Re: [Elecraft] [K2] 2nd Xtal Filter and Product Detector Output problems
Jim, If you had the expected output at U12 pin 8, but less than expected at U11 pin 1, then there is a problem between those two points. Look at the schematic in conjunction with these troubleshooting steps to find what lies between the two points - in this case, look in the lower right quadrant of RF Board schematic sheet 2. Since the signal is going through a crystal filter, move the frequency a little bit to see if the level increases. Concentrate on the 2nd IF filter before proceeding to the Product Detector. 73, Don W3FPR Jim Brown wrote: I am using the procedures in a Rev C manual, Appendix E, Page 10-11 to troubleshoot a dead receiver problem. All Rework Eliminators are installed. Signal tracing through the PLL/VCO and Low-Pass Filter, Bandpass Filter, and T-R Switch produced expected measurements. In the Mixer, I.F. Amp, and Xtal Filter section, some anomalies were found. Specifically, the 2nd Crystal Filter Output measured at U11 pin 1 expects 0.27Vrms but measures only 0.17Vrms (paragraph 9). The Product Detector Saturated Output measurement expects 0.58Vrms but measures only 0.08Vrms (paragraph 10). These measurements produced with input of 0.15Vrms as measured at U12, pin 8 per instructions in paragraph 8. I reheated solder joints on all components around these sections with no change of measurements. Any help appreciated. Regards, Jim Brown, K5JAZ __ 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 No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.325 / Virus Database: 270.12.21/2102 - Release Date: 05/07/09 05:57:00 __ 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] [K2] 2nd Xtal Filter and Product Detector Output problems
I am using the procedures in a Rev C manual, Appendix E, Page 10-11 to troubleshoot a dead receiver problem. All Rework Eliminators are installed. Signal tracing through the PLL/VCO and Low-Pass Filter, Bandpass Filter, and T-R Switch produced expected measurements. In the Mixer, I.F. Amp, and Xtal Filter section, some anomalies were found. Specifically, the 2nd Crystal Filter Output measured at U11 pin 1 expects 0.27Vrms but measures only 0.17Vrms (paragraph 9). The Product Detector Saturated Output measurement expects 0.58Vrms but measures only 0.08Vrms (paragraph 10). These measurements produced with input of 0.15Vrms as measured at U12, pin 8 per instructions in paragraph 8. I reheated solder joints on all components around these sections with no change of measurements. Any help appreciated. Regards, Jim Brown, K5JAZ __ 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] K2 - 2nd Xtal Filter
Anyone any experience of, or thoughts about adding another 3 crystals to the K2 2nd crystal filter ? 73 Stewart G3RXQ ___ 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] K2 - 2nd Xtal Filter
Hello Stewart, Tail end IF Filter: Given that the prime purpose of the 2nd IF Crystal filter is to reduce wideband noise created by the MC1350 IF amplifier, which comes out as audio hiss, yes a better filter would do a better job provided that it is wider than the SSB filter. BUT I suspect that the MC1350 would not be happy driving such a filter with its varying input impedance. More distortion / intermod would result than when driving the two crystal filter. The other possibility is that the drive to the AGC system could bounce due to these impedance variations, and depending on time constants etc oscillation at some frequency high or low could result. An Image Reject Demodulator can eliminate the need for any tail end filter, but no room, AGC Take-off point. Here I am guessing. It could be 1) To reduce the BFO signal leaking through the demodulator that might drive the AGC. The filter chops this down. 2) A simple matter of drive level 3) To reduce AGC Attack delay. 73. Geoff, GM4ESD - Original Message - From: Stewart Baker [EMAIL PROTECTED] To: Elecraft Reflector elecraft@mailman.qth.net Sent: Saturday, March 05, 2005 11:27 AM Subject: [Elecraft] K2 - 2nd Xtal Filter Anyone any experience of, or thoughts about adding another 3 crystals to the K2 2nd crystal filter ? 73 Stewart G3RXQ ___ 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
