[amsat-bb] FT-991A Transmit Interference

[Alan]

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 at amsat.org] On Behalf Of Paul
<Stoetzer
<Sent: Thursday, August 02, 2018 18:53 PM
<To: TERRY SURFACE <terrysurface1 at centurylink.net>
<Cc: VA3ASE <va3ase at gmail.com>; amsat-bb at 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 at 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 at gmail.com>
<> To: amsat-bb at 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
<> _______________________________________________
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<> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum
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<Opinions
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