Universal SSB IF

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M0XXQ
Posts: 484
Joined: Thu Sep 27, 2018 10:23 pm
Location: Newcastle upon Tyne
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Universal SSB IF

Unread post by M0XXQ »

Carrying on from the thread "What do you have planned for 2019? " I have decided to tackle a long time challenge I have been facing building my own SSB radios - a proper Transceiver IF stage.
All of my designs so far incorporate separate TX and RX IF stages using two or more crystal filters and mixers, very expensive parts these days so it is time to design an IF sub-system that can be replicated easily whilst allowing for flexibility on component choice.

Over the years there have been a few turnkey designs from the likes of Ron Taylor G4GXO with the Belthorn and Eden transceiver IF and Wes Hayward W7ZOI with the Hycas IF and AGC (Although not a complete transceiver sub-system but close).

So having spend hundreds of hours building gear over the years I have decided to simply, consolidate and produce something others can use as the cornerstone for their next homebrew SSB project that will designed with both simplicity and performance in mind.
As it currently stands after recently moving QTH, all of the workshop is packed away and will stay that way for some time until we are in a position to buy our own home, rented accommodation just doesn't lend itself to having a decent workshop and radio shack so the inital focus of this project will initially be design and simulation using the software tools I have such as Eagle CAD and LT Spice.

So, here are the key requirements for this project:
  • Bi-Lateral and shared stages between TX/RX
  • Use of high performance mixers such as ADE-1, SRA-1, SBL-1
  • Single Conversion receiver strip with simple roofing filter
  • IF Compressor using cheap 455KHz ceramic filters for the TX strip
  • Main SSB Crystal Filter shared between TX/RX
  • Use of discreet components where possible
  • Cascode Hybrid IF amplifiers
  • IF derived AGC
  • Modular main and daughter board PCB to accommodate the ability for easy filter interchange and experimentation, this will also keep the overall size to a minimum
  • In-Circuit test points for alignment of filters and debugging
I will use circuit ideas from the book EMRFD combined with my own and using PCB design techniques which I have adopted in previous projects such as modular filter daughter boards which lend themselves to quick removal for alignment and experimentation.

The tricky but will be keeping this as simple as possible whilst using readily available discreet components such as 2N3904 NPN and J310 FET devices, diode ring mixers are readily available in different shapes and sizes so this will become a plugin module to accommodate a different variety rather than a fixed PCB footprint for say and SRA-1.

So, next steps will be prototype design and simulation in LTSpice.