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
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.
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