Hi Bret, A typical sound card will record in 16 bit number per sample and at least 32K samples per second (I think that may be a conservative figure and it might be 44K some odd samples per second). At any rate the sampling is faster than the bias frequency on tape. And the 16 bit number means that you can get have a max number of 65,535 (64K). That is -32K down and +32K up. This means that each sample is represented as a number from - 32K to +32K. This is CD quality. The trick is to record it as close to max input as possible without any sample hitting the top or bottom number. What many folks do wrong is to record at too low of a level so that their max number hits 10K or 20K. They digitally "normalize" (Bringing the largest number = to +-32K and setting all other numbers to the percentage of increase). This puts a much larger voltage gap between samples than was there originally. This can cause the lower level nuances to become fuzzy sounding. I have made a number of very good recordings using a 16 bit sound card but it generally takes a couple of stabs at it to get the level set just right and not over drive. The alternative is to get a 24 bit sound card where max number is 16,777, 216 (16.7M) and sample rate is 96K /sec. With this sound card you can record at 10% of the max and still use more numbers than a 16 bit card would. After normalizing you will want to convert to 16 bit or high quality MP3 to be compatible for 16 bit card playback.
Hope this helps. John -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett gazdzinski Sent: Tuesday, March 07, 2006 8:36 AM To: 'Discussion of AM Radio' Subject: RE: [AMRadio] receiver tests for Theo My recording setup is an old cassette tape deck that happens to be rack mount. The receiver filter is 5.5Kc since my ears don't work well at high frequencies, so the recording is limited... I have never taken an analog tape and converted it to a digital format. I would wonder how good a typical sound card would work converting analog to digital. On the subject of picking a receiver, I got tired of the limitations or flaws of all the commercial stuff, it seems every receiver is a compromise between cost and function, some had great audio but you had no idea of the frequency you were on. Others did SSB very well, and AM lousy. Some did AM well, and ssb poorly. Some looked very cool, some were very ugly. Some drifted, some were stable. Some were very quiet (old stuff) some were very noisy (new stuff). Some had good bandwidth choices, others had poor or no choices. Some make no provision for TX muting. If you don't want to band hop, the r390 series works very well on AM, although it needs outboard audio and is on the noisy side. My homebrew receivers were built to function, I want low noise, low distortion, accurate frequency readout, 160, 80 and 40 meter coverage, a xtal BFO for zero beating AM signals, a scope output, an S meter, and good AM selectivity choices. As an added benefit, I made it look like the rest of the home brew stuff, and made it so when you switch bands it goes from 1880, to 3880, to 7290 when you change bands. They SEEM to work well, but I need someone with good hearing to really nit pick them. Eventually, I want to add many bandwidth choices, 4, 5, 6, and 8Khz maybe. Other than the homebrews, I only have the G76 and an Icom 756 pro. The G76 has audio amp limitations, the 756 is very noisy, and rolls off the low end even with outboard audio. There are many times I could not copy signals on the R390a or the 756 that were good copy on the homebrews, weak signals on quiet bands is where the homebrews really shine. I would think an NC300 or 303 with outboard audio might be reasonable and sound good. The R390 series has a scope output built in, and it works well on receive and transmit. Its got muting, its accurate, but it is expensive and trouble prone.. Just my two cents... Brett N2DTS > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of VJB > Sent: Monday, March 06, 2006 2:01 PM > To: amradio@mailman.qth.net > Subject: [AMRadio] receiver tests for Theo > > Theo, > > In addition to looking up some AMers around your area, > I'd recommend asking for some sound files from people > who can record from the receiver candidates. > > This past weekend Brett N2DTS and myself were in QSO > on 40m with a fellow running a very clean sounding > DX-100. We both rolled tape on a specific part of the > guy's transmission. Brett if you still have that sound > file, maybe render it down to an MP3 and I'll do the > same? > > We can then describe receivers. > > Meantime, there are some other sound files kicking > around that are worth downloading. I've got a few that > I remember what receiver I used: > > >From the diode of an SP600 at 13Kc selectivity: > http://www.wa3vjb.com/sound/HUZ-FT102%20(2).mp3 > > >From the diode of an R390 at 16kc selectivity: > http://www.wa3vjb.com/sound/W2DTC-doodler.mp3 > > >From the "line output" of an R390A at 8Kc: > http://www.wa3vjb.com/sound/W0VMC.mp3 > > Steve, WB3HUZ has a pile o' files too: > http://www.amwindow.org/audio/htm/audio.htm > > Here is the sound of a 51S-1F up on 10 meters AM: > http://www.amwindow.org/audio/mov/f5hsh.mov > > > In addition, check this batch of wav and MP3: > http://www.amfone.net/audio/ > > These will give a continuum of sound quality for sure. > > Paul/VJB > > > > > > > > > > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > ______________________________________________________________ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > ______________________________________________________________ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb