Band Switch Notes, Early Radios

All of this is for the SX-28. The early radios (not A) might look like they have modules but they don't. You have to completely demolish everything to get one of them out. The tube sockets are rivited to the main chassis and the coils are screwed in from the bottom of the sub-chassis parts. I don't even know how they managed to assemble these things.

For all of the following links, assume:

• The radio is upside down.
• The view is from the front panel side.
• "Up" means twards the ceiling, not the top of the radio. "Down" is the opposite.
• "Front" means twards the front of the radio and the viewer, "back" means away.
• Sometimes a single wafer will contain two switches - one on the front side, one on the back.
• There are 10 wafers numbered from the rear of the radio to the front.
1. Inside 1st RF - SW8-1 (except very early radios)
2. Inside 1st RF - SW8-2
3. Inside 1st RF - SW8-3 and SW8-4
4. Inside 2nd RF - SW8-5
5. Inside 2nd RF - SW8-6 and SW8-7
6. Inside mixer - SW8-8
7. Inside mixer - SW8-9 and SW8-10
8. Inside osc - SW8-11
9. Inside osc - SW8-12 and SW8-13
10. The wafer on the outside of the osc module - SW8-14 and on all but very early radios, SW8-15
• Although it looks like there are 10 different wafers, some of them are identical to ones in other modules.
  Please see this page for details.
• For the most part, the wafers in the early radios are the same as in the late but there are a few differences.
• There is a page to help you understand orientation here.

Follow the links to a page about the indicated set of switch wafers...

1. 1st RF module, earliest versions of the 28. Only two wafers
2. 1st RF module, later versions of the 28 (and not 28A). Three wafers
3. 2nd RF module, earliest versions of the 28. Companion to 1 above
4. 2nd RF module, later versions of the 28. Companion to 2 above
5. Mixer module
6. Oscillator module

Page: /Band_switch/Early/Early_band_switch.shtml

Last modified: Monday, 1 Jun 2026