Re: [Elecraft] AGC threshold
I have suggested an AGC setting where the response is linear until a maximum audio level is reached, where the AGC cuts in flat with with a slow decay that converts to fast decay over one second. To set up for this, turn your audio to your "normal" audio. Then tune in a very strong carrier. Adjust the audio limiter in config to the loudest tone you want to hear. Use the RF gain/PRE/ATT to get the band ambient noise at a comfortable level. For this "contest" AGC, "light" both the S and F on the display. I believe this will give the results of riding RF gain with no AGC, without the blasts. For myself, the above should be what you should get with AGC in the off position, but that is another discussion. 73, Guy. On Thu, Dec 9, 2010 at 10:05 AM, Dave Hachadorian wrote: > Need threshold higher than 8, and Slope with a number less than > zero, which translates to a steeper curve. > > With such settings, AGC would be used for hardware protection and > hearing protection only. The linear part of the curve would be > maximized. > > > Dave Hachadorian, K6LL > Yuma, AZ > > > > -Original Message- > From: Pete Smith > Sent: Thursday, December 09, 2010 7:01 AM > To: Elecraft List > Subject: [Elecraft] AGC threshold > > Are there engineering reasons why the AGC threshold level can be > set no > higher than 8? KE7X suggests that this value, if increased, > would lead > to better performance in receiving pileups, without having to > turn off > the AGC altogether. > > -- > 73, Pete N4ZR > > The World Contest Station Database, updated daily at > www.conteststations.com > The Reverse Beacon Network at http://reversebeacon.net, blog at > reversebeacon.blogspot.com, > spots at telnet.reversebeacon.net, port 7000 > > > __ > 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 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 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
Re: [Elecraft] AGC threshold
Need threshold higher than 8, and Slope with a number less than zero, which translates to a steeper curve. With such settings, AGC would be used for hardware protection and hearing protection only. The linear part of the curve would be maximized. Dave Hachadorian, K6LL Yuma, AZ -Original Message- From: Pete Smith Sent: Thursday, December 09, 2010 7:01 AM To: Elecraft List Subject: [Elecraft] AGC threshold Are there engineering reasons why the AGC threshold level can be set no higher than 8? KE7X suggests that this value, if increased, would lead to better performance in receiving pileups, without having to turn off the AGC altogether. -- 73, Pete N4ZR The World Contest Station Database, updated daily at www.conteststations.com The Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com, spots at telnet.reversebeacon.net, port 7000 __ 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 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] AGC threshold
Are there engineering reasons why the AGC threshold level can be set no higher than 8? KE7X suggests that this value, if increased, would lead to better performance in receiving pileups, without having to turn off the AGC altogether. -- 73, Pete N4ZR The World Contest Station Database, updated daily at www.conteststations.com The Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com, spots at telnet.reversebeacon.net, port 7000 __ 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
Re: [Elecraft] AGC Threshold Ok! (was Re: K2: AGC Threshold Too Low?)
FYI - 50 microvolts is the widely accepted "S9" signal level, not 20 over. I would guess the 1uV is around S1, but not sure about that one. More info in the Elecraft manual on the XG1 or XG2. Jerry W4UK At 10:43 AM 12/2/2007, Kurt Pawlikowski wrote: Sarah, ... I'm told that in a properly adjusted (and complete?) radio, a 1 micro-volt signal should register about S-3 and 50 micro-volt should be something like 20 db over 9. ___ 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 Threshold Ok! (was Re: K2: AGC Threshold Too Low?)
Hello Sarah, Having spent 10 years or so in apartments trying to operate HF I can recommend a couple of things to improve your evaluation of the K2. GET THE ANTENNA OUTSIDE AND IF POSSIBE MAKE IT REASONATE. I had a friend give me the remains of a couple of Hustler mobile antenna setups including two masts and 2 40 and 2 20 meter resonators. I used a mount I got at the time from a CB store to make a rotatable dipole and put it on a camera tripod with duct tape. Not pretty but it fit on the patio for the first test and made a usable receive antenna. Later I made an extension mast from the pole off a pool skimmer and put it in a TV tripod and just stood it on my balcony lashed to the handrail with bungee cords. This put the antenna up and away from the building which was stucco over wire and block. This type of construction acts like a faraday shield and won't let you hear diddly. I had to put it up and down each day I intended to use it so the mgmnt wouldn't have a fit but it worked well enough to keep me from being QRT. Good luck with your K2 project. You have the greatest resource at your fingertips with the company and this reflector so failure is unlikely. I know we will hear you on the air at some point. ;>) Michael Baker K7DD [EMAIL PROTECTED] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Sarah K Sent: Sunday, December 02, 2007 1:58 AM To: Elecraft@mailman.qth.net Subject: [Elecraft] AGC Threshold Ok! (was Re: K2: AGC Threshold Too Low?) Hi All, Good news... I got my K2's replacement voltage regulator (LM2930T-8) from Elecraft on Friday. Today I took out the old one and put in the new one... the output of the voltage regulator is now 8.04 volts, which is a whole lot better than the 7.53 volts I had gotten before! And after adjusting R1, the AGC threshold is reading 3.80, exactly where it should be! Elecraft also sent me a replacement R116 which was missing (I think!) so I was able to finish building Part II and move on to the alignment and test for Part II. Someone on the list (NM5B) had recommend I pick up a few of the Elecraft mini-modules, so I ordered the noise generator, the 50uV signal generator, and the dummy load. I put those together today too, with no issues, and used them to help work through the alignment and test. On the whole, I was quite happy with the results of the alignment and test; all of the instructions were fairly straightforward, and, even better, my K2 seemed to pass all of them perfectly! Yay! And the noise generator works; I can hear the noise. The signal generator works, too; when I tune around 7040 kHz, I can hear the 40m 50uV oscillator. Now comes my strange and possibly embarrassing question... Um... should I be able to receive anything yet? Keep in mind, this is my first radio... well, second, if you count my Yaesu VX-7R... and I don't entirely know what to expect. I have what is probably a very bad antenna; it's just two pieces of random wire I had laying around, soldered onto a BNC connector, and draped around the room. The total length is probably 20-25 feet, which I *know* isn't the right length for 40 meters... but it was the longest wire I had laying around. When I hook it to the K2 via a 3ft BNC patch cable, I definitely hear an increase in the noise level in the headphones. But I wasn't able to tune into anything that sounded like an actual transmission. No voice, no CW. I tried switching between CW, LSB, and USB. And I fiddled with the filter settings. I did hear a couple different kinds of things: I hear whistling noises that increase or decrease in pitch as I tune around. I hear "pops" that happen when I tune across some small range of frequencies. These pops seem to be mostly repeatable, as if I'm hitting something in the same spot in the band, but I was never able to tune in to anything. I do also hear several places where the noise is louder, and the S- meter increases by a notch or two... and once or twice I heard something that could possibly have been very, very garbled speech. But I wasn't ever able to tune into those, either, and in fact it could have been my imagination. And, so far... that's about it. Some other things that might be worth pointing out: I have a high- voltage transmission line and a substation about a block away from me... and my antenna is parallel to it. And I connected the VX-7R to the same antenna and it gets similar kinds of noise, and no signals on 40m either. Also, I'm on the 2nd floor of an apartment, and an outside antenna isn't going to be feasible here. I didn't try grounding the K2 to the electrical ground yet... I certainly can't install my own ground rod, either! I was running the K2 from 12 volts worth of D batteries, to minimize power s
Re: [Elecraft] AGC Threshold Ok! (was Re: K2: AGC Threshold Too Low?)
