Well said Bob. Harry WE1X
Sent from my Verizon Wireless BlackBerry -----Original Message----- From: "Bob Naumann" <[email protected]> Date: Wed, 21 Apr 2010 09:33:18 To: <[email protected]> Subject: Re: [Elecraft] K3 and Expert 1K-FA Paul, What if you have one of the 200w or new 400w output rigs? What if you have one of those radios that shoot out a spike of greater than 100w at the beginning of every transmission? Do people blast the inputs of their SS amps with 200w or 400w? You bet they do. They fry the FETs immediately too. We see them on a fairly frequent basis and we have gotten adept at swapping out FETs quickly - at significant expense to the owner of the amp. In the vast majority of cases, they had ALC disconnected and made a mistake when switching antenna outputs from these high-power transceivers. So, if you feel confident that you won't make a mistake, then go ahead and take the risk of not having ALC connected and adjusted properly. But, keep in mind the costly consequences that can result if you make a mistake. I do not understand why one would not connect the ALC when its purpose is to prevent damage. Not using ALC is not a "badge of courage"; instead, it is a foolish tempting of fate - in my opinion. Also, most amp manufacturers recommend that you only increase the output of the radio high enough to achieve the desired output from the amp - they do not recommend turning the radio output up "full-blast" and throttling the output back down with ALC - which, as we all know can cause distortion and all sorts of bad things. There is no downside to using ALC in the manner that SS amp manufacturers recommend. So, the bottom line is to follow the manufacturer's recommendation regarding ALC and setting your radio to work properly in conjunction with it. 73, Bob W5OV -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Paul Christensen Sent: Wednesday, April 21, 2010 9:10 AM To: [email protected] Subject: Re: [Elecraft] K3 and Expert 1K-FA > So, please do not advise someone with a solid state amp to disconnect > their ALC- unless you want to assume the cost of repairs. Overall, I agree with that assessment. However, I do no not make use of the K3's ALC line with my SPE solid-state amp. In looking at the SPE's protection circuitry, a fault buss is created that applies a high level of bias to the power MOSFETs when any of about 6-7 different fault conditions occur. The response time is exceptionally fast to the point where if I deliberately blast the SPE with full power from the K3 without ALC connected (don't try this at home - I'm a risk taker but did so only after reviewing the circuit), the SPE detects the presence of high input power and applies enough MOSFET bias to keep output power below about 1100 watts. How instantaneous? I have not measured the response time but it does respond well to the leading-edge power spike from another well-known transceiver. Today, a solid-state amp should be smart enough to know when it's being overdriven. Also, an unknown with the SPE amp is what happens to amplifier linearity when the bias protection circuitry begins to engage to keep power from exceeding 1KW? But the same question must be asked of any transceiver that interfaces to an amp while using an ALC line. I like to think that when an amp and transceiver come from a common manufacturer, the ALC circuitry is probably optimized since the designer knows exactly what's needed at the ALC "meet me" point between the amp and transceiver. Paul, W9AC ______________________________________________________________ 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 ______________________________________________________________ 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 ______________________________________________________________ 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
