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Re: LF: VO1NA Opera-32

To: <[email protected]>
Subject: Re: LF: VO1NA Opera-32
From: "Markus Vester" <[email protected]>
Date: Mon, 24 Jun 2013 10:54:05 +0200
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sorry, wrong link corrected. 73, Markus

Sent: Monday, June 24, 2013 10:49 AM
Subject: Re: LF: VO1NA Opera-32

Last night the EA5HVK Opera decoder and my opds correlation detector ran side by side here on one machine, fed by the same soundcard. Opera got the full passband (136-138.2 kHz) through SpecLab and VAC without further audio processing, whereas the other SpecLab instance for opds had a 160 Hz bandpass filter, noise blanker and audio AGC inserted before the 0.477 mHz FFT. The QRN background from the southeast was generally lower than the night before.
Results for both are in
and a screenshot
Although SNR results shown by Opera were consistently better than those for opds, Opera achieved two only decodes while opds produced ten hits (including three from VO1NA).
I am wondering whether this difference may have been exacerbated by the regular splatter from DCF39 which is quite strong in central Europe. This may also have affected the SNR estimates of either program. Maybe in this situation dedicated preprocessing might be helpful for Opera as well?
We may perhaps speculate that possible DCF suppression may be part of the loop advantage observed by DF2JP - Joe could you comment on your loop's orientation?
Best 73,
Markus (DF6NM)

Sent: Sunday, June 23, 2013 1:25 PM
Subject: Re: LF: VO1NA Opera-32

I have downloaded Opera v1.4.7 from the rosmodem website. It was easy to configure and is running smoothly in conjunction with SpecLab and VAC-3, which is needed here to convert from 135.5 to 136.0 kHz LO. With the waterfall disabled, average CPU usage on the slow Atom Netbook is an easy 20% from one of two virtual CPU's (10% shown in task manager).
Opds is running in parallel from a separate SpecLab instance. A locally generated test signal showed up both in Opera (-28 dB) and in opds (-36.4 dB), which means that the first round goes to Jose ;-) I will let both run for a while, hoping for some weak signals to compare.
Best 73,
Markus (DF6NM)
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