Fred and Van, Some comment follows.
On June 09, 2012 at 7:03 AM, Fred Jensen K6DGW wrote: <snip> > OK Van, multiple questions. What most folks call splatter is caused by > driving the last amplifier stage into saturation [i.e. it can't produce > any more power so it clips off the peaks]. It doesn't really involve > compression, they're just driving their amplifier into saturation, it > clips the peaks [a very non-linear occurrence], and all sorts of IMD is > generated around their signal. The cure is, "Don't drive your amplifier > into saturation." This is sometimes called flat-topping. Fred, although IMHO your advice is sound, please don't forget that prime law of physics which states that "Garbage in will result in Garbage out". Overdriving any amplifier in an exciter used to drive an amplifier (with some exeptions e.g. most pre-filter amplifiers) will result in splatter being transmitted, even if the final amplifier is squeaky clean and linear at any output power level. My intention for saying this is that the typical ALC arrangement is often incorrectly used as a means to control the level of power output from the exciter and/or amplifier to some chosen level, rather than as a protective device, and can be responsible for splatter. Van, the reason why a typical ALC can be responsible for splatter is because these ALC systems sample the output of an amplifier and/or exciter, and due to time delays cannot "throttle back" the drive power immediately. As a result a burst of excess drive power can be produced, especially during voice peaks, which can result in some amplifier(s) in the transmitter chain being overdriven and creating splatter. There are types of ALC system used which do not create this problem, but that's another subject. 73, Geoff LX2AO ______________________________________________________________ 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
