SDR Cube Transceiver
Online Assembly Guide
Detailed construction notes for building and testing each of the SDR Cube kit modules
Bill of Materials
RXAMP Multi-Rx X-LPF Internal Cable Set External Cable Set Main Enclosure Accessory Enclosure
Digital Subassembly Test Final Assembly RF Functional Test
|Building the RXAMP Board ... (Section version 1.0a)|
What Is It?
The "Rx Amp" is 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 RXAMP, greater front end sensitivity is able to be achieved, with greater user control over the wide-ranging signal levels encountered in a communications radio.
[____] STEP 1: Inventory the supplied parts
Check to make sure you received the RXAMP Kit bag and all the components that are pictured below. (Click on any photo to see a larger image.)
NOTE: For 17m band, L3 should be 0.68 uH and L4, L5 should be 0.33 uH
(Replacement inductors are being sent to all RXAMP kit and 17m card owners)
Designator QTY Description Source Loose P101 1 Pinheader, 0.1", 1x3 P1 1 Pinheader, 0.1", 2x2 P100 1 Pinheader, 0.1", 1x2 C3 1 Capacitor, .1uF, X7R, 0805 SMT RLY1, RLY2 2 Relay, DPDT, SMT, 5V (Axicom IM03GR) T1 1 Common Mode Transformer PCB-RXAMP 1 PCB, RXAMP
PARTS LAYOUT diagrams for the RXAMP Board ...
STEP 2: Install the surface mount capacitors and resistors from the SMT Card.
Using the order of the parts as listed on the SMT card as a guide, and the Parts Layout diagrams above (and on the board's silkscreen) as a guide, first attach the capacitors to their respective pads ...
[____] C1, C2, C4, C6
[____] C5 ... This 10 uF capacitor has no polarity. It can be installed in either direction.
STEP 3: Install the surface mount resistor R7, based desired gain
Emitter resistor R7 determines gain of the RF amplifier. Lowest value (10 ohms) = more gain, better for higher bands (~10m). Mid value (22 ohms) better for mid bands (~20m). Higher value (47 ohms) = less gain, better for low bands (~40m). Select as desired for memory segments you intend on using the RXAMP with ...
[____] R7a (10 ohms) ... or ... [____] R7b (22 ohms) ... or ... [____] R7c (47 ohms)
STEP 4: Install the rest of the surface mount resistors[____] R10
[____] R3 (39 ohms)[____] R101 ... NOTE: This resistor is missing from the pc board layout. Save it for mounting on top of C101 when you get to the Band-Specific section below.
[____] R6 ...[____] R4, R5
[____] R1, R2[____] R8
[____] R9[____] R11, R12
STEP 5: Install the SMD diodes[____] D1, D2
STEP 6: Install the SMD chokes[____] L1, L2
STEP 7: Install the transistors
[____] Q1, Q2[____] Q3
STEP 8: Install the Band-specific SMDs[____] C101 ... NOTE: This is the component on top of which you will be "piggy-back mounting" the R101 resistor mentioned above. See the photos below to see how this is easily done ...
[____] C7[____] C100
[____] L3[____] L4, L5
STEP 9: Install the attenuator relays RLY1 and 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.
[____] RLY1, RL2
STEP 10: Install the pinheader connectors
[____] 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.
[____] P1 ...2x2 ... Mount on the top of the board
[____] P100 ... 1x2 ... Mount on the bottom of the board.
STEP 11: Install the common mode transformer T1
[____] T1 ... Pin 1 is noted with small "WE" letters in one corner, but the device is symmetrical and may actually be installed in either orientation.
STEP 12: Install the separate SMT capacitor C3
[____] C3 ... This is the SMT part missing from the SMT card and included loose in the parts bag.
The RXAMP Board is complete! Set it aside and next move on to building the X-LPF Board.
Back to Construction Home
Copyright 2010 Midnight Design
Solutions, LLC. All Rights Reserved.
Page last updated: May 16, 2011