tag:blogger.com,1999:blog-7590176649168185428.post4542121471747497877..comments2024-03-27T17:14:31.032-04:00Comments on SolderSmoke Daily News: The Importance of Keeping the Noise FLATBill Mearahttp://www.blogger.com/profile/07662500663603350847noreply@blogger.comBlogger9125tag:blogger.com,1999:blog-7590176649168185428.post-58508463400240923062021-11-10T13:55:42.375-05:002021-11-10T13:55:42.375-05:00I apologize. Voice to Text struck again and I publ...I apologize. Voice to Text struck again and I published before proof reading. 'Mix 31' and 'split ferrite beads' should be substituted appropriately in the my reply above. Scott & Ginnyhttps://www.blogger.com/profile/10730342786188270790noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-56292328249192835822021-11-10T13:53:41.697-05:002021-11-10T13:53:41.697-05:00Thanks for the clarification. Could it be possibl...Thanks for the clarification. Could it be possibly entering on the shield of your antenna's coax? I've encountered that before and wound common mode choke and put it in the coax at my operating point. It worked nicely. For that I used a mix 31 core that is almost 4 in in diameter overall. I also keep on hand a couple Nick's 31 split fare right beads. You can open them up and wind five or six turns then simply close it and see what impact that has. They are pricey, but great for troubleshooting and RFI mitigation. Good luck. I know the feeling... NM8RScott & Ginnyhttps://www.blogger.com/profile/10730342786188270790noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-40653330161115425422021-11-08T15:15:58.307-05:002021-11-08T15:15:58.307-05:00Oh, yes, not 50MHz. 50*K*Hz! I guess it's comi...Oh, yes, not 50MHz. 50*K*Hz! I guess it's coming from a switching supply, but not in my house--at least I haven't been able to find it. It's not conducted noise coming from my own power supply because it's there on battery power, too, and it doesn't matter if the rig is open or buttoned-up in its shielded enclosure. It's coming in through the antenna. In truth, it's no more obnoxious than some over-driven blowhard parked on the same frequency . . . actually, it's less obnoxious.Todd K7TFChttps://www.blogger.com/profile/17909491674824360102noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-14564588891477842002021-11-08T10:53:47.629-05:002021-11-08T10:53:47.629-05:00I think he meant "every-50kHz spike"? T...I think he meant "every-50kHz spike"? That would be harmonics of typical switching power supplies that run at several tens of kilohertz.Dave Newhttps://www.blogger.com/profile/14606866637455669041noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-77883301729390761862021-11-08T07:23:06.322-05:002021-11-08T07:23:06.322-05:00K7TFC,
What is this "every-50MHz spike"...K7TFC,<br /><br />What is this "every-50MHz spike" you mention? Scott NM8RScott & Ginnyhttps://www.blogger.com/profile/10730342786188270790noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-80816059982585359072021-11-05T21:32:41.235-04:002021-11-05T21:32:41.235-04:00Hi Bill
Lot of choices on Ebay
https://www.ebay....Hi Bill<br /><br />Lot of choices on Ebay<br /><br />https://www.ebay.com/sch/i.html?_from=R40&_nkw=RF+Noise+Source+Noise+Generator+&_sacat=0&_pgn=1<br /><br />73<br />Jim AB9CNjimhttps://www.blogger.com/profile/09397895536206793525noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-43303283118815894622021-11-05T18:10:27.448-04:002021-11-05T18:10:27.448-04:00Some of the commercial RTL-SDR up-converters have ...Some of the commercial RTL-SDR up-converters have a built-in zener-based noise source (the Ham-It-Up converter is one), presumably because the dongles can be used as (really-cheap) spectrum analyzers. I just bought one of the Ham-It-Up units without the noise-source option because I want to embed it in a (also really-cheap) "homebrew" SDR receiver that will live on my operating bench and not my lab bench. I may or may not put together a dedicated noise generator using the Ham-It-Up design. <br /><br />There's not much to it. The zener has a breakdown voltage above 6V to get the avalanche noise, and from there it's just a few stages of broadband amplification. I need to look into Vasily's idea that a reversed-biased transistor might be better than a zener. Either way, having such a source will help as a "sanity" check on the NanoVNA, just as you used the VNA to check the results you got with the TinySA (though in this case not the SA's fault). I love those little "good-enough" analyzers, and I like the idea that one can be used to check the other.<br /><br />Of course I could just use my 40-meter antenna as a source. With a 37dBm noise floor (about S9!!!), it's barely usable as an antenna, and because I'm getting the same every-50MHz spike many others are now getting, I can also use the antenna as a marker generator! Keep on the sunny side of life, I always say. --Todd K7TFCTodd K7TFChttps://www.blogger.com/profile/17909491674824360102noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-29975048969254955742021-11-05T17:45:17.683-04:002021-11-05T17:45:17.683-04:00Now that's very interesting. I don't have ...Now that's very interesting. I don't have a white noise generate here so I've not been able to run this type of test.<br />I've always used my HP network analyzer to sweep it.<br />I will have to look into making a noise source.<br />Any suggestions?<br />Paul.<br />G0MIH /HS0ZLQ. Nemohttps://www.blogger.com/profile/14516132469067456611noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-45722825143656881652021-11-05T13:51:16.138-04:002021-11-05T13:51:16.138-04:00Thanks Bill
Digital white noise generators are ps...Thanks Bill<br /><br />Digital white noise generators are pseudo random whether the random number generation gets done via code, or by logic gates plus and a clock. The best digital [expensive] versions run long sequences with well defined amplitude.<br /><br />For decades, builders have relied on analog noise sources since they prove easy,cheap + provide true random white noise. Often this means reverse biasing a BJT with very low current so it functions as a zener diode. A transistor may produce more noise than an actual zener diodes. 1 or 2 op-amp stages are needed to boost the noise amplitude into something usable depending on your application.<br /><br />Regards<br />TVasily Ivanenkohttps://www.blogger.com/profile/17387516134063150119noreply@blogger.com