Transceiver Front Panel with LCDs Fitted

The AF/RF Gain control provides all variable gain functions in the transceiver, including, AF gain, RF Attenuator, IF Gain, and Line Out level.

The Function control provides access to all other functions, including, band selection, AGC, mode, tuning rate, functional presets, and calibration.

The Rear Panel was designed next. As with the Express Transmitter, the 2020 Transceiver will use a Pennywhistle 10W Power amplifier that mounts to the Rear Panel.

2020 Transceiver Rear Panel

The large cutout is for the Pennywhistle Power Amplifier heatsink. The connectors are provided for:

  • Combined Tx/RX Antenna
  • Rx Antenna
  • CAT / Audio Interface
  • USB Interface
  • External TR Switch Control
  • Speaker
  • DC Power
  • Aux / Amplifier Control

With the bookends done, the next decision was how to build the transceiver into the space available in such a way that is was practical to build, experiment with, and maintain. I settled on the idea of using a connectorized backplane with standard-sized 3.5″ x 7″ plug-in boards. With a 1-inch pitch, seven plug-in boards can be accommodated.

The backplane carries DC voltage (analog & digital), I2C bus, relay control signals, interface to front panel controls, and interface to the Pennywhistle Power Amplifier; thereby, eliminating all the blue wires seen in the Express Receiver and Transmitter.

The Backplane was sized to fit into the HP-436A chassis.

Backplane Mounted in the HP-436A Chassis

© 2014 – 2021 Rod Gatehouse AD5GH

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