[Elecraft] K3 #8862 unwanted sidebands
Elecrafters, i have 2 K3's, #8862 and #2878. Listeners using Panorama adapter gear like P3 or sdr radios report unwanted strong sidebands when #8862 i bought from a friend is in use. All is fine when #2878 is in use with same settings, power, external amp, antenna and same mic. The signal itself inside the ~3khz passband is fine, both K3's sound about the same , all ok. One listener said, the problem vanishes, when power is below 12W (only low power stage in use). I build a K2 (#2706) and the K3 #2878 myself, so i'm not scared to take #8862 apart to find the cause. Where to begin? TNX. -- 73, Martin __ 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
[Elecraft] K3 #8862 unwanted sidebands
Elecraft sells a 2T-Generator for those who want to check IMD performance of other rigs: https://elecraft.com/collections/2t-gen-model John AE5X https://ae5x.blogspot.com -- >The K3 has a built-in two-tone generator. I've done 100s of two-tone IMD tests >on my K3 and K3S using them and an SDR-IQ as a spectrum analyzer. __ 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] K3 #8862 unwanted sidebands
I may have had the same issue as you. Elecraft instructed me to listen to my SSB signal via the monitor, start at 10watts and as you speak start increasing the power. When you reach 12-15 watts I bet you will hear your audio become distorted, sounds sort of like RF on your audio. If not then you have a different issue. You may want to try that test. For me it require a trip to the factory for repair. Rich On 11/15/2022 8:27 AM, Martin Schmiedel wrote: Elecrafters, i have 2 K3's, #8862 and #2878. Listeners using Panorama adapter gear like P3 or sdr radios report unwanted strong sidebands when #8862 i bought from a friend is in use. All is fine when #2878 is in use with same settings, power, external amp, antenna and same mic. The signal itself inside the ~3khz passband is fine, both K3's sound about the same , all ok. One listener said, the problem vanishes, when power is below 12W (only low power stage in use). I build a K2 (#2706) and the K3 #2878 myself, so i'm not scared to take #8862 apart to find the cause. Where to begin? TNX. -- 73, Martin __ 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 rwnewbo...@comcast.net __ 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] K3 #8862 unwanted sidebands
Hi Martin, Do you observe (or hear) sidebands outside the nominal transmitted bandwidth with CW transmissions or only SSB transmissions? Can you perform a 2-tone test with an audio source other than speech? The fact that the unwanted sidebands are not observed when the KPA3 100 watt amplifier is bypassed suggests a possible change in the bias point of the PA transistors. If you have the original BJT version of the KPA3, not the LDMOS version of the KPA3A, perhaps you can measure the base or collector bias current when the KPA3 is engaged (PWR control set at 12 watts or above) with no audio modulation applied. That may be difficult to do without temporarily lifting a component lead. Perhaps Keith, WE6R from Elecraft can suggest a way of confirming proper bias point setting for the KPA3 without too much intrusion? 73, Mike, K8CN __ 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] K3 #8862 unwanted sidebands
The K3 has a built-in two-tone generator. I've done 100s of two-tone IMD tests on my K3 and K3S using them and an SDR-IQ as a spectrum analyzer. Wes N7WS. On 11/15/2022 11:37 AM, Michael Carter wrote: Hi Martin, Do you observe (or hear) sidebands outside the nominal transmitted bandwidth with CW transmissions or only SSB transmissions? Can you perform a 2-tone test with an audio source other than speech? The fact that the unwanted sidebands are not observed when the KPA3 100 watt amplifier is bypassed suggests a possible change in the bias point of the PA transistors. If you have the original BJT version of the KPA3, not the LDMOS version of the KPA3A, perhaps you can measure the base or collector bias current when the KPA3 is engaged (PWR control set at 12 watts or above) with no audio modulation applied. That may be difficult to do without temporarily lifting a component lead. Perhaps Keith, WE6R from Elecraft can suggest a way of confirming proper bias point setting for the KPA3 without too much intrusion? 73, Mike, K8CN __ 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 wes_n...@triconet.org __ 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] K3 #8862 unwanted sidebands
Thanks, Wes! As a 99.9% CW operator, I never looked into the Tech Mode options for SSB testing in my K3. That's a really useful feature! It's good to be reminded of the built-in troubleshooting utilities in the K3. 73, Mike, K8CN __ 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
