[Elecraft] PSK audio problems with K2
Can anyone shed any light on this please? I have connected tx and rx audio from/to the computer via isolation transformers on both audio in and out. Rx works fine. However, I have hit a problem trying to get acceptable transmit audio quality. I have the K2 stripped back to 10W at the moment so am not using my external KPA100 in order to remove that from the equation. I am feeding the audio from the computer via the isolating transformer straight to the microphone header with the microphone removed. I have turned the compressor off in all modes. I have no ALC showing and have tried the power control in various positions. The audio is extremely rough with various artifacts spreading widely above and below the tx frequency. I have the K2 feeding into a 100W Bird dummy load. I have listened both with my K1 with a few inches of wire as an antenna and my TS-480HX in the car parked outside. Same grotty received audio. I have checked the carrier balance on the ssb board. Although still audible in the K1¹s receiver I have minimised it for usb and lsb. I note that I can eliminate it almost altogether for lsb, but then the level at usb is high. So it¹s a compromise as I have read it would be. I have tried both my desktop pc (a mac) and my Dell laptop (XP) - no difference. I have listened directly to the audio output from the computers it sounds right. I must have used psk31 on a dozen or more radios in the last ten years or so, but never hit this severe a problem before. Listening to my ssb speech via the HM12 microphone, it doesn¹t sound great, but yet I am using the K1 to listen to it with so that¹s not too surprising. I don¹t use ssb at all except mobile, so have had no operating experience of the K2 in this mode. I am wondering if the problem lies deeper somewhere. I have googled, but hit nothing useful. Any thoughts would be much appreciated Thanks and 73, Stephen G4SJP ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] PSK audio problems with K2
Stephen, I believe you may be overdriving the microphone input of the K2. Do you have any attenuation between your soundcard output and the K2 microphone input? On the output (K2) side of the transformer connect a series resistor about 10k in value and a 1k across the wires to the microphone. That will drop the soundcard level down to about 1/10 of the soundcard output and keep from overdriving the microphone input. Reduce the 1k resistor if the soundcard still overloads the mic input of the K2. 73, Don W3FPR Stephen Prior wrote: Can anyone shed any light on this please? I have connected tx and rx audio from/to the computer via isolation transformers on both audio in and out. Rx works fine. However, I have hit a problem trying to get acceptable transmit audio quality. I have the K2 stripped back to 10W at the moment so am not using my external KPA100 in order to remove that from the equation. I am feeding the audio from the computer via the isolating transformer straight to the microphone header with the microphone removed. I have turned the compressor off in all modes. I have no ALC showing and have tried the power control in various positions. The audio is extremely rough with various artifacts spreading widely above and below the tx frequency. I have the K2 feeding into a 100W Bird dummy load. I have listened both with my K1 with a few inches of wire as an antenna and my TS-480HX in the car parked outside. Same grotty received audio. I have checked the carrier balance on the ssb board. Although still audible in the K1¹s receiver I have minimised it for usb and lsb. I note that I can eliminate it almost altogether for lsb, but then the level at usb is high. So it¹s a compromise as I have read it would be. I have tried both my desktop pc (a mac) and my Dell laptop (XP) - no difference. I have listened directly to the audio output from the computers it sounds right. I must have used psk31 on a dozen or more radios in the last ten years or so, but never hit this severe a problem before. Listening to my ssb speech via the HM12 microphone, it doesn¹t sound great, but yet I am using the K1 to listen to it with so that¹s not too surprising. I don¹t use ssb at all except mobile, so have had no operating experience of the K2 in this mode. I am wondering if the problem lies deeper somewhere. I have googled, but hit nothing useful. Any thoughts would be much appreciated Thanks and 73, Stephen G4SJP ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] PSK audio problems with K2
Don Well, once again you've come up trumps! I did as you suggested but have ended up finally with a 1:20 potential divider and the audio sounds much like it should do, although I feel it's not as good as it was with my TS-480HX but I am being very picky! I just got a -22dB IMD report from a DJ on 40m in a noisy band so it's at least adequate. I am (just) not showing any ALC and have set the output power control to 30W. So far I have been using LSB, now I need to set up those RTTY filters properly! Thanks again, and have a great Christmas! 73 Stephen On 18/12/07 14:13, Don Wilhelm [EMAIL PROTECTED] wrote: Stephen, I believe you may be overdriving the microphone input of the K2. Do you have any attenuation between your soundcard output and the K2 microphone input? On the output (K2) side of the transformer connect a series resistor about 10k in value and a 1k across the wires to the microphone. That will drop the soundcard level down to about 1/10 of the soundcard output and keep from overdriving the microphone input. Reduce the 1k resistor if the soundcard still overloads the mic input of the K2. 73, Don W3FPR Stephen Prior wrote: Can anyone shed any light on this please? I have connected tx and rx audio from/to the computer via isolation transformers on both audio in and out. Rx works fine. However, I have hit a problem trying to get acceptable transmit audio quality. I have the K2 stripped back to 10W at the moment so am not using my external KPA100 in order to remove that from the equation. I am feeding the audio from the computer via the isolating transformer straight to the microphone header with the microphone removed. I have turned the compressor off in all modes. I have no ALC showing and have tried the power control in various positions. The audio is extremely rough with various artifacts spreading widely above and below the tx frequency. I have the K2 feeding into a 100W Bird dummy load. I have listened both with my K1 with a few inches of wire as an antenna and my TS-480HX in the car parked outside. Same grotty received audio. I have checked the carrier balance on the ssb board. Although still audible in the K1¹s receiver I have minimised it for usb and lsb. I note that I can eliminate it almost altogether for lsb, but then the level at usb is high. So it¹s a compromise as I have read it would be. I have tried both my desktop pc (a mac) and my Dell laptop (XP) - no difference. I have listened directly to the audio output from the computers it sounds right. I must have used psk31 on a dozen or more radios in the last ten years or so, but never hit this severe a problem before. Listening to my ssb speech via the HM12 microphone, it doesn¹t sound great, but yet I am using the K1 to listen to it with so that¹s not too surprising. I don¹t use ssb at all except mobile, so have had no operating experience of the K2 in this mode. I am wondering if the problem lies deeper somewhere. I have googled, but hit nothing useful. Any thoughts would be much appreciated Thanks and 73, Stephen G4SJP ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] PSK audio problems with K2
Stephen When I do PSK with my K2 (or K3) I set the amplifier power at max value and then drive it with just enough audio signal to get 20-30 watts out. This yields a signal with -29 to -30 db IMD on my KK7UQ IMD meter. Hope this helps Bob KD8CGH ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
