Latest Posts

• Hunting Electrical Noise Sources - III

  Here, I continue my description of the PLT-like noise source that affects my radio reception and internet router. The initial description of the source is at 2022-02-18-Hunting-Electrical-Noise-Sources-II. The first article in the series describes a different noise source and is at 2022-01-04-Hunting-Electrical-Noise-Sources-I.

• Hunting Electrical Noise Sources - II

  Previously, I described hunting down a Switched Mode Power Supply (SMPSU) that was generating electrical noise that affected my reception of short wave radio signals. For some months, I have also been looking for another source that has much wider effects in the locality. As I began to research this post, I find that the same source has been probably been causing me problems for several years, since March 2018 or earlier. It affects not only my short wave radio but my broadband internet.

• Hunting Electrical Noise Sources - I

  Local electrical interference to amateur radio reception on shortwave and VHF now makes the hobby an unpleasant pastime, unless you live in the country, remote from other habitation. Most don’t; I don’t. This noise is an incidious form of electrical pollution with many causes. As a result, this is likely to be the first of a series of articles as I attempt to track down and, hopefully, eliminate some of my local noise sources.

• Quality in Data Transmission

  [Still a ‘Work in Progress’ at Feb 2022 ] Today’s Amateur Radio Data modes share one thing in common; an 'ideal' audio signal of relatively narrow bandwidth is translated by a Single Sideband Transmitter to a Radio Frequency signal. That RF signal should be an undistorted copy of the audio. If you have spent some time using these modes, you will be aware that in many instances this ideal is not met in practice. I have some suggestions as to 'why'.

• An Audio QSO Recorder with Instant Playback

  I searched for an audio recording program that would record continuously but allow me to replay repeatedly the last few seconds of the recording. I wanted this for Radio Contests. If I misheard some exchange, I could immediately replay the audio, if necessary several times. Not finding such a recorder, I wrote one. I modified an audio recording example from the CSCore Audio library. As you might expect, the first attempt has limitations. It can be improved.

• Experiments with FIR Digital Filter Design Software

  Since my early experiments with receiving Radio Teleprinting signals (RTTY) in the 1970s, I have been fascinated by the filtering required. At that time, the design problem was making linear-phase band-pass narrow audio filters built with high-Q toroidal inductors and RC active filters for post-demodulation filters; today the processes for both requirements are purely digital. When you play with Software Defined Radio software such as HPSDR or SDRUno, you can adjust the filtering dynamically by moving the cut-off points on the spectrum. My curiosity was aroused!. How do you design a filter on the fly and apply its design to a signal?

• Solar Panel Interference

  In early august 2014, my immediate neighbour had a 16 panel PV system installed on the rear SE-facing roof. Since the system became operational, the inverter switching has caused RF noise spikes from 11MHz to around 70MHz. 24MHz (12m) is now unusable for most amateur radio purposes. [Seven years on there is no resolution to this interference, nor is there likely to be. I live with it.]