Hi Martin,
Since I am new on this site I decided to spend some time finding out who is Mr. Owen Duffy,? VK20MD whom you have been frequently referencing regarding SND evaluation of loop antennae.
Is he australian HAM amateur representing National Association for Amateur Radio in Australia and a good practioner in radio field ?
I am honestly feel uncomfortably with introducing SDR concept. Why ?
The introduced equation is SND (S/N degradation ) = 10log ( N int. /N ext. + 1 ).? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? So basically, when N ext. >> N int. the SND ---> to 0 dB and when N ext. << N int.? the SND? exceeds greatly 0 dB value ( I considered? extreme conditions only for a better? comparision between both values
ambient electrical noise vs. internal amplifier noise levels to understand? the SND concept). Was it introduced by Owen Duffy or others ? What value of SDR expressed in dB would be better ?
When we deal with SNR concept, it is clear for everyone - higher value is better.?
By the way, Owen Duffy in 2012 had a presentation? "Noise and Receivers"? where he does not mention anything about SDR. Is it widely accepted by scientific and rado engineering media ?
In his presentation he wrote interesting thing that we discussed earlier: "MDS - minimum discernable signal - misleading term ( is it? possible to copy CW well below MDS )"
Later? I looked at the various plots which you presented in your published article "Broadband Loops " that shows different plots as SND= f ( d, Z inp, F ) where d - diameter of loop conductor, Z inp. - input impedance of amplifiers as a load for antenna loops and F -?frequnecy of interest.
All the work is for unshielded small loop antennas. Do you have for illustration purpose a plot for conventonal shielded loops as well, say with conductor diameter of 1 mm ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Let's Let's forget about Moebius antennas because they perform well only below about 1 MHz.
I am asking about shielded loop antennas because there is introduced another unknown? factor - self resonance frequency, say between 0.1 and 30 MHz range.
I guess, in range of 0.1 MHz up to the? self resonance frequency value your published plots can be considered for shielded loops because the inductive reactance of antenna will prevail.?
What results will you predict above a self resonance frequency up to 30 MHz where capacitance reactance of antenna will prevail? over inductive reactance of antenna impedance?
Your response would be greatly appreciated.
Regards,
Raphael
