Tom, Mike is right, the issue with audio overload is complex for most of new radios, most of them have A/D just at the MIC input, if the A/D overloads the RF chain is compromised. These radios have no actual filters, everything is digital, like the IC7600. An analog radio is BW limited by the SSB crystal filter but SDR don't, when the A/D overloads, there are spoors everywhere several KHz far from the carrier; enough to trash the entire band.
Using a SDR water fall it is easy to see the signal transitions and associate the trash with the main signal. I've seen several spoors every 10 KHz almost 100KHz up and down 1838. This is a growing problem. 73, JC N4IS -----Original Message----- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Mike Waters Sent: Monday, December 30, 2013 1:31 PM To: Tom W8JI Cc: Topband Subject: Re: Topband: Digital mode spurious issues Tom, I believe the mode that operates at 1873-1838 is JT65, and WSJT is needed to decode it. I never tried it. It was developed by K1JT for weak-signal and EME work. http://www.physics.princeton.edu/pulsar/K1JT/wsjt.html A common scenario with digital modes is that the audio into the mic input is too high, causing unwanted spurs. 73, Mike www.w0btu.com On Mon, Dec 30, 2013 at 11:11 AM, Tom W8JI <w...@w8ji.com> wrote: > ... a digimode station up roughly around 1837 came on with a LSB > "spurious" signal on 1833. His signal was a series of slowly changing > stepped tones. I don't know what mode that was. His unwanted sideband > suppression was about 40 dB, but that was not nearly enough. He was 15 > dB out of noise with his unwanted sideband. > > Does anyone know of a universal software to decode signals? Since the > FCC does not require a CW ID, I think that is the only way to identify > stations. ... > _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband