Re: [Flexradio] Spurs on 10 meters and 6 meters
Jeff, As in all technologies, there are tradeoffs. In this case the tradeoff is phase noise vs. spurs at discrete frequencies. If we had used a traditional PLL type LO, my observations indicate that we would probably have 20dB lower close spacing dynamic range due to phase noise that is present at ALL frequencies. This is opposed to spurious output of a DDS, which is present only at predictable discrete frequencies. When you are trying to achieve almost 100dB of 2KHz spacing IMD DR3, a DDS is the only way I know to do that. There are very expensive and well known PLL based rigs on the market that only get 80dB of third order dynamic range at 2KHz spacing due to phase noise limitations. The worst case spurs on a DDS occur at integer divisors of the clock, which in our case is 200 MHz. As you go down in frequency (larger divisors) the spurs will reduce in amplitude according to the formula sin(x)/x. This means that as you go to lower frequencies the spurs become more closely spaced but also much lower in amplitude. Fortunately, atmospheric band noise covers the vast majority on the lower bands. In our case, we offset the DDS by 11.025 KHz +/- about 1.5 KHz. This number must be added to the display frequency to find the spurs. There are singular worst case spurs in only one location on 10m and on 6m respectively. They will show up around 28.582 (200/7 + .011) and 50.011 (200/4 +.011). The simplest method will be to just move the software IF down 22 KHz when we are near integer multiples. This would not involve shrinking the panadapter bandwidth. The IF frequency is arbitrarily chosen within the 48 KHz bandwidth. This is something that should be fairly easy to do so I will see that we move it up high in the software priority list. A longer term method is to map the spurs and linearly subtract them in the frequency domain. This subtraction would have NO effect on the signals of interest since power is additive in the frequency domain. The net-net is that I would rather implement software to do frequency planning at integer divisors of the clock than to sacrifice 20dB of dynamic range at ALL frequencies with a PLL type synthesizer. There is no way I know of to remove uncorrelated phase noise in software. 73, Gerald K5SDR FlexRadio Systems -Original Message- From: Jeff Anderson [mailto:[EMAIL PROTECTED] Sent: Tuesday, December 13, 2005 10:36 AM To: Gerald Youngblood; FlexRadio@flex-radio.biz Subject: RE: [Flexradio] Spurs on 10 meters and 6 meters Gerald, I like the radio and I very much enjoyed meeting you at Pacificon (I was talking with you when the fire broke out on Sunday), but your remarks (and those of others) and their implication that those who are concerned about the spurs really ought not be (and the perceived denigration implicit within that), beg for a reply. First, please, do not presume that the locations of the worst case spurs don't really matter. What may be don't care locations to you might be important to me or someone else. Fortunately, 10 meters isn't a happening-place at the moment, but someday... Second, I paid in the ballpark of three thousand bucks for this radio. Shouldn't I expect performance to be commensurate with this amount, and, if there are short comings, haven't I paid for the right to question these performance issues, if and when they occur, and to wonder how they can be improved upon? Third, yes - one of the radio's virtues is that performance can be improved with software updates. But if we're going to bring some reality into the discussion, then I'd prefer not to hear Marketing spin. Let's also discuss the negatives of any proposed approaches (if negatives exist), and not just the positives. I've been in the biz long enough to know that software fixes to hardware problems are usually not a panacea and often involve compromises. Are there trade-offs associated with the proposed spur fixes? E.g. shrinking of the panadapter display bandwidth (if shifting the IF)? Loss of a signal that might have been masked by a spur (if notch the spurs)? The panadapter display is a great feature. It, and the possibility of its width being expanded with a future s/w rev, were the two main reasons why I purchased this radio. And thus, to the extent that the display is anything other than perfect (with perfection being max possible displayed bandwidth no spurs (neither masking signals nor in my audio passband)), I would like to know about it. With that said, please recognize that, despite my grousing, I like the radio. But, I would also like it to be better. Best regards from a Flex-Radio customer. - Jeff, WA6AHL P.S. While I'm at it - could I make a recommendation? I would like to recommend that, when shipping the radio, you include with the radio the following items (to minimize customer grumbling and unanticipated trips to Radio Shack): 1
Re: [Flexradio] Spurs on 10 meters and 6 meters
