Noise reduction and receive antenna relocation
After some prompting, I’ve been persuaded to document some of my amateur radio activities in a blog. Over the next few weeks, I will provide further detail of the steps taken to reduce received noise and the composition of the developing receiver and demodulation system.
Much useful information about noise reduction can be gained from the entries in Jim’s blog:
After taking the following steps at the home location:
1) Using ferrites (Fair-Rite 2631801202 FT114D-31)
2) Replacing switched mode power supplies (SMPS) with linear supplies
3) Using shielded ethernet cable
4) Removing powerline adapters
5) Trying a QRM eliminator
6) Employing mains filters
It became evident that, even though the above steps had been helpful, I was fighting a losing battle as noise sources seemed to be increasing in type and variety.
The concept was straightforward. Move the receive antenna away from suburbia into the countryside, away from man-made noise sources. Provide access to the antenna over the internet using a KiwiSDR and use additional devices such as Red Pitayas to process data onsite and upload.
|Wellbrook Loop ALA100LN, 50m wire circumference (a bit hard to see!)|
Over the weekend of 9/10 December 2017, a test antenna was constructed and erected at the remote site. 50m of RG213 feeds the signal from the head unit back to the building which contains the receivers. The internet connection from the receivers is a mixture of WiFi/ADSL and somewhat fragile – the connection drops sometimes. This is an area that needs improvement.
Testing and evaluation is now in progress. The Wellbrook ALA100LN Loop is primarily designed for low band reception, but can receive up to 30 MHz. First impressions are that the project has delivered significant improvements and was worthwhile. Further investigation of remaining noise and an assessment of receive performance across the HF spectrum will be needed.
|80m SSB in the afternoon|
The KiwiSDR is at the following link: