Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube)
Jim, your recommendation that all shack equipment uses a single source and green wire, like the high quality distribution illustrated in your PDF is spot on, thank you. I guess weather in the UK is pretty benign, although we do have our moments. I remember working in Poland; in February I was surprised to see the lightning protection. In August I understood why. Kind regards Paul G3NJV Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Jim Brown Sent: Wednesday, August 14, 2019 8:12:05 PM To: WSJT software development Subject: Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube) I would certainly hope that you would want it for your personal safety, and for the non-destruction of your home and your equipment! It also happens that proper bonding of equipment, and obtaining power for all interconnected equipment from outlets that share the same green wire, minimizes hum, buzz, and RFI. That is the focus of my advice. Another observation. The prevalence of lightning varies widely around the world, as shown on this map. Those of living in high frequency strike areas pay a lot more attention to it than do others. https://geology.com/articles/lightning-map.shtml http://lightningsafety.com/nlsi_info/lightningmaps/US_FD_Lightning.pdf http://lightningsafety.com/nlsi_info/lightningmaps/worldlightning.html 73, Jim K9YC On 8/14/2019 4:52 AM, Paul Randall wrote: > There is no requirement for lightning protection in all buildings in the > UK although there are laws which govern businesses separately. As a > result, the lightning protection in the average domestic UK home > approximates to “none at all”, ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube)
I would certainly hope that you would want it for your personal safety, and for the non-destruction of your home and your equipment! It also happens that proper bonding of equipment, and obtaining power for all interconnected equipment from outlets that share the same green wire, minimizes hum, buzz, and RFI. That is the focus of my advice. Another observation. The prevalence of lightning varies widely around the world, as shown on this map. Those of living in high frequency strike areas pay a lot more attention to it than do others. https://geology.com/articles/lightning-map.shtml http://lightningsafety.com/nlsi_info/lightningmaps/US_FD_Lightning.pdf http://lightningsafety.com/nlsi_info/lightningmaps/worldlightning.html 73, Jim K9YC On 8/14/2019 4:52 AM, Paul Randall wrote: There is no requirement for lightning protection in all buildings in the UK although there are laws which govern businesses separately. As a result, the lightning protection in the average domestic UK home approximates to “none at all”, ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube)
Jim There is no requirement for lightning protection in all buildings in the UK although there are laws which govern businesses separately. As a result, the lightning protection in the average domestic UK home approximates to “none at all”, as Douglas Adams would say. Even with the open invitation of overhead power wire, telephone wire, satellite or TV aerial, installers bring the wires direct into the property with no ground or ground bonding. Most people get away with it and insurance companies make no requirements. There are strict requirements for certification of electrical installers and installations and as a plain resident the general rule is “don’t mess with the power wiring Paul”. If I do my property may not pass the electrical inspection needed before it can be sold. This is apart from any other consequence and sadly I could find nothing in the Laws of Physics to make my trip work again if I bypass it. 73 Paul G3NJV Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Jim Brown Sent: Tuesday, August 13, 2019 9:13:18 PM To: WSJT software development Subject: Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube) Last I looked, the Laws of Physics still govern what happens when lightning strikes. We have a similar issue with common practice by wired telephone installers here in the former colonies failing to properly bond their installations. My recommendations are in line with those laws and the National Electric Code, which has been adopted by local authorities through nearly all of North America, and thus carries the force of law. If you find conflict with my recommendations, I suggest that you may not fully understand them. 73, Jim K9YC On 8/12/2019 7:26 PM, Paul Randall wrote: > The advice is written and in the UK would render you liable to > litigation in the event of an accident. That is why I say it is unwise. ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube)
Last I looked, the Laws of Physics still govern what happens when lightning strikes. We have a similar issue with common practice by wired telephone installers here in the former colonies failing to properly bond their installations. My recommendations are in line with those laws and the National Electric Code, which has been adopted by local authorities through nearly all of North America, and thus carries the force of law. If you find conflict with my recommendations, I suggest that you may not fully understand them. 73, Jim K9YC On 8/12/2019 7:26 PM, Paul Randall wrote: The advice is written and in the UK would render you liable to litigation in the event of an accident. That is why I say it is unwise. ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube)
Jim, the PDF you attached has a huge amount of information thank you. However what I see is pages of illustrations of ground loops and how to short them out with big bonding straps. Does this prove they don't exist? For me it highlights them. Perhaps I missed something important in the language? When utilities provide power to domestic premises their only concern is profit whilst complying with local safety regulations. They don't give a hoot for EMI or lightning protection. This is in contrast to the good engineering practice universally employed in professional equipment installations where all factors are taken into account and bonding reigns supreme. Giving blanket advice to retrospectively interfere with domestic AC wiring and grounding IS risky unless you are completely appraised of all the relevant regulations and codes of practice that apply in every country and locality where people may be reading your advice. You also need to be aware of the requirements for certification in every country and locality that are needed to perform such modifications legally. Jim, I thought your blanket ground bonding ideas in a domestic situation were unwise. The advice given in the PDF on “Home Power Wiring, the green wire” is clearly wrong and can be outright dangerous. Why? I checked my house wiring. All of the ground wires (green wires) in my house lead back to the switch/fuse/breaker panel where they connect to the primary safety device, a ground leakage circuit breaker, the other side of which goes to a PME bonded “ground” connection. The bonding recommended in the PDF (house ground to a "real" ground rod) bypasses this circuit breaker, rendering it inoperative and leaving the building occupants vulnerable to lethal electric shock. The advice is written and in the UK would render you liable to litigation in the event of an accident. That is why I say it is unwise. In a professional installation the requirements for electrical safety, EMI, efficient RF grounding and lightning protection do not conflict. In a domestic situation they do. There may be no blanket solutions that apply everywhere, in all circumstances, in the domestic environment. This is not about good engineering practice, it is about how to work within electrical safety regulations and get as close as possible to what is needed in a good ham station. My friend would turn up at locations all around the world, sometimes only minutes before a broadcast, armed with a battery of equipment designed to combat the hum and noise inducing ground loops he would surely encounter, without the luxury of time to re-engineer all the wiring in the vicinity. Claude, I completely agree, a desktop will be much quieter at audio and RF and of course has a very obvious ground. The setup I describe had to be airline transportable for operating as VK2/G3NJV so I must use the (Lenovo) laptop. This has neither an internal chassis or a “D” connector. The only “grounded” metalwork visible are the HDMI and USB sockets, neither of which are accessible for bonding and which, upon inspection, connect to exactly the same internal PCB ground plane as the ground in the audio socket. Bond to a USB shell or the audio pin? Difference? Three inch wide copper strip to a USB or headphone on a laptop? Let's get real. Let us not lose sight of the point of this discussion which is to try to transmit a nice clean signal without added hum and noise. In my case there was a simple solution to the problem I unexpectedly encountered with the isolated cable which was to link the gound from laptop to rig. Spectrum analyser software run on the computer can check for hum and noise on receive, asking a local ham to listen to your transmission is good on transmit. One last point, how many people remember to disable their microphone when the PC is plugged to the accessory socket running WSJT-X? Listening in the FT8 band, clearly lots of people don't. Best regards Paul G3NJV From: Jim Brown Sent: 11 August 2019 08:43 To: wsjt-devel@lists.sourceforge.net Subject: Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube) On 8/10/2019 6:09 PM, Paul Randall wrote: > Jim > > Double insulated equipment like a laptop charger doesn’t have any > physical access to a metal part that can be bonded to ground. That’s > what double insulated means. Even if the charger has a 3 pin (hot, > neutral and ground) AC connector there is little likelihood that the dc > output side is connected to the ground pin. That does not change the fact that chassis-to-chassis bonding is good engineering practice, and audio interconnects should never be depended on for bonding. One of the reasons that proper bonding is critical to solve RFI and hum/buzz issies is the Pin One Problem. See my website for a lot of detail on that, and point your broadcast engineer friend to that, an
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube)
I made a quick-connect bond for the seldom used VGA port on my laptop by dismantling a DB-9 male connector to remove the inner plastic body that holds the pins so I had just the metal shell. Hadn't thought of the USB ports. Great idea! 73 -Jim NU0C On Sun, 11 Aug 2019 00:50:16 -0700 Jim Brown wrote: > On 8/10/2019 6:09 PM, Paul Randall wrote: > > Double insulated equipment like a laptop charger doesn’t have any > > physical access to a metal part that can be bonded to ground. > > Sorry, I failed to comment on this. Most computers have DB15 connectors > for video, and the shells of these connectors should be bonded to the > chassis. Modern computers also have USB connectors, the shells of which > SHOULD be bonded to the chassis. If they are not, any shielding in the > cables doesn't work. > > 73, Jim K9YC > > > ___ > wsjt-devel mailing list > wsjt-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/wsjt-devel ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube)
On 8/10/2019 6:09 PM, Paul Randall wrote: Double insulated equipment like a laptop charger doesn’t have any physical access to a metal part that can be bonded to ground. Sorry, I failed to comment on this. Most computers have DB15 connectors for video, and the shells of these connectors should be bonded to the chassis. Modern computers also have USB connectors, the shells of which SHOULD be bonded to the chassis. If they are not, any shielding in the cables doesn't work. 73, Jim K9YC ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube)
On 8/10/2019 6:09 PM, Paul Randall wrote: Jim Double insulated equipment like a laptop charger doesn’t have any physical access to a metal part that can be bonded to ground. That’s what double insulated means. Even if the charger has a 3 pin (hot, neutral and ground) AC connector there is little likelihood that the dc output side is connected to the ground pin. That does not change the fact that chassis-to-chassis bonding is good engineering practice, and audio interconnects should never be depended on for bonding. One of the reasons that proper bonding is critical to solve RFI and hum/buzz issies is the Pin One Problem. See my website for a lot of detail on that, and point your broadcast engineer friend to that, and to AES48. In this case using the laptop for WSJT relies on the connecting wire running from the laptop to the rig to provide a ground. If that wire is deliberately built to be isolated then it CAUSES a hum problem rather than avoids one. This is counter-intuitive and so even though it has nothing to do with software development, I felt it was worth contributing to the “bad signal” discussion going on in this forum. As an aside, I think it very unwise to make a blanket statement that bonding everything together is good engineering practice. Sorry, that is a fact. Someone reading that may unwittingly bypass a safety ground leakage circuit breaker by bonding the building’s safety ground to a radio antenna ground rod. Worse, large AC currents may flow in this connection if the power utility company uses one of a number of different PME (protective multiple earth) supply systems where the building’s safety ground is actually bonded to the neutral supply wire and only to “real” ground back at the supply transformer. I suggest that you study the tutorial on grounding and bonding in the link I posted. And if that isn't sufficient, buy N0AX's recent ARRL book on Grounding and Bonding, which is largely based on by work, and which cites the link I posted to it. Finally, my friend gave a big grin when he read that “The concept of a so-called "ground loop" is completely false”. He is a professional sound and television broadcast engineer. I am a retired audio and broadcast professional, vice-chair of the EMC Working Group of the Audio Engineering Society Standards Committee, principal author of all AES Standards on EMC, and a Fellow of the AES. My first job in Broadcasting was in 1959. Your broadcast colleague might also want to look at the White Paper on the topic I was commissioned to write on the topic, as well as the slides for talks I was hired to give to audio and video contractors and national conventions. They are in the pro audio section of my website. There are, indeed, differences in the way power is distributed around the world, and the White Paper addresses those differences. "Ground Loops" are a fiction that lead us to wrong solutions to real problems. Bill Whitlock (also a Fellow of the AES, and with strong RF chops) correctly identified the real issues, and my advice is based on his model. I suggest that you study my tutorial material. 73, Jim K9YC Cheers Paul G3NJV Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 *From: *Jim Brown <mailto:k...@audiosystemsgroup.com> *Sent: *08 August 2019 19:20 *To: *wsjt-devel@lists.sourceforge.net <mailto:wsjt-devel@lists.sourceforge.net> *Subject: *Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube) The concept of a so-called "ground loop" is completely false. It has no basis in physics. The "buzz" we hear when equipment is not properly bonded consists of triplen harmonics of the mains frequency, 50 or 60 Hz, depending on where you live. What DOES couple this trash is the failure to follow proper engineering practice, which is to bond together the chassis of every piece of equipment in a system, to bond all grounds in a building, and to bond that combination of equipment to the combination of building grounds. (my friends in the UK substitute the word "earth" for "ground.") A second important part of good practice is to get power for all interconnected equipment from mains (power) outlets that have the same Green Wire (protected earth conductor), or whose green wires are bonded together. When all of this done, the station is safe for lightning, and no "isolation" is needed. Details of proper practice is at http://k9yc.com/GroundingAndAudio.pdf 73, Jim K9YC On 8/8/2019 3:43 AM, Paul Randall wrote: > The point of the isolated interface is to prevent noise/hum caused by > ground loops but if there is no ground at all, it is not only useless > but actually causes a big problem. I can only assume that if I saw lots > of 50Hz spurs on receive, there was a good chance they were there on > transmit as well. ___
