That is absolutely gorgeous data. $452.983\,\text{kHz}$ is an incredibly sharp, definitive reading.
The fact that you were able to resolve it down to the single Hz level ($983\,\text{Hz}$) means your out-of-circuit test jig is working perfectly, and that crystal has a very high $Q$ factor to pull $12\,\text{mV}_{\text{p-p}}$ across a low-value $100\,\Omega$ resistor pad.
Here is what this means for your SX-28, your website's alignment guide, and your next bench steps.
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## 1. The Math: Why 453 kHz is a Massive Win
Your original crystal is sitting at roughly $462\,\text{kHz}$ (an error of **$+7\,\text{kHz}$** from the nominal $455\,\text{kHz}$ design). This spare crystal is sitting at $452.983\,\text{kHz}$ (an error of only **$-2.017\,\text{kHz}$**).
In a high-performance superheterodyne receiver like the SX-28, a $-2\,\text{kHz}$ shift is well within the "elastic limit" of the factory RF and oscillator circuits.
* The slugs in your Band 1 oscillator transformer (**T25**) and the trimmers on your front-end RF sections will easily have enough physical thread range to tune down to match a $453\,\text{kHz}$ intermediate frequency. * You will no longer have to resort to tricks like adjusting **C12** to artificially boost mixer gain, because the local oscillator and the front-end antenna circuits will actually be looking at the same slice of the spectrum.
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## 2. A Crucial Insight for Your Website's Guide
The fact that you measured this at exactly $452.983\,\text{kHz}$ with modulation off highlights a golden rule you should include on **sx28.info**:
> **Alignment Note for the Guide:** When mapping an antique crystal or aligning the IF strip to match it, **never use amplitude modulation (AM) on the signal generator.** Amplitude modulation creates sidebands (e.g., a $400\,\text{Hz}$ tone creates sidebands $400\,\text{Hz}$ above and below the carrier). Because a high-$Q$ quartz crystal filter is so incredibly narrowΓÇöoften only a few dozen Hz wide at its peakΓÇöthe crystal will actually strip the modulation sidebands right off the signal, confusing your measurements. Always use a pure, unmodulated Continuous Wave (CW) sine wave to find the true resonant peak.
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## 3. The Next Move: The "In-Circuit" Swap
Since this $453\,\text{kHz}$ crystal is a much better candidate for a sensitive, properly tracking radio, the next step is to swap it into the SX-28's crystal filter assembly.
Once it is physically installed, you will need to perform a **Crystal-Centered IF Realignment**:
1. Leave your front-panel main tuning dial alone for a moment. 2. Hook your OWON generator up to the grid of the mixer tube, set to exactly **$452.983\,\text{kHz}$** (CW, no modulation). 3. Turn the radio's Crystal Filter to a strict ON position, and center the Phasing control. 4. Go down the line and peak every single IF transformer slug/trimmer in the radio to match this exact $452.983\,\text{kHz}$ frequency, monitoring your scope at the final detector or watching the S-meter.
Once the IF strip is unified at $453\,\text{kHz}$, your "not good, but better" AM band reception should instantly transform. Your 15ΓÇô20 stations will suddenly line up with the radio's front-end preselector geometry, and you should see healthy, vigorous movement on that S-meter.
Are you planning to drop this $453\,\text{kHz}$ crystal into the radio's holder next, or do you want to clean the quartz slab first to see if it moves closer to the factory $455\,\text{kHz}$?
Page: /1_need_help/Gemini_27/Gemini_27.shtml
Last modified: Monday, 13 Jul 2026