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LF: To KL7UK - SDR-IQ, bounced emails

To: RSGB LF Group <[email protected]>
Subject: LF: To KL7UK - SDR-IQ, bounced emails
From: wolf_dl4yhf <[email protected]>
Date: Tue, 19 Oct 2010 11:28:16 +0200
Reply-to: [email protected]
Sender: [email protected]
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv: Gecko/20100915 Thunderbird/3.1.4
Sorry for having to post this to the group, but my PMs to Laurence keep bouncing
with errors like
"SMTP error from remote mail server after MAIL FROM:[email protected] SIZE=6299:
    host []: 421 RP-001 
    Unfortunately, some messages from weren't sent. 
    Please try again. We have limits for how many messages 
    can be sent per hour and per day.

73, Wolf .

Original message to KL7UK below.


  Hi Laurence,

My last response bounced so here it comes again, this time w/o attachment :

Just a quick update on the SDR-IQ :

I left my receiver at home running for 12 hours at 196 kSamples now,
using DCF 77 (77.5 kHz) as the frequency reference, to measure both the
DCF77 signal one of the Alpha beacon with a 40 uHz frequency resolution.

The result doesn't looks as it should (see attachment) :

The DCF77 line looks sharp as a needle - only the center 40 uHz line is
filled with signal energy, the neigbours are over 30 dB down (but they
*should*  be even lower).

But the 'Alpha' line on 11904.7x Hz looks terribly "wobbly", somehing
which has never happened when I did the same experiment with an E-MU
0202 soundcard (running at 192 kSamples).

My guess is that the SDR-IQ, or (which is more likely) its USB driver
occasionally loses a few samples, causing a step change in the phase.
The frequency stabilizer shifts the 77.5 kHz phase back where it should
be (thus the signal looks coherent in the 77.5 kHz spectrum), but the
phase continuity of the Alpha signal is lost, causing the "smeared"

I will need some time to investigate this - maybe it can be cured with a
newer driver software, since mine is very old, or there is a bug in the
USB buffering in my own software. The ugly thing about this bug is that
it only occurrs once in an hour, making it difficult to find.
At least, updating the FTDI "D2XX" driver from V2.4 to V2.8 greatly 
reduced the number of drop-outs from about two per hour to one in two hours.
But still too much for this application.

The reason may be related to the issues you mentioned (lost samples
somewhere, depending on sampling rate and processor speed).

I will keep you informed about further progress with the SDR-IQ !

    73,  Wolf  DL4YHF .

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