Hi Chuck, >I'm expecting > to get a 1Khz signal in one channel and 2Khz in another channel, > but end up with the two getting mixed etc. >Now if I disconnect the wire connect J19 to J48 ch1 & ch2 indeed flatline as expected. How do ch 3 & 4 look when you disconnect the wire connect J19 to J48.
You only set the tx_freq for channel 0 sink.set_tx_freq(0,5e6) You should also do sink.set_tx_freq(1,5e6) This means you output frequencies of 5.001 Mhz and 5.002 MHz. On the receive side you then also have to set the DDC frequency to 5Mhz to get back to 1 kHz and 2 kHz. I have been playing with the usrp_oscope and found I got similar signals when I used high interpolation and DDC freq set to zero using just one channel. I used an external source (signal generator) which I connected to J19. source few hundred kHz, DDC freq set to 0, decimation 128 But of course you can't get a few hundred kHz if you use a decimation of 128. This should give me a sinus at a mirror frequency, or nothing at all, but I got a signal similar to what you saw. (Probably it is a sinus but I don't get the complete signal, so the next period starts before the previous period is finished or something like that) I think the cordic doesn't handle this setup like I expected. The signals started to look good when I used a DDC freq which was close to the signal frequency (and lower decimation factors and higher frequencies.) source 4.433619 Mhz, DDC freq set to 4.433618 MHz, decimation 32 I got a nice 1 kHz complex sinus output. greetings, Martin cswiger wrote:
Hi - this may be more involved that anyone wants to get into, just asking in case I'm missing something obvious. I'm trying to make two seperate circuits go thru the usrp - but they're are interacting somewhere. Anyway here's a web page showing the test setup and unexpected results - I'm expecting to get a 1Khz signal in one channel and 2Khz in another channel, but end up with the two getting mixed etc. On the TX side, two complex sig sources are interleaved and the usrp is setup for 2 channels and mux set to send one signal to DAC0 and the other to DAC1. J48 and 49 are looped back to J19 and 18. The oscope is setup for 2 channels and mux set to send ADC0 to DDC0 and ADC1 to DDC1. http://webpages.charter.net/cswiger/usrp_diagrams/question.html Thanks --Chuck _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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