A reader of Do I ‘need’ a masthead preamp to work satellites on 2m? – space noise scenario has written to say he does not like my comments on the hammy adaptation of G/T.
Above is an archived extract of a spreadsheet that was very popular in the ham community, both with antenna designers and sellers and end users (buyers / constructors). It shows a column entitled G/T which is actually the hammy calculation. The meaning possibly derives from (Bertelsmeier 1987), he used G/Ta.
Ta is commonly interpreted by hams to be Temperature – antenna. It is true that antennas have an intrinsic equivalent noise temperature, it relates to their loss and physical temperature and is typically a very small number. But as Bertelsmeier uses it, it is Temperature – ambient (or external), and that is how it is used in this article.
Let’s calculate the G/Ta statistic for the three scenarios in Do I ‘need’ a masthead preamp to work satellites on 2m? – space noise scenario.
Base scenario
Above is a calculation of the base scenario, G/T=-29.74dB/K.
Also shown in this screenshot is G/Ta=-23.98dB/K. Continue reading Do I ‘need’ a masthead preamp to work satellites on 2m? – G/T vs G/Ta