Real-World RF Noise Test: EM8-40S13R820 13.8V Converter on Ham Radio

📋 Why We Ran This Test

Switching converters have a reputation among radio operators for generating RF hash that can wipe out weak-signal reception. Since our EM8-40S13R820 13.8V 20A Boost-Buck Power Conditioner is marketed specifically for Amateur, GMRS, and commercial radio use, we wanted real bench data rather than just a spec sheet claim. A fellow ham radio operator volunteered to put the converter through its paces on his own test equipment, and shared his full results below.

🔧 Test Setup

The converter was fed from an RF-quiet, linear regulated DC power supply — chosen specifically so the supply itself wouldn't contribute any switching noise to the measurements. Two loads were used on the output: a 2A load (a 24-watt automotive tail lamp) and a 10A load (a resistive heating coil). One of the load leads was coupled through a mix-31 ferrite toroid into a Rigol DSA815 spectrum analyzer, allowing the converter's conducted/radiated switching noise to be observed directly on the current path.

📊 Spectrum Analyzer Results

Three conditions were captured on the Rigol DSA815, spanning 100 kHz to 2 MHz:

Boost Mode (10V Input)

With the converter boosting a 10V input up to 13.8V, several noise spikes appeared between roughly 100 kHz and 1 MHz, with the first and strongest spike at 138 kHz. Noise levels in Boost mode were noticeably stronger than in Buck mode.

Buck Mode (16V Input)

With the converter bucking a 16V input down to 13.8V, the same general spike pattern was present but at noticeably lower amplitude. A 40V input test looked essentially identical to the 16V result, indicating the noise profile is stable across the buck operating range.

Converter Off (Baseline)

With the converter powered off, this trace shows the test setup's inherent noise floor for comparison against the Boost and Buck traces above.

In all three conditions, little energy was seen above 2 MHz, and the converter was quiet across the VHF and UHF bands. Switching between the 2A and 10A loads shifted the exact spike frequencies and count somewhat, but did not meaningfully change the overall noise level.

📡 On-Air Receiver Testing

Beyond the spectrum analyzer bench test, the converter was used to directly power an Icom IC-7300 and an Icom IC-9700. No added noise was heard on 80 meters, 2 meters, or 70 centimeters in either Boost or Buck mode. A separate test placed a loaded converter near a KiwiSDR receiver, and no added noise was observed across the entire 0-30 MHz range, again in both Boost and Buck mode.

✅ Conclusion

Per the operator's own summary: "Unless you transformer couple it into the antenna port of a low frequency receiver, it looks like you've got a good converter." The measured switching noise — concentrated between 100 kHz and 1 MHz and centered near the converter's rated 120 ± 10 kHz switching frequency — falls well outside the HF, VHF, and UHF bands used for on-air communication, and no degradation was observed on real radios during actual operation.

📄 Documentation & Resources

• EM8-40S13R820 Product Page
• EM8-40S13R820 User Guide

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Test results shared here reflect one operator's independent bench evaluation and are provided for informational purposes. Individual results may vary based on equipment, wiring, and installation. Envistia LLC (dba Envistia Mall) makes no warranty regarding RF performance in any specific installation. Always follow proper electrical safety practices when working with electronic components.