Ross, Thanks for bringing some reality back into the discussion. The simple fact is that the locations of the worst case spurs don't really matter. Those frequencies are rarely if ever used. Also, most spurs are well below the atmospheric noise floor on HF so you don't hear them in normal operation. I own a late model Japanese radio (I paid more than the SDR-1000) that you can hear spurs everywhere if you remove the antenna. With the antenna on, most of them can't be heard. With that said, the nice thing about a software radio is that there is more we can do to remove spurs in the software. This we will do in future releases as we get time. Since most spurs are well below the atmospheric noise floor, we have not put a high priority on it yet. 73, Gerald K5SDR FlexRadio Systems -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ross Stenberg Sent: Monday, December 12, 2005 3:34 PM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Spurs on 10 meters and 6 meters Sorry. but sometimes it takes a marketing person to bring the engineers back to reality; does it really matter in the scheme of normal amateur radio operation if there is a spur at 50.011025 MHz and 28.582454 MHz? Please accept my sarcasm with the sincerest form of respect :) 73 Ross K9COX ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Spurs on 10 meters and 6 meters
At 06:49 AM 12/13/2005, Gerald Youngblood wrote: Ross, Thanks for bringing some reality back into the discussion. The simple fact is that the locations of the worst case spurs don't really matter. Those frequencies are rarely if ever used. Also, most spurs are well below the atmospheric noise floor on HF so you don't hear them in normal operation. I own a late model Japanese radio (I paid more than the SDR-1000) that you can hear spurs everywhere if you remove the antenna. With the antenna on, most of them can't be heard. I think it's important to distinguish between spurs you can hear (birdies) and spurs in the LO that result in poor adjacent signal rejection. The former are covered up by the noise, as you mention, and realistically, are no different than any other interfering signal. The latter, however, reduce the useful dynamic range of the system and adversely affect selectivity. A telling test would be to look at spurs that appear when you have a moderately strong input signal from an otherwise clean source (so the spurious signal isn't covered up by the noise sidebands of the signal) James Lux, P.E. Spacecraft Radio Frequency Subsystems Group Flight Communications Systems Section Jet Propulsion Laboratory, Mail Stop 161-213 4800 Oak Grove Drive Pasadena CA 91109 tel: (818)354-2075 fax: (818)393-6875
Re: [Flexradio] Spurs on 10 meters and 6 meters
Gerald, I like the radio and I very much enjoyed meeting you at Pacificon (I was talking with you when the fire broke out on Sunday), but your remarks (and those of others) and their implication that those who are concerned about the spurs really ought not be (and the perceived denigration implicit within that), beg for a reply. First, please, do not presume that the locations of the worst case spurs don't really matter. What may be don't care locations to you might be important to me or someone else. Fortunately, 10 meters isn't a happening-place at the moment, but someday... Second, I paid in the ballpark of three thousand bucks for this radio. Shouldn't I expect performance to be commensurate with this amount, and, if there are short comings, haven't I paid for the right to question these performance issues, if and when they occur, and to wonder how they can be improved upon? Third, yes - one of the radio's virtues is that performance can be improved with software updates. But if we're going to bring some reality into the discussion, then I'd prefer not to hear Marketing spin. Let's also discuss the negatives of any proposed approaches (if negatives exist), and not just the positives. I've been in the biz long enough to know that software fixes to hardware problems are usually not a panacea and often involve compromises. Are there trade-offs associated with the proposed spur fixes? E.g. shrinking of the panadapter display bandwidth (if shifting the IF)? Loss of a signal that might have been masked by a spur (if notch the spurs)? The panadapter display is a great feature. It, and the possibility of its width being expanded with a future s/w rev, were the two main reasons why I purchased this radio. And thus, to the extent that the display is anything other than perfect (with perfection being max possible displayed bandwidth no spurs (neither masking signals nor in my audio passband)), I would like to know about it. With that said, please recognize that, despite my grousing, I like the radio. But, I would also like it to be better. Best regards from a Flex-Radio customer. - Jeff, WA6AHL P.S. While I'm at it - could I make a recommendation? I would like to recommend that, when shipping the radio, you include with the radio the following items (to minimize customer grumbling and unanticipated trips to Radio Shack): 1. A female-to-female stereo coupler. 