[amsat-bb] FT-991A Transmit Interference

[Paul Stoetzer]

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 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!
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