Re: Re: [Elecraft] K2 - signal loss in band-pass filter
My 8V is as low as yours Kristinn but I do not have the same problem. This leads me to think that you have another problem... In fact, I am quite sure - especially since you're not able to see all LED's with RF-Gain nor signal input. Have you EVER seen the LED's on the far right lit? I would check the soldering around the LED array. Are - LB3SA TF3KX wrote: Well, I agree that the basic receiving performance of the rig may not be significantly affected, or even noticed at all. But in my case I am not able to set the range of the S-meter properly, which I attribute to the low 8V level. My S-meter can not be adjusted to turn all LEDs off when no signal is present, and I do not get the S-meter quite up to full scale when the RF gain is turned fully CCW. If I am correct, this is due to the low 8V and that would be an incentive to get that voltage fixed. -- View this message in context: http://www.nabble.com/K2---signal-loss-in-band-pass-filter-tp17294418p17691603.html Sent from the Elecraft mailing list archive at Nabble.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: Re: [Elecraft] K2 - signal loss in band-pass filter
Are LB3SA wrote: But if you have a hard time getting the ALC voltage up to 3.8 volt according This voltage is related to AGC, not ALC. to the manual you can solder a 10K resistor across RP6 pins 3-4 on the My impression is that people worry too much about this. With all components exactly on value this voltage is only achievable with R1 at the end stop (I can't remember if it is just achievable or just not achievable). What really matters is whether or not you can get a sensible AGC threshold within the control range of R1, which you can only do once you have the whole receiver. control board (Gary from Elecraft suggested this for me). This works great and I now see 3.8V but it doesn't really make much of an audible difference. -- David Woolley The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio List Guidelines http://www.elecraft.com/elecraft_list_guidelines.htm ___ 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: Re: [Elecraft] K2 - signal loss in band-pass filter
Well, I agree that the basic receiving performance of the rig may not be significantly affected, or even noticed at all. But in my case I am not able to set the range of the S-meter properly, which I attribute to the low 8V level. My S-meter can not be adjusted to turn all LEDs off when no signal is present, and I do not get the S-meter quite up to full scale when the RF gain is turned fully CCW. If I am correct, this is due to the low 8V and that would be an incentive to get that voltage fixed. 73 - Kristinn, TF3KX David Woolley (E.L) wrote: Are LB3SA wrote: But if you have a hard time getting the ALC voltage up to 3.8 volt according This voltage is related to AGC, not ALC. to the manual you can solder a 10K resistor across RP6 pins 3-4 on the My impression is that people worry too much about this. With all components exactly on value this voltage is only achievable with R1 at the end stop (I can't remember if it is just achievable or just not achievable). What really matters is whether or not you can get a sensible AGC threshold within the control range of R1, which you can only do once you have the whole receiver. control board (Gary from Elecraft suggested this for me). This works great and I now see 3.8V but it doesn't really make much of an audible difference. -- David Woolley The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio List Guidelines http://www.elecraft.com/elecraft_list_guidelines.htm ___ 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 -- View this message in context: http://www.nabble.com/K2---signal-loss-in-band-pass-filter-tp17294418p17682216.html Sent from the Elecraft mailing list archive at Nabble.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] K2 - signal loss in band-pass filter
Thanks for the input Dave. It sounds like a good solution. But I'm curious: Why does lifting the ground leg of the regulator and 'inserting' a diode in series compromise the regulator's short circuit protection? Does it require a direct connection to ground? David Lankshear wrote: Of course, this jacking up compromises the regulator's inbuilt short circuit protection *snip* -- View this message in context: http://www.nabble.com/K2---signal-loss-in-band-pass-filter-tp17294418p17640033.html Sent from the Elecraft mailing list archive at Nabble.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] K2 - signal loss in band-pass filter
Thanks for the input Dave. It sounds like a good solution. But I'm curious: Why does lifting the ground leg of the regulator and 'inserting' a diode in series compromise the regulator's short circuit protection? Does it require a direct connection to ground? David Lankshear wrote: Of course, this jacking up compromises the regulator's inbuilt short circuit protection *snip* -- View this message in context: http://www.nabble.com/K2---signal-loss-in-band-pass-filter-tp17294418p17641042.html Sent from the Elecraft mailing list archive at Nabble.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: [SPAM] [Elecraft] K2 - signal loss in band-pass filter
Dave, If you jack up the the type of 8V regulator used in the K2 by adding a diode in series with the regulators ground lead, have you found any sign of oscillation at the regulator's 8V output terminal? Also, if my memory is working properly, the regulator's ground lead is connected to its heatsink tab which would require that an insulated thermal pad be added and non-conductive (DC) hardware used for mounting the regulator. In my opinion the reverse connected diode which you mention as a protective device should always be used with these three terminal voltage regulators. FWIW the regulators made by Motorola or ST which I have purchased from Farnell in the past have always produced the correct output voltage be it 5V, 8V, 10V or 15V, both positive and negative. 73, Geoff GM4ESD David Lankshear G3TJP wrote on Tuesday, June 03, 2008 at 10:00 PM From postings on the reflector, it would seem that more than a few of K2 8v regulators are on the low side, including mine. I've just ordered a couple from a local supplier to see if they are any better, but if they are not, I will jack up the ground lead of the 8v regulator by connecting a diode in series with it - i.e. interposed between the regulator's ground lead and the ground it was connected to. A silicon diode like a 4148 (or 4001 to 4007) will effect about a 0v6 increase in output voltage and a schottky or germanium diode will give about 0v2 to 0v3 increase. Of course, this jacking up compromises the regulator's inbuilt short circuit protection but in a stable environment like the K2 it can either be accepted that it is unlikely to ever be called to work into a short circuit, or a reverse connected diode can be introduced between output and ground as protection. 73 DaveL G3TJP ___ 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 - signal loss in band-pass filter
Thanks to both for info and assistance. You were right Don about the 'weirdness' when injecting signals by C7. It turns out that the sensitivity issue was caused by a tiny solder bridge on the SMD MC1350 (IF amp) which I found by injecting a signal @ IF freq. before and after the IF Amp. The receiver is now working very nice with an IMD of -136db. The filter/BFO set-up went without a hitch and RX sounds like a million bucks with absolutely no signs of ringing with tight filtering. Are - LB3SA KX1# 1864 K2# 6498 K3: Delivery late July Don Wilhelm wrote: Are, The 'wierd' symptoms you report could be normal depending on the output characteristics of your signal generator. The capacitors C7 and C8 in the 40 meter bandpass form a voltage divider that is intended to match the high impedance of the filter parallel tuned circuits down to a lower impedance level. If a signal is arbitrary injected at the top end of C7, there can (and likely will) be more voltage developed across the filter than if the same signal voltage is injected at the junction of C7 and C8 (a similar argument applies to the other bands). Put RFC7 and W6 back in place to give the proper termination for the filter. A valid comparison is to compare the signal at the junction of C7 and C8 with the signal at the junction of C4 and C5. That would give an indication of the loss through the bandpass filter. That comparison is more easily done in transmit than receive (the filter is bi-lateral). Compare the RF voltage at the junction of D6 and D7 with the RF voltage at W6 using a transmit power level of 1 to 2 watts. If the bandpass filter is not indicating a substantial loss, then you may have some other problem in the receive path. If your bandpass filter does show a substantial loss, try re-peaking it first, and if that does not produce adequate results, then look for an impedance mismatch at the filter terminations - check R36 and R5 first for proper values and good soldering. There are many other places other than the bandpass filter that can cause weak receive. If your K2 develops full output power on all bands, then the bandpass filter is likely not the problem area. 73, Don W3FPR -- View this message in context: http://www.nabble.com/K2---signal-loss-in-band-pass-filter-tp17294418p17627350.html Sent from the Elecraft mailing list archive at Nabble.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] K2 - signal loss in band-pass filter
Just out of curiosity... Where was that solder bridge on the MC1350? Was it already on the SMD assembly when you received it, or was it something you caused by your soldering? The reason I ask is that I had a problem with my SMD MC1350, never found out what caused it, and just replaced it. If there is something there to watch out for, it may help others... 73 - Kristinn, TF3KX Are LB3SA wrote: Thanks to both for info and assistance. You were right Don about the 'weirdness' when injecting signals by C7. It turns out that the sensitivity issue was caused by a tiny solder bridge on the SMD MC1350 (IF amp) which I found by injecting a signal @ IF freq. before and after the IF Amp. The receiver is now working very nice with an IMD of -136db. The filter/BFO set-up went without a hitch and RX sounds like a million bucks with absolutely no signs of ringing with tight filtering. Are - LB3SA KX1# 1864 K2# 6498 K3: Delivery late July Don Wilhelm wrote: Are, The 'wierd' symptoms you report could be normal depending on the output characteristics of your signal generator. The capacitors C7 and C8 in the 40 meter bandpass form a voltage divider that is intended to match the high impedance of the filter parallel tuned circuits down to a lower impedance level. If a signal is arbitrary injected at the top end of C7, there can (and likely will) be more voltage developed across the filter than if the same signal voltage is injected at the junction of C7 and C8 (a similar argument applies to the other bands). Put RFC7 and W6 back in place to give the proper termination for the filter. A valid comparison is to compare the signal at the junction of C7 and C8 with the signal at the junction of C4 and C5. That would give an indication of the loss through the bandpass filter. That comparison is more easily done in transmit than receive (the filter is bi-lateral). Compare the RF voltage at the junction of D6 and D7 with the RF voltage at W6 using a transmit power level of 1 to 2 watts. If the bandpass filter is not indicating a substantial loss, then you may have some other problem in the receive path. If your bandpass filter does show a substantial loss, try re-peaking it first, and if that does not produce adequate results, then look for an impedance mismatch at the filter terminations - check R36 and R5 first for proper values and good soldering. There are many other places other than the bandpass filter that can cause weak receive. If your K2 develops full output power on all bands, then the bandpass filter is likely not the problem area. 73, Don W3FPR -- View this message in context: http://www.nabble.com/K2---signal-loss-in-band-pass-filter-tp17294418p17627941.html Sent from the Elecraft mailing list archive at Nabble.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] K2 - signal loss in band-pass filter
It was actually one of your earlier posts (thanks!) that prompted me to inject the IF signal before and after the IF Amp. At that point I had pulled out lot of hair and lost sleep over a low sensitivity K2. As to when the solder bridge got there... I'm not 100% certain that a bridge was the problem. But after I realized that the IF Amp was not amplifying I went over the solder points around the chip (I actually removed the chip and installed it again). The radio then started to work. It was actually a bit of a surprise since I never saw the problem - especially since I looked very closely at all the points through an amplifying glass many times before AND since all the voltages at MC1350 measured at specs while I had the problem. It was just the IF signal that wasn't amplifying leading me to at first think that the chip itself was defect. I only assume it was a solder bridge. And if that's the case it was probably made by me. Are - LB3SA TF3KX wrote: Just out of curiosity... Where was that solder bridge on the MC1350? Was it already on the SMD assembly when you received it, or was it something you caused by your soldering? The reason I ask is that I had a problem with my SMD MC1350, never found out what caused it, and just replaced it. If there is something there to watch out for, it may help others... 73 - Kristinn, TF3KX -- View this message in context: http://www.nabble.com/K2---signal-loss-in-band-pass-filter-tp17294418p17628522.html Sent from the Elecraft mailing list archive at Nabble.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] K2 - signal loss in band-pass filter
Are, Et Al, JAT: It could be that the act of removing/reseating the MC1350 fixed the problem. Sometimes sockets don't! Regards, kurtt Kurt Pawlikowski, AKA WB9FMC The Pinrod Corporation [EMAIL PROTECTED] (773) 284-9500 http://pinrod.com Are LB3SA wrote: It was actually one of your earlier posts (thanks!) that prompted me to inject the IF signal before and after the IF Amp. At that point I had pulled out lot of hair and lost sleep over a low sensitivity K2. As to when the solder bridge got there... I'm not 100% certain that a bridge was the problem. But after I realized that the IF Amp was not amplifying I went over the solder points around the chip (I actually removed the chip and installed it again). The radio then started to work. It was actually a bit of a surprise since I never saw the problem - especially since I looked very closely at all the points through an amplifying glass many times before AND since all the voltages at MC1350 measured at specs while I had the problem. It was just the IF signal that wasn't amplifying leading me to at first think that the chip itself was defect. I only assume it was a solder bridge. And if that's the case it was probably made by me. Are - LB3SA TF3KX wrote: Just out of curiosity... Where was that solder bridge on the MC1350? Was it already on the SMD assembly when you received it, or was it something you caused by your soldering? The reason I ask is that I had a problem with my SMD MC1350, never found out what caused it, and just replaced it. If there is something there to watch out for, it may help others... 73 - Kristinn, TF3KX ___ 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 - signal loss in band-pass filter
