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SDR Radio/GNU Radio Companion

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Dave Turner:
I know it's late but I wish you all the best condiments for the seasoning.

I've just started to look at the GNU Radio Companion.

Does anyone know of a USB 'dongle' that will allow bi-directional communication with GNU Radio Companion?

For those of us working on an extremely limited budget spectrum analysers and other instruments are a pipe dream. However with a decent computer, the GNU Radio Companion software, and an appropriate interface (ie IO dongle) one could have a lot of fun. For example send a swept frequency into discrete components such as a filter and read the results back to display them. IF the GNU Radio Companion (et al) has the ability.

Any ideas/pointers please.


I'm just barely sticking my toe into the SDR waters, so I'm just joining the thread to follow along.


--- Quote from: Dave Turner on January 11, 2019, 11:55:22 pm ---Any ideas/pointers please.

--- End quote ---

If you are on a budget you should be able to start with a sound-card, both for ADC (RX) and DAC (TX).
For RF-frequencies you'd then mix the sound-card signals up/down - there are "SoftRock" SDR-designs out there that use this approach.

The simplest way of sweeping a filter with an SDR uses an analogue noise source in conjunction with an SDR receiver displaying an FFT.

If you want to use an SDR for transmit, GNURadio certainly supports full-duplex operation however finding a cheap USB dongle capable of full duplex and with two antenna ports with sufficient isolation might prove a challenge.  It may be possible to use two dongles, one dedicated to transmit and the other to receive - this makes isolation much easier. Whether you can connect both to the same GNURadio Companion signal processing chain will depend on whether the SDR device driver supports this.

An SDR isn't a very good way to measure the response of a filter/network if it even works at all. Of the low cost SDR transceivers that can do full duplex (transmit and receive at the same time) all are based on a single chip with everything integrated, and TX-RX isolation is very poor. On the other hand if you use the noise source approach the resulting graph will be, well, noisy. :-DD Really it's far easier to build your own network analyzer for fairly cheap, and there are even existing open source designs out there.


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