SDRplay RF gain and transmitting problem

[Sergei Konev]

I have SDRplay RSPdx and 2xFT818ND for satellites QSO.

RF=0, AGC=False - my only way to see moving watefall..
If AGC=True so waterfall stopped.
It seems my TX signal is too strong for my SDRplay RSPdx, hitting the receiver's gain, preventing the program from decoding and correcting it. There are so many interference signals on the screen, it's unclear what my primary transmitter signal is.

I have a 144 MHz filter on the transmitter (FT-818ND), but it doesn't help... the 435 MHz band is clogged with interference during transmission.

Second problem with my TX signal. It seems 
Anyway, I can nor recognize my TX signal , too many interference signals on the screen...and very strong and loude audio.
And no way fix it using manual correction. As the result, my TX signal not managing by Doppler at all, no Sat QSO available...
Who can advice anything?

Thanks,
Sergey Konev, ER1KW

[Jack Blake]

What software are you using for Doppler? Since you’re using Yaseu radio the CSN box will not work for you. What antenna are you using? I would suggest skip using the SDRplay for a downlink radio and use one the Yaesu radio. Also try using SatPC32 or HRD for Doppler control. Keep your uplink power down it will cut down on your desense. I would use SkyRoof for sat QSO. It’s great for decoding telemetry or just capturing the downlink. If you’re using two antenna one up one down there is a trick using a duplexer and leaving the 2 meter side not connected. Check Amsat website for more information 

Jack L. Blake

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[Sergei Konev]

Hello Jack,

Yes, 5 years long I'm  using two FT-818ND's as RX+TX (fell duplex) for SAT QSO (with SatPC32,  see  www.qrz.com/db/er1kw ), and I can still use them, but I want waterfall to have, you see....

And  SkyRoof with SDRplay RSPdx doing nice receiving and waterfall, indeed, untill I am starting to transmitt...After I start TX  - everything is over, I'getting a lot of splatters on the screen and Doppler control in SkyRoof doesn't work.
I am using two separate Yagi'es , one for 144MHZ and second for 435MHz.

I have two FT-818ND and I have a lot QSO's on satellites with such set, but I would like to have waterfall and Doppler control in one software... And I believed SkyRoof is right choice, but no way yet...
What about  a  a trick using a duplexer? I just (half hour ago)  tried  same idea to use duplexer MX72 - ANT 432 IN, TX 145 IN , ANT 145 OUT, but no signal to RX . WHich way to use duplexer did you meant?

Sergey Konev, ER1KW

пятница, 24 апреля 2026 г. в 17:48:53 UTC+3, Jack Blake: