K3 RF Power Meter Accuracy
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I've been using my K3 #4359 now for several years w/o any issues. Just this past week I acquired an LDG AT-600ProII auto tuner and the matching M-600 analog meter. I calibrated the M-600 per the instructions. What I'm seeing is that the M-600 meter is showing me higher RF output than the K3's bar graph on most bands. As an example, after setting the KAT3 to Bypass, using the AT-600 to bring an antenna to a match (close to 1:1) with 5 watts out of the K3, I turn the K3 power output to 25 watts. A key-down on the K3 shows 25 watts on the K3 bar graph, but the M-600 tells me that the power is about 39-40 watts. It is like this on nearly all the bands, 160-10 meters. On 6 meters, the M-600 reads about 20% LOWER than the K3.
I sent an email to LDG and asked them what's up - which is correct - the K3, or the LDG unit? Their response is that the K3 most likely is incorrect, as they calibrate their equipment with an Alpha 4500. That's a tad of an expensive meter, to say the least. Are the LDG folks tweaking me on this, or is that M-600 really more accurate than the RF bar graph on the K3? Jim / W6JHB ______________________________________________________________ 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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Jim,
What is the comparison power measurement into a 50 ohm dummy load. If your dummy load is not rated for upwards of 50 MHz, test it with an antenna analyzer. Measurements made into an antenna are always suspect. A variation of 20% between power meters are common, and 20 percent of 25 watts is 5 watts - which would be 20 to 30 watts. Your reported 39-40 watts is outside that range, but since you are operating into an antenna, I would suspect that you are "within the ballpark". If you have not calibrated the K3 wattmeter (see the manual calibration section, that could explain the difference. Again I say that the calibration must be done with a 50 ohm non-reactive load to be valid. 73, Don W3FPR On 1/6/2013 10:30 PM, Jim Bennett wrote: > I've been using my K3 #4359 now for several years w/o any issues. Just this past week I acquired an LDG AT-600ProII auto tuner and the matching M-600 analog meter. I calibrated the M-600 per the instructions. What I'm seeing is that the M-600 meter is showing me higher RF output than the K3's bar graph on most bands. As an example, after setting the KAT3 to Bypass, using the AT-600 to bring an antenna to a match (close to 1:1) with 5 watts out of the K3, I turn the K3 power output to 25 watts. A key-down on the K3 shows 25 watts on the K3 bar graph, but the M-600 tells me that the power is about 39-40 watts. It is like this on nearly all the bands, 160-10 meters. On 6 meters, the M-600 reads about 20% LOWER than the K3. > > I sent an email to LDG and asked them what's up - which is correct - the K3, or the LDG unit? Their response is that the K3 most likely is incorrect, as they calibrate their equipment with an Alpha 4500. That's a tad of an expensive meter, to say the least. Are the LDG folks tweaking me on this, or is that M-600 really more accurate than the RF bar graph on the K3? > ______________________________________________________________ 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 Jim Bennett
Hi Jim
I don't have any LDG meters anymore but do have others a digital in my Palstar HF-Auto tuner, an Alpha 4510 and a Palstar DL2K dummy load/wattmeter. My K3 set at 50w the HF-Auto read 48w, the Alpha 4510 49w on analog/digital meters both and the dummy load 41w. If you have a bird to place in line try that but my Alpha is 100% reading scale as a fresh calibrated bird and new slugs on mine from 5w it goes down to .3w and 2400w goes to 3000w. But like you said quite a bit of money but matches my amp well. You need to come up with a known meter before going any further or I would in that case. 73, Fred/N0AZZ -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Jim Bennett Sent: Sunday, January 06, 2013 9:30 PM To: Elecraft Reflector Reflector Subject: [Elecraft] K3 RF Power Meter Accuracy I've been using my K3 #4359 now for several years w/o any issues. Just this past week I acquired an LDG AT-600ProII auto tuner and the matching M-600 analog meter. I calibrated the M-600 per the instructions. What I'm seeing is that the M-600 meter is showing me higher RF output than the K3's bar graph on most bands. As an example, after setting the KAT3 to Bypass, using the AT-600 to bring an antenna to a match (close to 1:1) with 5 watts out of the K3, I turn the K3 power output to 25 watts. A key-down on the K3 shows 25 watts on the K3 bar graph, but the M-600 tells me that the power is about 39-40 watts. It is like this on nearly all the bands, 160-10 meters. On 6 meters, the M-600 reads about 20% LOWER than the K3. I sent an email to LDG and asked them what's up - which is correct - the K3, or the LDG unit? Their response is that the K3 most likely is incorrect, as they calibrate their equipment with an Alpha 4500. That's a tad of an expensive meter, to say the least. Are the LDG folks tweaking me on this, or is that M-600 really more accurate than the RF bar graph on the K3? Jim / W6JHB ______________________________________________________________ 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 Jim Bennett
I would trust a Bird43 meter to be more accurate (but even they only
claim 5% of full range). I have compared my 1976 era Bird43 with one that is only a couple years old using the same element and had 10% disagreement in readings using a Bird dummy load. My old meter read lower in power. On another note I have measured the output of my K3 in TEST mode and 1.0mw is pretty close when measured with a HP432A mw power meter. I trust the K3 meter is as accurate as my Bird43. Power readings into an antenna are relative and will vary with reactance of the load. Not uncommon to see more output than the radio can deliver when into a reactive load. All SWR meters are reading RF voltage on the line and that depends where on the line you look unless the load is perfectly resistive 50-ohms. I spent about six weeks making coax line loss and matching measurements on my eme array in 2010. Load variations drove me crazy with non repeatable measurements. Only after carefully using the same test leads and loads was I able to get a satisfactory set of measurements (on all 8 antennas). IN the end my line loss came out to 1.7 dB +/- 0.1 dB. I did determine that I improved loss by about 0.2 dB by replacement of bad cables. That represents 5% of my power or 65w. 1.7 dB line loss means I get 68% of my 144-MHz transmit power to the antenna (1000w for 1500w output). The rest is warming my cables (LMR600 and 1-5/8 inch Heliax). 73, Ed - KL7UW ______________________________________________________________ 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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