[Elecraft] [K2] How much AF volts at 1kHz to get full RF power using KSB2?
I have K2 serial no 03885. I've recently finished building the KSB2 SSB adapter, but I'm having problems getting it to work. The problem is very low output power when I speak into the mic. I'm using an Icom MK36 mic and I've set the P1 header as per the KSB2 manual; including the resistor to get Mic bias. The options as set SSBA = 2, SSBC = 2-1 and I've done the carrier balance. On 7MHz, LSB, with the power set to 1W, when I "tune" the rig into a dummy load I get 1W, but when I talk or whistle into the Mic, the most I can get is about 100mW. Nomatter how load I yell, I cannot get full output power :-) and the bar graph hardly moves. I've checked all the DC voltages and they are OK. I used a scope on U5 (NE602) and there is an enormous disparity between the voltages on pin 6 (hi) and on pin 1 (very low). The waveform on U3 pin 7 (the compressed AF out) is greater than that on pin 4, (the AF input), but not by much. I want to eliminate the Mic as the source of the problem (It works perfectly with the IC-756 Pro II) by using an AF sig gen, but I'm not sure how much AF drive should cause 100% output power. Gareth - M5KVK __ 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] [K2] How much AF volts at 1kHz to get full RF power using KSB2?
Gareth, During transmit you should have about 1.4 volts DC on pin 1 or the balanced modulator U5. I just measured the U5 pin 1 audio using a 'scope with a 10X probe and found the peak to peak voltage ranged from 200 to 400 millivolts. If you have a good microphone, you should see a similar amplitude signal. The RF output at U5 pin 4 should have a similar amplitude. The BFO injection at U5 pin 6 should be greater than 200 millivolts peak to peak and on the one I just measured there was a 1 volt BFO signal there. 73, Don W3FPR On 9/29/2014 4:52 AM, Gareth - M5KVK wrote: I have K2 serial no 03885. I've recently finished building the KSB2 SSB adapter, but I'm having problems getting it to work. The problem is very low output power when I speak into the mic. I'm using an Icom MK36 mic and I've set the P1 header as per the KSB2 manual; including the resistor to get Mic bias. The options as set SSBA = 2, SSBC = 2-1 and I've done the carrier balance. I've checked all the DC voltages and they are OK. I used a scope on U5 (NE602) and there is an enormous disparity between the voltages on pin 6 (hi) and on pin 1 (very low). The waveform on U3 pin 7 (the compressed AF out) is greater than that on pin 4, (the AF input), but not by much. I want to eliminate the Mic as the source of the problem (It works perfectly with the IC-756 Pro II) by using an AF sig gen, but I'm not sure how much AF drive should cause 100% output power. Gareth - M5KVK __ 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] [K2] How much AF volts at 1kHz to get full RF power using KSB2?
Thanks, Don I'm getting more or less the same as you except for the RF out on U5 pin 4. I'm seeing the BFO of about 400mV pp with no AF, and then going up to 800mV pp when I whistle into the Mic. Doh! I thought I had the carrier balance right, but obviously not. Switching on the SSBA=BAL shows a bif signal on U5 pin 4. I've adjusted that down to almost zero on the 'scope, but I'm still not getting much RF out. 73, Gareth, M5KVK On 29 September 2014 16:38, Don Wilhelm wrote: > Gareth, > > During transmit you should have about 1.4 volts DC on pin 1 or the > balanced modulator U5. > I just measured the U5 pin 1 audio using a 'scope with a 10X probe and > found the peak to peak voltage ranged from 200 to 400 millivolts. If you > have a good microphone, you should see a similar amplitude signal. The RF > output at U5 pin 4 should have a similar amplitude. > The BFO injection at U5 pin 6 should be greater than 200 millivolts peak > to peak and on the one I just measured there was a 1 volt BFO signal there. > > 73, > Don W3FPR > > On 9/29/2014 4:52 AM, Gareth - M5KVK wrote: > >> I have K2 serial no 03885. I've recently finished building the KSB2 SSB >> adapter, but I'm having problems getting it to work. >> >> The problem is very low output power when I speak into the mic. I'm using >> an Icom MK36 mic and I've set the P1 header as per the KSB2 manual; >> including the resistor to get Mic bias. >> >> The options as set SSBA = 2, SSBC = 2-1 and I've done the carrier balance. >> >> >> >> I've checked all the DC voltages and they are OK. I used a scope on U5 >> (NE602) and there is an enormous disparity between the voltages on pin 6 >> (hi) and on pin 1 (very low). The waveform on U3 pin 7 (the compressed AF >> out) is greater than that on pin 4, (the AF input), but not by much. >> >> I want to eliminate the Mic as the source of the problem (It works >> perfectly with the IC-756 Pro II) by using an AF sig gen, but I'm not sure >> how much AF drive should cause 100% output power. >> >> Gareth - M5KVK >> >> > __ 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] [K2] How much AF volts at 1kHz to get full RF power using KSB2?
Gareth, Is D4 mounted with the correct orientation. - the line on the silkscreen points to the cathode end. 73, Don W3FPR On 9/29/2014 4:16 PM, Gareth - M5KVK wrote: Thanks, Don I'm getting more or less the same as you except for the RF out on U5 pin 4. I'm seeing the BFO of about 400mV pp with no AF, and then going up to 800mV pp when I whistle into the Mic. Doh! I thought I had the carrier balance right, but obviously not. Switching on the SSBA=BAL shows a bif signal on U5 pin 4. I've adjusted that down to almost zero on the 'scope, but I'm still not getting much RF out. 73, __ 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] [K2] How much AF volts at 1kHz to get full RF power using KSB2?
I’m rapidly getting nowhere with this problem. I need to understand how the overall circuit works and what I should expect to see on the ‘scope. My understanding is that RF Power is basically under the control of a feedback loop controlled by the VRFDET circuit on the RF board. The front panel PWR OUT is simply an input to Control Board U8, which generates V PWR via U8. V PWR sets the target level in the ALC block and affects V ALC. V ALC goes to Q24 and controls the o/p level of the BFO, which then flows through filters etc to the PA, where VREFDET is generated. In CW mode, that’s all there is, and it works. Varying PWR OUT varies the RF power generated. The problem comes in SSB mode. With the KSB2 installed, and in CW mode, the BFO signal goes in and out of the KSB2 via Q3. All OK. In SSB mode, the KSB2 has an additional ALC circuit block that uses VRFDET, ALC THR and PWR CTRL to throttle the SSB generated on the KSB2 which then goes back out via Q2. This doesn’t work. In SSB mode, the AF mixes in the balanced modulator but changing PWR OUT has no effect. If my understanding is correct, the problem would seem to lie in one of two places: a) the ALC circuit block on the KSB2 or b) the AF compressor circuit. I want to remove the Mic as a source of variability but I don’t know what AF voltage should cause 100% of the set o/p power. 73 Gareth - M5KVK On 1 October 2014 22:10, Gareth - M5KVK wrote: > Thanks for the help Don.I really appreciate it. > Apart from finding that R7 was not fitted (how many times had I looked at > the board?), I can see nothing untoward. Fitting it made no difference. > > I note that these were the ones changed in the Rev E errata. Relevant? > Mine is a Rev D board and (e.g.) R9 is 10k rather than 3.9k as per the Rev > D manual. > > The receive audio is slightly down with OP1 but not a lot. Diodes are all > the right way around and T2 appears to be OK, no shorts and buzzes through > OK. > > I did see a suspicious poor solder joint with R69 on the RF board, but > again it made no difference. > > On 1 October 2014 18:16, Don Wilhelm wrote: > >> Gareth, >> >> The PWR CTRL on the KSB2 does not do much at all, so what you are seeing >> is about right. >> The power control is done from the VRFDET feeding the base of Q1. It >> causes Q1 to conduct and alters the voltage to the base of Q2. The SSB >> signal is 'throttled' after the signal is generated and passed through the >> OP1 filter. The BFO injection should not change for SSB operation like it >> does for CW mode. >> >> Check resistors R4 and R9 for proper values and good soldering. Check >> the orientation of D2. >> >> If you are still not getting adequate signal at D4, then you may have a >> problem with T2 or a solder bridge on one of the capacitors in the filter >> area that is dragging the signal down. >> How does the OP1 filter behave in receive. If the RX signal is >> attenuated more than with the variable filter, that problem may be related >> to your TX problem. >> >> The VRFDET signal level is a level determined by the actual power output >> of the K2 - it comes from the wattmeter forward power detection in either >> the KAT2 or the KPA100 - without either of those options, it comes from the >> RF Detector D9 on the RF Board. >> >> 73, >> Don W3FPR >> >> >> On 10/1/2014 11:17 AM, Gareth - M5KVK wrote: >> >> Don, Yes, D4 seems to be OK >> >> I've done some further probing and I'm wondering if the problem lies in >> the ALC circuit. Basically, the power doesn't vary as I change the POWER >> control. >> >> Scoping U2. There is data on pin 8, but only the second nibble changes. >> ALC THR goes up as I change POWER, but PWR CTRL stays stuck at about 5.6V >> regardless of where POWER is set or what AF there is. >> >> What is the purpose of PWR CTRL? Should it be changing? >> >> Gareth - M5KVK >> >> On 29 September 2014 21:45, Don Wilhelm wrote: >> >>> Gareth, >>> >>> Is D4 mounted with the correct orientation. - the line on the silkscreen >>> points to the cathode end. >>> >>> 73, >>> Don W3FPR >>> >>> >>> On 9/29/2014 4:16 PM, Gareth - M5KVK wrote: >>> Thanks, Don I'm getting more or less the same as you except for the RF out on U5 pin 4. I'm seeing the BFO of about 400mV pp with no AF, and then going up to 800mV pp when I whistle into the Mic. Doh! I thought I had the carrier balance right, but obviously not. Switching on the SSBA=BAL shows a bif signal on U5 pin 4. I've adjusted that down to almost zero on the 'scope, but I'm still not getting much RF out. 73, >>> >> >> > __ 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-arc
Re: [Elecraft] [K2] How much AF volts at 1kHz to get full RF power using KSB2?
Gareth, You should find between 200 and 400 mV peak to peak (dependent on the particular speech patterns) from an electret microphone such as the Elecraft MH2. That is 70 to 140 mV RMS. That is sufficient to drive the SSB output to pull power. 73, Don W3FPR On 10/6/2014 3:57 PM, Gareth - M5KVK wrote: I want to remove the Mic as a source of variability but I don’t know what AF voltage should cause 100% of the set o/p power. __ 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] [K2] How much AF volts at 1kHz to get full RF power using KSB2?
On Mon,10/6/2014 1:56 PM, Don Wilhelm wrote: You should find between 200 and 400 mV peak to peak (dependent on the particular speech patterns) from an electret microphone such as the Elecraft MH2. That is 70 to 140 mV RMS. That is sufficient to drive the SSB output to pull power. I once owned a pair of K2/100s and used them for contesting. I found the audio chain rather gain-starved and with excessive low-frequency bandwidth, so I changed a few resistor and capacitor values to increase the gain and reduce the LF. I think I managed about 6 dB. I believe that I passed those mods along to you, Don. The changes allowed me to hit the Limiter a bit harder, increasing its compression ratio. 73, Jim K9YC __ 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] [K2] How much AF volts at 1kHz to get full RF power using KSB2?
Don, Jim Thanks. I finally got there. Once I removed the Mic from the chain, the problem disappeared. With 150mV RMS @ 1kHz, I got just over 4W when the rig was set to deliver 5W. Close enough for me. The problem is that the fist Mic I use (Icom MH36) and my Heil Proset 5 are both low output Mics. I'll get an Elecraft MH2 and put a pre amp in the Pro Set's line. 73, Gareth On 6 October 2014 21:56, Don Wilhelm wrote: > Gareth, > You should find between 200 and 400 mV peak to peak (dependent on the > particular speech patterns) from an electret microphone such as the > Elecraft MH2. That is 70 to 140 mV RMS. > That is sufficient to drive the SSB output to pull power. > > 73, > Don W3FPR > > > On 10/6/2014 3:57 PM, Gareth - M5KVK wrote: > >> I want to remove the Mic as a source of variability but I don’t know what >> AF voltage should cause 100% of the set o/p power. >> >> >> > __ 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
