[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Pulses

Hi Leif,

THanks for the note! I did get the first one but didn't see that it required a response, and knowing how busy you must be after the vacation, I didn't want to add to your mountain of email ;)

Unfortunately, since the last email indicated that things were OK with the pulses, today I took the pulser back to Hilltop. I will go back there tomorrow to get it, and bring it back home and then will make an S file of the pulses again.

I made the recording using Cool-Edit at 96kHz sampling rate using the Delta44 as input.

I hope it was a 'wav' file problem and not that there is something intermittently wrong with the pulser...

I will send you the S file...

Happy New Year, and

Roger Rehr

Quoting Leif Asbrink <leif@xxxxxxxxxx>:

Hi Roger,

I do not know if the mail below reached you. It is frustrating
with the E-mail problems. I tend to press "reply" and then
the mail goes away and I get a note from the robot the next day
or later.

I will change the ISP anyway, the old one was payed by
Antennspecialisten and it is a long time since I had
anything to do with them;-)

The new ISP will be a low cost one. Maybe they are not
blacklisted...  I will find out within the near future.

I have looked closer at the calibration pulses. Something
is wrong, the calibration becomes reasonable although not
quite correct. What is alarming is that the smart blanker
can not remove the pulses used for calibration. I do not
understand what is wrong. There are discontinuities in the
phase function.

The calibration file dsp_wcw_corr that you sent does not have
these errors. Seems to be something related to the wav format.

How did you make the recording? Can you make a new file with
similar pulses, but make the recording as an S-file with
Linrad? That should be ok since you could calibrate ok.

I can then convert from .raw to .wav and check if there
is something wrong with Linrads reading from .wav files.



From: Leif Asbrink <leif@xxxxxxxxxx>
To: Roger Rehr <w3sz@xxxxxxxxxxx>
Subject: Re: noise not removed
Date: Mon, 31 Dec 2007 22:07:33 +0100
X-Mailer: Sylpheed version 2.3.0beta5 (GTK+ 2.8.20; i486-pc-linux-gnu)

Hello Roger,

I found some brief pulse noise that was not removed by the blankers [I
didn't fiddle with them at all to improve performance].

I made an S file and a wave file of this noise and put them at:
Thank you:-)

This interference seems to be a pulse train with too many
pulses. With 90kHz bandwidth they are not resolved and
therefore they constitute a fairly long time of VERY
high white noise. The smart blanker is totally useless.

It is possible to set the threshold for the dumb blanker
very low and cut long holes in the signal to make
copying easier. It is also possible to set fast AGC or to
allow the AF to go into saturation at a signal level just
above the desired station.

This file is reasonably close to what I asked for to be
able to implement the baseband noise blanker. What is missing
is a couple of very strong signals that make the dumb blanker
fail when the threshold is set very low.

It is by far the best candidate I have at the moment. I will
wait for a couple of other examples where the blankers fail
before trying to implement a narrowband blanker. It will
not become a major improvement except, maybe, for QRSS. But
a couple of more buttons to play with;-) In a situation like
in this file, blanker operation should become less critical
because there will be no need to set the dumb blanker threshold
very low (and risk to have to change it repeatedly)

Thanks for these files! I am interested in recordings like this.
Anything that does not work well:-)



Roger Rehr