With EER a class C or D amplifier can deliver an IMD of at least -80 DB but with pre-distortion it could be even better.
Sent from my iPad > On May 19, 2019, at 3:38 AM, Roger <ro...@mulzer.de> wrote: > > As pointed out "PreEmphasis/DeEmphasis" and "PreDistortion" are two > different things. So it is important to keep this in mind. To describe the > process a little bit better it the introduction of "DeDistortion" would > help. While DeEmphasis was done at the receiver end DeDistortion is done at > the transmitter end by the amplifier. Just using one part of Distortion (or > Emphasis) would really not reflect the true signal that is going into the > microphone. As any amplifier stage is adding distortion it is appropriate to > call the procedure done in the SDR (the ones that are capable of) > PreDistortion. The DeDistortion in the amplifier gives you a much better > approximation of a true linear amplification. Just ADDING Predistortion and > not adding or better SUBTRACTING the proper amount of Dedistortion sure > would make and leave the signal distorted. > > 3rd order IMD in the range of -60 dB and with careful design even more is > possible. > > Consider this: the best receiver doesn´t help if a lot of average or below > average quality signals are around and splattering into your "communication > channel". The same is true if someone with a radio that creates a lot of > phase noise is next to you - your radio can have a clean oscillator signal > with low phase noise but still the other dirty signal will go into the > equation. > > So after it has been acknowledged that high phase noise oscillators are a NO > GO these days the next consequent step would be to clean up the transmit > signal in terms of intermodulation. > > If someone tuning a motorcycle or a car he better not only tunes the engine > for power but also adapt the brake system the chassis and everything else > affected to handle the more power. > > 73 Roger, DL5RBW > > -----Original Message----- > From: elecraft-boun...@mailman.qth.net > [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim Brown > Sent: Sunday, May 19, 2019 2:09 AM > To: elecraft@mailman.qth.net > Subject: Re: [Elecraft] K4 and Predistortion > >> On 5/18/2019 4:01 PM, Phil Kane wrote: >> Those >> of us with engineering backgrounds knew that what I was referring to >> as "pre-distortion" was the pre-emphasis / de-emphasis curves commonly >> used in FM broadcast audio chains. > > All of which emphasizes the need for using the right words to describe > things. The word "distortion" is most commonly used to describe > non-linearity, not frequency response. And, BTW, that > pre-emphasis/de-emphasis is a Standard, not just "commonly used." You know > the Regs far better than I, but I suspect it's there too. > > As I'm sure you know, it was also common practice to go FAR beyond that, > with multi-band dynamics processing and the tricky stuff that Bob Orban was > doing. The engineering "rule of thumb" was that if you could see the > modulation monitor needle move, you weren't doing enough.:) > > I did some research on the Orban FM processor, which I published as an AES > Paper in 1986. http://k9yc.com/AESPaper-TDS.pdf > > 73, Jim K9YC > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
