Radial Free Verticals By the QRM Guru team From time-to-time we receive emails about QRM and TVI associated with these radial free verticals. The symptoms will usually present as TVI, RF feedback and sometimes an inability to achieve a desirable SWR on the lower bands. We also hear of situations where the antennas appear deaf […]
Category: Case Studies
A BlueRay Player problem
A remarkably interesting fault. By Bob Tait VK3XP Recently I decided to upgrade my UHF TV antenna. Whist connecting the coaxial F connector to the antenna I got a small tingle. I also noticed broadband 50Hz QRM on 40 and 80 metres. Where was this coming from? There were a number of possibilities. I recently […]
Noise Canceller Kit – from VK5TM
With thanks to Phil VK3VB for this case study Early March 2020 saw me working from home due to COVID-19. This led to re-establishment of the long-neglected shack, which was also the home-office. First, the digital modes were re-established with DSTAR, DMR and NXDN along with the standard 2m/70cm FM. Over the past few years, […]
No House Electrical Earth… interference to neighbours
Thanks Roy VK3GB for this somewhat left-field story about interference. Interference, there is always a sign! Some years ago I moved house and as normal spent the first year renovating and redesigning the garden. Why so you long you may ask? I was laying 120 radials ready for my Butternut HF2 vertical. Once erected you […]
Finding power line noise using a VHF AM receiver
Thanks to George Smith G8AOJ and the RSGB. “For several months I had been experiencing random variable level wide-band impulsive noise across the whole 2m band. This manifested itself at times as a strength seven continuous crackling noise.” Read on to see how George traced the offending noise source. This article is copyright of the […]
Eliminate Interference with the MFJ-1026 Noise Canceller
A great demonstration video from Hayden VK7HH and this Noise Cancelling device in a real world scenario. Thanks Hayden.
Finding and killing QRM in the home with ferrite toroids & snap-ons
From Josh KI6NAZ Josh has put together a great Youtube video on reducing RFI in and around the house. Using simple techniques to find the noise source and then using toroids and snap-ons to reduce or illuminate the noise. A very useful video. “For most of us, RFI is around us all the time. It […]
DF Loop kit and noise cancelling techniques
The following case study sourced from Grant VK5GR One thing I have found very helpful for finding sources is to build this kit: https://www.minikits.com.au/electronic-kits/high-frequency/hf-active-antenna/EME234-HF-Active-Loop Click this link to visit minikits website. For the antenna, get some ½” soft copper pipe and form a loop about 30cm diametre and use that in place of the wire […]
LED Lights – Test Results
Some of the most common RF noisy products around the house are LED downlights. We have had reports of banks of LED lights (60+ lights) causing QRM for HF radio at distances of up to 400 metres. Plenty of retailers sell LED lights of various brands, but it is almost impossible to tell if these […]
The best thing you can do to reduce noise in your radio shack
We’ve spoken about the importance of having good house-keeping in your goal for a low noise environment. Other posts on QRM Guru talk about various techniques and tools you can use, but in this video Peter, VK3YE provides a great practical demonstration of how you can reduce noise in your shack. Using Ferrite rings and […]