2. A DC Power cable (6-8 feet?). -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Gerald Youngblood Sent: Tuesday, December 13, 2005 6:50 AM To: 'Ross Stenberg'; FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Spurs on 10 meters and 6 meters Ross, Thanks for bringing some reality back into the discussion. The simple fact is that the locations of the worst case spurs don't really matter. Those frequencies are rarely if ever used. Also, most spurs are well below the atmospheric noise floor on HF so you don't hear them in normal operation. I own a late model Japanese radio (I paid more than the SDR-1000) that you can hear spurs everywhere if you remove the antenna. With the antenna on, most of them can't be heard. With that said, the nice thing about a software radio is that there is more we can do to remove spurs in the software. This we will do in future releases as we get time. Since most spurs are well below the atmospheric noise floor, we have not put a high priority on it yet. 73, Gerald K5SDR FlexRadio Systems -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ross Stenberg Sent: Monday, December 12, 2005 3:34 PM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Spurs on 10 meters and 6 meters Sorry. but sometimes it takes a marketing person to bring the engineers back to reality; does it really matter in the scheme of normal amateur radio operation if there is a spur at 50.011025 MHz and 28.582454 MHz? Please accept my sarcasm with the sincerest form of respect :) 73 Ross K9COX ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Spurs on 10 meters
Aloha Gerald, The ones on 10 meters from 28.850 to 28.585 do not go away when the antenna is unplugged. There are also numerous others on 10 meters which dont go away when the antenna is unplugged. Why is this problem so obvious on 10? 28.580-28.585 are really bad. I did a screen shot of it but file is over 6meg. I would be happy to send it to you if there was some place to upload it to like an FTP site. Stan AH6JR On Monday 12 December 2005 06:04 am, Gerald Youngblood wrote: Bill has made two interesting observations on his web page, both of which are correct. 1) Not all spurs are inside the radio. 2) Spurs caused by the DDS can be mapped and dodged The first one we can't do much about. I hear spurs on 20m here that I have confirmed go away when I unplug the antenna from the SDR-1000. Virtually all radios have spurs somewhere. On the other hand, there are software improvements that can be made to minimize or even eliminate spurs from the receiver passband. We have discussed these but they have not yet come to the top of our long wish list. There are two primary approaches that have been discussed: 1) The spurs are mathematically predictable and can thus be avoided by moving the IF pass band anywhere in the 48KHz bandwidth of the sound card. This is exactly the method Bill has documented in his experiments on the link provided below. A DDS acts like a single balanced mixer where the harmonics of the fundamental frequency mix with the 200 MHz oscillator and its harmonics. Since the mathematics are well understood, all you need to do is to predict the locations and automatically move the IF to a better frequency as Bill has demonstrated. 2) A second method is to map the spurs empirically and simply subtract them from the signal in the frequency domain. In fact the subtraction could be part of the filter itself. This is a completely linear operation. 3) We could combine both of these to get the best of both worlds. The bottom line is that it can and will be done in software when it pops to the top of the list. It will be a free download when it does. 73, Gerald K5SDR -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bill Tracey Sent: Sunday, December 11, 2005 5:21 PM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Spurs on 10 meters How sure are folks that grunge they are seeing and hearing at 28.500 MHz and thereabouts are DDS spurs? I did a little playing with this with different DDS frequencies and listening with another radio to the same frequency and have a feeling I'm hearing my computer. What I'm hearing is dependent on what is on my computer display, and can be heard on another radio with the SDR 1000 powered off. Some screenshots of various DDS tuning options and the spurs generated in the neighborhood of 28.500 are at: http://ewjt.com/kd5tfd/sdr1k-notebook/spurs/index.html Better Radio thru Software Regards, Bill ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz -- He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, Faithful and true, to the last beat of his heart. You owe it To him to be worthy of such devotion.
