SW-3 Project Step 1: Choose and Consolidate

The National SW-3 “All A.C.” Version at KY6R

The first thing I had to do is decide which of two SW-3’s I would use for my receiver. The “All A.C.” model won because:

  • It had two of the three coil sets that I wanted – the 40 and 20M band and the upper end of the broadcast band and Top Band (1500 – 2000 kc). I want to get the “orange” coil set which covers 690 – 1500 kc
  • The power requirements seem easier to manage – there are just two voltages needed – 180v for B+ and 2.5v for the filaments. Plus, the fellow I purchased the receiver from is shipping me his home brewed power supply where he had the face painted the same color “black crinkle” as he has the SW-3 painted by a restorer. I will use his power supply – which uses tubes for now – but will build my own solid state version as a follow on project. If his case is nice – I’ll breadboard the solid state and then swap the circuits out. He also has a speaker in his PS – so that’s a big bonus – I’d rather not use cannonball high impedance cans with this rig – I want the shack filled with “swoopy” regenerative signals via a speaker

The circuit in my SW-3 “All A.C.” version

The second set is now my parts set, and the first thing I did was move the better “Velvet Vernier” dial mechanism from the parts box to this box. I also was able to put the cover that looks like a shiny round ball over the vernier mechanism – and now it looks really great.

I was able to order a set of tubes from Antique Electronic Supply, and they were very reasonably priced. Two 6C6’s and one 27 tube. These are NOS – and I think its pretty cool that these old tubes are still available and priced as well as they are. WIth the second set of parts – I will be set and will be able to do my own work. I’ve already learned a lot about the design of this receiver – from that James Millen article, reading online forums on what to consider and watch for with the different versions of this receiver, and the power supply considerations.

 

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