QRM to Telstra NBN FTTN modem

This great case study from a VK amateur…. I have a Telstra NBN modem, used for a FTTN service.  It is installed on a shelf in the garage My 40m dipole runs across the garage – the end is about 7m away from the modem.  Whenever I transmitted, RF would cause the modem to lose […]

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Audit your power packs / wall warts

Check your power supplies  With the New Year comes New Year Resolutions.  The little 5V plug pack that came with the laser show Christmas Present was stamped with a working range of 100 – 240VAC, 50/60 Hz.   It will work well in the USA on 110V and even in China where the mean voltage is […]

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Radial Free Verticals

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 […]

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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 […]

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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, […]

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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 […]

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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 […]

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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 […]

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