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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:

http://www.antennspecialisten.com/~sm5bsz/linuxdsp/install/dlevel.htm on Leif's website.

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 [1] you have a bit of a noise problem in one direction and [2] 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" command produces information at the bottom left corner of the display. I cannot find the description of what it all means. The number after the word "floor" means what? I have a noisy direction that makes this number go as high as 120+. Using the dumb blanker I am still able to copy weak signals in this direction.
Thanks Stan, KA1ZE

Roger Rehr