Re: [Elecraft] AGC 8 volts? (Nope)
http://smallbusiness.yahoo.com/resources/ ___ 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] AGC 8 volts? (Nope)
W3FPR - Don Wilhelm wrote: > No, I do not believe the last digit on your measurement [...] I didn't think so. :-) (But now you know where my earlier incorrectly remembered number of 7.92 V came from.) > my guess is: because your 8 volt rail is > 0.12 volts low, you should initially set the AGC threshold so the voltage is > about 0.06 volts lower than specified in the manual (set to 3.74 volts). Thanks, Don, hearing it explained makes perfect sense. Debugging on my own in the midst of building, though, is difficult so I greatly appreciate the pointers! > I do recommend optimizing your AGC Threshold after you have the K2 up and > running on all bands. [...] Further > refinements/adjustments are possible, but I cannot go into all the details > in a reasonable length reflector post. [...] When I get to this point in the build I'll probably bug, er, contact, you off-list for the particulars if that's ok. I'm sure once the building becomes part of history I'll be glad to have an excuse to tweak and otherwise mess around with the K2. But for now, back to Step 2 in the RF assembly. Last night I finished installing the first armload of resistors. Tonight will probably be the similarly long list of capacitors. And then, oh no, on to winding some toroids. Many thanks, Mike AB3AP Avondale, PA >>-Original Message- >> >>Thanks very much, Don, for your ideas. My email had faulty numbers as a >>result of a faulty (human!) memory. I remeasured voltages just now at >>Control Board locations you measured and got these results: >> >> - U2 pin 5: maxes out at 3.792 Vif you believe that many >> significant figures. >> >> - P1 pin 6: 1.2 mV >> >> - U4 OUT: 7.88 V ... the culprit? >> >>I will disassemble and check my solder connections you mentioned. >> >>Thanks and 73, >>Mike AB3AP >>Avondale, PA ___ 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] AGC 8 volts? (Nope)
Mike, No, I do not believe the last digit on your measurement - call it 3.79 and be done with it - that is close enough. Yes, U4 is the culprit here. Everything will likely work FB with the 7.88 volts, and the main thing you will observe is that the 'bogey value' AGC Threshold should be lowered a bit - my guess is: because your 8 volt rail is 0.12 volts low, you should initially set the AGC threshold so the voltage is about 0.06 volts lower than specified in the manual (set to 3.74 volts). I do recommend optimizing your AGC Threshold after you have the K2 up and running on all bands. With no antenna attached, there should be no audible difference between the AGC on and AGC off conditions (using a 0.70 width CW filter on 40 meters with the Preamp off). To achieve that, I would believe that you will end up with an AGC Threshold somewhere between 3.65 volts and 3.70 volts - but that remains to be seen for your particular K2. Further refinements/adjustments are possible, but I cannot go into all the details in a reasonable length reflector post. If you want to do this optimization, the goal should be to achieve a condition where the receiver gain is not reduced by internal receiver noise while retaining 'good' S-meter activity (the CAL S-LO and CAL S-HI setting interact with the AGC Threshold and can create a lot of work if you choose to 'get it just right' - and what is 'right' is subject to individual interpretation). 73, Don W3FPR > -Original Message- > > Thanks very much, Don, for your ideas. My email had faulty numbers as a > result of a faulty (human!) memory. I remeasured voltages just now at > Control Board locations you measured and got these results: > >- U2 pin 5: maxes out at 3.792 Vif you believe that many >significant figures. > >- P1 pin 6: 1.2 mV > >- U4 OUT: 7.88 V ... the culprit? > > I will disassemble and check my solder connections you mentioned. > > Thanks and 73, > Mike AB3AP > Avondale, PA > > >>from Delaware once I make a portable dipole for 20m. Maybe another > >>month, plus or minus a little. In my year and a half on the air as a > >>ham I've never checked into a CW net, though, so that'll probably be an > >>adventure itself! > >> > >>Mike AB3AP > >> > ___ 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] AGC 8 volts? (Nope)
Thanks very much, Don, for your ideas. My email had faulty numbers as a result of a faulty (human!) memory. I remeasured voltages just now at Control Board locations you measured and got these results: - U2 pin 5: maxes out at 3.792 Vif you believe that many significant figures. - P1 pin 6: 1.2 mV - U4 OUT: 7.88 V ... the culprit? I will disassemble and check my solder connections you mentioned. Thanks and 73, Mike AB3AP Avondale, PA W3FPR - Don Wilhelm wrote: > Mike, > > Are you measuring on the correct pin, and do you have the RF GAIN at full > Clockwise rotation (Max gain)? > > I see no indication that 8 volts should be measured for the AGC. The manual > page 47 calls for setting the AGC Threshold pot to achieve a voltage of 3.80 > volts as measured at Control Board U2 pin 5. If you are not able to adjust > that high, check the soldering of Control Board RP6 and pot R1 carefully, > make certain the resistance from Control Board P1 pin 6 to ground is close > to zero (if it is higher, check the connectors), and lastly check the > voltage available at the OUT terminal of Control Board U4. There are no > active devices in this part of the circuit - it is just a resistive voltage > divider with two legs and driven by the 8 volt supply rail. > > 73, > Don W3FPR > > >>-Original Message- >> >>Last night I completed what the manual calls "Assembly, Part I" of the >>RF board. What a great feeling to power up the K2 to check out the >>control and display boards, and to hear the relays click and see the >>menus working. So far the only thing that hasn't quite reached >>recommended values is that my control board AGC voltage maxes out at >>7.92 V rather than the 8 V mentioned in the manual. I'll have to search >>& see if anyone has reported a similar thing. >> >>Anyway, once the K2 is up and running I'll be glad to check into the net >>from Delaware once I make a portable dipole for 20m. Maybe another >>month, plus or minus a little. In my year and a half on the air as a >>ham I've never checked into a CW net, though, so that'll probably be an >>adventure itself! >> >>Mike AB3AP >> > > > > ___ > 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
[Elecraft] AGC 8 volts?
Mike, Are you measuring on the correct pin, and do you have the RF GAIN at full Clockwise rotation (Max gain)? I see no indication that 8 volts should be measured for the AGC. The manual page 47 calls for setting the AGC Threshold pot to achieve a voltage of 3.80 volts as measured at Control Board U2 pin 5. If you are not able to adjust that high, check the soldering of Control Board RP6 and pot R1 carefully, make certain the resistance from Control Board P1 pin 6 to ground is close to zero (if it is higher, check the connectors), and lastly check the voltage available at the OUT terminal of Control Board U4. There are no active devices in this part of the circuit - it is just a resistive voltage divider with two legs and driven by the 8 volt supply rail. 73, Don W3FPR > -Original Message- > > Last night I completed what the manual calls "Assembly, Part I" of the > RF board. What a great feeling to power up the K2 to check out the > control and display boards, and to hear the relays click and see the > menus working. So far the only thing that hasn't quite reached > recommended values is that my control board AGC voltage maxes out at > 7.92 V rather than the 8 V mentioned in the manual. I'll have to search > & see if anyone has reported a similar thing. > > Anyway, once the K2 is up and running I'll be glad to check into the net > from Delaware once I make a portable dipole for 20m. Maybe another > month, plus or minus a little. In my year and a half on the air as a > ham I've never checked into a CW net, though, so that'll probably be an > adventure itself! > > Mike AB3AP > ___ 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