Sarah, While I'm not familiar with the VX-7R and don't own a K2, it sounds like things are working. If you receive something from the noise generator and the signal generator (particularly if you switch the latter to 1 micro-volt), your rig is probably working correctly. I don't know how much that will change when you have completed the radio. I'm told that in a properly adjusted (and complete?) radio, a 1 micro-volt signal should register about S-3 and 50 micro-volt should be something like 20 db over 9. Part of what you are experiencing is the relatively poor HF band conditions and part is from the low gain antenna. If you tune around during the day, you should probably hear *something* in at least the 40 meter CW portion... Hope that helps! Have fun. Regards, kurtt Kurt Pawlikowski, AKA WB9FMC The Pinrod Corporation [EMAIL PROTECTED] (773) 284-9500 http://pinrod.com Sarah K wrote: Hi All, Good news... I got my K2's replacement voltage regulator (LM2930T-8) from Elecraft on Friday. Today I took out the old one and put in the new one... the output of the voltage regulator is now 8.04 volts, which is a whole lot better than the 7.53 volts I had gotten before! And after adjusting R1, the AGC threshold is reading 3.80, exactly where it should be! Elecraft also sent me a replacement R116 which was missing (I think!) so I was able to finish building Part II and move on to the alignment and test for Part II. Someone on the list (NM5B) had recommend I pick up a few of the Elecraft mini-modules, so I ordered the noise generator, the 50uV signal generator, and the dummy load. I put those together today too, with no issues, and used them to help work through the alignment and test. On the whole, I was quite happy with the results of the alignment and test; all of the instructions were fairly straightforward, and, even better, my K2 seemed to pass all of them perfectly! Yay! And the noise generator works; I can hear the noise. The signal generator works, too; when I tune around 7040 kHz, I can hear the 40m 50uV oscillator. Now comes my strange and possibly embarrassing question... Um... should I be able to receive anything yet? Keep in mind, this is my first radio... well, second, if you count my Yaesu VX-7R... and I don't entirely know what to expect. I have what is probably a very bad antenna; it's just two pieces of random wire I had laying around, soldered onto a BNC connector, and draped around the room. The total length is probably 20-25 feet, which I *know* isn't the right length for 40 meters... but it was the longest wire I had laying around. When I hook it to the K2 via a 3ft BNC patch cable, I definitely hear an increase in the noise level in the headphones. But I wasn't able to tune into anything that sounded like an actual transmission. No voice, no CW. I tried switching between CW, LSB, and USB. And I fiddled with the filter settings. I did hear a couple different kinds of things: I hear whistling noises that increase or decrease in pitch as I tune around. I hear "pops" that happen when I tune across some small range of frequencies. These pops seem to be mostly repeatable, as if I'm hitting something in the same spot in the band, but I was never able to tune in to anything. I do also hear several places where the noise is louder, and the S-meter increases by a notch or two... and once or twice I heard something that could possibly have been very, very garbled speech. But I wasn't ever able to tune into those, either, and in fact it could have been my imagination. And, so far... that's about it. Some other things that might be worth pointing out: I have a high-voltage transmission line and a substation about a block away from me... and my antenna is parallel to it. And I connected the VX-7R to the same antenna and it gets similar kinds of noise, and no signals on 40m either. Also, I'm on the 2nd floor of an apartment, and an outside antenna isn't going to be feasible here. I didn't try grounding the K2 to the electrical ground yet... I certainly can't install my own ground rod, either! I was running the K2 from 12 volts worth of D batteries, to minimize power supply noise. And I turned off all the fluorescent lights, which dropped the noise considerably, but didn't reveal anything underneath the noise. So... does this sound appropriate given the current situation? Should I be hearing more than this? Am I not understanding how the K2 works? Am I missing something very basic about ham radio? Am I doing something silly? :-) Should I try a better/different antenna? I now have about 150ft of 12ga stranded wire that I can use for a second test antenna; if I run it perpendicular to the high voltage line I think I can go 40ft in a mostly straight line, and probably 50ft with one right-angle bend in it. I can't get to 67ft without some major contortions; my apartment just isn't that big
[Elecraft] AGC Threshold Ok! (was Re: K2: AGC Threshold Too Low?)
Sarah If the 50 uV signal generator indicates a signal level of around S9 on your K2, that is exactly how it should be. Your length of wire in the room may not receive signals well, depending on the type of materials used to build your house it could be shielding signals by quite a few dBs. I would be tempted to run the wire out of a window or door and out to a support, it doesn't need to be very high - even at 6 feet high it should be picking up signals. During most of the day you should be hearing plenty on 20m and 40m, after dark you would need to move down in frequency as 20m will close. 73 Dave, G4AON K1, K2/10 and K3/100 ___ 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 Threshold Ok! (was Re: K2: AGC Threshold Too Low?)
