KXPA100 Hi PA current ?
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I have had my KXPA100 for 5 months or so now. I have loaded the latest firmware Wayne sent out a few weeks ago for beta testing. My KXPA100 has the Automatic antenna tuner installed. I run the amp into a Carolina Windom 40 and the automatic antenna tuner works well using this antenna on all the bands except 160 meters of course. I normally don't operate on that band anyway.
I was running the amp on 40 meters at 100 watts doing back to back rag chewing CW QSO's this evening. The amp shutdown and my KX3 display showed Hi PA current. The amp was very hot to the touch which makes me believe the amp had to shut down to protect the finals. The antenna SWR shows under 1.2. to 1. Is this normal behavior for the KXPA100? Thanks, Glenn WA7SPY ______________________________________________________________ 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 Message delivered to [hidden email] |
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Glenn,
What was the DC voltage at 100 watts keydown? It should be 12 volts or greater - more is better, 13+ is good. If the voltage drops, the current will increase (and I believe the efficiency decreases) to maintain your 100 watt output level. More current, more heat. An off center fed antenna may present a reasonable SWR, but SWR does not tell the whole tale. OCF antennas are infamous for RF-in-the-shack problems, so you might have some RF floating around to create 'strange happenings'. 73, Don W3FPR On 6/1/2014 1:06 AM, WA7SPY wrote: > I have had my KXPA100 for 5 months or so now. I have loaded the latest firmware Wayne sent out a few weeks ago for beta testing. My KXPA100 has the Automatic antenna tuner installed. I run the amp into a Carolina Windom 40 and the automatic antenna tuner works well using this antenna on all the bands except 160 meters of course. I normally don't operate on that band anyway. > > I was running the amp on 40 meters at 100 watts doing back to back rag chewing CW QSO's this evening. The amp shutdown and my KX3 display showed Hi PA current. The amp was very hot to the touch which makes me believe the amp had to shut down to protect the finals. The antenna SWR shows under 1.2. to 1. Is this normal behavior for the KXPA100? > > ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by WA7SPY
Hi Don,
Thank you for the information and input about OCF antennas. I did a measurement of the supply voltage to the KXPA100. here is what I Measure with my Fluke 77 meter: The voltage measurement was taken at the supply power plug from the amp that plugs into the KX3 to power it. I have the internal batteries installed in the KX3 so doing the test was easy. I am using an Alinco DM-330 MVP power supply with a very short cable run the the KXPA100. The supply voltage reads 15.1 volts without the amp or KX3 transmitting. With the power setting on the KX3 set to max 110 watts. When the KX3 is keyed and the amp is active I measure 14.6 volts. The voltage drop is not that big in my opinion. I have a 10 foot ground round sunk all the way down with a heavy braided cable less than a 6 foot run to a 1/4 inch thick brass 8x8 inch plate. I then have braided jumpers going to the KX3 and KXPA100 less than 8 inches from the brass plate to my equipment. What else should I do or look for? I have to say my Carolina Windom performs extremely well! Thank you, Glenn WA7SPY Glenn Maclean ______________________________________________________________ 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 Message delivered to [hidden email] |
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Glenn,
That voltage is very good, so rule that out. There seems to be a lot of confusion in the ham community when dealing with RF in the Shack - a very common response is "my equipment is well grounded" That grounding may be fine for AC mains grounding, static grounding, and perhaps even some help with lightning protection, BUT it usually does nothing for the RF in the shack problem. The wire to earth has some length and that length is part of the reason it does not work. Think of an 8 foot connection to the ground point - the connection point to earth is at a low impedance, but at the shack end it is quite a high impedance at 28 MHz because it is 1/4 wave long - that wire acts like a transmission line or as an antenna element to any RF that may be on shack equipment. It will have some impedance to ground at any frequency - I just use 8 feet and 28 MHz as a convenient example. About the only way to eliminate RF in the shack is to keep it off the feedline shield in the first place, and that means use of common mode current chokes. The 'balun' at the antenna feedpoint may not be doing the job effectively, or if the feedline is not arranged perpendicular to the antenna for at least 1/4 wavelength, the feedline may couple with the radiator and actually pick up RF. K9YC has provided information on effective common mode chokes in his "A Ham's Guide to RFI". You may need to install such a choke not only at the antenna feedpoint, but also at the point where the feedline enters the shack. I recommend that approach to anyone who uses an OCF antenna. 73, Don W3FPR On 6/1/2014 11:54 PM, WA7SPY wrote: > Hi Don, > Thank you for the information and input about OCF antennas. I did a measurement of the supply voltage to the KXPA100. here is what I Measure with my Fluke 77 meter: > > The voltage measurement was taken at the supply power plug from the amp that plugs into the KX3 to power it. I have the internal batteries installed in the KX3 so doing the test was easy. I am using an Alinco DM-330 MVP power supply with a very short cable run the the KXPA100. The supply voltage reads 15.1 volts without the amp or KX3 transmitting. With the power setting on the KX3 set to max 110 watts. When the KX3 is keyed and the amp is active I measure 14.6 volts. The voltage drop is not that big in my opinion. > > I have a 10 foot ground round sunk all the way down with a heavy braided cable less than a 6 foot run to a 1/4 inch thick brass 8x8 inch plate. I then have braided jumpers going to the KX3 and KXPA100 less than 8 inches from the brass plate to my equipment. > > What else should I do or look for? I have to say my Carolina Windom performs extremely well! > > Thank you, > Glenn WA7SPY > > Glenn Maclean > > ______________________________________________________________ > 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 > Message delivered to [hidden email] > ______________________________________________________________ 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 Message delivered to [hidden email] |
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