View source for QRP Labs High Performance SDR Receiver

[[file:QRP-Labs_P1956-720px.jpg]]

== Features ==

* Three modules
** [http://qrp-labs.com/receiver QRP Labs High Performance Receiver Module]
*** Direct Conversion Receiver
*** Uses a Quadrature Sampling Detector (QSD), also known as a Tayloe Detector
*** [https://www.onsemi.com/pdf/datasheet/fst3253-d.pdf FST3253] Mixer is arranged as a double-balanced mixer for maximum performance
*** Circuit to mute receiver during transmit
*** [https://www.ti.com/lit/ds/symlink/lm4562.pdf Low noise LM4562 op-amps] are used in instrumentation amplifier configuration to provide excellent common mode noise rejection
*** The audio output of the module is isolated using two 600:600-ohm transformers to reduce or eliminate the ground loop problems which can easily occur in SDR systems
*** The module is designed to directly drive a stereo input sound-card or with a polyphase filter card
*** Receiver board has a socket for the standard QRP Labs Band Pass Filter kit which can be routed to an external bandpass filter switch card
*** The receiver requires a local oscillator (LO) input at 4x the receive frequency
*** [http://qrp-labs.com/images/receiver/receiver2.pdf Receiver Build instructions]
** [[RF Band Pass Filters|QRP Labs Band Pass Filter]]
*** [http://qrp-labs.com/bpfkit.html 10/15/20/40/80M QRP Labs Band Pass Filter Kits]
*** [https://qrp-labs.com/images/bpfkit/bpf2.pdf Band Pass Filter Build instructions]
*** Can be used with a [https://qrp-labs.com/ultimatelpf.html Switched Bandpass filter board] for multiband operation
**** [https://www.qrp-labs.com/images/ultimatelpf/assembly_ulpf.pdf Relay Switched Kit Build Instructions]
***** [https://www.qrp-labs.com/ultimatelpf/relaydriver Relay driver for Relay Switched Kit]
** [https://qrp-labs.com/polyphase QRP Labs Polyphase filter]
*** Polyphase network plug-in module kit cancels the unwanted sideband and produces a single sideband (SSB) output
*** [http://qrp-labs.com/images/polyphase/polyphase2a.pdf Polyphase Filter Build instructions]
* Band Pass Filter and Polyphase filter mount on Receiver Module
* Current draw - measured total 70 mA (5V regulator
* The receiver module is sized 80 x 37mm

=== Build / Assembly ===

* Power supply + 12V in
** Distribute 12V using [[TinyGrid85]] card with caps
** Needs 5V supply
*** Partly populated [[TinyGrid85]] card with caps and 5V regulator (no ATTiny85 chip)
** Opamps can be powered from 5V or 12-14V (for higher dynamic range)
* [[AudioAmp386|Audio Amplifier]]
* The receiver requires a local oscillator (LO) input at 4x the receive frequency
** Using [[VFO-003]] with [https://github.com/land-boards/lb-Arduino-Code/tree/master/LBCards/VFO-003_4X 4x output option software]
*** [https://github.com/etherkit/Si5351Arduino/tree/master/src Si5351 Driver]
** CLK0 = VCO clock
*** 14MHz
*** 4x
** CLK1 - RF test signal
*** 60 dB attenuator into RF input
*** 60+40 dB = 100 dB attenuator into RF input
** CLK2 turned off
* [[SMA-HDRS]] board to feed LO into card
** Mount 1x3 female flat to board
* Used right angle SMT for RF in connector - works well

== Silkscreen / Pinout ==

[[file:IQ_RX_PCB.PNG]]

=== Pins ===

* IQ pins
* I, GND, Q outputs
* Power pins
* GND, +5V, +5V or +12V to +14V
* Tx Mute Input
** 5V mutes inputs
* LO input
** 3.3V from Si5351A oscillators
* IF input
** From external Bandpass Filter Switch

== Receiver Module ==

[[file:QRP-Labs_Receiver-Base_P1969-720px.jpg]]

== Polyphase Module ==

*  Important to observe part outlines
** Adjacent resistors can be put in "sideways"

[[file:QRP-Labs_Polyphase-Filter_P1966-500px.jpg]] [[file:Polyphase-pcb.PNG]]

[[file:Polyphase-pcb-2.png]]

[[file:Polyphase-Schematic.PNG]]

* USB/LSB select jumpers
** Set to USB in the above picture

[[file:Polyphase_LSB-USB-Jumpers.PNG]]

== Bandpass Module ==

* [[RF_Band_Pass_Filters#QRP_Labs_Bandpass_Filter|Bandpass Filter module]]
* 20M - 14 MHz Filter

[[file:QRP-Labs_BandPass-Filter_P1963-720px.jpg]]

[[file:Bandpass_Filter_Schematic.PNG]]

* NanoVNA
** 12-16 MHz

[[FILE:14MHz_12-16MHz_Band_Pass_Filter-2.png]]

* Data

[[FILE:14MHz_12-16MHz_Band_Pass_Filter-Data.png]]

[[FILE:  14MHz_12-16MHz_Band_Pass_Filter-Analysis.png]]

== Build Issues ==

* Transformers don't fit well and crowd parts around them
** 3.5mm jack crowded
** C1/C2 footprints overlap
* QRP Labs polyphase module pics are for older revision card before 47 ohm resistors were added
* One of the two variable caps on the Bandpass filter was very hard to turn even after the first turn

== Reference Documents ==

* [https://wparc.us/presentations/SDR-2-19-2013/Tayloe_mixer_x3a.pdf Ultra Low Noise, High Performance, Zero IF Quadrature Product Detector and Preamplifier]
* [http://antennoloog.nl/data/documents/Understanding_and_designing_Polyphase_networks_V4.0.pdf Understanding and Designing Sequence Asymmetric Polyphase Networks]
* [https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1991/12/page29/ The double-tuned Circuit: An experimenter's tutorial]
* [http://hanssummers.com/polyphase 40/80m CW/SSB receiver]
* [http://hanssummers.com/images/stories/polyphase/polyphase.pdf Experimental Polyphase Receiver]
* [http://www.arrl.org/files/file/Technology/tis/info/pdf/030304qex020.pdf A Software Defined Radio for the Masses]
* [http://norcalqrp.org/files/AustinNC2030Presentation.pdf Very High Performance Image Rejecting Direct Conversion Receivers] - NC2030 Radio