I've been accumulating some of the hard-to-find parts needed for this project for a couple of months. I believe I have enough to make a start. The circuit is based on one published in "Solid State Design for the Radio Amateur" beginning on page 132. My receiver will have SSB & AM I.F. filters rather than SSB & CW as per the original project. I 'll also be using Murata ceramic filters in place of the original Collins mechanical filters. An AM detector circuit will need to be included. As this is just a single band receiver I expect It will be a more physically compact build than my Progressive Receiver which is described on another page.
Some CA3028A integrated circuits and some miniature 455KHz I.F. transformers have been sourced. The JW Miller I.F. transformers specified are no longer available. The VFO PCB has been built and tested and a National Velvet Vernier dial was found in the junk box. It is similar in appearance to the one used in the original article.
All PCB artworks have been completed for all of the circuit boards required for this receiver including the fixed tuned preselector, tunable preselector, RF amplifier/mixer, AGC amplifier, I.F. amplifier/product detector, I.F. ceramic filter switching, BFO and audio amplifier circuits.
Tuesday, 12th June 2018
A Homebrew 160 Metre AM & SSB Superheterodyne Receiver
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Page last updated December 5th, 2018
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I have finished building and testing the AGC amplifier, SSB/AM ceramic filter switching, and the 455 KHz I.F. amplifier circuit boards and initial tests indicate that they are working for the most part as per the original design. However, I found that the post filter amplifier stage, a 2N2222A was oscillating at about 300KHz so I had to introduce some negative feedback between the collector and base to tame it. I used a 10N cap and 10K resistor in series and it's now very stable.
Monday 12th November 2018
Sunday 2nd December 2018
I built the VFO and put it in a diecast box for further testing. It did not end up as I had first imagined. The Toko style coil in a can was totally unusable. It made a very unreliable and drifty oscillator so I resorted to modifying the PCB layout to incorporate a toroid style coil as displayed in the photo below. This version is much more stable but I'm not yet convinced I have it as stable as it needs to be.
I let the VFO run overnight and recorded 32Hz of drift in 7 hours but of course I don't know what it did in between those times. At least I know that it does not drift in one direction continually.