Re: [digitalradio] center of the waterfall question
Bill Aycock wrote: Frank- I think that there is MUCH confusion in our ranks on this subject. For instance, I set my rig to one frequency (usually 14,070.00) and leave it there. I tune to different signals by moving the marker that shows the offset from the base frequency on the waterfall. The radio bandwidth is many times as wide as the signal width (for PSK31), and many signals can be accommodated in the passband. I have a tuneable Digital filter, and one of the most educational tricks is to shift the upper and lower audio limits of the filter, and watch the result on the waterfall One of the sources of the confusion is the ambiguity in the meaning of best. I think that it is highly improbable that we can get a clear definition. Good luck- Bill-W4BSG In my opinion there are two classes of radios for digital use, and which type you have dictates how you handle the center frequency question. Older legacy radios do not allow use of narrow crystal filters (originally intended for CW) in the digital modes. The designers of these radios either ignored the digital modes altogether (requiring, for example, interfacing the radio through the mic connector) or simply didn't care much (my FT-900, an otherwise good radio, falls into this category). These radios can be used for digital, but lack the most important QRM-fighting tools--the crystal and mechanical filters. For these radios you can get away with tuning by leaving the VFO alone and simply moving the marker on the waterfall to the signal you wish to receive. But you will miss receiving many, many signals if the band is at all crowded if you tune using this technique. Newer radios generally all allow use of the narrow crystal and mechanical filters in the digital modes and typically have a special DIGI mode setting for this purpose. For radios of this type, it is *very important* to tune the station that you are working to the center frequency rather than simply moving the marker on the waterfall and not touching the VFO. The reason is that otherwise you cannot use the crystal and mechanical filters of your rig effectively. The optimal way to tune a station with a modern rig is to place the received signal in the center frequency passband, typically either 1000hz (most Yaesu radios, for example) or 1500 hz, and then utilize the rig's narrow filter. For PSK31, literally the narrower the better -- for example, my Mark V's 250hz filters are super for PSK modes, and the 500hz filters are great for MFSK, 500hz Olivia, Domino, and MT63. Doing this also makes the IF width and shift controls much more effective, and often you can use these controls to eliminate even a QRMing signal that is inside the narrow passband corridor. Placing the received signal in the center frequency passband often makes a huge difference in your ability to receive a signal. Often if there is a strong PSK signal elsewhere on the band, it will desensitze your receiver through AGC action to the point where you are not receiving the weaker signals at all. Kick in the narrow filters, and this problem will disappear. This is true even with higher-end rigs such as the FT1000MP/Mark V. Sure, you can work stations by simply moving the marker to the station you want to work rather than tuning the same station to your rig's center frequency, but this technique is sub-optimal and makes the signal you wish to receive subject to QRM and AGC desensitization even from signals 1Khz or more away. You can usually readily see how important 1) tuning the received signal to the center frequency and 2) kicking in the narrow filters actually is, by watching the waterfall. Often the waterfall on the rig will be dark when the passband is wide open, and much lighter on the received signal once the filters are kicked in. This is because some stronger signal outside of the filter passband is desensitizing the receiver. I can often copy signals with the filters in the circuit that are completely invisible on the waterfall without the filters. The best digital programs recognize the importance of tuning the received signal to the center passband frequency, and make this easy to do. DM780 has a center frequency marker, and with one click of an icon it automatically tunes the received signal to the center passband (moves the received signal marker to the C center frequency marker). One more click and you can kick in whichever narrow filters your rig has that are appropriate for the mode, e.g. 500hz for MFSK, much narrower for PSK. MixW also enables the user to do this with a few clicks by use of an easy-to-program macro function. As the band conditions start to improve, with more signals on the band (remember, we are presently right at the solar minimum) using the narrow filters on digital modes will become more and more important. de Roger, W6VZV
Re: [digitalradio] center of the waterfall question
- Original Message - From: Roger J. Buffington [EMAIL PROTECTED] As the band conditions start to improve, with more signals on the band (remember, we are presently right at the solar minimum) using the narrow filters on digital modes will become more and more important. It will be very, very interesting in two or three years. I expect that we will use 14.070 to 14.076 or so... Simon HB9DRV
Re: [digitalradio] center of the waterfall question
Roger- thanks for an excellent set of comments. With my rig (FT-920), my best filtering is in the audio, which limits me. I do have a narrower (INRAD) filter than the stock one and that helps. I can dream about a tuneable RF filter, though, can't I? Thanks- Bill-W4BSG At 05:37 AM 10/1/2007, you wrote: Bill Aycock wrote: Frank- I think that there is MUCH confusion in our ranks on this subject. For instance, I set my rig to one frequency (usually 14,070.00) and leave it there. I tune to different signals by moving the marker that shows the offset from the base frequency on the waterfall. The radio bandwidth is many times as wide as the signal width (for PSK31), and many signals can be accommodated in the passband. I have a tuneable Digital filter, and one of the most educational tricks is to shift the upper and lower audio limits of the filter, and watch the result on the waterfall One of the sources of the confusion is the ambiguity in the meaning of best. I think that it is highly improbable that we can get a clear definition. Good luck- Bill-W4BSG In my opinion there are two classes of radios for digital use, and which type you have dictates how you handle the center frequency question. Older legacy radios do not allow use of narrow crystal filters (originally intended for CW) in the digital modes. The designers of these radios either ignored the digital modes altogether (requiring, for example, interfacing the radio through the mic connector) or simply didn't care much (my FT-900, an otherwise good radio, falls into this category). These radios can be used for digital, but lack the most important QRM-fighting tools--the crystal and mechanical filters. For these radios you can get away with tuning by leaving the VFO alone and simply moving the marker on the waterfall to the signal you wish to receive. But you will miss receiving many, many signals if the band is at all crowded if you tune using this technique. Newer radios generally all allow use of the narrow crystal and mechanical filters in the digital modes and typically have a special DIGI mode setting for this purpose. For radios of this type, it is *very important* to tune the station that you are working to the center frequency rather than simply moving the marker on the waterfall and not touching the VFO. The reason is that otherwise you cannot use the crystal and mechanical filters of your rig effectively. The optimal way to tune a station with a modern rig is to place the received signal in the center frequency passband, typically either 1000hz (most Yaesu radios, for example) or 1500 hz, and then utilize the rig's narrow filter. For PSK31, literally the narrower the better -- for example, my Mark V's 250hz filters are super for PSK modes, and the 500hz filters are great for MFSK, 500hz Olivia, Domino, and MT63. Doing this also makes the IF width and shift controls much more effective, and often you can use these controls to eliminate even a QRMing signal that is inside the narrow passband corridor. Placing the received signal in the center frequency passband often makes a huge difference in your ability to receive a signal. Often if there is a strong PSK signal elsewhere on the band, it will desensitze your receiver through AGC action to the point where you are not receiving the weaker signals at all. Kick in the narrow filters, and this problem will disappear. This is true even with higher-end rigs such as the FT1000MP/Mark V. Sure, you can work stations by simply moving the marker to the station you want to work rather than tuning the same station to your rig's center frequency, but this technique is sub-optimal and makes the signal you wish to receive subject to QRM and AGC desensitization even from signals 1Khz or more away. You can usually readily see how important 1) tuning the received signal to the center frequency and 2) kicking in the narrow filters actually is, by watching the waterfall. Often the waterfall on the rig will be dark when the passband is wide open, and much lighter on the received signal once the filters are kicked in. This is because some stronger signal outside of the filter passband is desensitizing the receiver. I can often copy signals with the filters in the circuit that are completely invisible on the waterfall without the filters. The best digital programs recognize the importance of tuning the received signal to the center passband frequency, and make this easy to do. DM780 has a center frequency marker, and with one click of an icon it automatically tunes the received signal to the center passband (moves the received signal marker to the C center frequency marker). One more click and you can kick in whichever narrow filters your rig has that are appropriate for the mode, e.g. 500hz for MFSK, much narrower for PSK. MixW also enables the user to do this with a few clicks by use of an easy-to-program macro function. As the band conditions
Re: [digitalradio] center of the waterfall question
So which is better, park the dial and move the audio center frequency (ACF) ldquo;markerrdquo;, or park the marker and move the frequency dial? The former seems to be the standard method used for PSK31 (when using programs like Digipan and PSK31), but the latter seems to make more sense in the context of finding your peak output point in the bandpass and leave your marker there for best decoding. Is it partially dependant on the available filters and/or the age of the rig and its ability to handle digital modes? This latter concept seems to fly in the face of guidance (at least for modes like Olivia) provided on hflink.com and other tutorial sites where the ACF marker is supposed to be set in accordance with the tone pair/mode in use and the frequencies are voluntarily set based on the ldquo;sub-bandrdquo; (.65 or .50, etc). This suggests that both the frequency and ACF should be fixed or channelized, regardless of rig or bandpass ldquo;sweet spotsrdquo;. From the context of making it easier to find signals and establish QSOrsquo;s, this guidance makes sense, assuring (to some degree) that if your dial is set to a specific frequency and your ACF marker is in the proper spot for the tone pair in use, any one who comes along can find you quickly. If everyone running Olivia between 14104 and 14109 used ldquo;channelsrdquo; on .50, a tone pair of 1000/32 and a marker on 1000hz (at least to call CQ) QSOs would be much easier to locate and lock onto. Between 14072 and 14078, ldquo;channelsrdquo; should be on .65, running 500/16 with an ACF of 750Hz. Easier, but is it at the expense of best decoding, power output, and QRM avoidance? Again, this is all by gentlemenrsquo;s agreement, but there seems to be little other established guidance in print or on the web. Was this originally suggested to assist in happily co-existing with other ldquo;channelizedrdquo; modes frequently found in these sub-bands, like Pactor? Wouldnrsquo;t the ldquo;park the marker, move the dialrdquo; method make it difficult to post and follow digital spots on sites like Andyrsquo;s (K3UK) if everyonersquo;s dial showed a different frequency? (A minor concern, maybe, but certainly a huge help on these sparse bands!) Finally, could this same question be applied equally to RTTY, where it depends on the software used, despite long established rules for mark/space frequencies? If I use MixW, I can keep my rig dial fixed and click on any of several signals in the passband, decoding them all equally (easy, certainly but not optimal). Is this just the wrong way to use this software? Should the ACF be locked centered between the standard RTTY M/S audio frequencies and the dial moved? Using MMTTY, the marker stays fixed and the dial is adjusted so itrsquo;s not a concern. Is one better than the other, personal preference, or rig dependent? R/ Glenn KD4ULB Bill Aycock wrote: Frank- I think that there is MUCH confusion in our ranks on this subject. For instance, I set my rig to one frequency (usually 14,070.00) and leave it there. I tune to different signals by moving the marker that shows the offset from the base frequency on the waterfall. The radio bandwidth is many times as wide as the signal width (for PSK31), and many signals can be accommodated in the passband. I have a tuneable Digital filter, and one of the most educational tricks is to shift the upper and lower audio limits of the filter, and watch the result on the waterfall One of the sources of the confusion is the ambiguity in the meaning of best. I think that it is highly improbable that we can get a clear definition. Good luck- Bill-W4BSG In my opinion there are two classes of radios for digital use, and which type you have dictates how you handle the center frequency question. Older legacy radios do not allow use of narrow crystal filters (originally intended for CW) in the digital modes. The designers of these radios either ignored the digital modes altogether (requiring, for example, interfacing the radio through the mic connector) or simply didn't care much (my FT-900, an otherwise good radio, falls into this category). These radios can be used for digital, but lack the most important QRM-fighting tools--the crystal and mechanical filters. For these radios you can get away with tuning by leaving the VFO alone and simply moving the marker on the waterfall to the signal you wish to receive. But you will miss receiving many, many signals if the band is at all crowded if you tune using this technique. Newer radios generally all allow use of the narrow crystal and mechanical filters in the digital modes and typically have a special DIGI mode setting for this purpose. For radios of this type, it is *very important* to tune the station that you are working to the center frequency rather than simply moving the marker on the waterfall and not touching the VFO. The reason is that otherwise you
Re: [digitalradio] center of the waterfall question
Frank- I think that there is MUCH confusion in our ranks on this subject. For instance, I set my rig to one frequency (usually 14,070.00) and leave it there. I tune to different signals by moving the marker that shows the offset from the base frequency on the waterfall. The radio bandwidth is many times as wide as the signal width (for PSK31), and many signals can be accommodated in the passband. I have a tuneable Digital filter, and one of the most educational tricks is to shift the upper and lower audio limits of the filter, and watch the result on the waterfall One of the sources of the confusion is the ambiguity in the meaning of best. I think that it is highly improbable that we can get a clear definition. Good luck- Bill-W4BSG At 10:27 PM 9/4/2007, you wrote: Hey group, this is Frank K2NCC, Just wanted to ask what is surely a noobie question or two. If my waterfall (using MixW) can receive a signal between 300KHz and 3000KHz on the spectrum, that's my bandwidth of the radio, right? Seems to match what the manual says, 2700. I've read where PSK31 is best at 1000KHz on the audio marker in a QSO. But, one could QSO pretty far on either side of that line if you avoid the fringes. Right? Oh, if it matters, the radio is TS-830S and a Signalink. Well, the halfway point on the waterfall for me is about 1650 on the audio marker. I'm guessing that whatever frequency I'm on when I tune the signal to that 1650 point, is the frequency they're transmitting on. I asked and have been very close, but can only hope that my rig is on the mark. Either way, it's not been off by more than 3Hz. Since the rig only has six digit display, I round it off anyway. Is that the best place to transmit and receive? Dead center of the frequency seems to be the ideal place if both sides are doing the same. 73. Frank K2NCC Announce your digital presence via our Interactive Sked Page at http://www.obriensweb.com/drsked/drsked.php Yahoo! Groups Links We batter this Planet as if we had someplace else to go.
