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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/63GIXGML4U6JOVMTCBOINCEJEUULXRFL/", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/", "message_id": "CAKhHsXH-ciTZV_E2HxREHVCrnqgf476AMsxVdxw9HEiZyyfzbg@mail.gmail.com", "message_id_hash": "63GIXGML4U6JOVMTCBOINCEJEUULXRFL", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/63GIXGML4U6JOVMTCBOINCEJEUULXRFL/", "sender": { "address": "alan.b.johnston (a) gmail.com", "mailman_id": "b7dbdfbee2b1477889b2d3aa984fba1e", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/b7dbdfbee2b1477889b2d3aa984fba1e/emails/" }, "sender_name": "Alan Johnston", "subject": "Re: [amsat-bb] FT-991A Transmit Interference", "date": "2018-08-04T14:22:01Z", "parent": null, "children": [], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "> I'm using a quality TrippLite USB cable with molded chokes\nat each end.\n\nHi Alex,\n\nI've found that if I use any length of USB cable between my PC and SDR, I\nget overloaded on transmit by my Kenwood TR-9500. Only plugging my RTL-SDR\nv3 directly into my PC avoids it.\n\nGood luck with it!\n\n73,\nAlan\nKU2Y\n\nOn Fri, Aug 3, 2018 at 9:35 PM, <[email protected]> wrote:\n>\n> Date: Fri, 3 Aug 2018 11:07:05 -0400\n> From: VA3ASE <[email protected]>\n> To: Mike Sprenger <[email protected]>\n> Cc: AMSAT-BB <[email protected]>, Paul Stoetzer <[email protected]>\n> Subject: Re: [amsat-bb] FT-991A Transmit Interference\n> Message-ID:\n> <CACgQwJ-w++Ww5eSyaToettQ2YO-VQT7We-dOJkkQNeMrRxu-XQ@mail.\n> gmail.com>\n> Content-Type: text/plain; charset=\"UTF-8\"\n>\n> Thank you to everyone who has replied, I appreciate it. I'll try to address\n> everything in one reply.\n>\n> Paul, Alan and Trevor, I borrowed a duplexer rated for 40dB isolation. I\n> tried installing it on both the transmit side and on the receive side in\n> various configurations. I think that counts as a band pass filter. It made\n> no noticeable changes. I did read the QST report on the FT-991A mentioning\n> the output, but my impression was that it wasn't a huge deal. I would be\n> surprised if that was bad enough to cause this.\n>\n> Zach my understanding is that the RSP1A is still shielded despite the\n> plastic box, but I actually have access to an RSP2pro in a metal case that\n> I can try out as well. I've never heard of a USB EMI filter before, I'll\n> look into that. I'm using a quality TrippLite USB cable with molded chokes\n> at each end.\n>\n> Mike, I've tried both a linear power supply and a newer switching supply to\n> power the 991 with no change. In the video I was using the same supply on\n> both rigs. The SDR is powered through my laptop's USB port. I might have\n> already tried transmitting into a dummy load but I'll try it again. I do\n> know that switching the transmit antenna from my yagi to a rooftop vertical\n> eliminates the problem, which suggests to me that the interference is not\n> coming from inside the shack but from the transmit antenna's near field. I\n> made the switch at an outdoor patch panel, so nothing inside changed.\n>\n> Terry, this is the first time I've heard of any other 991 owners with the\n> same problem. While it isn't what I want to hear, at least it might not\n> just be me.\n>\n> My 991 is still in the shop (Radioworld) but I can try to pick it up this\n> weekend and keep experimenting. My original plan was to buy this FT-991A\n> and SDRplay to run a satellite base station, but I recently inherited an\n> FT-847 from a close friend, Brad VE3HII (SK). That opens a lot of\n> (probably\n> superior) options for my station but I'd still really like to see the\n> FT-991A working as originally planned, and as it should. My friend's\n> satellite antennas are still on his tower so I may also try to take my 991\n> there and repeat my tests.\n>\n> 73,\n> Alex VA3ASE\n>\n>\n", "attachments": [] }