Sorry for the dyslexia. I've been meaning to type APD, not ADP. Paul, W9AC
Sent from my iPhone5 > On Aug 3, 2014, at 10:58 AM, Paul Christensen <[email protected]> wrote: > > Tom, > > Also consider a situation where a solid-state transceiver is driving a class > B amp with, for example, -20 dBc 3rd order IMD -- and that IMD is much worse > than the driving transmitter. In that case ADP is correcting IMD products > where IMD is generated primarily from the amp. > > Paul, W9AC > > Sent from my iPhone5 > >> On Aug 3, 2014, at 10:25 AM, "Tom W8JI" <[email protected]> wrote: >> >> You¹ll final several references of ANAN users who have improved internal >> transceiver shielding so that RF detection comes only from the sample port >> and not internal leakage. Otherwise, the ADP algorithm is trying to >> simultaneously correct for non-linearity of two amplifiers (internal and >> external) and not just one < when only the external amp requires IMD >> optimization. >>>>>>>>> >> >> I know Paul knows how it works, but the explanation was incorrect. >> >> The bulk of distortion is almost always, with the exception of a few radios >> and amplifiers, from the transceiver. Most external amplifiers, with the >> exception of the common poorly designed tetrode systems and low voltage >> solid state amps, are significantly more linear than the exciter. A grounded >> grid triode amplifier using 8877 tubes, or even 811A tubes, is significantly >> cleaner than most radios (even when the amplifier is being hammered). The >> general exception are tetrodes with improper screen and bias regulation that >> lack the heavy negative feedback of grounded grid amps, or the rare radios >> with exceptional transmitter linearity. >> >> Distortion correction *must* include the exciter, but it must be at the >> antenna port. >> >> Unwanted coupling from the exciter does not cause the ADP system to correct >> the exciter. Unwanted coupling introduces a sample that is not >> representative of what is actually on the antenna port. This effect is >> commonly observed when we try to monitor our own transmitters with other >> receivers at the operating position. We often hear hum, noise, distortion, >> and artifacts that are not on the antenna line. >> >> 73 Tom >> _________________ >> Topband Reflector Archives - http://www.contesting.com/_topband > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband
