SDR PLAY 2 Front End Protection?

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SDR PLAY 2 Front End Protection?

Postby dosformat » Mon Oct 02, 2017 9:41 pm

Hi all

I have recently purchased a SDRPLAY Pro 2 a few weeks ago and would like some advice if that is OK.

I am a radio ham and transmit quite a bit on HF & VHF.

Now I have always disconnected the antenna from my sdrplay 1 and currently sdr play 2 when I transmit but it is getting a bit of a pain.

Now I know a high amount of RF will kill the device but I am wondering is that only when it is receiving (so for example I am listening to a signal on the waterfall)

Will it still be damaged if the coax is connected to the sdr play, usb connected to the computer but no program running decoding anything?

Is it safe to transmit like that or is it best to either just unplug the aerial or unplug the USB lead from the device?

Any way of having to save me unplugging my westflex 103 coax which is a pain to do at the best of time will save me a lot of time and trouble as westflex is a brittle cable and easy to snap.



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Re: SDR PLAY 2 Front End Protection?

Postby vk3alb » Thu Oct 05, 2017 9:43 am

There have been a number of discussions about RX isolation such as viewtopic.php?t=1158

Bottom line, you need to keep the signal to 0dBm or less at the RSP input and the best way to do that is with an isolating relay or as you are already doing, disconnecting the cable.

Hook up with a local ham that has the gear to do the measurement with you. It's an interesting experiment.

Personally, I would not worry about the software running or not. A relay connected to your PTT that isolates your RSP is cheap insurance.

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Re: SDR PLAY 2 Front End Protection?

Postby kennyboz » Thu Nov 02, 2017 2:10 pm

I asked the same question, getting ready to use the SDRplay as a HF receiver along with my rig for transmitting. I have a manual coax relay I will try, followed by acquiring an electronically switched relay of some sort, perhaps rf sensed. You must measure isolation between the switched ports. If you use a linear amp, it is even more critical to do so. My relay has about 70dB isolation, which puts about -8dBm into the SDR during 1500W transmitting. Isolation should be measured on a network analyzer, but you can do it using a 100W rig, oscilloscope and dummy load, measuring voltage coming out of the unused port. You know 100W is 70.7Vrms, take it from there. I won't go into the math figuring out dB and voltage.

Another problem I'm having is my neighbor about 200 yds from me runs high power and my SDR is terribly overloaded - not going to burn up, but distorted with signals off the top of the screen. I have had the RF gain all over the place to no avail. He does the same thing to my Kenwood receiver. My only solution is probably going to be an in-line attenuator, several of which the Kenwood has built in. The SDRplay is sensitive enough to still pick up weak signals with some attenuation in line. Maybe there is something else in the SDRplay I can adjust?
Last edited by kennyboz on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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