K3 Sub RF gain
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I have noticed a difference in behavior of K3 main and sub receiver RF gain
behavior. Listening to a strong signal over S9 on the main Rx as I turn down the RF gain the signal disappears around the 11:30 position. On the sub receiver the signal is still fully copyable with the RF gain full counter clockwise. 12 O'clock on the main is like full CCW on the sub Rx. Both appear full gain at the full CW position. I am operating in diversity at the moment on 40M with ATT in and preamp off, I checked both Receivers show the same. I am listening to both Rx using 2.7 KHz filters. I have performed the K3 gain calibration procedure using an XG2. I am using what I think is the latest utility version 1.3.10.15. Is it possible that others see this behavior and do you find it normal? AE6WA Mike Scott Tarzana CA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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I always experienced a significant difference when comparing main/sub signal levels.
Mike's message triggered me to search for the cause. Step 1: Changed RF/AF controls back to independent: SQ MAIN = 0; SQ SUB = 0; SUB AF = nor. No luck, the sub signal level was still much lower than main. Step 2: Filter parameters. The filter loss compensation values did not match! Forgot to enter gain values after having added more filters to the sub RX. Using the K3 Utility I copied the filter gain values from main to sub. Same bandwidth = same gain value in both main and sub. Problem solved: At identical settings (PRE, ATT, RF/AF Gain), main and sub signal lelvels are now fully identical. 73, Markus |
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In reply to this post by Mike Scott-7
I followed the procedure Markus suggested with no change to my K3 RF gain
tracking between main and sub Rx. I have been listening through the 2.7 KHz stock filter in both receivers with identical PRE and ATT and both filter gains set to 0 and identical IF filter bandwidth settings and both receivers sharing the main antenna. I have SQ MAIN = 0; SQ SUB = 0, SUB AF = nor. The offsets are matched on both filters and set properly. Still full CCW on the sub is about 12:00 O'clock on the main. At full RF gain both are about equal. Strong signals are still copyable on the sub Rx with full off RF gain, the main is dead when RF gain is minimum. So I tried an experiment, set main IF Filter (stock filter) to a maximum of +8 dB gain leaving the sub at 0. I still have more gain on the sub Rx than the main at low RF gain settings. At high gain settings, now the main is louder than the sub. So back to zero on the filter gain and very different gain tracking between the receivers. Audio gain perfectly tracks by the way. My K3 behavior is as if Wayne were reading every other RF-Sub gain control impulse and every one on Main. I received a few direct emails from other K3 users and theirs act just like mine. Markus' K3 is now the only one I have heard of that is acting like expectations. AE6WA Mike Scott Tarzana, CA >>Markus said: Problem solved: At identical settings (PRE, ATT, RF/AF Gain), main and sub signal lelvels are now fully identical. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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> I received a few direct emails from other K3 users and theirs act > just like mine. Markus' K3 is now the only one I have heard of that > is acting like expectations. Both of mine operate as expected (same RF/AF gain response for main and KRX3). Have you performed the RF Gain calibration on both of the receivers using a calibrated 50 uV signal source (e.g., XG-2)? 73, ... Joe, W4TV On 10/23/2010 3:30 PM, Mike Scott wrote: > I followed the procedure Markus suggested with no change to my K3 RF gain > tracking between main and sub Rx. > > I have been listening through the 2.7 KHz stock filter in both receivers > with identical PRE and ATT and both filter gains set to 0 and identical IF > filter bandwidth settings and both receivers sharing the main antenna. I > have SQ MAIN = 0; SQ SUB = 0, SUB AF = nor. The offsets are matched on both > filters and set properly. > > Still full CCW on the sub is about 12:00 O'clock on the main. > > At full RF gain both are about equal. Strong signals are still copyable on > the sub Rx with full off RF gain, the main is dead when RF gain is minimum. > > > > So I tried an experiment, set main IF Filter (stock filter) to a maximum of > +8 dB gain leaving the sub at 0. I still have more gain on the sub Rx than > the main at low RF gain settings. At high gain settings, now the main is > louder than the sub. So back to zero on the filter gain and very different > gain tracking between the receivers. > > Audio gain perfectly tracks by the way. > > My K3 behavior is as if Wayne were reading every other RF-Sub gain control > impulse and every one on Main. > > I received a few direct emails from other K3 users and theirs act just like > mine. Markus' K3 is now the only one I have heard of that is acting like > expectations. > > > > AE6WA > > Mike Scott > > Tarzana, CA > > > >>> Markus said: Problem solved: At identical settings (PRE, ATT, RF/AF > Gain), main and > > sub signal lelvels are now fully identical. > > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Mike Scott-7
With my XG2 as a 40m source, I observe a similar phenomenon with my K3 (SN 4181) Main/Sub RF gains, though the details are quite different. I'm running without PRE or ATT and the behavior is the same whether the BW is 2.8 kHz or 100 Hz. At max gain, both the Sub and the Main generate the same audio level in my two ears (precision instruments). And, as the gains are reduced, the audio falls off similarly such that they are both just about inaudible at the 11:00 position on their respective gain knobs. But the behavior on reducing the gain further is very different. The Sub remains inaudible all the way to full CCW. However, by about 10:00 on the Main gain, the response goes through a non-linearity where the audio jumps up to a level similar to about 3:00 on the gain dial. Further reduction of the main gain reduces the audio again, but never to inaudibility. Interestingly, the S meter also displays this non-linear response, climbing from S7 to S9+30, as the main gain is reduced from the max, until at the 10:00 position it suddenly falls to about S8. Further reduction of the gain does not affect the S meter level. I've repeated the RF Gain Calibration several times with both the 40m and 20m XG2 signals. I have seen no change in the behavior as a result. Does anyone else see this kind of behavior?
73, Stan - KR7C
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In reply to this post by Mike Scott-7
Joe (W4TV)
Yes I have performed the gain calibration many times on both receivers using the K3 Utility with the XG2. I recently did it after loading the new K3 Utility that supposedly fixed some issue about writing receiver gains to memory. So now you make two people whose RF gain tracks. I can't begin to speculate anymore as to the difference in RF gain behavior in the two receivers. So to repeat: same antenna (to XG2), same stock filters with matched offset, same (0) filter gain, same ATT on, same PRE off, same IF filter width, same NB off, same NR off. Sub Rx gain set to minimum I can still copy signals and hear band noise, Main Rx RF gain set to minimum is dead band. This difference in RF-gain tracking makes it difficult to use reduction in RF gain as a method to manage high band noise conditions. I can't just grab both controls and move them the same, like I can with AF controls which track very well. Stan KR7R Main Rx RF gain behavior is bizarre. In the days of old potentiometers this would be explainable but not with gain controlled by firmware. Maybe a bad RF gain control with odd switch bounce behavior at some gain setting... I would try to move the RF gain knob while K3 is shut down to a new position and then turn it back on to see if the RF gain nonlinearity location changed to someplace other than 9 o'clock. AE6WA Mike Scott Tarzana, CA >>Joe W4TV said. Both of mine operate as expected (same RF/AF gain response for main and KRX3). Have you performed the RF Gain calibration on both of the receivers using a calibrated 50 uV signal source (e.g., XG-2)? ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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I assume that you are always making this test after hitting A>B two
times in quick succession. Listening to daytime 160m noise I set both RF gains to max and adjust the AF to get equal irritation levels in both speakers, I get the same 11 oclock for both RX. If I then come up from RF min to where I just barely hear the noise equally in both, I get an identical 1 oclock setting for both. But remembering that this ain't your daddy's analog radio... The RF gain calibration is only made from the MCU to the output. It determines what internal number results in what gain. It has no means currently to test the RF gain pots themselves because it does not ask you to provide full CW and full CCW as part of the calibrate. The RF gain pots are doing a linear divide on an accurate 5 volts which then goes to ADC pins on the MCU to convert to numeric advice. If the pot itself was not linear, then the numbers advising position would likewise be biased. Currently they are not running a test for linearity of the pots themselves -- it is presumed they are linear, min produces a zero numerical advice, max produces a 255 or some equivalent to that. There could be a missing SMD solder joint keeping the divide from happening properly. If the top of the resistor surface was connected and the wipe was connected, and the bottom of the resistor surface was NOT connected, this could result in that behavior, because you could never get to zero, just to pot max in series with what ever sink resistance in the ADC circuit in the MCU chip. It would have to be the ground connection on VR2REAR that was bad. If you can get at it somehow, you should be able to see the resistance on the wipe go down from 5 volts to zero if it's good. If it's not the pot... It could be that the VR2REAR ADC pin on the MCU has a bad embedded ADC connected to it. Can only fix that with a new board. This control sequence emerges on the KRX3 side of the MCU et all as VIFGAIN2. With no signal on input, taking RF gain from max to minimum should swing the voltage on the U3 side of R22 from zero to 3 volts. If you grab the schematics you may be able to find these voltages and check them out. Using VR2REAR and VIFGAIN2 will find you the schematic spots in question. Maybe this will help. 73, Guy. On Sun, Oct 24, 2010 at 2:22 PM, Mike Scott <[hidden email]> wrote: > Joe (W4TV) > > Yes I have performed the gain calibration many times on both receivers using > the K3 Utility with the XG2. I recently did it after loading the new K3 > Utility that supposedly fixed some issue about writing receiver gains to > memory. So now you make two people whose RF gain tracks. > > I can't begin to speculate anymore as to the difference in RF gain behavior > in the two receivers. So to repeat: same antenna (to XG2), same stock > filters with matched offset, same (0) filter gain, same ATT on, same PRE > off, same IF filter width, same NB off, same NR off. Sub Rx gain set to > minimum I can still copy signals and hear band noise, Main Rx RF gain set to > minimum is dead band. > > > > This difference in RF-gain tracking makes it difficult to use reduction in > RF gain as a method to manage high band noise conditions. I can't just grab > both controls and move them the same, like I can with AF controls which > track very well. > > > > Stan KR7R Main Rx RF gain behavior is bizarre. In the days of old > potentiometers this would be explainable but not with gain controlled by > firmware. Maybe a bad RF gain control with odd switch bounce behavior at > some gain setting... I would try to move the RF gain knob while K3 is shut > down to a new position and then turn it back on to see if the RF gain > nonlinearity location changed to someplace other than 9 o'clock. > > > > AE6WA > > Mike Scott > > Tarzana, CA > > > >>>Joe W4TV said. > > > > Both of mine operate as expected (same RF/AF gain response for main > > and KRX3). Have you performed the RF Gain calibration on both of > > the receivers using a calibrated 50 uV signal source (e.g., XG-2)? > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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