The oft asked question of how much an LNA improves a 70cm weak signal station – Rules of Thumb

The article The oft asked question of how much an LNA improves a 70cm weak signal station solicited some comment on optimal configurations. This article deals with the notion / Rule of Thumb that optimal LNA gain is just sufficient to offset line losses. This article explains with graphs the relationship between Signal / Noise degradation … Continue reading The oft asked question of how much an LNA improves a 70cm weak signal station – Rules of Thumb

The oft asked question of how much an LNA improves a 70cm weak signal station

A recent online post seeking opinions on the chap’s 70cm weak signal configuration is an interesting subject for study, and one that should be of interest to many weak signal DXers. This article focusses on just one question in a quite similar configuration, what is the advantage given by the LNA? Study configuration The scenario … Continue reading The oft asked question of how much an LNA improves a 70cm weak signal station

Loop in ground (LiG) for rx only on low HF – #8 measurement and observation

This article was revised 03/01/2021 to correct an error: the NEC-5.0 model reported was actually the KK5JY LoG, fixed, apologies. The Loop in Ground project is about a receive only antenna for low HF, but usable from MF to HF. The objective is an antenna of that is small, low profile, and can be located … Continue reading Loop in ground (LiG) for rx only on low HF – #8 measurement and observation

Loop in ground (LiG) – #10 – implementation – earthworks

The Loop in Ground project is about a receive only antenna for low HF, but usable from MF to HF. The objective is an antenna that has low Signal to Noise Degradation (SND), and low noise pickup by virtue of some separation of near field radiators. The antenna comprises a square loop of 3m sides … Continue reading Loop in ground (LiG) – #10 – implementation – earthworks

Quantifying performance of a simple broadcast receive system on MF

I see online discussions struggling to try to work out if a receiving system is sufficiently good for a certain application. Let’s work an example using Simsmith to do some of the calculations. Scenario: 20m ground mounted vertical base fed against a 2.4m driven earth electrode @ 0.5MHz; 10m RG58A/U coax; and Receiver with 500+j0Ω … Continue reading Quantifying performance of a simple broadcast receive system on MF

Desk review of the AAA-1C as an active dipole antenna

The AAA-1C is an amplifier for small receiving antennas by LZ1AQ. The amplifier is designed for use with one or two small loops or a short dipole (possibly comprising two small loops). The datasheet contains some specifications that should allow calculation of S/N degradation (SND) in a given ambient noise context (such as ITU-R P.372). … Continue reading Desk review of the AAA-1C as an active dipole antenna

Small untuned loop for receiving – a design walk through #4

Small untuned loop for receiving – a design walk through #1 arrived at a design concept comprising an untuned small loop loaded with a broadband amp with input Z being a constant resistive value and with frequency independent gain and noise figure. In that instance, the design approach was to find a loop geometry that … Continue reading Small untuned loop for receiving – a design walk through #4

Noise figure of active loop amplifiers – some thoughts

Review of noise Let’s review of the concepts of noise figure, equivalent noise temperature and measurement. Firstly let’s consider the nature of noise. The noise we are discussing is dominated by thermal noise, the noise due to random thermal agitation of charge carriers in conductors. Johnson noise (as it is known) has a uniform spectral … Continue reading Noise figure of active loop amplifiers – some thoughts

Small untuned loop for receiving – a design walk through #3

Small untuned loop for receiving – a design walk through #1 arrived at a design concept comprising an untuned small loop loaded with a broadband amp with input Z being a constant resistive value and with frequency independent gain and noise figure. Small untuned loop for receiving – a design walk through #2 developed a … Continue reading Small untuned loop for receiving – a design walk through #3

Small untuned loop for receiving – a design walk through #2

Small untuned loop for receiving – a design walk through #1 arrived at a design concept comprising an untuned small loop loaded with a broadband amp with input Z being a constant resistive value and with frequency independent gain and noise figure. Loop amplifier There have been many credible designs of loop amplifiers of gain … Continue reading Small untuned loop for receiving – a design walk through #2