Band Switch Introduction


This stage provides the capability to switch among the 4 band segments, corresponding to the four crystals installed.

Optional Approaches

Band Switch from Original Design

The G3020 band switch consists of 2 DPDT three position switches (ON-OFF-ON) and 4 yellow LED diodes which indicates the selected oscillator.

The switches and diodes are connected as per diagram below. The band switch is connected to main PCB board with 6 wires JP1 (1,2,3), J5 and JP2 (1,2). The wires are then connected to pins as marked on photos below.

The JP1 Pin 2 is located between pins 1 and 3. The J5 is located on the top-right corner of PCB.

Band Switch Using Rotary Switch

Another version of the bandswitching (uses a rotary switch and no LEDs) is provided, thanks to John Farley (see below)

Connector Option

Nick has provided an elegant way of plug-in/plug-out connections for the band switch, utilizing a single 5 line Molex connector set and some under-board point-to-point wiring

This method can be made to work with either type of switch (but will require a separate power lead for the LEDs, if used). It is described on the reflector in message #521

(go directly to build notes)

Band Switch Schematic

Band Switchschematic

(go directly to build notes)

Band Switch Bill of Materials

Stage Bill of Materials

(resistor images and color codes courtesy of WIlfried, DL5SWB's R-Color Code program)

4yellow LEDLED
1user-furnished switchboardMisc
2SPDT 3 positionSPDT

Band Switch Summary Build Notes

Band Switch Detailed Build Notes

Top of the Board

Band Switch Top View

Provide, Cut, and Drill Switchboard

The builder is required to provide a temporary switchboard. (the switches and diodes are provided with the kit).

Provide, Cut, and Drill Switchboard photo
misc3-1user-furnished switchboardMisc 

Install LEDs and Switches

Insert the LED diodes in 3mm holes as shown here: the longer lead (Anode) facing the switches.

Install LEDs and Switches photo
D3-1yellow LEDLED 
D3-2yellow LEDLED 
D3-3yellow LEDLED 
D3-4yellow LEDLED 
SW3-1SPDT 3 positionSPDT 
LO BandSwitch
SW3-2SPDT 3 positionSPDT 
LO BandSwitch

Wire leds and switches

Wire the switches and diodes as per photo. For details, refer to the schematic diagram as shown above.

Note: the cathodes ("K") of the diodes are the shorter leads and are wired together with the lead going to J5 on the main board.

Wire leds and switches photo

Connect the Wires to the Board

Connect to points on the board

You may want to make these connections temporary until you have reached the end of the project. Otherwise, these will cause handling problems as you turn, twist, and otherwise manipulate the board in the follow-on build stages. The stages which will require you to switch from one to another crystal for testing purposes can easily be handled using the "Wire 1-a" through "Wire 1-d" arrangements in the test section of the local oscillator stage.

Connect the Wires to the Board photo

Optional switching Method

The builder may prefer to use another approach to band-switching. This approach involves obtaining a simple rotary switch with at least 4 poles ( Radio Shack has a model number 275-1386 for $2.99 that is a six-pole switch) and some polarized header pins and plugs.

John Farley, a G3020 builder provided the specs as indicated below. It is strongly adviseable to obtain 2 and 3 pin polarized header pins (and matching plugs) to plug into the corresponding 2 and 3 hole locations JP2 and JP1) such that the bandswitch can be removed for your convenience during follow-on assembly stages

Here is the diagram depicting the band-switching using a rotary switch:

rotary switch installation

And here is a view mapping the logical switching diagram against the physical (rear view) switch and its corresponding lugs:

Optional switching Method photo

Band Switch Testing