Re: [Flexradio] Spurs on 10 meters
Tim, Were your screen shots done with spur reduction on or off? With spur reduction on, I do not get the nine spurs you see on 28.581, I get one big spur about 5.9 khz above. Spur situation does not change @ 28.582 except the big spur is now only 4.9 khz above. For my setup with spur reduction on, the DDS is running at 28.570102 MHz for these frequencies. (This probably depends on the DDS clock offset currently set, in my case it's 7500) @ 28.582661 the DDS goes to 28.573154 and I now have three spurs visible. They march across the screen as I tune up and. At about 28.5843 on of the spurs begins to intrude on a 2.6 khz passband (one case where an alternate tuning algo would be useful) @ 28.585711 the DDS goes to 28.576206 and no spurs are evident. If I turn spur reduction off, I get something that looks like your 28.581 pic at about 28.5838, and about 1 khz above that I see a 4 spur pattern somewhat like your 28.582 pic. I suspect the difference in the exact frequencies we're seeing are probably due to different clock offset settings. I have no doubt what you're seeing are DDS spurs. The point of my post was that I think they can be avoided with a more aggressive spur dodging tuning algorithm I believe the current spur reduction algorithm simply tunes the DDS to a spur reduced pint that is within about 3 +/- khz of the frequency of interest. With +/- 24 khz of IF tuning capability I think we can dodge most (if not all) of the spurs with a cleverer tuning algorithm -- 'Better Radio thru Software. Regards, Bill (kd5tfd)
Re: [Flexradio] Spurs on 10 meters
Well stated Bill. Basically, the long and short of it is that we can improve the Spur Reduction algorithm to be a bit smarter about handling frequencies around integral dividers of the clock. But this will not eliminate noise if it is coming from another source. Eric Wachsmann FlexRadio Systems -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] radio.biz] On Behalf Of Bill Tracey Sent: Sunday, December 11, 2005 5:21 PM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Spurs on 10 meters How sure are folks that grunge they are seeing and hearing at 28.500 MHz and thereabouts are DDS spurs? I did a little playing with this with different DDS frequencies and listening with another radio to the same frequency and have a feeling I'm hearing my computer. What I'm hearing is dependent on what is on my computer display, and can be heard on another radio with the SDR 1000 powered off. Some screenshots of various DDS tuning options and the spurs generated in the neighborhood of 28.500 are at: http://ewjt.com/kd5tfd/sdr1k-notebook/spurs/index.html Better Radio thru Software Regards, Bill ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Spurs on 10 meters and 6 meters
Sorry. but sometimes it takes a marketing person to bring the engineers back to reality; does it really matter in the scheme of normal amateur radio operation if there is a spur at 50.011025 MHz and 28.582454 MHz? Please accept my sarcasm with the sincerest form of respect :) 73 Ross K9COX
Re: [Flexradio] Spurs on 10 meters
Theres a very small spur at 28.700 there are a few at up and down from 28.707 Same with 28.711 - up and down from 28.727 Basically there a quite a few all over 10 meters but the worse are at 28.580 to 28.585 Stan AH6JR On Saturday 10 December 2005 05:16 pm, you wrote: Stan, Do you see little spurs at 28.700 with Spur Reduction on as well? -Tim --- Tim Ellison ( [EMAIL PROTECTED] ) Integrated Technical Services ( http://www.itsco.com ) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Stan Sent: Saturday, December 10, 2005 9:02 PM To: FlexRadio@flex-radio.biz Subject: [Flexradio] Spurs on 10 meters While tuning around 10 meters today I came across the worst case of spurs I have ever seen on any radio. From 28.580 to 28.585 is nothing but spurs. Turning off the spur reduction makes it even worse. This 5khz is not usable for me. Its totally destroyed by the spurs. Anyone else seeing this or have I got a problem with this radio. Stan AH6JR ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz -- He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, Faithful and true, to the last beat of his heart. You owe it To him to be worthy of such devotion.
Re: [Flexradio] Spurs on 10 meters
Aloha Jeff, Well, I suppose if a new DDS chip is the answer I dont have a problem if the guys at Flex come up with one and I have to spend a few bucks to see the improvement. It is a great radio but I think this spur problem needs to be put at the top of the pile and resolved somehow. Stan AH6JR On Sunday 11 December 2005 04:17 am, Jeff Anderson wrote: Spurs are worse near frequencies which are an integral divisor of 200 MHz, plus the IF frequency. Spur reduction alleviates the problem, but does not eliminate it. For example, spurs are terrible around 50.011025 MHz (but not at the *exact* frequency of 50 MHz + IF). 50 MHz is 200 / 4. Let's take another integer divisor: 7. 200 / 7 = 28.57142857(...) MHz. Add to 11.025 KHz and you get 28.582(etc.) MHz. And the spurs are terrible in this range, too. And although spur-reduction allieviates the problem, it unfortunately does not cure it. When I received my SDR1K (about a month ago), these spurs were the most obvious problem with an otherwise great radio. Unfortunately, I think it will take a hardware change (new dds chip and...?) to reduce them - I think software's done about as much as it can do. - Jeff, WA6AHL -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Stan Sent: Sunday, December 11, 2005 12:00 AM To: Tim Ellison Cc: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Spurs on 10 meters Theres a very small spur at 28.700 there are a few at up and down from 28.707 Same with 28.711 - up and down from 28.727 Basically there a quite a few all over 10 meters but the worse are at 28.580 to 28.585 Stan AH6JR On Saturday 10 December 2005 05:16 pm, you wrote: Stan, Do you see little spurs at 28.700 with Spur Reduction on as well? -Tim --- Tim Ellison ( [EMAIL PROTECTED] ) Integrated Technical Services ( http://www.itsco.com ) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Stan Sent: Saturday, December 10, 2005 9:02 PM To: FlexRadio@flex-radio.biz Subject: [Flexradio] Spurs on 10 meters While tuning around 10 meters today I came across the worst case of spurs I have ever seen on any radio. From 28.580 to 28.585 is nothing but spurs. Turning off the spur reduction makes it even worse. This 5khz is not usable for me. Its totally destroyed by the spurs. Anyone else seeing this or have I got a problem with this radio. Stan AH6JR ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz -- He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, Faithful and true, to the last beat of his heart. You owe it To him to be worthy of such devotion. ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz -- He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, Faithful and true, to the last beat of his heart. You owe it To him to be worthy of such devotion.