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube)
Jim Double insulated equipment like a laptop charger doesn’t have any physical access to a metal part that can be bonded to ground. That’s what double insulated means. Even if the charger has a 3 pin (hot, neutral and ground) AC connector there is little likelihood that the dc output side is connected to the ground pin. In this case using the laptop for WSJT relies on the connecting wire running from the laptop to the rig to provide a ground. If that wire is deliberately built to be isolated then it CAUSES a hum problem rather than avoids one. This is counter-intuitive and so even though it has nothing to do with software development, I felt it was worth contributing to the “bad signal” discussion going on in this forum. As an aside, I think it very unwise to make a blanket statement that bonding everything together is good engineering practice. Someone reading that may unwittingly bypass a safety ground leakage circuit breaker by bonding the building’s safety ground to a radio antenna ground rod. Worse, large AC currents may flow in this connection if the power utility company uses one of a number of different PME (protective multiple earth) supply systems where the building’s safety ground is actually bonded to the neutral supply wire and only to “real” ground back at the supply transformer. Finally, my friend gave a big grin when he read that “The concept of a so-called "ground loop" is completely false”. He is a professional sound and television broadcast engineer. Cheers Paul G3NJV Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Jim Brown<mailto:k...@audiosystemsgroup.com> Sent: 08 August 2019 19:20 To: wsjt-devel@lists.sourceforge.net<mailto:wsjt-devel@lists.sourceforge.net> Subject: Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube) The concept of a so-called "ground loop" is completely false. It has no basis in physics. The "buzz" we hear when equipment is not properly bonded consists of triplen harmonics of the mains frequency, 50 or 60 Hz, depending on where you live. What DOES couple this trash is the failure to follow proper engineering practice, which is to bond together the chassis of every piece of equipment in a system, to bond all grounds in a building, and to bond that combination of equipment to the combination of building grounds. (my friends in the UK substitute the word "earth" for "ground.") A second important part of good practice is to get power for all interconnected equipment from mains (power) outlets that have the same Green Wire (protected earth conductor), or whose green wires are bonded together. When all of this done, the station is safe for lightning, and no "isolation" is needed. Details of proper practice is at http://k9yc.com/GroundingAndAudio.pdf 73, Jim K9YC On 8/8/2019 3:43 AM, Paul Randall wrote: > The point of the isolated interface is to prevent noise/hum caused by > ground loops but if there is no ground at all, it is not only useless > but actually causes a big problem. I can only assume that if I saw lots > of 50Hz spurs on receive, there was a good chance they were there on > transmit as well. ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? (Paul Kube)
The concept of a so-called "ground loop" is completely false. It has no basis in physics. The "buzz" we hear when equipment is not properly bonded consists of triplen harmonics of the mains frequency, 50 or 60 Hz, depending on where you live. What DOES couple this trash is the failure to follow proper engineering practice, which is to bond together the chassis of every piece of equipment in a system, to bond all grounds in a building, and to bond that combination of equipment to the combination of building grounds. (my friends in the UK substitute the word "earth" for "ground.") A second important part of good practice is to get power for all interconnected equipment from mains (power) outlets that have the same Green Wire (protected earth conductor), or whose green wires are bonded together. When all of this done, the station is safe for lightning, and no "isolation" is needed. Details of proper practice is at http://k9yc.com/GroundingAndAudio.pdf 73, Jim K9YC On 8/8/2019 3:43 AM, Paul Randall wrote: The point of the isolated interface is to prevent noise/hum caused by ground loops but if there is no ground at all, it is not only useless but actually causes a big problem. I can only assume that if I saw lots of 50Hz spurs on receive, there was a good chance they were there on transmit as well. ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals?
