Hello Chuck, > I'd like to see you expand the scope of #4 to include splatter from any > source. Sure, if someone would be kind enough to send a recording:-)
> For those of us that mostly DX the AM broadcasters, splatter is the > huge enemy. Really? Are there bad AM transmitters out there or do you want to listen near a strong local AM station? > A solution that I'd like to see is a sort of Costas loop where: > (1) the signal is split into two paths where one is demodulated with an > in-phase carrier and the second with a 90 degree shifted carrier, Linrad already has this feature: http://www.sm5bsz.com/linuxdsp/run/am.htm > (2) the "Q" output is shifted an additional 90 degrees, and (3) the two > demodulated > outputs are selectably added or substracted. This will be equivalent to receiving one sideband or the other, Linrad sends both I and Q to stereo head-phones to allow your brains to do the processing. I think that will often be a better solution. If one wants one sideband only, I think it will be a better idea to just set the appropriate filter and use the BFO to receive the SSB signal that remains. BUT, if the problem is splatter, much better solutions are possible. The splatter is a distortion on the modulation. It should be possible to detect the modulation in the offending channel and to compute the expected splatter which could then be removed. In principle Linrad could learn exactly what non-linearities the offending station suffers from and then build exactly the emitted signal with an accuracy detemined by the S/N of the main components of the offending station. To try to implement something like this, I need a wideband recording. Wide enough to include all of the desired station as well as the full spectrum of the offending station (splatter on both sides included.) 73 Leif / SM5BSZ > > Chuck > WD4ELO > > -----Original Message----- > From: Linrad mailinglist [mailto:[EMAIL PROTECTED] On Behalf Of > Leif Asbrink > Sent: Sunday, October 28, 2007 10:31 AM > To: Linrad mailinglist > Subject: [linrad] Challenges!! > > Hi All, > > Any interference that is not random can in principle be > modelled and subtracted. In real life it might be too > difficult, but I guess there are man-made interferences > that could be significantly reduced. Improvements are > also possible with random interference in some cases. > > I think the interference fighting in Linrad can be > significantly improved, but I do not want to work on > artificial signals where I try to simulate various forms > of QRM - mistakes are easily done so I look for real life > recordings of signals that are at the detection limit or > slightly below. > > Is there really nobody reading this who has problems in > copying "the other station" occasionally? I have asked > before, but still I have no recordings to work with. > > Currently I am only interested in the traditional modes > CW, SSB, AM or NBFM. Here are a few examples: > > 1) SSB in white noise but with inadequate S/N. Rather than using > a rectangular filter Linrad could use a filter that is shaped > as the power spectrum of the signal. > > 2) Interference from TV transmitters on 50 MHz. > > 3) Lightening crashes on (low?) HF bands. > > 4) Splatter from local amateurs. > > On Nov 05 I will leave for one month spending my time in > a more pleasent climate than what Sweden can offer this time > of the year. I will have plenty of time to work on any > challenges you might give me. > > The Tx side of Linrad is now producing 10mW on 144 MHz, but > I can not work on it when away from home because the next step > will be to arrange for the Rx/Tx switching for QSK in CW and > SSB. It is possible to listen while talking, one can "cut holes" > in the transmitted signal occasionally to generate perhaps 1% of > silence without affecting intelligibility. Will allow monitoring > of what happens in a pileup etc. > > The next version, Linrad-02.40 will work under Windows Vista, > but only with 16 bit audio. Please report all bugs you have > noted in 02-39, I will upload 02-40 before leaving. > > 73 > > Leif / SM5BSZ > > > ############################################################# > This message is sent to you because you are subscribed to > the mailing list <linrad@antennspecialisten.se>. > To unsubscribe, E-mail to: <[EMAIL PROTECTED]> > To switch to the DIGEST mode, E-mail to > <[EMAIL PROTECTED]> > To switch to the INDEX mode, E-mail to <[EMAIL PROTECTED]> > Send administrative queries to <[EMAIL PROTECTED]> > > > > ############################################################# > This message is sent to you because you are subscribed to > the mailing list <linrad@antennspecialisten.se>. > To unsubscribe, E-mail to: <[EMAIL PROTECTED]> > To switch to the DIGEST mode, E-mail to <[EMAIL PROTECTED]> > To switch to the INDEX mode, E-mail to <[EMAIL PROTECTED]> > Send administrative queries to <[EMAIL PROTECTED]> > ############################################################# This message is sent to you because you are subscribed to the mailing list <linrad@antennspecialisten.se>. To unsubscribe, E-mail to: <[EMAIL PROTECTED]> To switch to the DIGEST mode, E-mail to <[EMAIL PROTECTED]> To switch to the INDEX mode, E-mail to <[EMAIL PROTECTED]> Send administrative queries to <[EMAIL PROTECTED]>
