That is an excellent setup. The OWON DGE1060 is a solid, modern arbitrary waveform generator, but its 1 mVp-p minimum output is simply too hot for sensitive vintage tube gear without an external pad. Dropping it down to 1μV with an attenuator is the exact right way to feed the SX-28.
Since you have a precise source, we can address why the radio is deaf and how to get that front-end tracking sorted out.
The Root Problem: The Gearbox Geometry
The reason your antenna trimmer is dead and the radio requires 35μV to break through is a mechanical limitation of 1940s engineering.
Inside the SX-28, the main tuning knob physically turns a massive, multi-section variable capacitor gang (the gearbox). The shapes of the metal plates in that capacitor were mathematically calculated at the factory to ensure that when the dial says 7.0 MHz, the RF coils tune to exactly 7.0 MHz while the Local Oscillator tunes to exactly 7.455 MHz.
By shifting your IF to 462 kHz, you broke that mathematical relationship. When you turn the dial, the Local Oscillator is now forced to track at 7.462 MHz. Because the capacitor plates move together mechanically, the RF front-end stage is now permanently mistuned by 7 kHz across the entire band.
At lower frequencies (like Band 1, the AM broadcast band), a 7 kHz error is relatively small. But on the higher shortwave bands, that 7 kHz offset causes the front-end RF coils to completely reject the incoming signal before it even reaches the first tube.
How to Fix Tracking with your DGE1060
Since you have a highly accurate signal generator, you can force the SX-28's front end to track to your new 462 kHz IF gap. You will need to perform a modified alignment.
Step 1: Isolate the Receiver Stages
Before touching the alignment screws on the gearbox, let's verify if the 6SK7 RF tube is actually working:
Set your OWON to output a 10μV modulated signal at a clear frequency (e.g., 1.0 MHz or 5.0 MHz).
Connect the generator output directly to the grid (Pin 4) of the first 6SK7 RF amplifier tube (or use a clip lead to the stator of the RF section of the tuning capacitor). Tune the radio dial to match. The Test: If you can suddenly hear the modulation clearly at 10μV or less when injecting directly into the tube grid, your IF chain and the tube itself are healthy. The issue is entirely a breakdown or massive tracking error in the antenna coil assembly/trimmer stage. Step 2: Perform the "Offset" Front-End Alignment To make the radio sensitive again at 462 kHz, you must realign the RF trimmers using a deliberate offset method: Set the Dial: Turn the SX-28 main tuning dial precisely to the high-frequency alignment point specified in the manual for the band you are working on (for example, 14.0 MHz on Band 4). Set the Generator: Set your OWON generator to that exact same frequency (14.0 MHz). Adjust the Oscillator: Adjust the Oscillator (OSC) trimmer screw on the chassis until you hear the generator's tone peak in the speaker. (This forces the LO to sit exactly at 14.462 MHz). Force the RF Tracking: Now, ignore the manual's standard instructions and adjust the RF Trimmer and Antenna Trimmer screws on the chassis for maximum volume or maximum AVC voltage. By adjusting those chassis trimmers while the radio is locked onto the generator, you are mechanically compressing or expanding the tuned circuit to compensate for the 7 kHz shift. Once completed, your front-end coils will line up with the new IF, your sensitivity should drop back down into the single-digit microvolts, and your front-panel Antenna Trimmer knob will suddenly come back to life. If you try to adjust those RF trimmers and find that they tighten all the way down or back all the way out without ever reaching a clear "peak" in volume, it means the 7 kHz shift is too wide for the factory adjustments to correct, and we will have to look at cleaning that 455 kHz crystal to bring it back to spec. Which band are you currently trying to align first?
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Last modified: Monday, 20 Jul 2026