Checking Shackmaster Power 500 RF emissions in High-Frequency bands


Shackmaster Power 500 is the 13.8 V 35A pulse power supply both for professional and amateur radio use. 

It is a well-known fact, that linear power supplies do not generate RF noise contrary to pulse power supplies which, if badly designed or don’t have quality input AC and output DC filters, can generate RF harmonics across the whole HF spectrum making the reception of weak DX signals especially on 160 and 80 meters extremely difficult or even impossible. On the other hand, linear power supplies with heavy transformers and large capacitors inside are not practical for use in DXPeditions and during Field Day events.

This study aimed to determine if the Shackmaster Power 500 pulse power supply is “RF quiet” enough to be used with modern amateur transceivers to enable noiseless reception on low-frequency bands.

Hardware Setup

The RigExpert FOBOS SDR receiver with the short sense whip antenna and -20dB attenuator was used in this study.  Shackmaster Power 500 delivered out 4A at 13.8 V. This current is the average value that modern transceivers consume in receive mode.

Software Setup

The HDSDR software is configured especially to work with  RigExpert FOBOS SDR was used.


The noise level of  FOBOS SDR in the configuration described above is S3 or -130dB.

When Power 500 is switched ON. the signal level remains S3 but the waterfall shows the minor noise increase across the whole HF spectrum.

Fortunately, there were neither noise level increases nor spurious signals within the low band of the HF spectrum.


Shackmaster Power 500 is the 13.8 V 35A pulse power supply that can be successfully used in quiet rural environments, in DXpeditions to remote islands and other places where the man-made RF noise level is low.