Spurious signals with no antenna

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kingtux
Posts: 2
Joined: Fri Jun 07, 2019 11:35 am

Spurious signals with no antenna

Post by kingtux » Fri Jun 07, 2019 12:01 pm

Hello

I'm a new RSP1A user and I've been playing with it to see it's limitations.

I've connected a 50 ohm terminator to see the device noise baseline and I've observed repetitive signals trough the available spectrum.
For example, a spike is at exactly 120.00MHz ( in the air-band ).
It's not affected by the LNA / IF GAIN settings.
The same signal is present with an open input.
I've tested under Windows / Linux with the provided sofware / drivers and custom builds - the signals are present in all cases.

Is it normal ?
Is it some sort of LO leakage ? Or is it generated by the front end architecture ?
Last edited by kingtux on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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Mike2459
Posts: 318
Joined: Mon Jul 24, 2017 8:24 pm

Re: Spurious signals with no antenna

Post by Mike2459 » Fri Jun 07, 2019 3:01 pm


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Tech_Support
Posts: 497
Joined: Mon Jun 01, 2015 7:00 pm

Re: Spurious signals with no antenna

Post by Tech_Support » Fri Jun 07, 2019 4:32 pm

It's actually the 5th harmonic of the Clock which is 24 MHz. All radios generate spurs at harmonics of the clock frequency but with an SDR, you actually 'see' them. Some software 'hides' these spurs by placing a software notch at these harmonics, that also notches signals, so it doesn't alter the fact that they are always there.

Sincerely

Tech_Support

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kingtux
Posts: 2
Joined: Fri Jun 07, 2019 11:35 am

Re: Spurious signals with no antenna

Post by kingtux » Fri Jun 07, 2019 5:22 pm

So it's something expected.
It's my first hi-end SDR so I did not know if it's normal or not, until now I've been playing with "tayloe mixer" based devices that don't show LO leakage, as they work only up to LO/4.

Thanks,
Alex
Last edited by kingtux on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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