Hi All, Good news... I got my K2's replacement voltage regulator (LM2930T-8) from Elecraft on Friday. Today I took out the old one and put in the new one... the output of the voltage regulator is now 8.04 volts, which is a whole lot better than the 7.53 volts I had gotten before! And after adjusting R1, the AGC threshold is reading 3.80, exactly where it should be! Elecraft also sent me a replacement R116 which was missing (I think!) so I was able to finish building Part II and move on to the alignment and test for Part II. Someone on the list (NM5B) had recommend I pick up a few of the Elecraft mini-modules, so I ordered the noise generator, the 50uV signal generator, and the dummy load. I put those together today too, with no issues, and used them to help work through the alignment and test. On the whole, I was quite happy with the results of the alignment and test; all of the instructions were fairly straightforward, and, even better, my K2 seemed to pass all of them perfectly! Yay! And the noise generator works; I can hear the noise. The signal generator works, too; when I tune around 7040 kHz, I can hear the 40m 50uV oscillator. Now comes my strange and possibly embarrassing question... Um... should I be able to receive anything yet? Keep in mind, this is my first radio... well, second, if you count my Yaesu VX-7R... and I don't entirely know what to expect. I have what is probably a very bad antenna; it's just two pieces of random wire I had laying around, soldered onto a BNC connector, and draped around the room. The total length is probably 20-25 feet, which I *know* isn't the right length for 40 meters... but it was the longest wire I had laying around. When I hook it to the K2 via a 3ft BNC patch cable, I definitely hear an increase in the noise level in the headphones. But I wasn't able to tune into anything that sounded like an actual transmission. No voice, no CW. I tried switching between CW, LSB, and USB. And I fiddled with the filter settings. I did hear a couple different kinds of things: I hear whistling noises that increase or decrease in pitch as I tune around. I hear "pops" that happen when I tune across some small range of frequencies. These pops seem to be mostly repeatable, as if I'm hitting something in the same spot in the band, but I was never able to tune in to anything. I do also hear several places where the noise is louder, and the S- meter increases by a notch or two... and once or twice I heard something that could possibly have been very, very garbled speech. But I wasn't ever able to tune into those, either, and in fact it could have been my imagination. And, so far... that's about it. Some other things that might be worth pointing out: I have a high- voltage transmission line and a substation about a block away from me... and my antenna is parallel to it. And I connected the VX-7R to the same antenna and it gets similar kinds of noise, and no signals on 40m either. Also, I'm on the 2nd floor of an apartment, and an outside antenna isn't going to be feasible here. I didn't try grounding the K2 to the electrical ground yet... I certainly can't install my own ground rod, either! I was running the K2 from 12 volts worth of D batteries, to minimize power supply noise. And I turned off all the fluorescent lights, which dropped the noise considerably, but didn't reveal anything underneath the noise. So... does this sound appropriate given the current situation? Should I be hearing more than this? Am I not understanding how the K2 works? Am I missing something very basic about ham radio? Am I doing something silly? :-) Should I try a better/different antenna? I now have about 150ft of 12ga stranded wire that I can use for a second test antenna; if I run it perpendicular to the high voltage line I think I can go 40ft in a mostly straight line, and probably 50ft with one right-angle bend in it. I can't get to 67ft without some major contortions; my apartment just isn't that big! I have the internal antenna tuner for my K2 but of course I haven't put it together yet! Or could there be something wrong with my partly-assembled K2? To date, I've heard almost nothing on *any* HF band... once or twice I've been able to hear faint strains of music on the VX-7R, when using the pre-programmed "Shortwave Broacast" built-in memory. And I have another little transistor radio that has shortwave bands on it... and I've never heard anything on that either. Could I somehow be in a location where I can't receive much of anything? (I do hear stuff on VHF bands with the VX-7R.) Suggestions/recommendations welcome! Thanks, Sarah AF6FH On Nov 23, 2007, at 12:53 PM, Sarah K. wrote: [quoted bit corrected for typos!] Hi, I'm Sarah, AF6FH! I just got my license a couple weeks ago, and I'm now assembling K2# 06322, which will be my first HF radio.
Re: [Elecraft] AGC Threshold voltage?
Thanks to everyone for the suggestions and help... As Don pointed out the IF gain decreases with an increase in voltage. I set the voltage at a point where there is no difference in the background noise with AGC on and off and the sensitivity is betterI built the little Elecraft generator a few minutes ago that I had been putting off for months :) The new K2 shows SO-9 in the 50 micro position and the old one does too... AGC threshold voltage is only 3.30v now though, but everything seems to be working fine... I guess that won't be a problem.. thanks again Tim Nz8J - Original Message - From: "NZ8J" <[EMAIL PROTECTED]> To: Sent: Monday, July 25, 2005 12:57 PM Subject: [Elecraft] AGC Threshold voltage? > The overall receiver gain of the K2 I just built (serial number 4993) seems > low as compared with my older serial number 315 K2. > > The max AGC threshold voltage I can get is 3.82 volts. (3.8 is what is > called for in alignment and Test Part I), but the troubleshooting section > says you can increase the voltage to increase the overall no-signal IF gain > and that a typical setting might be 3.9 volts. Mine is maxed out at 3.8... > does this sound correct? > > Thanks > Tim > Nz8J > > > ___ > 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] AGC Threshold voltage?
The max on K2 #4090 was 3.78V, too. I moved on and didn't worry about it. The radio works great! If it was more than .5V difference, I probably would have been more concerned. 73 de Larry W2LJ ___ 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 Threshold voltage?
Tim, Actually that troubleshooting section of the manual is incorrect - the gain of the receiver will increase if you DECREASE the AGC THRESHOLD voltage. The really optimized voltage for the AGC Threshold is the highest voltage that shows no change in internal noise (no antenna connected) when changing from AGC On to AGC Off (press AGC and PRE/ATT buttons together to toggle AGC on/off). I normally find that a setting in the range of 3.7 to 3.8 volts will be the optimum point, but it will vary from K2 to K2. Try monitoring the voltage at Control Board U2 pin 5 to convince yourself that a lower voltage will result in higher gain. The max voltage that one can find at U2 pin 5 will be determined by the actual voltage on the 8A line - it will be a bit less than half that voltage - and is not really an indication of any problem. The 8A voltage can vary from 7.6 volts to 8.4 volts and the regulator will still be in spec (and OK for use in the K2). 73, Don W3FPR > -Original Message- > > The overall receiver gain of the K2 I just built (serial number > 4993) seems > low as compared with my older serial number 315 K2. > > The max AGC threshold voltage I can get is 3.82 volts. (3.8 is what is > called for in alignment and Test Part I), but the troubleshooting section > says you can increase the voltage to increase the overall > no-signal IF gain > and that a typical setting might be 3.9 volts. Mine is maxed out > at 3.8... > does this sound correct? > > Thanks > Tim > Nz8J > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.338 / Virus Database: 267.9.4/57 - Release Date: 7/22/2005 ___ 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 Threshold voltage?
Hello Tim, I had the same experience. Mine was max 3.78V but it seems nothing to worry about. I do agree that the given figures and the real ones don't give the right feeling. I was worried as well. It would haven been "better" to have the real figures somewhere midway the lower and maximum limits to give a proper feeling of being normal. Evert, PA2KW K2 #4836 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of NZ8J Sent: 25 July 2005 18:58 To: elecraft@mailman.qth.net Subject: [Elecraft] AGC Threshold voltage? The overall receiver gain of the K2 I just built (serial number 4993) seems low as compared with my older serial number 315 K2. The max AGC threshold voltage I can get is 3.82 volts. (3.8 is what is called for in alignment and Test Part I), but the troubleshooting section says you can increase the voltage to increase the overall no-signal IF gain and that a typical setting might be 3.9 volts. Mine is maxed out at 3.8... does this sound correct? Thanks Tim Nz8J ___ 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 Threshold voltage?
The overall receiver gain of the K2 I just built (serial number 4993) seems low as compared with my older serial number 315 K2. The max AGC threshold voltage I can get is 3.82 volts. (3.8 is what is called for in alignment and Test Part I), but the troubleshooting section says you can increase the voltage to increase the overall no-signal IF gain and that a typical setting might be 3.9 volts. Mine is maxed out at 3.8... does this sound correct? Thanks Tim Nz8J ___ 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 Threshold Adjustment by Changing R1
In the reply to Mike, VK1KCK I said "R1 is given as 50K preset. In the world outside the USA this would indeed equate to 47K" I found that this is not quite correct as although for carbon presets and controls have changed to the same decade values as fixed resistors in Europe at least, cermet presets which most probably Elecraft will be using for R1, still retain the older values such as in this case 50K for some reason. A visual check on my K2 is that R1 when set for 3.70V at U2B-5, being the optimum AGC threshold setting for my K2, the control is not far from half rotation, i.e. about 25K ohms. Working out the maths for the various resistors in series and parallel, including the RF gain control to form the potential divider from the 8A rail comes out fairly close to this voltage. The preset R1 is as shown in the K2 Control Board schematic, maximum resistance for fully CCW. Bob, G3VVT K2 #4168 ___ 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 Threshold Adjustment by Changing R1
Hi Bob, I have an A model K2, so R1 was originally installed as a 51K. I removed it and put in a variable and determined on a quiet band, subjectively by ear, where noise with AGC on and off seemed the same. I got different readings each time I did the test, but a mid 40k reading seemed to occur the most often so I went with that. Now trying to see what others got as I'm still not 100% confident. Mike VK1KCK K2 #2599 _ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Thursday, 6 January 2005 9:45 PM To: [EMAIL PROTECTED] Subject: Re: [Elecraft] AGC Threshold Adjustment by Changing R1 Hi Mike, In the latest revision of the K2 manual version F, 29 January 2004, R1 is given as 50K preset. In the world outside the USA this would indeed equate to 47K. The preset has one end strapped to the wiper so would be a continuously variable resistor from in your case 47K down to zero which is in series with the 5.1K in RP6. The preset apparently normally comes out at somewhere near half rotation or in other words about 23 to 25K. Believe the earlier versions of the K2 had a fixed resistor for R1 selected on test (SOT). Not sure of the start value used, though there seemed to be less emphasis on the adjustment then to what is current now to ensure AGC is fully off with no signal. Seems to have been a few reports recently with the resistor at one end though they did not quote which end to know the value. Regards, Bob, G3VVT K2 #4168 ___ 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 Threshold Adjustment by Changing R1
Hi, In following the changes in the A to B mod instructions for adjusting R1 to fix AGC threshold I ended up reducing R1 to 47K. Is this typical of other K2 user experience? Mike VK1KCK K2 #2599 ___ 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 Threshold question - K2
Neil, Yes you apparently have something wrong. The voltage measurement comes from a purely resistive network fed by 8 volts, and there is not much to troubleshooting it - that is if you can manage to probe the pins of R-Pak RP6. With the RF gain in the full clockwise setting, you should read close to 0 volts on pin 6 of RP6 - and you should find 8 volts from the power source on pin 3 (of RP6). The voltage at pins 4 and 5 should be at the same voltage as pin 5 of U6, and the voltage should be adjustable by changing R1. The voltage on pin 7 of RP1 will depend on the setting of R1. Check out the schematic of the Control Board - look in the AGC section in the lower left corner to see how these resistors are connected. If you find a voltage that is unusual, first check the soldering, and next be certain RP6 is the 5.1k package (the numbers 512 should appear in the labeling). If the voltage on pin 3 of RP6 is much lower than 8 volts, the 8 volt regulator (U4) may be the problem. However, the last person I helped who had a reading similar to yours did not have the probe on pin 5 of U6. Pin 5 is the topmost pin and toward the side panel. 73, Don W3FPR - Original Message - > I am just at the first alignment and test stage of my K2. Everything checked out just fine except the step where I am to adjust R1 on the control board for 3.80 v on pin 5 of U2. The highest I can get the voltage to go is 3.38v. Is this something to worry about? If so, any clues? ___ 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 Threshold question - K2
Hi, I am just at the first alignment and test stage of my K2. Everything checked out just fine except the step where I am to adjust R1 on the control board for 3.80 v on pin 5 of U2. The highest I can get the voltage to go is 3.38v. Is this something to worry about? If so, any clues? Thanks Neal - k3nc ___ 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
