On 6/9/2012 5:14 AM, Geoffrey Mackenzie-Kennedy wrote: > 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.
The ONLY proper ways to set power output are 1) to turn down the transceiver's output power by turning down the power control on the transceiver; or 2) using a resistive attenuator (voltage divider) between the transceiver and the amplifier. W8JI, who has designed a lot of power amps, and, as part of that design work, has studied the behaviour of lots of ham transceivers, has written an excellent and detailed tutorial on this matter, and on how some ham transceiver ALC systems badly misbehave, and NEED to use option 2. The K3 (and the FT1000MP) do not have this problem, and work fine with option 1. ALC from the power amp to the transceiver should NEVER be used to set transmit power, for the reasons you've noted. It is provided for on most ham products because many hams think they need it. If used at all, transceiver output level should be set so that ALC ONLY protects the amplifier by backing off the drive when something in the antenna system breaks, creating a load that the power amp is unhappy with. Note also that this advice is NOT new, and applies equally to old power amps. I first saw this advice in the manual for my 35 year old Ten Tec power amps. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
