[amsat-bb] FT-991A Transmit Interference

[Paul Stoetzer]

Did you try a duplexer on both the input and output side?

73.

Paul, N8HM

On Thu, Aug 2, 2018 at 2:35 PM, VA3ASE <va3ase at gmail.com> wrote:
> 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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