When those sidebands are 60 Hz steps from the main signal, then there is a 60 Hz mains and the audio going into an nonlinear part in the transmitter and those signals are mixed together. More often the sidebands are in 120 Hz steps due to full wave rectification in power supply. If in an power amplifier its gain is dependent of voltage, then it acts as an amplitude modulator and the modulation waveform is a kind of triangle 120 Hz that contains multiples of 120 Hz. That happens easier, when most output power is pressed from the amplifier. Keeping amplifier in linear range normally helps. 40 dB down is quite good, but could be better; there are many signal with sidebands a bit more than 30 dB down. 73, Reino oh3ma -Original Message- From: Jim Brown [mailto:k...@audiosystemsgroup.com] Sent: 6. heinäkuuta 2019 9:28 To: wsjt-devel@lists.sourceforge.net Subject: Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals? There are two common causes of sidebands with a station that is properly adjusted and uses good equipment. 1) The best gear (Elecraft K3, K3S, or a Flex 6000-series), and a first class power amp) have sidebands roughly 40 dB down on both sides of their signal due to IM distortion in the RF stages. These sidebands are generally symmetrical, and the total -40 dB bandwidth is about 680 Hz. 2) Doppler shift produced by reflections from aircraft. These sidebands are generally asymmetrical (that is, on one side or the other of the main signal). Here in the SF Bay Area, which includes Silicon Valley and extends down along the Monterey Bay, we have glide paths for major airports in San Jose and San Francisco. There are roughly a dozen or so locals running 500W with gear like this, and we all regularly experience what you're seeing. 73, Jim K9YC On 7/5/2019 11:02 PM, Paul Kube wrote: > ’ve seen various kinds of problematic FT8 signals that I think I > understand -- “barcode” harmonics etc. – but what is going on here: ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals?
BTW -- IMD that's 40 dB down is quite good and better than FCC type-acceptance specs -- it takes a very good rig and a first rate tube or solid state power amp to achieve that. 73, Jim K9YC On 7/5/2019 11:27 PM, Jim Brown wrote: There are two common causes of sidebands with a station that is properly adjusted and uses good equipment. 1) The best gear (Elecraft K3, K3S, or a Flex 6000-series), and a first class power amp) have sidebands roughly 40 dB down on both sides of their signal due to IM distortion in the RF stages. These sidebands are generally symmetrical, and the total -40 dB bandwidth is about 680 Hz. 2) Doppler shift produced by reflections from aircraft. These sidebands are generally asymmetrical (that is, on one side or the other of the main signal). Here in the SF Bay Area, which includes Silicon Valley and extends down along the Monterey Bay, we have glide paths for major airports in San Jose and San Francisco. There are roughly a dozen or so locals running 500W with gear like this, and we all regularly experience what you're seeing. 73, Jim K9YC On 7/5/2019 11:02 PM, Paul Kube wrote: ’ve seen various kinds of problematic FT8 signals that I think I understand -- “barcode” harmonics etc. – but what is going on here: ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals?
There are two common causes of sidebands with a station that is properly adjusted and uses good equipment. 1) The best gear (Elecraft K3, K3S, or a Flex 6000-series), and a first class power amp) have sidebands roughly 40 dB down on both sides of their signal due to IM distortion in the RF stages. These sidebands are generally symmetrical, and the total -40 dB bandwidth is about 680 Hz. 2) Doppler shift produced by reflections from aircraft. These sidebands are generally asymmetrical (that is, on one side or the other of the main signal). Here in the SF Bay Area, which includes Silicon Valley and extends down along the Monterey Bay, we have glide paths for major airports in San Jose and San Francisco. There are roughly a dozen or so locals running 500W with gear like this, and we all regularly experience what you're seeing. 73, Jim K9YC On 7/5/2019 11:02 PM, Paul Kube wrote: ’ve seen various kinds of problematic FT8 signals that I think I understand -- “barcode” harmonics etc. – but what is going on here: ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
[wsjt-devel] 60 Hz + harmonics sidebands on FT8 signals?
I’ve seen various kinds of problematic FT8 signals that I think I understand -- “barcode” harmonics etc. – but what is going on here: [image: multiple decode.PNG] The “blackbox” station there (call elided, no need to name names) has multiple sidebands on his main signal, some of them strong enough to be separately decoded, all at multiples of 60 Hz. What is causing this? Inadequate power supply filtering? Pretty sure it’s not in my receive chain; I see many signals stronger than this +12 dB one that are perfectly clean. 73, Paul K6PO ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
