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Re: [linrad] "A" Keyboard Command
I am not at my Linrad site and haven't been there in several weeks, and my
memory is imperfect [and getting moreso every day]. But I think I have
what you want. By the way, I hope everyone on the list appreciates what
your post states about the 'incredible' noise reduction capabilities of
Linrad. I suspect that they do. Its those NOT on the list we need to get
to understand this. ;)
The "A" key gives amplitude margins [to saturation] at the level of the
2nd fft and the 2nd backwards fft if I recall correctly. See figure 1 on
http://www.antennspecialisten.com/~sm5bsz/linuxdsp/linroot.htm if like me
you have trouble remembering just where in the chain these are ;)
The "noise" number is the noise floor in bits RMS [see the quote below].
The A function is described at:
Here is a quote, but I recommend reading the entire page:
To set First FFT amplitude, first press A to get the amplitude information
in the lower left corner. The bottom line gives the noise floor in bits
RMS. If you have a nice location with a noise floor that is essentially
white noise of constant amplitude, you should find the noise floor
somewhere between 10 and 30 dB when using the default parameter value
1000. The Floor RMS value should be in the range 3 to 30. The soundboard
itself should be somewhere between -5 and +5dB and your analog hardware
should add between 15 and 25 dB. In most situations there is no reason to
do anything, just use the default value of 1000.
This is referenced from the Linrad starter page:
under the "Checking the dynamic range of your hardware" section.
It does sound like  you have a bit of a noise problem in one direction
and  Linrad is doing a great job [as usual] with its blanker as you are
still copying weak signals in all that noise.
Your results are further proof of the fact that the world that doesn't
know Linrad just doesn't know what it is missing. Those of us on the list
know, though ;)
Sometimes in discussing Linrad with non-list readers I can see their eyes
glaze over in that "yeah, sure" manner [or detect the similar "no
response" phenomenon in posts to non-Linrad lists about the very relevant
benefits of Linrad]. At those times I am reminded of the old saying
"Never try to teach a pig to sing. It will just waste your time, and
severely annoy the pig." In spite of the saying, Linrad is so incredible
that I think we must continue to spread the word. So please invite some
of the non-believers over to witness what you can do with Linrad. If they
come away non believers after seeing a demo with your antennas pointed in
your noisy direction, then they must surely 'oink'. ;)
Thanks for the very interesting post. If you want to make some audio
files of a weak signal in all that noise received by Linrad with and
without the noiseblanker, it would be great to post them on your website /
Leif's website / my website / where ever you want and then for you to send
a short email to moon-net and the vhf and microwave lists to advertise the
posting and spread the word. An audio file is worth a thousand words ;)
Hope that helps!
On Mon, 14 Feb 2005 16:00:41 EST, <Stanka1ze@xxxxxxx> wrote:
The Linrad web site has much information. I need some help, The "A"
produces information at the bottom left corner of the display. I cannot
the description of what it all means. The number after the word "floor"
what? I have a noisy direction that makes this number go as high as
Using the dumb blanker I am still able to copy weak signals in this
Thanks Stan, KA1ZE