If you have access to the ARRL QST test archives, their review of the FT-991A is worth reading. While meeting all FCC requirements, neither TX or RX signals are as clean as some other rigs. That _might_ be enough to account for the differences.
73,
Alan WA4SCA
<-----Original Message----- <From: AMSAT-BB [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Paul <Stoetzer <Sent: Thursday, August 02, 2018 18:53 PM <To: TERRY SURFACE terrysurface1@centurylink.net <Cc: VA3ASE va3ase@gmail.com; amsat-bb@amsat.org <Subject: Re: [amsat-bb] FT-991A Transmit Interference < <It sounds like the FT-991A’s harmonic suppression isn’t quite up to par. < <73, < <Paul, N8HM < <On Thu, Aug 2, 2018 at 19:51 TERRY SURFACE terrysurface1@centurylink.net <wrote: < <> Hello. I have two 991A radios, and both do the same thing. I am unable to <> use them for transmit on two meters without killing the 70 CM RX. I use a <> Kenwood TS 2000 for transmit and 991A for receive. Not the way I want to <do <> it, but I am for now, this allows the spectrum and waterfall for checking <> out the entire transponder. Hope someone finds a solution. <> 73,N4IQV, Terry <> <> ----- Original Message ----- <> From: "VA3ASE" va3ase@gmail.com <> To: amsat-bb@amsat.org <> Sent: Thursday, August 2, 2018 2:35:54 PM <> Subject: [amsat-bb] FT-991A Transmit Interference <> <> Hi AMSAT friends, <> <> I'm having a technical problem and was wondering if anyone had any <> suggestions. I've been experimenting with using an FT-991A transmitter and <> SDR receiver to run full-duplex on the satellites. My problem is as soon as <> I key the FT-991A transmitter, my SDR receiver waterfall goes completely <> white and I don't hear anything but static. Classic overload symptoms. <> <> I've tried several things: <> - Upgrading my receiver from an RTL-SDR to an SDRplay RSP1A: no <> improvement. <> - Adding a duplexer as a band pass filter: no improvement. <> - Transmitting with a vertical antenna about 40' away from my yagis: YES it <> did solve the problem but is not a suitable solution. <> <> I'm using the same yagi antenna setup that I've used successfully for years <> with an FT-847, and have also had the same problem with a handheld Arrow. <> <> At last I tried transmitting with a different radio, and the problem <> disappears. I figured the problem was in my FT-991A so I sent it for <> warranty repair, but just got the call that they can't find anything wrong <> with it. It has no measurable spurious or out of band emissions. I'm at a <> loss here... I know people are using the same equipment (FT-991 + SDRplay) <> successfully; Simon Brown comes to mind. <> <> Here is a video I created demonstrating the problem with the FT-991 and <> showing that it doesn't appear with an Icom ID-880H. <> https://youtu.be/gXOIK5gLjgs <> <> I still think the problem must be in the radio, but if they can't find <> anything to fix then I'm out of luck. I'd love to hear any suggestions or <> feedback. <> <> Thanks, <> Alex VA3ASE <> _______________________________________________ <> Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum <available <> to all interested persons worldwide without requiring membership. <Opinions <> expressed <> are solely those of the author, and do not reflect the official views of <> AMSAT-NA. <> Not an AMSAT-NA member? Join now to support the amateur satellite <program! <> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb <> _______________________________________________ <> Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum <available <> to all interested persons worldwide without requiring membership. <Opinions <> expressed <> are solely those of the author, and do not reflect the official views of <> AMSAT-NA. <> Not an AMSAT-NA member? Join now to support the amateur satellite <program! <> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb <> <_______________________________________________ <Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available <to all interested persons worldwide without requiring membership. Opinions <expressed <are solely those of the author, and do not reflect the official views of AMSAT- <NA. <Not an AMSAT-NA member? Join now to support the amateur satellite <program! <Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb