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Re: [SPAM][Linrad] Re: system gain
- Subject: Re: [SPAM][Linrad] Re: system gain
- From: Chris <gmail.com; kc2rgw@xxxxxxxxxxxxxxxx>
- Date: Wed, 8 Apr 2009 13:36:40 -0400
There's also SDR-Shell
I never got them working properly due to a firewire FA-66 sound card
issue I was having but that one may be a bit more straightforward to
get going. I keep meaning to make cables for my built in sound card
just to play around but haven't got to it yet.
On Wed, Apr 8, 2009 at 12:37 PM, Dave Sublette <k4to@xxxxxxxx> wrote:
> Just now I think I determined that the width of the audio filter in the
> at baseband in my setup is more than 1 Khz. I believe this is at least
> part of the cause of my poor s/n ratio in the decoded output. I now have
> to figure out how to change that filter width. ÂI believe that there are
> other filters in other places in LINRAD that also may have to be changed
> by using the setup parameters. I am reading everything again, trying to
> get smarter. ÂThen maybe things will sound better.
> Dave Sublette wrote:
>> Good morning Chris,
>> I have tried setting the scale on the left side of the spectrum display,
>> using the various little up and down arrows. It is currently set to a
>> maximum of 40 and a minimum of -10 dB. My system noise floor is at 0 to
>> +2 dB. Changing this range affects the usefulness of the display but
>> doesn't affect the sensitivity of the system, as far as I can tell.
>> I should have stated my concern more clearly. I am talking about the
>> waterfall display and the audio demod features. I have adjusted the
>> various contrast settings, using the two boxes in the lower right hand
>> corner of the waterfall display to be able to see weak signals. I have
>> also compared the signal to noise ratio of the demodulated CW from the
>> LINRAD system to that of the IF radio,. In all cases, the IF radio hears
>> better and can hear signals that cannot be seen on the waterfall.
>> That's good, but with the poorer performance at the waterfall, I feel
>> that I am missing off frequency signals that might be calling me.
>> It occurs to me that the band width of the filter in LINRAD's
>> demodulation window (sorry I know I am probably not using correct
>> terminology here) is affecting the signal to noise of the audio output.
>> I have fiddled with the little green ellipses, but can't get them to go
>> any narrower and really don't understand how this all works. I have read
>> W3SR, VK2DU and Leif's instructions until I am cross-eyed. I just don't
>> seem to "get it". Sorry to be such a lame brain Â:-)
>> All of these comments apply only to the "weak CW" or "A" mode. I don't
>> try anything else.
>> I hope I have been able to clarify my concerns as presented earlier.
>> Thanks very much for your response.
>> Chris wrote:
>>> Just for clarification...what are your Hi and Low markers set to on
>>> the left side of the spectrum display?
>>> Is it possible that you are just set to 0db high and -140db low or
>>> something too wide like that? ÂThat will flatten out all but the very
>>> strongest signals, where if you set for -55 high and -100 low or
>>> something similar to suit the signals, you would see a lot more
>>> response on the pan.
>>> How to adjust those in linrad, I don't know, but you definitely should
>>> be able to and if you can hear the signals the same, that's all you
>>> need to adjust to 'see' them better.
>>> On Wed, Apr 8, 2009 at 10:57 AM, Dave Sublette <k4to@xxxxxxxx> wrote:
>>>> The IF radio hears signals better than the LINRAD system displays them.
>>>> My whole point is to bring the LINRAD system up to or better than the
>>>> sensitivity of the IF radio. Of course this is a better problem to have
>>>> than the other way around--I think :-).
73 de Chris KC2RGW
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