Small untuned loop for receiving – a design walk through #1

This series of articles develops a simple design for a small receive only broadband loop for the frequency range 0.5-10MHz, and to deliver fairly good practical sensitivity. Fairly good practical sensitivity is to mean that the recovered S/N ratio is not much worse than the off-air S/N ratio. Let’s quantify not much worse as the … Continue reading Small untuned loop for receiving – a design walk through #1

Small untuned loop for receiving – it’s not rocket science

I have written several articles on untuned loops for receiving, as have others. A diversity of opinions abounds over several aspects, but opinions don’t often translate to sound theory. This article analyses a simple untuned / unmatched loop in the context of a linear receive system. An example simple loop for discussion Let’s consider a … Continue reading Small untuned loop for receiving – it’s not rocket science

Towards understanding the YouLoop-2T at MF/lowHF

Small untuned loop for receiving – simple model with transformer gave a simple model for analysing a loop. If you haven’t already read it, you should. It provides a step towards understanding the YouLoop-2T at frequencies where is is a small loop (perimeter<λ/10). Above is the Airspy Youloup-2T. Try to put the two turns thing … Continue reading Towards understanding the YouLoop-2T at MF/lowHF

Small untuned loop for receiving – simple model with transformer

I have written several articles on untuned loops for receiving, as have others. A diversity of opinions abounds over several aspects, probably none more than the idea of an optimal load impedance for the loop. This article analyses a simple untuned / unmatched loop in the context of a linear receive system (ie no IMD) … Continue reading Small untuned loop for receiving – simple model with transformer

Optimum receive system noise figure for given ambient noise – Flex 6700

This article is a follow up to Optimum receive system noise figure for given ambient noise – Flex 6600 using data published at (Farson 2014) to make similar estimates for the Flex 6700. How to determine the amount of RF Preamp gain to apply for band conditions suggests that the 6700 figures might also apply … Continue reading Optimum receive system noise figure for given ambient noise – Flex 6700

Optimum receive system noise figure for given ambient noise – Flex 6600

Gerald Youngblood (K5SDR) of FlexRadio wrote of optimal receiver noise figure relationship to antenna noise in a blog posting about SDR receivers. This article discusses that posting in the context of linear receivers, ie effects of intermodulation distortion are not included. His gives the following advice: For optimal weak signal performance near the atmospheric (antenna) … Continue reading Optimum receive system noise figure for given ambient noise – Flex 6600