[Elecraft] KPA500 powercycling at higher wattages into KPA500
My KAT500 is getting power-cycled in CW and RTTY modes at various drive levels from the K3 on different bands. I can run SSB full power with no problems at all, and receive superb audio reports (no hint of RF in my transmissions). I am thinking I have either an excessive voltage drop on the AC circuit or perhaps there is enough RF getting into the shack to trip up the KAT500 power when using the higher duty cycle modes. Everything is running on the same 120v house circuit. I experimented with moving both the amp and the KAT500 to a different circuit in the same room, but this did not solve the problem. Let me first describe the equipment, and then I'll list the frequencies and power thresholds that tripped the KAT500 into a power cycle: Antenna: Traffie Hex Beam. Very low SWR, typically 1.2 or less, sometimes 1.5 on 10 and 12 meters. The antenna is over a portion of the house, and about 20 feet away from the shack. The coax is grounded at the base of the antenna (two ground rods, through a lightning arrestor). KAT500: I have this in BYPASS mode. I don't really need the tuner for the hex beam, but I plan on using it with a future vertical for 40m. I am powering the KAT500 with its own AC power adapter. For good measure, I wrapped about 4 turns of the power cord through a ferrite bead at the transformer end of the cable. This is a 15V 1000mAh power adapter from Radio Shack. KPA500 is plugged into the same circuit on its own outlet at the wall. HV reads 78.5 at rest. The unit is sitting on top of the KAT500 with the foldout legs extended. K3 is powered with an Astron RS-35M, on the same house circuit. P3 is powered by the K3 VDC out On 15 meters CW, the KAT500 begins to experience power cycles driving 20-22 watts. The amp, when it crosses about 450 watts, the KAT500 power cycles. I ran 30 watts into it for about 620+ out with no problems on SSB, SWR never exceeded 1.2 on the KAT500's indicator lamps. On 12 meters CW, the KAT500 begins to experience power cycles driving just 9 watts (about 180w out). SWR on this band is a steady 1.5. I did have some success by moving the KAT500's power adapter to the other circuit in the room and was able to push the K3 to 22 watts (480 out) before the powercycling returned. This lead me to believe I had a voltage drop issue, perhaps from running the amp on the same 110 circuit. But on 10 meters I still had problems even using the other circuit to power the KAT500. That makes me think noise is getting into the KAT500, or perhaps RF from the antenna is putting noise on my AC house circuits. I was able to run the amp to full power on SSB with no power cycling of the KAT500. On 10 meters the KAT500 power cycles with just 6 watts drive (170 out). On phone I can run full power with no issues. SWR is 1.2 on this band. I have a Morgan AC line filter arriving tomorrow and I'll see if the problem persists with it filtering the house circuit feeding the shack equipment. Do these symptoms smell more like a noise issue (RF in the shack) or a line voltage deficiency with the house circuit? I'm think probably taxing the line in the higher duty cycles, and it just manifests at different thresholds on different frequencies. When transmitting a long string of CW or RTTY, if the KAT500 gets into repeated power cycles the KPA500 eventually throws a fault. Some other observations: If I turn on my desk lamps, at the higher outputs the lamps will modulate slightly with my voice. I think I'm sucking too much juice from the circuit, but this is just a guess on my part. Generally the only other piece of equipment in the house that seems to be affected by RF is our DirectTV receiver (the notorious touch-panel design). It is generally only affected on 10 meters, with a high duty cycle mode like RTTY. Can anyone provide me some more troubleshooting tips? Thanks!Jeff, W6UX __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA500 powercycling at higher wattages into KPA500
I suspect voltage sag off the 120v line. Lights flickering is a symptom. The specs call for 1000VA in and that translates to about 8 amps at 120v. The specified fuse is 12 amps so peaks may be higher. Add everything else in and consider you may have a 15 amp line with a long way back to the fusebox and it is possible your voltage is dropping. Measure the AC voltage with the key down by plugging a voltmeter into the outlet. Also check the HV in the Amp. From the manual: The KPA500 operates to full specifications when the HV under full load is between 60V and 85V as shown on the LCD (Tap HV to display the voltage under CW “key down” conditions at full power). The maximum voltage is set using transformer taps as described on pg. 9. The KPA500 will operate with reduced performance at voltages as low as 40V. When the voltage is less than 60V the maximum output power may be less than 500W and distortion products will increase. K4ia Buck Fredericksburg, VA On 1/28/2015 2:15 PM, Jeff Hall wrote: My KAT500 is getting power-cycled in CW and RTTY modes at various drive levels from the K3 on different bands. I can run SSB full power with no problems at all, and receive superb audio reports (no hint of RF in my transmissions). I am thinking I have either an excessive voltage drop on the AC circuit or perhaps there is enough RF getting into the shack to trip up the KAT500 power when using the higher duty cycle modes. Everything is running on the same 120v house circuit. I experimented with moving both the amp and the KAT500 to a different circuit in the same room, but this did not solve the problem. Let me first describe the equipment, and then I'll list the frequencies and power thresholds that tripped the KAT500 into a power cycle: Antenna: Traffie Hex Beam. Very low SWR, typically 1.2 or less, sometimes 1.5 on 10 and 12 meters. The antenna is over a portion of the house, and about 20 feet away from the shack. The coax is grounded at the base of the antenna (two ground rods, through a lightning arrestor). KAT500: I have this in BYPASS mode. I don't really need the tuner for the hex beam, but I plan on using it with a future vertical for 40m. I am powering the KAT500 with its own AC power adapter. For good measure, I wrapped about 4 turns of the power cord through a ferrite bead at the transformer end of the cable. This is a 15V 1000mAh power adapter from Radio Shack. KPA500 is plugged into the same circuit on its own outlet at the wall. HV reads 78.5 at rest. The unit is sitting on top of the KAT500 with the foldout legs extended. K3 is powered with an Astron RS-35M, on the same house circuit. P3 is powered by the K3 VDC out On 15 meters CW, the KAT500 begins to experience power cycles driving 20-22 watts. The amp, when it crosses about 450 watts, the KAT500 power cycles. I ran 30 watts into it for about 620+ out with no problems on SSB, SWR never exceeded 1.2 on the KAT500's indicator lamps. On 12 meters CW, the KAT500 begins to experience power cycles driving just 9 watts (about 180w out). SWR on this band is a steady 1.5. I did have some success by moving the KAT500's power adapter to the other circuit in the room and was able to push the K3 to 22 watts (480 out) before the powercycling returned. This lead me to believe I had a voltage drop issue, perhaps from running the amp on the same 110 circuit. But on 10 meters I still had problems even using the other circuit to power the KAT500. That makes me think noise is getting into the KAT500, or perhaps RF from the antenna is putting noise on my AC house circuits. I was able to run the amp to full power on SSB with no power cycling of the KAT500. On 10 meters the KAT500 power cycles with just 6 watts drive (170 out). On phone I can run full power with no issues. SWR is 1.2 on this band. I have a Morgan AC line filter arriving tomorrow and I'll see if the problem persists with it filtering the house circuit feeding the shack equipment. Do these symptoms smell more like a noise issue (RF in the shack) or a line voltage deficiency with the house circuit? I'm think probably taxing the line in the higher duty cycles, and it just manifests at different thresholds on different frequencies. When transmitting a long string of CW or RTTY, if the KAT500 gets into repeated power cycles the KPA500 eventually throws a fault. Some other observations: If I turn on my desk lamps, at the higher outputs the lamps will modulate slightly with my voice. I think I'm sucking too much juice from the circuit, but this is just a guess on my part. Generally the only other piece of equipment in the house that seems to be affected by RF is our DirectTV receiver (the notorious touch-panel design). It is generally only affected on 10 meters, with a high duty cycle mode like RTTY. Can anyone provide me some more troubleshooting tips? Thanks!Jeff, W6UX
Re: [Elecraft] KPA500 powercycling at higher wattages into KPA500
First thing, unplug the antenna and plug in a dummy load, then retest. If there is no problem, then you have a partial answer. Try running the KAT500 from the same 13.8 supply as the transceiver. You could have RF getting in to the power supply feeding the KAT500. Make sure the output of that supply does not go above 15V, or you could experience other problems with the KAT500, such as component failure or regulator shutdown from high power supply voltage. If things work right with the dummy load, you are probably experiencing problems with unbalanced currents on the feedline to the Hex Beam. In fact I would bet on this in any case. A good Choke “balun” on the feedline will work wonders. I use several, starting with about a dozen toroids at the antenna feedline (in my case an old A3 tribander) with additional toroids at the feedline entry. In fact all coax coming my shack now gets this same treatment, which has quieted things immensely as far as RF is concerned. See the excellent paper by K9YC at his web site for details on how to handle this stuff. The url: http://audiosystemsgroup.com/RFI-Ham.pdf - Jack Brindle, W6FB On Jan 28, 2015, at 11:15 AM, Jeff Hall w...@ymail.com wrote: My KAT500 is getting power-cycled in CW and RTTY modes at various drive levels from the K3 on different bands. I can run SSB full power with no problems at all, and receive superb audio reports (no hint of RF in my transmissions). I am thinking I have either an excessive voltage drop on the AC circuit or perhaps there is enough RF getting into the shack to trip up the KAT500 power when using the higher duty cycle modes. Everything is running on the same 120v house circuit. I experimented with moving both the amp and the KAT500 to a different circuit in the same room, but this did not solve the problem. Let me first describe the equipment, and then I'll list the frequencies and power thresholds that tripped the KAT500 into a power cycle: Antenna: Traffie Hex Beam. Very low SWR, typically 1.2 or less, sometimes 1.5 on 10 and 12 meters. The antenna is over a portion of the house, and about 20 feet away from the shack. The coax is grounded at the base of the antenna (two ground rods, through a lightning arrestor). KAT500: I have this in BYPASS mode. I don't really need the tuner for the hex beam, but I plan on using it with a future vertical for 40m. I am powering the KAT500 with its own AC power adapter. For good measure, I wrapped about 4 turns of the power cord through a ferrite bead at the transformer end of the cable. This is a 15V 1000mAh power adapter from Radio Shack. KPA500 is plugged into the same circuit on its own outlet at the wall. HV reads 78.5 at rest. The unit is sitting on top of the KAT500 with the foldout legs extended. K3 is powered with an Astron RS-35M, on the same house circuit. P3 is powered by the K3 VDC out On 15 meters CW, the KAT500 begins to experience power cycles driving 20-22 watts. The amp, when it crosses about 450 watts, the KAT500 power cycles. I ran 30 watts into it for about 620+ out with no problems on SSB, SWR never exceeded 1.2 on the KAT500's indicator lamps. On 12 meters CW, the KAT500 begins to experience power cycles driving just 9 watts (about 180w out). SWR on this band is a steady 1.5. I did have some success by moving the KAT500's power adapter to the other circuit in the room and was able to push the K3 to 22 watts (480 out) before the powercycling returned. This lead me to believe I had a voltage drop issue, perhaps from running the amp on the same 110 circuit. But on 10 meters I still had problems even using the other circuit to power the KAT500. That makes me think noise is getting into the KAT500, or perhaps RF from the antenna is putting noise on my AC house circuits. I was able to run the amp to full power on SSB with no power cycling of the KAT500. On 10 meters the KAT500 power cycles with just 6 watts drive (170 out). On phone I can run full power with no issues. SWR is 1.2 on this band. I have a Morgan AC line filter arriving tomorrow and I'll see if the problem persists with it filtering the house circuit feeding the shack equipment. Do these symptoms smell more like a noise issue (RF in the shack) or a line voltage deficiency with the house circuit? I'm think probably taxing the line in the higher duty cycles, and it just manifests at different thresholds on different frequencies. When transmitting a long string of CW or RTTY, if the KAT500 gets into repeated power cycles the KPA500 eventually throws a fault. Some other observations: If I turn on my desk lamps, at the higher outputs the lamps will modulate slightly with my voice. I think I'm sucking too much juice from the circuit, but this is just a guess on my part. Generally the only other piece of equipment in the house that seems to be affected by RF is our DirectTV
Re: [Elecraft] KPA500 powercycling at higher wattages into KPA500
That would not cause the KAT500 to shut down, though. In the situation you describe the KPA500 would continue to output power unless the HV supply drops below 40V. What I am saying is that if the 117V power supply on the KPA500 sags, the amplifier will just keep going, using what it gets. The output will show a corresponding sag, but no failures should result. The KPA should use the beefiest power cable you can find. Use of a small cable will also cause the power to sag, again with the output sagging, but that is all. A good feel of the power cable will show it to be somewhat warm, which means you are losing power through I squared losses in the cable. A heavier cable (like the one supplied) should not show this nearly as much. Again, I don’t believe this is the problem that W6UX is seeing in the KAT500, though. - Jack B, W6FB Elecraft Engineering On Jan 28, 2015, at 11:50 AM, Craig Buck via Elecraft elecraft@mailman.qth.net wrote: I suspect voltage sag off the 120v line. Lights flickering is a symptom. The specs call for 1000VA in and that translates to about 8 amps at 120v. The specified fuse is 12 amps so peaks may be higher. Add everything else in and consider you may have a 15 amp line with a long way back to the fusebox and it is possible your voltage is dropping. Measure the AC voltage with the key down by plugging a voltmeter into the outlet. Also check the HV in the Amp. From the manual: The KPA500 operates to full specifications when the HV under full load is between 60V and 85V as shown on the LCD (Tap HV to display the voltage under CW “key down” conditions at full power). The maximum voltage is set using transformer taps as described on pg. 9. The KPA500 will operate with reduced performance at voltages as low as 40V. When the voltage is less than 60V the maximum output power may be less than 500W and distortion products will increase. K4ia Buck Fredericksburg, VA On 1/28/2015 2:15 PM, Jeff Hall wrote: My KAT500 is getting power-cycled in CW and RTTY modes at various drive levels from the K3 on different bands. I can run SSB full power with no problems at all, and receive superb audio reports (no hint of RF in my transmissions). I am thinking I have either an excessive voltage drop on the AC circuit or perhaps there is enough RF getting into the shack to trip up the KAT500 power when using the higher duty cycle modes. Everything is running on the same 120v house circuit. I experimented with moving both the amp and the KAT500 to a different circuit in the same room, but this did not solve the problem. Let me first describe the equipment, and then I'll list the frequencies and power thresholds that tripped the KAT500 into a power cycle: Antenna: Traffie Hex Beam. Very low SWR, typically 1.2 or less, sometimes 1.5 on 10 and 12 meters. The antenna is over a portion of the house, and about 20 feet away from the shack. The coax is grounded at the base of the antenna (two ground rods, through a lightning arrestor). KAT500: I have this in BYPASS mode. I don't really need the tuner for the hex beam, but I plan on using it with a future vertical for 40m. I am powering the KAT500 with its own AC power adapter. For good measure, I wrapped about 4 turns of the power cord through a ferrite bead at the transformer end of the cable. This is a 15V 1000mAh power adapter from Radio Shack. KPA500 is plugged into the same circuit on its own outlet at the wall. HV reads 78.5 at rest. The unit is sitting on top of the KAT500 with the foldout legs extended. K3 is powered with an Astron RS-35M, on the same house circuit. P3 is powered by the K3 VDC out On 15 meters CW, the KAT500 begins to experience power cycles driving 20-22 watts. The amp, when it crosses about 450 watts, the KAT500 power cycles. I ran 30 watts into it for about 620+ out with no problems on SSB, SWR never exceeded 1.2 on the KAT500's indicator lamps. On 12 meters CW, the KAT500 begins to experience power cycles driving just 9 watts (about 180w out). SWR on this band is a steady 1.5. I did have some success by moving the KAT500's power adapter to the other circuit in the room and was able to push the K3 to 22 watts (480 out) before the powercycling returned. This lead me to believe I had a voltage drop issue, perhaps from running the amp on the same 110 circuit. But on 10 meters I still had problems even using the other circuit to power the KAT500. That makes me think noise is getting into the KAT500, or perhaps RF from the antenna is putting noise on my AC house circuits. I was able to run the amp to full power on SSB with no power cycling of the KAT500. On 10 meters the KAT500 power cycles with just 6 watts drive (170 out). On phone I can run full power with no issues. SWR is 1.2 on this band. I have a Morgan AC line filter arriving tomorrow and I'll see if the problem persists with it