Interesting. In my case I never resolved if the MC1350 actually was bad. I soldered the entire assembly out of the circuit, but managed to find an original full size chip at a local store, put it in and it simply worked. So, the problem - whatever it really was - might have been the same as yours, and the SMD assembly might have worked if I had put it back into the rig the second time. At any rate, good that you are on track, and hope others may learn from this. My K2 (#6425) is working perfectly, aside from the fact that my 8V is low (about 7,56V), and as a result the S-meter can not be calibrated properly. I will ask Elecraft to send me a new regulator. 73 and good luck! - Kristinn, TF3KX Are LB3SA wrote: It was actually one of your earlier posts (thanks!) that prompted me to inject the IF signal before and after the IF Amp. At that point I had pulled out lot of hair and lost sleep over a low sensitivity K2. As to when the solder bridge got there... I'm not 100% certain that a bridge was the problem. But after I realized that the IF Amp was not amplifying I went over the solder points around the chip (I actually removed the chip and installed it again). The radio then started to work. It was actually a bit of a surprise since I never saw the problem - especially since I looked very closely at all the points through an amplifying glass many times before AND since all the voltages at MC1350 measured at specs while I had the problem. It was just the IF signal that wasn't amplifying leading me to at first think that the chip itself was defect. I only assume it was a solder bridge. And if that's the case it was probably made by me. Are - LB3SA TF3KX wrote: Just out of curiosity... Where was that solder bridge on the MC1350? Was it already on the SMD assembly when you received it, or was it something you caused by your soldering? The reason I ask is that I had a problem with my SMD MC1350, never found out what caused it, and just replaced it. If there is something there to watch out for, it may help others... 73 - Kristinn, TF3KX -- View this message in context: http://www.nabble.com/K2---signal-loss-in-band-pass-filter-tp17294418p17630518.html Sent from the Elecraft mailing list archive at Nabble.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] K2 - signal loss in band-pass filter
My 8 volt regulator also outputs exactly 7.56V. I replaced it with one I bought here in Norway last week. It's also quite low at 7.62 volt. Specs guarantee it to be over 7.5V if I remember correctly so I guess we can't complain too much. But if you have a hard time getting the ALC voltage up to 3.8 volt according to the manual you can solder a 10K resistor across RP6 pins 3-4 on the control board (Gary from Elecraft suggested this for me). This works great and I now see 3.8V but it doesn't really make much of an audible difference. Are - LB3SA TF3KX wrote: In my case I never resolved if the MC1350 actually was bad. I soldered the entire assembly out of the circuit, but managed to find an original full size chip at a local store, put it in and it simply worked. So, the problem - whatever it really was - might have been the same as yours, and the SMD assembly might have worked if I had put it back into the rig the second time. At any rate, good that you are on track, and hope others may learn from this. My K2 (#6425) is working perfectly, aside from the fact that my 8V is low (about 7,56V), and as a result the S-meter can not be calibrated properly. I will ask Elecraft to send me a new regulator. -- View this message in context: http://www.nabble.com/K2---signal-loss-in-band-pass-filter-tp17294418p17631255.html Sent from the Elecraft mailing list archive at Nabble.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] K2 - signal loss in band-pass filter
From postings on the reflector, it would seem that more than a few of K2 8v regulators are on the low side, including mine. I've just ordered a couple from a local supplier to see if they are any better, but if they are not, I will jack up the ground lead of the 8v regulator by connecting a diode in series with it - i.e. interposed between the regulator's ground lead and the ground it was connected to. A silicon diode like a 4148 (or 4001 to 4007) will effect about a 0v6 increase in output voltage and a schottky or germanium diode will give about 0v2 to 0v3 increase. Of course, this jacking up compromises the regulator's inbuilt short circuit protection but in a stable environment like the K2 it can either be accepted that it is unlikely to ever be called to work into a short circuit, or a reverse connected diode can be introduced between output and ground as protection. 73 DaveL G3TJP ___ 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] K2 - signal loss in band-pass filter
I recently completed my K2 and everything seemed to work OK. All tests are ok with exception of a slightly low 8V regulator output (7.59V). The sensitivity seems low however (my KX1 is much better at this point). Tracing the receiver revealed that sensitivity is top notch at certain points. This is where it gets weird... When I inject a signal on the north side (according to schematic) of C7 (40m), C15 (80M), C24 (20M) and the same on all other bands, the sensitivity is great. But when I inject the signal on the other side of these capacitors (pin 8 on the relays), the level drops (at least 20db) to the same as what it is at antenna, W6, W1,D2/D3, D3/D4 and all other points along the signal path. I removed W6 and RFC7 to isolate the problem and to see if anything in the T-R switch or Low Pass filters could pull the signal down but there is no change. I still only hear a weak signal when I inject a signal at pin7 or 8 on the respective relays. But as soon as I touch either side of C6 for 40m, L7 for 80m, C22 for 20m etc, it is as strong as it should be. I have measured all the relays for potential shorts but they seem to be fine. Any ideas out there? 73, Are - LB3SA -- View this message in context: http://www.nabble.com/K2---signal-loss-in-band-pass-filter-tp17294418p17294418.html Sent from the Elecraft mailing list archive at Nabble.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] K2 - signal loss in band-pass filter
Are, Do you have anything attached to J13 (Xverter Interface)? If not a resistance measurement between pin 7 of one of the relays K1, K2 etc and ground with the K2 switched OFF, and W6 removed, should read a very high value, I would expect 1 Megohm. There is also the remote possibility that one of the relays is stuck with its pin 7 connected to its pin 8, something which could be checked with a resistance measurement with the K2 turned off. 73, Geoff GM4ESD Are, LB3SA, wrote on Saturday, May 17, 2008 6:44 PM I recently completed my K2 and everything seemed to work OK. All tests are ok with exception of a slightly low 8V regulator output (7.59V). The sensitivity seems low however (my KX1 is much better at this point). Tracing the receiver revealed that sensitivity is top notch at certain points. This is where it gets weird... When I inject a signal on the north side (according to schematic) of C7 (40m), C15 (80M), C24 (20M) and the same on all other bands, the sensitivity is great. But when I inject the signal on the other side of these capacitors (pin 8 on the relays), the level drops (at least 20db) to the same as what it is at antenna, W6, W1,D2/D3, D3/D4 and all other points along the signal path. I removed W6 and RFC7 to isolate the problem and to see if anything in the T-R switch or Low Pass filters could pull the signal down but there is no change. I still only hear a weak signal when I inject a signal at pin7 or 8 on the respective relays. But as soon as I touch either side of C6 for 40m, L7 for 80m, C22 for 20m etc, it is as strong as it should be. I have measured all the relays for potential shorts but they seem to be fine. Any ideas out there? 73, Are - LB3SA ___ 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 - signal loss in band-pass filter
Are, The 'wierd' symptoms you report could be normal depending on the output characteristics of your signal generator. The capacitors C7 and C8 in the 40 meter bandpass form a voltage divider that is intended to match the high impedance of the filter parallel tuned circuits down to a lower impedance level. If a signal is arbitrary injected at the top end of C7, there can (and likely will) be more voltage developed across the filter than if the same signal voltage is injected at the junction of C7 and C8 (a similar argument applies to the other bands). Put RFC7 and W6 back in place to give the proper termination for the filter. A valid comparison is to compare the signal at the junction of C7 and C8 with the signal at the junction of C4 and C5. That would give an indication of the loss through the bandpass filter. That comparison is more easily done in transmit than receive (the filter is bi-lateral). Compare the RF voltage at the junction of D6 and D7 with the RF voltage at W6 using a transmit power level of 1 to 2 watts. If the bandpass filter is not indicating a substantial loss, then you may have some other problem in the receive path. If your bandpass filter does show a substantial loss, try re-peaking it first, and if that does not produce adequate results, then look for an impedance mismatch at the filter terminations - check R36 and R5 first for proper values and good soldering. There are many other places other than the bandpass filter that can cause weak receive. If your K2 develops full output power on all bands, then the bandpass filter is likely not the problem area. 73, Don W3FPR Are LB3SA wrote: I recently completed my K2 and everything seemed to work OK. All tests are ok with exception of a slightly low 8V regulator output (7.59V). The sensitivity seems low however (my KX1 is much better at this point). Tracing the receiver revealed that sensitivity is top notch at certain points. This is where it gets weird... When I inject a signal on the north side (according to schematic) of C7 (40m), C15 (80M), C24 (20M) and the same on all other bands, the sensitivity is great. But when I inject the signal on the other side of these capacitors (pin 8 on the relays), the level drops (at least 20db) to the same as what it is at antenna, W6, W1,D2/D3, D3/D4 and all other points along the signal path. ___ 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
