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" [email protected] To: [email protected] 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 [email protected]. 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