Re: [Discuss-gnuradio] Flummoxed!

[Cinaed Simson]

On 09/24/2016 12:34 PM, liverpudd wrote:
> Working on  the GNURADIO gr-rds to try and find out why it appears to be
> finicky with what source drives it.

Unfortunately I don't know anything about RDS.

But as strange as this might sound, it almost appears as if the RDS
module is configured to use RTL dongle raw I/Q data pairs and not the
complex I/Q pairs used by the USRP and HackRF One?

> 
>  
> 
> Set up three sources. USRP1, RTL Dongle(NooElec Blue with 0.5ppm TXCO )
> and the HackRF.
> 
>  
> 
> Plugged a decent antenna and tuned to R2 (88.3MHz) a nice strong signal.
> Whilst the radio works OK with all three sources, the RDS decoding would
>  only work with the RTL Dongle.
> 
>  
> 
> Checked the input IQ level from the RTL dongle and adjusted the input
> level to be the same from the USRP1 and the HackRF. No joy – no change
> with either the USRP or HackRF decoding the RDS!
> 
>  
> 
> Adjusted the Rx frequency 88.3MHz +/- 200KHz. The RDS decoder packed in
> beyond +/- 100KHz on the RTL dongle. No joy with either the USRP or
> HackRF, no matter what frequency offset I dialled in.
> 
>  
> 
> Next adjusted the 1Msps sample rate using a Polyphase Arbitrary
> Respampler.  Adjusted it from 1Msps to +/- 50Ksps in small increments.
> RTL dongle packed in the RDS decode a few Ksps either side of the
> nominal centre of 1Msps. No joy from the USRP or HackRF no matter what
> sample rate I set it to!!!
> 
>  
> 
> Grasping at straws now, I put a phase rotator in line (can’t say I know
> what exactly this block does!) but in any case I adjusted the phase by
> +/- 5 degs. The RTL dongle packed in the RDS decode at about +/- 0.2
> degs. No joy with the USRP or HackRF, no matter what phase value I set
> it to!!!
> 
>  
> 
> So current situation is I do not know what is going on. I have adjusted
> all that I can to no avail. Any ideas?
> 
>  
> 
> Alistair
> 
> 
> 
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