Re: [Elecraft] K3 voltage under load
First I would like to thank all who have provided advice and comments. This is a great reflector!Second I will fully explain my setup: Astron RS-35M to a Samlex BBM-12100 battery backup module to a RIGrunner 4012 to the K3. The cable between the Astron and the Samlex is #10 and about 6'6 long. Between the Samlex and the RIGrunner is #10 about 5'6 long. Finally from the RIGrunner to the K3 was the entire #12 cable supplied by Elecraft about 5'2 long.As someone noted there is about .4v loss in the Samlex and probably a bit in the 4012. Ased on the collective advice I have removed about 8'6 of cable, only 2'3 was off the #12 wire. The results are now 14.1v receiver only load and 13.0v under full load. So I have reduced losses by a full .5v or about31.25%. I am happy with this result. Thanks again to all that provided advice. Harris K9RJ __ 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
Re: [Elecraft] K3 voltage under load
When switching my K3 from RX to TX 100W FM, I measured these voltage drops: 0.03V directly at the Astron RS-35M's output 0.25V at an unused output of a WMR RIGrunner, connected to the RS-35M by a 2ft cable 1.00V as indicated by the K3, connected to the RIGrunner by a 4ft cable By cable I mean the type supplied with the K3. Certainly not as good as the 400mV reported by Guy K2AV. Still better than the 1.7V reported by Harris K9RJ. Corresponds to the 700mV reported by Joe W4TV (direct connection, no RIGrunner) Guess the major problem resulting from voltage drop is a reduced efficiency of the KPA3. 73, Markus HB9BRJ -- View this message in context: http://n2.nabble.com/K3-voltage-under-load-tp3010557p3019971.html Sent from the Elecraft mailing list archive at Nabble.com. __ 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
Re: [Elecraft] K3 voltage under load
If this is a serious issue to folks as it appears to be, use a power supply with remote sense and attach the sense lines at the Powerpole at the back of the K3. My gut feel is the DX will never know the difference. Terry - Original Message - From: hb9brj To: elecraft@mailman.qth.net Sent: Wed, 3 Jun 2009 17:59:42 + (UTC) Subject: Re: [Elecraft] K3 voltage under load When switching my K3 from RX to TX 100W FM, I measured these voltage drops: 0.03V directly at the Astron RS-35M's output 0.25V at an unused output of a WMR RIGrunner, connected to the RS-35M by a 2ft cable 1.00V as indicated by the K3, connected to the RIGrunner by a 4ft cable By cable I mean the type supplied with the K3. Certainly not as good as the 400mV reported by Guy K2AV. Still better than the 1.7V reported by Harris K9RJ. Corresponds to the 700mV reported by Joe W4TV (direct connection, no RIGrunner) Guess the major problem resulting from voltage drop is a reduced efficiency of the KPA3. 73, Markus HB9BRJ -- View this message in context: http://n2.nabble.com/K3-voltage-under-load-tp3010557p3019971.html Sent from the Elecraft mailing list archive at Nabble.com. __ 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
Re: [Elecraft] K3 voltage under load
On Wed, 2009-06-03 at 10:59 -0700, hb9brj wrote: ... Guess the major problem resulting from voltage drop is a reduced efficiency of the KPA3. Actually, for a given power level the KPA3 probably has better efficiency. For lowest heat in the PA, the supply voltage should be as low as possible that still works at the selected power level. But the system efficiency is lower because of the power loss in the cables. Al N1AL __ 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
Re: [Elecraft] K3 voltage under load
I guess the most interesting thing is that we never heard back from Harris, K9RJ, about his setup! What se ye, Harris? 73, Steve NN4X __ 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
Re: [Elecraft] K3 voltage under load
I've made some measurements of my K3's efficiency versus DC supply voltage, output and frequency at http://www.cliftonlaboratories.com/elecraft_k3_efficiency.htm Jack K8ZOA www.cliftonlaboratories.com Alan Bloom wrote: On Wed, 2009-06-03 at 10:59 -0700, hb9brj wrote: ... Guess the major problem resulting from voltage drop is a reduced efficiency of the KPA3. Actually, for a given power level the KPA3 probably has better efficiency. For lowest heat in the PA, the supply voltage should be as low as possible that still works at the selected power level. But the system efficiency is lower because of the power loss in the cables. Al N1AL __ 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
Re: [Elecraft] K3 voltage under load
The graphs show: the lower the power supply voltage, the higher the efficiency. The reason: When you set the K3 to, say, 100W it has to put 1.4A into the 50-ohm dummy load (P = I^2R = 1.4^2 x 50 = 100). The DC current through the PA transistors is pretty much directly proportional of the RF current through the transistors. Whatever DC current the PA transistors require to achieve 1.4A of RF into the load doesn't depend on the power supply voltage. Since the transistor current is the same no matter the power supply voltage, you get best efficiency (lowest power dissipation) at the lowest voltage that is capable of sustaining the desired power level. Al N1AL On Wed, 2009-06-03 at 19:04 -0400, Jack Smith wrote: I've made some measurements of my K3's efficiency versus DC supply voltage, output and frequency at http://www.cliftonlaboratories.com/elecraft_k3_efficiency.htm Jack K8ZOA www.cliftonlaboratories.com Alan Bloom wrote: On Wed, 2009-06-03 at 10:59 -0700, hb9brj wrote: ... Guess the major problem resulting from voltage drop is a reduced efficiency of the KPA3. Actually, for a given power level the KPA3 probably has better efficiency. For lowest heat in the PA, the supply voltage should be as low as possible that still works at the selected power level. But the system efficiency is lower because of the power loss in the cables. Al N1AL __ 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
Re: [Elecraft] K3 voltage under load
Alan, Your analysis is correct - BUT -- Efficiency is one thing. but it has been previously discussed that higher DC voltages result in improved IMD. So the best voltage to be used is a compromise (efficiency alone is not the only consideration). My preference is to stay with the 13.8 volt output of my power supply and keep the voltage drop under full load to a minimum by using #12 or larger conductors and low drop (APP) connectors. My vote is to stay with a systems approach rather than concentrating on only one parameter. YMMV. 73, Don W3FPR Alan Bloom wrote: The graphs show: the lower the power supply voltage, the higher the efficiency. The reason: When you set the K3 to, say, 100W it has to put 1.4A into the 50-ohm dummy load (P = I^2R = 1.4^2 x 50 = 100). The DC current through the PA transistors is pretty much directly proportional of the RF current through the transistors. Whatever DC current the PA transistors require to achieve 1.4A of RF into the load doesn't depend on the power supply voltage. Since the transistor current is the same no matter the power supply voltage, you get best efficiency (lowest power dissipation) at the lowest voltage that is capable of sustaining the desired power level. Al N1AL On Wed, 2009-06-03 at 19:04 -0400, Jack Smith wrote: I've made some measurements of my K3's efficiency versus DC supply voltage, output and frequency at http://www.cliftonlaboratories.com/elecraft_k3_efficiency.htm Jack K8ZOA www.cliftonlaboratories.com __ 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
Re: [Elecraft] K3 voltage under load
Very true. There is a tradeoff between efficiency and distortion. The K3 has good cooling, so for a fixed station where power consumption is not an issue, you might as well keep the PS voltage fairly high. It also might give you a little more power output 6 meters which tends to run a little low. Al N1AL On Wed, 2009-06-03 at 23:42 -0400, Don Wilhelm wrote: Alan, Your analysis is correct - BUT -- Efficiency is one thing. but it has been previously discussed that higher DC voltages result in improved IMD. So the best voltage to be used is a compromise (efficiency alone is not the only consideration). My preference is to stay with the 13.8 volt output of my power supply and keep the voltage drop under full load to a minimum by using #12 or larger conductors and low drop (APP) connectors. My vote is to stay with a systems approach rather than concentrating on only one parameter. YMMV. 73, Don W3FPR Alan Bloom wrote: The graphs show: the lower the power supply voltage, the higher the efficiency. The reason: When you set the K3 to, say, 100W it has to put 1.4A into the 50-ohm dummy load (P = I^2R = 1.4^2 x 50 = 100). The DC current through the PA transistors is pretty much directly proportional of the RF current through the transistors. Whatever DC current the PA transistors require to achieve 1.4A of RF into the load doesn't depend on the power supply voltage. Since the transistor current is the same no matter the power supply voltage, you get best efficiency (lowest power dissipation) at the lowest voltage that is capable of sustaining the desired power level. Al N1AL On Wed, 2009-06-03 at 19:04 -0400, Jack Smith wrote: I've made some measurements of my K3's efficiency versus DC supply voltage, output and frequency at http://www.cliftonlaboratories.com/elecraft_k3_efficiency.htm Jack K8ZOA www.cliftonlaboratories.com __ 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
Re: [Elecraft] K3 voltage under load
I don't think that this is normal. It depends upon the voltage drop on cable between the radio and power supply, as well as any voltage drop inside of the radio. I actually was measuring this yesterday. My supply reads between 13.7 and 13.8 on the K3 meter under receive. With 100W keydown, it was reading 13.2. This was a quick measurement and I didn't verify that the supply maintained constant voltage (it should have as it is a 25A supply). I have about 12 of 10AWG cable from the supply to the radio. I think that this drop is typical or maybe even slightly high. Your drop of 1.7V is way too high. I would inspect your DC cabling to the radio, correct installation of your powerpoles on that cable, and the connector pins on the KPA3 and KPAIO3. At 6/2/2009 02:07 AM, Harris Leck wrote: I am running my K3 off an Astron RS-35M. No load voltage at the rig is 14.0V (per the K3 display). Running approximately 100W this reading drops to 12.3V. Is this the norm? BTW current reads just under 18 amps. The amp meter reading on the Astron is way off.73 Harris K9RJ __ 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
Re: [Elecraft] K3 voltage under load
I own an Astron analog power supply, and there is NO fluctuation of voltage under full load, without load, or anything in between. That's what a regulated power supply is supposed to do. I would say you have a defective power supply. Bill W5WVO Harris Leck wrote: I am running my K3 off an Astron RS-35M. No load voltage at the rig is 14.0V (per the K3 display). Running approximately 100W this reading drops to 12.3V. Is this the norm? BTW current reads just under 18 amps. The amp meter reading on the Astron is way off.73 Harris K9RJ __ 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
Re: [Elecraft] K3 voltage under load
At 6/2/2009 08:26 AM, Bill W5WVO wrote: I own an Astron analog power supply, and there is NO fluctuation of voltage under full load, without load, or anything in between. That's what a regulated power supply is supposed to do. I would say you have a defective power supply. No, not necessarily. He stated that the 12.3V was measured inside of the radio. That reflects any IR loss to that point and not necessarily poor regulation on the supply. More data is necessary to come to that conclusion. Harris Leck wrote: I am running my K3 off an Astron RS-35M. No load voltage at the rig is 14.0V (per the K3 display). Running approximately 100W this reading drops to 12.3V. Is this the norm? BTW current reads just under 18 amps. The amp meter reading on the Astron is way off.73 Harris K9RJ __ 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
Re: [Elecraft] K3 voltage under load
Harris - This is likely due to I squared * R losses in your DC cable; the voltage is being reduced by the resistance of the cable. I had the same problem. How long is it? What gauge is it? Are there any fuses or other items in-line with it? 73, Steve NN4X On Tue, Jun 2, 2009 at 2:07 AM, Harris Leck vk...@yahoo.com wrote: I am running my K3 off an Astron RS-35M. No load voltage at the rig is 14.0V (per the K3 display). Running approximately 100W this reading drops to 12.3V. Is this the norm? BTW current reads just under 18 amps. The amp meter reading on the Astron is way off.73 Harris K9RJ __ 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
Re: [Elecraft] K3 voltage under load
It only takes about ** a tenth of an ohm ** between K3 and power supply to drop 1.7 volts at 18 amps. Size of wire, bad crimp in a connector, tiny bit of corrosion, etc., etc. AND, the tenth of an ohm may be spread out in different places. I have three feet of #10 to the K3, and I drop from 14.2 to 13.8 at 100 watts using an Astron RS 35A I adjusted up just a teeny. 73, Guy. - Original Message - From: S Sacco nn4x.st...@gmail.com Harris - This is likely due to I squared * R losses in your DC cable; the voltage is being reduced by the resistance of the cable. I had the same problem. How long is it? What gauge is it? Are there any fuses or other items in-line with it? 73, Steve NN4X On Tue, Jun 2, 2009 at 2:07 AM, Harris Leck vk...@yahoo.com wrote: I am running my K3 off an Astron RS-35M. No load voltage at the rig is 14.0V (per the K3 display). Running approximately 100W this reading drops to 12.3V. Is this the norm? BTW current reads just under 18 amps. The amp meter reading on the Astron is way off.73 Harris K9RJ __ 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
Re: [Elecraft] K3 voltage under load
This drop is excessive. With the standard (factory assembled) K3 power cable, I see 13.9V no load and 13.2V at 20 A with an Astron RS-35. I would be concerned ... 73, ... Joe, W4TV -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Harris Leck Sent: Tuesday, June 02, 2009 2:08 AM To: elecraft@mailman.qth.net Subject: [Elecraft] K3 voltage under load I am running my K3 off an Astron RS-35M. No load voltage at the rig is 14.0V (per the K3 display). Running approximately 100W this reading drops to 12.3V. Is this the norm? BTW current reads just under 18 amps. The amp meter reading on the Astron is way off.73 Harris K9RJ __ 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
Re: [Elecraft] K3 voltage under load
At 6/2/2009 05:09 PM, Hector Padron wrote: Certainly there is mot enough evidence to blame the PS yet,he will have to read the drop at the PS output poles to see if is the same or worse,otherwise its losses at his DC cable or something lose in the DC line at the K3,even a cold solder can create that,but if the radio makes 100W all the time,why to worry? There are a number of reasons to worry. If there is a defective connection, it could (and will) heat up and melt (or self destruct), causing other problems. I have seen the plastic on power poles melt due to incorrect installation and high resistance. Typically, the voltage to the PA is not regulated, in the sense that it uses the voltage supplied to the radio which it assumes is regulated. It does that because there is no room to supply a 20A regulator in the radio. (if you want that, you will be buying a bigger and more expensive radio) But if the voltage becomes modulated with the audio or other parameters, you will introduce RF distortion and other unwanted byproducts. Not a good thing either. AD4C The difference between genius and stupidity is that genius has its limits. -- Albert Einstein --- On Tue, 6/2/09, Ed K1EP k1ep.l...@gmail.com wrote: From: Ed K1EP k1ep.l...@gmail.com Subject: Re: [Elecraft] K3 voltage under load To: Bill W5WVO w5...@cybermesa.net, Harris Leck vk...@yahoo.com, elecr...@mailman.qth..net Date: Tuesday, June 2, 2009, 12:39 PM At 6/2/2009 08:26 AM, Bill W5WVO wrote: I own an Astron analog power supply, and there is NO fluctuation of voltage under full load, without load, or anything in between. That's what a regulated power supply is supposed to do. I would say you have a defective power supply. No, not necessarily. He stated that the 12.3V was measured inside of the radio. That reflects any IR loss to that point and not necessarily poor regulation on the supply. More data is necessary to come to that conclusion. Harris Leck wrote: I am running my K3 off an Astron RS-35M. No load voltage at the rig is 14.0V (per the K3 display). Running approximately 100W this reading drops to 12.3V. Is this the norm? BTW current reads just under 18 amps. The amp meter reading on the Astron is way off.73 Harris K9RJ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecrafthttp://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htmhttp://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net/http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.htmlhttp://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
Re: [Elecraft] K3 voltage under load
Maybe there's too much concern to do all the hand wringing? It all depends on what's between the PS and the radio. In my case, for example, my 13.8v supply feeds a West Mountain Radio battery charger (200AH of battery), and there's a drop there (.4V). then to a WMR distribution box and on to the radio. I have 13.5v no load and 12.5v transmit at 100W. All of the wiring is #10 as short as possible. The APP's are 45A and are properly terminated. And the radio just keeps on chugging. I've chosen not to be concerned about it. I may try to increase the RS-70M output to as close to 15v as I can, but my motivation is lacking to open up the box and try to adjust the unreachable output adjust since nothing is broken. Grant/NQ5T On Jun 2, 2009, at 4:41 PM, Ed K1EP wrote: At 6/2/2009 05:09 PM, Hector Padron wrote: Certainly there is mot enough evidence to blame the PS yet,he will have to read the drop at the PS output poles to see if is the same or worse,otherwise its losses at his DC cable or something lose in the DC line at the K3,even a cold solder can create that,but if the radio makes 100W all the time,why to worry? There are a number of reasons to worry. If there is a defective connection, it could (and will) heat up and melt (or self destruct), causing other problems. I have seen the plastic on power poles melt due to incorrect installation and high resistance. Typically, the voltage to the PA is not regulated, in the sense that it uses the voltage supplied to the radio which it assumes is regulated. It does that because there is no room to supply a 20A regulator in the radio. (if you want that, you will be buying a bigger and more expensive radio) But if the voltage becomes modulated with the audio or other parameters, you will introduce RF distortion and other unwanted byproducts. Not a good thing either. __ 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
