Re: LF: TXing WSPR on 630m on a Raspberry Pi, Stefan in QRPPPP...

[DK7FC <73dk7fc@googlemail.com>]

Hi Mauro,

Yes, for a TX power below 20 dBm i do not care to much about spectrum so 
i just spent a simple pi filter. For higher power levels i would use a 
higher order filter, like my PA does anyway. I can see the 
in-band-spectrum on my local receiver at 
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_remote_Grabber.html 
(RX still on the table here for testing) with > 50 dB SNR. Here, the 
spectrum looks very clean.
73, Stefan

Am 23.03.2015 19:20, schrieb IK1WVQ Mauro:
> Hi Stefan,
> I use the RASPY from 2 years to produce WSPR and QRSS (I wrote a 
> software to do this).
> Consider what the RF is produced by the internal fractional-divider 
> "modulated" by a DMA sequence, to increase the resolution of the 
> fractional_divider.
> The result is a NOT SO CLEAN spectrum !!!  take a lock with a spectrum 
> analyzer !!
> When used with lo power this is not a problem (my "PA" in HF is a 
> 74AC541 all paralleled.. 450mW @ 30meters)
> My QRSS software can use only the fractional divider, without DMA ..
> The spectrum is VERY clean, but it is impossible to generate the WSPR 
> tone .. only QRSS, CW and OPERA ...
> 73 de Mauro IK1WVQ