Are you sure it is the KPA500 that is causing the drop off? There are a lot of variables here. The exciter could be scaling back, the power source (110/220) could be limiting you or something else may be happening. As power cords heat, they tend to restrict the electron flow. Especially if you are powered from 110V, that could be the source of several problems. Be sure not to replace the supplied power cord with a smaller one - this is a recipe for reduced output in itself.
We have also seen transmitters decrease their output power when keyed down for a long time. This might be due to heating in the TX, ALC action, or other things specific to the radio. I would suggest adding a wattmeter between the exciter and the KPA500 so you can monitor power between the devices. Also check the power source wiring to make sure there are no limitations there. In general, look to see if there are other factors external to the KPA causing power reduction. Jack B, W6FB On Jan 27, 2012, at 8:57 AM, n...@aol.com wrote: > Sorry if this has been covered before, but I can't recall that it > has. Is > there any reason why power output > falls off over time? Here's what I did: using MMTTY, I "diddled" > into a > 50-Ohm dummy load for one minute. > I initially had a power output of 525 Watts which went to 500 W > shortly and > went down to about 465 W > when MMTTY "diddling" timed out. I repeated that process later, > monitoring > current and noted that it also > went down over time...makes sense! > But my question is WHY? I was under the impression that I needed to > run the > amp at 500 W on RTTY for > optimum efficiency because in an earlier posting I noted that at 150W > output (in BPSK31), the amp was very inefficient and the fan was > pretty loud. If > I can't derate the output and I can't run full output, what do I do > with > the KPA500 in the digital modes? > > Bert, N4CW > > > ______________________________________________________________ > 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
