I'm using a quality TrippLite USB cable with molded chokes

at each end.

Hi Alex,

I've found that if I use any length of USB cable between my PC and SDR, I get overloaded on transmit by my Kenwood TR-9500. Only plugging my RTL-SDR v3 directly into my PC avoids it.

Good luck with it!

73, Alan KU2Y

On Fri, Aug 3, 2018 at 9:35 PM, [email protected] wrote:

Date: Fri, 3 Aug 2018 11:07:05 -0400 From: VA3ASE [email protected] To: Mike Sprenger [email protected] Cc: AMSAT-BB [email protected], Paul Stoetzer [email protected] Subject: Re: [amsat-bb] FT-991A Transmit Interference Message-ID: <CACgQwJ-w++Ww5eSyaToettQ2YO-VQT7We-dOJkkQNeMrRxu-XQ@mail. gmail.com> Content-Type: text/plain; charset="UTF-8"

Thank you to everyone who has replied, I appreciate it. I'll try to address everything in one reply.

Paul, Alan and Trevor, I borrowed a duplexer rated for 40dB isolation. I tried installing it on both the transmit side and on the receive side in various configurations. I think that counts as a band pass filter. It made no noticeable changes. I did read the QST report on the FT-991A mentioning the output, but my impression was that it wasn't a huge deal. I would be surprised if that was bad enough to cause this.

Zach my understanding is that the RSP1A is still shielded despite the plastic box, but I actually have access to an RSP2pro in a metal case that I can try out as well. I've never heard of a USB EMI filter before, I'll look into that. I'm using a quality TrippLite USB cable with molded chokes at each end.

Mike, I've tried both a linear power supply and a newer switching supply to power the 991 with no change. In the video I was using the same supply on both rigs. The SDR is powered through my laptop's USB port. I might have already tried transmitting into a dummy load but I'll try it again. I do know that switching the transmit antenna from my yagi to a rooftop vertical eliminates the problem, which suggests to me that the interference is not coming from inside the shack but from the transmit antenna's near field. I made the switch at an outdoor patch panel, so nothing inside changed.

Terry, this is the first time I've heard of any other 991 owners with the same problem. While it isn't what I want to hear, at least it might not just be me.

My 991 is still in the shop (Radioworld) but I can try to pick it up this weekend and keep experimenting. My original plan was to buy this FT-991A and SDRplay to run a satellite base station, but I recently inherited an FT-847 from a close friend, Brad VE3HII (SK). That opens a lot of (probably superior) options for my station but I'd still really like to see the FT-991A working as originally planned, and as it should. My friend's satellite antennas are still on his tower so I may also try to take my 991 there and repeat my tests.

73, Alex VA3ASE