Skip
----- Original Message ----- From: "David Little" <[EMAIL PROTECTED]> To: <digitalradio@yahoogroups.com> Sent: Wednesday, March 12, 2008 4:25 PM Subject: RE: [digitalradio] Re: 10 Tips for the PSK31 Digital Mode One more consideration is AGC recovery time. Slow AGC and static crashes are not a good combo in many of the digital modes. No AGC or Fast AGC will make a difference in that situation. This may not apply to PSK-31 as much as more complex digital modes, but a point worth considering. DSP filtering of signals above and below the signal you are trying to copy are also a great help; if your rig will allow that narrow of a passband. David KD4NUE You never want to use Fast AGC on PSK31, because the receiver will attempt to follow the PSK31 signal and cause distortion. Always use the slowest AGC setting you have, or no AGC at all. BTW, to accurately measure IMD, reduce your RF gain until the IMD reading stops falling and report that as the IMD reading. The reason for this is that the receiver must amplify linearly for PSK31 and if a signal is strong enough to distort the RF amplifier or IF amplifers, you get a false (usually poorer) IMD reading. Also, IMD is the measure of the first set of unwanted sidebands and if the signal to noise ratio is poor, the software will be measuring the noise at the same point as unwanted sidebands and reporting a poor IMD. It is better just to look for unwanted sidebands and report if you see any or not. The caveat is that the unwanted sidebands may be so far down in the noise you cannot see them, even though they are there, but as far as you, or a station with the same reception as yours, it does not matter, as the unwanted sidebands are not going to bother an adjacent station. Still, the best practice is to always transmit with a linear, clean, signal so your unwanted sidebands do not QRM any adjacent station, either near to you or somewhere else 73, Skip KH6TY .
