David, >From Bodo's response, I interprete it as: first, calibrate with signal generator, then second, terminate with 50R and measure noise power.
Bodo's justification why this is a MDS measurement, is that when a signal of equal power is injected, it can be received at 3 dB above the noise level. Guido. On Thu, May 22, 2008 at 6:44 AM, drmail377 <[EMAIL PROTECTED]> wrote: > So you measure the received power in 500Hz with 50 Ohm termination on > the antenna input, then replace the antenna with the generator and > increase the signal power until you see a 3dB increase in the receive > power, the generator output level is then the MDS level? Is my > interpretation correct? > > I wish there was a standardized procedure for this. > > Rgds, David > > --- In [email protected], "ad9850" <[EMAIL PROTECTED]> wrote: > > > > Hi, > > > > I am following a very simple procedure described some time ago by Bob, > > N4HY in the old FlexRadio forum. I am measuring the noise power in 500 > > Hz bandwidth, the antenna input terminated by 50 ohms. This is the MDS > > because a signal of equal power will increase the level by 3 dB. I am > > using Duncans KGKSDR to determine the power in 500 Hz bandwidth. The > > software is calibrated for each band. A Rohde&Schwarz signal generator > > is used for the calibration. > > > > 73 Bodo, DJ9CS > > > > > > --- In [email protected], "Alan" <g4zfq@> wrote: > > > > > > > > > ----- Original Message ----- > > > From: "ad9850" > > > > > > > > sorry I forgot to mention this. I followed the more or less standard > > > > of 500 Hz bandwith. > > > > > > > > > > There was an article in the RSGB magazine recently that said MDS is > > not a > > > substitute for NF (Noise Factor) but the concept of Minimum > Detectable > > > Signal seems easier to understand. > > > I can make an approximate reading of the smallest signal I can > > receive but > > > how do I know what bandwidth I am looking at? > > > I can do it by ear or by looking at a waterfall, I will get vastly > > different > > > results. By ear I may be using a 500Hz filter, by using a waterfall > > I could > > > be looking at a fraction of a Hz. > > > Under what conditions are these measurements made? > > > > > > 73 Alan G4ZFQ > > > > > > > > > ------------------------------------ > > Yahoo! Groups Links > > > >
