SDR Cube Transceiver Online Assembly Guide Detailed construction notes for building and testing each of the SDR Cube kit modules
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What Is It?

"Multi-Rx" is a multi-band receiver attenuator/filter/amplifier module that plugs into the Softrock Base Board to enable reception across the HF spectrum (2-30 MHz) without the need to manually change receive modules (as was necessary with the four individual RXAMP modules when the Cube was introduced.)  The Multi-Rx board contains four automatically-selected filters (2-4, 4-8, 8-15 and 15-30 MHz) along with two switchable attenuator pads and a 20 dB amplifier.  And like the single-band RXAMP module before, the Multi-Rx serves as a higher-performance plug-in module that replaces the standard RX BPF plug-in provided when the Softrock RXTX 6.3 was previously available on the market.  To help make the Softrock perform better, we used a different bandpass filter, a pair of relay-controlled attenuator pads, and a 20 dB amplifier. With the Multi-Rx, greater front end sensitivity is able to be achieved, with greater user control over the wide-ranging signal levels encountered in a communications radio.

Multi-Rx Schematic:

Multi-Rx BPF Filter Response Plots:

Magenta:  2-4 MHz

Green:  4-8 MHz

Red:  8-15 MHz

Blue: 15-30 MHz

CONSTRUCTION STEPS

[____]  STEP 1: Inventory the supplied parts

Check to make sure you received all three parts cards pictured below:

  

 

 

 

 

PARTS LAYOUT  diagrams for the Multi-Rx Board  ...

 

 

 

STEP 2:  Install the surface mount parts from Parts Card #1

[____]  C1, C2, C4, C6, C17, C18, C29

[____]  C3, C20, C21, C22, C23, C24, C25, C26, C27, C28

[____]  C5, C19 ... These 10 uF capacitors have no polarity.  They can be installed in either direction.

[____]  D1, D2

[____]  L1, L2

[____]  R10, R7

[____]  R3

[____]  R101

[____]  R6

[____]  R4, R5

[____]  R1, R2

[____]  R8

[____]  R9, R13, R14, R17, R18

[____]  R11, R12, R15, R16

[____]  Q1, Q2

[____]  Q3

 

STEP 3:   Install the surface mount parts from Parts Card #2

2-4 MHz

[____]  C14, C15

[____]  C16

[____]  L14

[____]  L12, L13

4-8 MHz

[____]  C11, C12

[____]  C13

[____]  L11

[____]  L9, L10

 8-15 MHz

[____]  C8, C9

[____]  C10

[____]  L8

[____]  L6, L7

15-30 MHz

[____]  C7, C101

[____]  C100

[____]  L3

[____]  L4, L5

 

STEP 4:  Install the parts from Parts Card #3  (Note:  The installation order is different from the listed order)

a) IC and Relays

[____]  IC1

[____]  RLY1, RLY2 ... Be careful to mount these relays in the right direction.  "Pin 1" is on the end marked with the dark bar (actually it's very small bold lettering). 
                                  And if you look closely at the pins, there is a larger gap that should of course match up with the pads for the device.

b) Pinheaders

[____]  P100 ... 1x2 ... Mount on the bottom of the board.  Ensure that it is mounted straight (perpendicular) to the pcb.

[____]  P101 ... 1x3  ... Mount on the bottom of the board.  NOTE:  Snip off the leads on the top of the board as low as possible to allow T1 to mount flat over top these pads.

[____]  P102  ...2x3   ... Mount on the top of the board

c) Common Mode Transformer

[____]  T1 ... it doesn't matter which orientation is used.

d) Bandswitching Cable

[____]  T1

 

STEP 5:  Create the Bandswitching Cable #8 -- This is the 2-wire, 6.5-inch ribbon cable that connects the bandswitching signals from the DSP Board to the Multi-Rx board.

[____]  Strip and tin about 1/8" from both wires on both ends of the 2-wire ribbon cable

[____]  Slide a red and blue piece of heat shrink on the wires of one end, and solder the wires to the terminals of a 2-position receptacle connector.

[____]  Do the same for the other end of the 2-wire ribbon cable, ensuring that the red and blue heat shrinks are on the same wires as the other end.

[____]  "Shrink" the heat shrink pieces to protect the receptacle terminals, using a hot air gun or by gently rubbing the top tip of your soldering iron over the heat shrink pieces until they shrink down firmly over the terminal connections.

 

STEP 6:  Make the C30 Mod on SRBase Board -- The C30 trace on the SRBase board needs to be rerouted from J2 pin 5 to J2 pin 1. 
               This can be accomplished with a simple trace cut and jumper add.  See the bottom of the Multi-Rx page for the details.

 

The Multi-Rx Board is complete!  Set it aside and next move on to building the X-LPF Board.

 

 

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