Hello all. I’ve made another measurement of the observed noise level in the 80 metre band as a follow-up to the measurement done in early October and do see some expected changes. Here’s the plot:
It should be immediately obvious that the noise trend during daylight hours is less saturated at the -110 dBm. level than it was in the October record, which is consistent with the premise that the lower sun angle will cause less D Layer ionisation. Yet, there are a couple more observations I take from this measurement when compared to that of October:
1 – The night time noise mean level is lower than October. Could it be that the lower sun angle is also causing less F Layer ionisation, thus there being less “visible” area being refracted back to the observer?
2 – The day time saturation level of -110 dBm. is essentially unchanged from that observed in October. I’m not sure about why this is, other than this level being the result of my antenna+coax noise temperature. I re-checked the instrumentation noise level, i.e. that of only the digitiser with antenna disconnected, and it sits at around -117 dBm., as it was in October, so it would seem that there’s at least enough separation between the noise floor of the measurement set and the coax+antenna+sky.
So there it is. I’ll continue with these measurements once a month until the summer of 2020 and perhaps combine all the monthly jpegs into a movie to have a more dynamic view of how things change throughout the year.