Thank you Eric. That is interesting and impressive. I will be seriously considering a kit.
73 Geoff G3UCK ----- Original Message ----- From: "Eric Swartz - WA6HHQ, Elecraft" <[email protected]> To: "Geoffrey Downs" <[email protected]> Cc: <[email protected]> Sent: Wednesday, May 11, 2011 7:10 PM Subject: Re: [Elecraft] KPA500 and SWR above 1.5:1 > The KPA500 bases its SWR protection on reflected power level, not an > absolute SWR. The KPA500 is happy up to a 2:1 SWR at 500-W out. As long as > the actual reflected power is below that for a 2:1 SWR at 500W, it will > not reduce its power. This means you can operate into a higher than 2:1 > SWR load at full amplifier gain if you reduce the amp's output power > slightly. > > The amp "soft-faults" and reduces output power by about 2.5 dB by > switching in an input attenuator at the 500W 2:1 reflected power point, > and it flashes a red LED to alert you to this so you can adjust driver > power (or SWR via an external tuner) down a bit. Once this is corrected > below this threshold by the operator, the KPA500 automatically goes back > to full gain. It also does this for minor overdrive conditions. > > Of course, for excessive SWR events (wrong antenna, open antenna etc), and > severe overdrive, the amp protects itself by immediately hard faulting and > going into bypass mode. After correcting the fault, just push the > operate/standby switch to get back on-line. While at Contest University, > our Italian representative surprised me by demonstrating this feature to > customers by pulling the coax from the dummy load while the amp was > transmitting. After I recovered from my surprise, I realized the amp was > perfectly happy and had protected itself as advertised :-) But don't try > this at home, as he also received a minor RF burn to help him remember > this event.. > > 73, Eric WA6HHQ > www.elecraft.com > ==== > > On 5/11/2011 9:24 AM, Geoffrey Downs wrote: >> The manual says the bargraph shows green ("normal") up to an SWR of >> 1.5:1, >> yellow ("marginal") from 1.5:1 to 2.1:1 and red ("excessive") above that. >> Does this mean no inhibition of output by the protection system (and no >> need for it) up to 1.5:1 but progressive reduction of output above? If >> so, >> will the amp operate without damage in the yellow zone and what % >> reductions in output might be expected up to 2.1:1? Also in what >> conditions >> of SWR does the intelligent 2.5db output reduction apply; and at what SWR >> does output shut off altogether - ie the REFL HI fault condition. >> >> 73 to all >> >> Geoff >> G3UCK > > ______________________________________________________________ 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
