TX Test Mode garbage
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I have observed this since receiving my K3s shortly after its
introduction. Even though I was told on the telephone that it was not possible, I sent in the K3s to have it analyzed and to have another PA issue resolved. I later received an email confirming the issue stating that there is some leakage and that it was on their list for a fix. That was two years ago. Yes, the K3s does put out power during this clicking and it has been observed by operators who live close by. Power and SWR are noted on a digital power meter. 73, Dan ------------------------------------------------------------------------ I received an email from a German ham telling me that he's observing the same thing that I reported a couple of years ago. Specifically an audible "clicking" sound in both my K3S and KPA500 that coincides with CW keying. See this thread: http://elecraft.365791.n2.nabble.com/KPA500-clicking-td7596512.html Since there was no "fix" from Elecraft I guess time dulled my sensitivity to it until I received the email and then I thought to listen for it again. It's thunderstorm season here in the AZ desert so my antenna cables are all disconnected. Because the problem manifests whether or not RF is being generated I put the K3S into TX Test mode and put the KPA500 into operate. As before, the clicking is still there in both the K3S and KPA500. But while doing this I noted that the SWR LEDs on the KAT500 were flashing. Since the antennas are disconnected this would be normal if RF was being generated, however as stated, I'm in Test mode. One of my tuner ports has a dummy load attached so I switched to it and lo and behold the amp output LED was showing ~50W. I have an original K3 so I tuned it to the K3S frequency, keyed the K3S and listened on the K3. I could hear a non-coherent, clicky "garbage" signal that seemed to have a spectrum roughly the width of the TX filter. Because both radios were running on the same power supply to eliminate the possibility of crosstalk via that path I fired up an SDR-IQ running on a totally separate computer and looked at the spectrum. Although it's non-synchronous to the keying I can see a signal that does have an envelope roughly shaped like a BPF although it's far from flat in the passband. The amplitude of this is affected by the output power setting and is present with the KPA500 in Standby. It also seems to be thermally sensitive; becoming less conspicuous the longer things run. Wes N7WS . ______________________________________________________________ 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 Message delivered to [hidden email] |
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Out of curiosity I just checked this with my K3S and found the same oddity. During CW key down into a dummy load in TX Test mode the K3S draws 2.5 amps from the 1 amp in RX, and the hash signal heard in another receiver into a different dummy load appears to be 2.7Khz wide. Starts out as full scale signal in the receiver and drops quickly to S5 but never goes away during key down. Cant detect any power indication on the dummy load power meter during key down. Maybe a pre driver stage getting bias in TEST MODE?
Interesting... Gene N9TF > On July 26, 2017 at 9:03 AM Dan Atchison via Elecraft <[hidden email]> wrote: > Yes, the K3s does put out power during this clicking and it has been > observed by operators who live close by. Power and SWR are noted on a > digital power meter. > > 73, > Dan > ______________________________________________________________ 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 Message delivered to [hidden email] |
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Thanks for confirming, Gene. Dan's message did not come through on my service.
But it's not the clicking that develops the power. Key down does it. Wes N7WS ps. Olaf, if you are reading, your direct email bounces. Perhaps that is why the Elecraft reflector rejects your posts. On 7/26/2017 8:00 PM, EUGENE GABRY wrote: > Out of curiosity I just checked this with my K3S and found the same oddity. During CW key down into a dummy load in TX Test mode the K3S draws 2.5 amps from the 1 amp in RX, and the hash signal heard in another receiver into a different dummy load appears to be 2.7Khz wide. Starts out as full scale signal in the receiver and drops quickly to S5 but never goes away during key down. Cant detect any power indication on the dummy load power meter during key down. Maybe a pre driver stage getting bias in TEST MODE? > Interesting... > > Gene > N9TF > >> On July 26, 2017 at 9:03 AM Dan Atchison via Elecraft <[hidden email]> wrote: >> Yes, the K3s does put out power during this clicking and it has been >> observed by operators who live close by. Power and SWR are noted on a >> digital power meter. >> >> 73, >> Dan >> > ______________________________________________________________ > 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 > Message delivered to [hidden email] > ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by EUGENE GABRY
Hi Dan,
I see exactly the same thing, although, on my analog watt meter, even running dits continuously, I don't see any movement of the needle. Must be micro watts leaking in extremely fast/short duration. I guess I would have thought precautions for clamping down in the TX chain, prior to antenna coupling, would have been implemented, so no RF leaking could occur. I'm even more curious now to find out what all is engaging during key down in test mode to be drawing an additional 1.5 amps. I'm assuming it should only be circuitry to engage cw keyer and side tone in test mode, but obviously a path in the TX chain is activating that maybe should not, allowing leak through. Guess I'll pop this thing open for the first time an do some tracing :) I've added our thread back to the reflector, as I don't think this should be a normal operating function. If the intent of a test mode is to test without actually emitting a signal, then this oddity of RF leaking is not acceptable. 73 Gene, N9TF > On July 27, 2017 at 6:49 AM Dan Atchison <[hidden email]> wrote: > > I think that is normal, Gene, as all the oscillators in the TX chain are working. What I and others are seeing is short spikes of power when doing CW in TX mode. > > Try this: Hook up your K3s to a dummy load through a digital wattmeter and send a long string of dots. You will eventually see power out - enough power to show SWR. The resultant signal is heard as key clicks and can be heard as key clicks (with no CW "tone") miles away. It's a very short duration signal (only microseconds of an entire dit) and is only heard as clicks. Note, you can only "see" the issue with a good instantaneous reading digital wattmeter because of the short duration. I measure several watts of this intermittent click. > > 73 > Dan > > > > > > On 7/26/2017 11:00 PM, EUGENE GABRY wrote: > > > > > > Out of curiosity I just checked this with my K3S and found the same oddity. During CW key down into a dummy load in TX Test mode the K3S draws 2.5 amps from the 1 amp in RX, and the hash signal heard in another receiver into a different dummy load appears to be 2.7Khz wide. Starts out as full scale signal in the receiver and drops quickly to S5 but never goes away during key down. Cant detect any power indication on the dummy load power meter during key down. Maybe a pre driver stage getting bias in TEST MODE? > > Interesting... > > > > Gene > > N9TF > > > > > > > > > > > > On July 26, 2017 at 9:03 AM Dan Atchison via Elecraft <[hidden email]> mailto:[hidden email] wrote: > > > > > > > > > > > > > > > > > > > > Yes, the K3s does put out power during this clicking and it has been > > > observed by operators who live close by. Power and SWR are noted on a > > > digital power meter. > > > > > > 73, > > > Dan > > > > > > > > > > > > > > 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 Message delivered to [hidden email] |
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You guys should go back to the first message in this thread and reread it.
This is not a key click situation. It is band-limited noise and can be heard in XMIT, no need for keying. I believe it is thermally sensitive; worse right after powering up the radio and diminishing with warm up. On 50 MHz. I can see over 50W indicated on the KPA500 bar graph. Wes N7WS On 7/27/2017 5:38 AM, EUGENE GABRY wrote: > Hi Dan, > > > I see exactly the same thing, although, on my analog watt meter, even running dits continuously, I don't see any movement of the needle. Must be micro watts leaking in extremely fast/short duration. I guess I would have thought precautions for clamping down in the TX chain, prior to antenna coupling, would have been implemented, so no RF leaking could occur. > > I'm even more curious now to find out what all is engaging during key down in test mode to be drawing an additional 1.5 amps. I'm assuming it should only be circuitry to engage cw keyer and side tone in test mode, but obviously a path in the TX chain is activating that maybe should not, allowing leak through. > > Guess I'll pop this thing open for the first time an do some tracing :) > > > I've added our thread back to the reflector, as I don't think this should be a normal operating function. If the intent of a test mode is to test without actually emitting a signal, then this oddity of RF leaking is not acceptable. > > > 73 Gene, N9TF > >> On July 27, 2017 at 6:49 AM Dan Atchison <[hidden email]> wrote: >> >> I think that is normal, Gene, as all the oscillators in the TX chain are working. What I and others are seeing is short spikes of power when doing CW in TX mode. >> >> Try this: Hook up your K3s to a dummy load through a digital wattmeter and send a long string of dots. You will eventually see power out - enough power to show SWR. The resultant signal is heard as key clicks and can be heard as key clicks (with no CW "tone") miles away. It's a very short duration signal (only microseconds of an entire dit) and is only heard as clicks. Note, you can only "see" the issue with a good instantaneous reading digital wattmeter because of the short duration. I measure several watts of this intermittent click. >> >> 73 >> Dan >> >> >> >> >> >> On 7/26/2017 11:00 PM, EUGENE GABRY wrote: >> >> > > >>> Out of curiosity I just checked this with my K3S and found the same oddity. During CW key down into a dummy load in TX Test mode the K3S draws 2.5 amps from the 1 amp in RX, and the hash signal heard in another receiver into a different dummy load appears to be 2.7Khz wide. Starts out as full scale signal in the receiver and drops quickly to S5 but never goes away during key down. Cant detect any power indication on the dummy load power meter during key down. Maybe a pre driver stage getting bias in TEST MODE? >>> Interesting... >>> >>> Gene >>> N9TF >>> >>> >>> > > > >>>> On July 26, 2017 at 9:03 AM Dan Atchison via Elecraft <[hidden email]> mailto:[hidden email] wrote: >>>> >>>> > > >>> >>> >>> > > > >>>> Yes, the K3s does put out power during this clicking and it has been >>>> observed by operators who live close by. Power and SWR are noted on a >>>> digital power meter. >>>> >>>> 73, >>>> Dan >>>> >>>> >>>> > > >>> > ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by EUGENE GABRY
Hasn't anyone done any real measurements of this phenomenon? Just
because it is heard doesn't make it bad or in violation of the FCC Spectral Purity of Emissions. And it is generally reported to be 2.7 kHz wide, i.e. the same as the SSB filter. In measuring my K3S, s/n 10163, the worst case is - 42 dBm at the test frequency. I did check several bands and found the same result. In all cases, it is evident the low pass transmit filter is doing its job as there is more TX noise below the transmit frequency than above. My measurement indicates the noise is in the -60 dBm to -70 dBm range, depending on band. There are some other emissions which are -85 dBm {~15.9 MHz} and -91 dBm {~31.9MHz}. These are seen within a span of 1..0 MHz to 50 MHz on the HP spectrum analyzer, connected directly to the output of the transceiver, ANT 1 port. The K3S is in CW mode, Test Mode, keyed with a straight key. As to seeing power on an external device, at these levels, it likely won't be observed. Further I observe when the PWR is reduced to zero watts, the emissions do not change except at the point when the KPA switches out {~ <12 watts} , there is about a 10 dB decrease as expected. All in all, I'd say the radio is quite clean with regard to my measurements and spectral purity. 73 Bob, K4TAX On 7/26/2017 10:00 PM, EUGENE GABRY wrote: > Out of curiosity I just checked this with my K3S and found the same oddity. During CW key down into a dummy load in TX Test mode the K3S draws 2.5 amps from the 1 amp in RX, and the hash signal heard in another receiver into a different dummy load appears to be 2.7Khz wide. Starts out as full scale signal in the receiver and drops quickly to S5 but never goes away during key down. Cant detect any power indication on the dummy load power meter during key down. Maybe a pre driver stage getting bias in TEST MODE? > Interesting... > > Gene > N9TF > ______________________________________________________________ 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 Message delivered to [hidden email] |
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