Design Reference Compendeum

While putting together ideas for homebrew radios, I often find myself trying to pull together ideas from different design families. How do different designers, profession or homebrew, handle, say, the link between an LM386 and NE602, or T/R switching, or IF strips between two mixers, and so on…

Below is a list of links and resources for some specific design areas of personal interest. It’s not an exhaustive list, and many links are duplicated where a design or resource applies to multiple categories.

LM386

• Lorem
• Ipsum

Audio Pre-Amps

• ‘Oasis Blue’ Audio-Amp (N6QW) – 2n3904 common emitter, about ~3db gain into LM386
• Original BITX (VU2ESE) – Single Common-emitter amp with no emitter degeneration into LM386
  • 2 Band Transceiver is similar
• VU2ESE DC Receiver – Common base to common emitter amplifier, with active decoupling
• ZIA Transceiver – NE5534 as pre-amp

NE602/LM386 Direct Conversion Receivers

• Micro-40 – VK3YE Design (also documented by AA7EE), transceiver
• The Virgin – KK9JEF design (my own!)
• MRX-40 and MRX-80 – By K8IDN, in QST from 1997, and K7SZ, respectively.
• NorCal Forty-9er – Design by N6KR
• eBay Forty-9er – A Derivative Design of the above, now widely available on eBay. Schematic can be found in this document that accompanied a QST project based on the same.
• Sudden Receiver Series – From GQRP. LC (not XTAL) oscillator, uses IF cans for tuned circuits and inductor.
• QRPme Sudden Storm – Includes mute control and interchangeable band modules
• The Rugster – From AA7EE. Interesting tuned front-end, uses Hi-Per-Mite board as audio out (4-section bandpass op-amp filter and LM386).
• Related: ‘Helping the NE612/LM386’ by VK2AWC. Ideas for oscillator control, gain control, etc.
• Relayed: YU1LM ‘Renaissance of the DC HF Receiver‘

NE602 Superhets

• Elecraft KX1 Manual/Schematic – Variable bandwidth 3-pole XTal filter, common collector into the filter, L-Match out
• Elecraft K1 Manual/Schematic – Similar variable bandwidth 3-pole xtal filter, common collector into filter, toroidal transformer out, with muting circuit into LM386.
• KN-Q7 (ZL2PD Schematic) – 5-pole xtal filter, no matching in or out, MC1350 IF amp on receive only, filter is bi-directional for SSB
• Hendricks PFR-3B – 4-pole (Cohn?) filter, interesting inductor on the input, otherwise no matching
  • QRPKits Tribander uses same arrangement
• QRPKits Survivor Radio – 5-pole Xtal filter (Cohn?) w/ common collector into filter
• QRPKits Simple Receiver – Uses NE602 as BFO/Product Detector, with AGC
• VK3YE SSB Transceiver

Double Sideband Transceivers

• ozQRP MDT

Twin Crystal Filter Transceivers

• VK3XU – The grandaddy of twin crystal filter rigs.
• VK3HN TCF – Based on VK3XU Rig
• VK3YE TCF

Phasing SSB Transceivers

• VK3YE SSB trx – LM386 shared as mic amp and receiver audio amp, diode ring mixer, simple phasing arrangements.

IF Amplifiers

• Original BITX (VU2ESE) – Bi-directional amplification stages
• ‘Oasis Blue’ Final Amp (N6QW) – Bilateral amps with PNP, NPN switching
• Minima (VU2ESE) – Termination insensitive amplifier, low noise

T/R Switching Ideas

• QRPKits Easy TR Switch – RF-Sensing using BS170 and 2n3906 to control DPDT relay
• 7N3WVM – Multiple ideas, and a compilation of others
• KN-Q7 – Simple trannsistor-based power switching

RF Power Amplifiers

• ‘Oasis Blue’ Final Amp (N6QW) – 2n3904, 2n3866, IRF510, ~8W output
• VU2ESE Two-Band Transceiver – 3 broadband stages into IRF510, ~7W output with 12V PA drive
• Original BITX – NPN to 2n2218 to IRF510, ~6W
• 20M Shirt Pocket (N2CQR) – A la EMRFD, 2n3904 to 2n3866 to IRF510
• G0KLA IRF510 amp – Push-pull in the EMRFD style, 50W with 28V supply.

Magnetic Loop Antennas

• G4ILO Wonder Loop –

Other Interesting Ideas (aka Unsorted)

• KISS Mixer in the Minima (VU2ESE) – Uses two JFETs to chop up the incoming signal, feed directly into the XTal filter
• Shirt Pocket 20M SSB (N2CQR) –

Other Link Collections:

• QRP Webring
• UR-QRP (Link is to google-translated English version of site)