KPA500 questions
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As a potential future buyer of the KPA500, I have a few questions, for those who actually own it:
What have you found to be the actual output power, on a dummy load using a good power meter other than the internal one. Is the maximum output the same on all modes (CW/AM/FM etc.)? Is the maximum output the same on all bands (what happens on 30 meters)? In the event of a high SWR, does the output begin to drop progressively, and/or does it just stop at some point? What is the typical SWR that will keep it happy at full output (without getting into a discussion of resonance and actual power out the antenna)? Finally, I read about the duty cycle of 10 minutes on and 5 minutes off, and I still wonder how it would keep it up with modes such as WSJT, where there is typically 30 seconds on and 30 seconds off? 73 de Sebastian, W4AS ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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See answers below
Mike W0MU J6M CQ WW DX CW Contest 2011 J6/W0MU November 21 - December 1 2011 W0MU-1 CC Cluster w0mu.net On 11/14/2011 2:15 PM, Sebastian, W4AS wrote: > As a potential future buyer of the KPA500, I have a few questions, for those who actually own it: > > What have you found to be the actual output power, on a dummy load using a good power meter other than the internal one. Easily over the quoted 500 watts. Do you know that the internal meter is inaccurate? Seems pretty good to me. > > Is the maximum output the same on all modes (CW/AM/FM etc.)? Yes on CW and SSB. I don't use AM or FM > > Is the maximum output the same on all bands (what happens on 30 meters)? Like every other amp it has maximum output on 30m. Not all countries have to run 200 watts like the USA. It is up to the operator to make sure the output is within the regulations of their license. > > In the event of a high SWR, does the output begin to drop progressively, and/or does it just stop at some point? What is the typical SWR that will keep it happy at full output (without getting into a discussion of resonance and actual power out the antenna)? The amp runs full out until it trips. I can run 2:1 most places and the amp chugs along. Much over that at full output and the amp will fault or trip off. > Finally, I read about the duty cycle of 10 minutes on and 5 minutes off, and I still wonder how it would keep it up with modes such as WSJT, where there is typically 30 seconds on and 30 seconds off? 10mins on and 5 off is greater duty than 30 seconds on and off. I have used the amp with RTTY and no problems with some heavy Xmit times. The fan kicks on a bit faster. It is a great small footprint amp. Auto band switching without other cabling. It senses the freq off the coax. No bandswitching and no tuning is great! If they would build a 1.5k version I would be on the list for one. > > 73 de Sebastian, W4AS > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Sebastian, W4AS
On 11/14/2011 1:15 PM, Sebastian, W4AS wrote:
> What have you found to be the actual output power, on a dummy load > using a good power meter other than the internal one. Same as what the LED's say when the highest one just comes on. > > Is the maximum output the same on all modes (CW/AM/FM etc.)? Yes, don't know about FM, never used it but it sounds like RTTY, see below. AM will have 50% of the power in the "carrier" [which "carries" nothing], and 25% in each of the two identical sidebands. PEP will be 500W. > > Is the maximum output the same on all bands (what happens on 30 > meters)? It will allow you to operate illegal if you choose [200W max on 30m] > > In the event of a high SWR, does the output begin to drop > progressively, and/or does it just stop at some point? It runs fine for me at about 2:1, then it trips off. What is the > typical SWR that will keep it happy at full output (without getting > into a discussion of resonance and actual power out the antenna)? 2:1 > > Finally, I read about the duty cycle of 10 minutes on and 5 minutes > off, and I still wonder how it would keep it up with modes such as > WSJT, where there is typically 30 seconds on and 30 seconds off? Don't do WSJT but I'm sure just fine. I have run it @500W in RTTY contests and watch the PA Temp. It rises, the fans come on, it goes back down. Does this all day, as long as I can keep my butt in the chair. I thought WSJT was a low power mode. 73, Fred K6DGW - Northern California Contest Club - CU in the 2012 Cal QSO Party 6-7 Oct 2012 - www.cqp.org ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Sebastian, W4AS
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Thanks for the comments on my questions on the KPA500 amp.
To expand on some of the comments: I have no reason to believe the amp's meter isn't accurate. Since I haven't seen one yet, it appears to me the meter is of the LED type, which for me is a bit difficult to read. I find it easier to read an external analog meter. With the exception of one person (who was very specific), everyone either said the output is 500 watts, or above. I asked this question because in the past I have found the rated output power of a transistorized amplifier is often higher than what is actually obtained. I imagine overdriving it to obtain more than the rated output would stress the transistors and/or power supply and/or affect the signal quality (or all of those). Naturally, a difference between 500 and 600 watts can't be discerned anyway. As far as WSJT, no that's not a lower power mode. A weak signal mode, doesn't mean a low power mode. The subset mode JT65A is becoming very popular on HF. That mode wasn't designed for HF, it was designed for 6 meter EME, where you use all the power you have. My primary interest with WSJT and the KPA500 is for meteor scatter on 6 meters, using FSK441 where you use the most power that you have. Often, it takes 30 - 45 minutes to complete a contact, so my concern was if this amp could handle the stress for such a long period of time. 73 de Sebastian, W4AS ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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I don't think you can over drive it as there is a overdrive fault and
output leds change color to let you know how much power you are putting out. Mine is packed for J6 so I don't recall if it is green, yellow, red. I set the radio output so the amp puts out 500w. An extra 100 watts probably is not going to make much of a difference on hf so I don't feel the need to push the amp. If your duty cycle is 50/50 I would assume the amp will be just fine. The suggestion to ask support is a good one. If any amp on the market can handle the load this is the one. It is a tank. Mike W0MU J6M CQ WW DX CW Contest 2011 J6/W0MU November 21 - December 1 2011 W0MU-1 CC Cluster w0mu.net On 11/14/2011 7:45 PM, Sebastian, W4AS wrote: > Thanks for the comments on my questions on the KPA500 amp. > > To expand on some of the comments: I have no reason to believe the amp's meter isn't accurate. Since I haven't seen one yet, it appears to me the meter is of the LED type, which for me is a bit difficult to read. I find it easier to read an external analog meter. > > With the exception of one person (who was very specific), everyone either said the output is 500 watts, or above. I asked this question because in the past I have found the rated output power of a transistorized amplifier is often higher than what is actually obtained. > > I imagine overdriving it to obtain more than the rated output would stress the transistors and/or power supply and/or affect the signal quality (or all of those). Naturally, a difference between 500 and 600 watts can't be discerned anyway. > > As far as WSJT, no that's not a lower power mode. A weak signal mode, doesn't mean a low power mode. The subset mode JT65A is becoming very popular on HF. That mode wasn't designed for HF, it was designed for 6 meter EME, where you use all the power you have. > > My primary interest with WSJT and the KPA500 is for meteor scatter on 6 meters, using FSK441 where you use the most power that you have. Often, it takes 30 - 45 minutes to complete a contact, so my concern was if this amp could handle the stress for such a long period of time. > > 73 de Sebastian, W4AS > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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