[Flexradio] Spurs on 10 meters etc
Would having a 2nd refence for the DDS chip and being able to select between 200mhz and oh for example161.1328MHzbe a cure for the spurs? The frequency where the spur occurs would shift and surely a PC could do the math to provide the DDS with the proper number to hit the same frequency. -- If you can read, thank a teacher.If you can read in English., thank a soldier.
Re: [Flexradio] Spurs on 10 meters etc
Yes. Bob N4HY David Queen wrote: Would having a 2nd refence for the DDS chip and being able to select between 200mhz and oh for example 161.1328MHz be a cure for the spurs? The frequency where the spur occurs would shift and surely a PC could do the math to provide the DDS with the proper number to hit the same frequency. -- If you can read, thank a teacher. If you can read in English., thank a soldier. ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz -- Laziness is the number one inspiration for ingenuity. Guilty as charged!
Re: [Flexradio] Spurs on 10 meters etc
David At the risk of being apolitical: I thoroughly enjoyed the signature line! Yet it is a sad commentary and conundrum! Merry Christmas Eric2 From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of David Queen Sent: Sunday, December 11, 2005 3:41 PM To: FlexRadio@flex-radio.biz Subject: [Flexradio] Spurs on 10 meters etc Would having a 2nd refence for the DDS chip and being able to select between 200mhz and oh for example 161.1328MHz be a cure for the spurs? The frequency where the spur occurs would shift and surely a PC could do the math to provide the DDS with the proper number to hit the same frequency. -- If you can read, thank a teacher.If you can read in English., thank a soldier.
Re: [Flexradio] Spurs on 10 meters
How sure are folks that grunge they are seeing and hearing at 28.500 MHz and thereabouts are DDS spurs? I did a little playing with this with different DDS frequencies and listening with another radio to the same frequency and have a feeling I'm hearing my computer. What I'm hearing is dependent on what is on my computer display, and can be heard on another radio with the SDR 1000 powered off. Some screenshots of various DDS tuning options and the spurs generated in the neighborhood of 28.500 are at: http://ewjt.com/kd5tfd/sdr1k-notebook/spurs/index.html Better Radio thru Software Regards, Bill
Re: [Flexradio] Spurs on 10 meters
Hi Bill, Certainly not all of the gunk is DDS related. But I think the tall-sharp spurs, in general, are. Try this experiment: 1. Set receiver to USB and Spur Reduction OFF. 2. Set receiver frequency to 28.581700 MHz. 3. Tune up in frequency (I use 10 Hz steps). You should see a picket-fence of spurs which come closer and closer together until, at about 28.582454 MHz they should disappear altogether (but you may hear a slight beating from your speakers). As you tune through and past this frequency, the spurs will reappear very close together, and then their spacing will increase as the frequency increases away from 28.582454. (You can also do the same test tuning up and through 50.011025 MHz.) Given that 28.582454 = (200/7)+ 0.011025 MHz (rounding the result), that is, 200/7 + IF frequency, and it is at this frequency that the spurs disappear, I think it's reasonable to assume that the picket-fence is DDS related. The Spur-Reduction does a good job in minimizing the spurs (by, in essence, selecting frequencies that result in subsets of the picket-fence pattern). You can check this by tuning from 28.581700 through 28.582454 with spur reduction ON and OFF. You'll see a dramatic difference in the spurs with Spur Reduction ON, and you should see some similarities between the spur-spacing with reduction ON, compared to the spacing at certain frequencies with the reduction Off. If you try this, I'd be very interested to know what you think about it... Best Regards, - Jeff, WA6AHL P.S. Note - the spur-reduction algorithm has an or term (see email from Eric W. posted Friday) whose purpose I don't understand - it would be interesting to try spur-reduction with and without this or term, and see which method gives the best overall spur-reduction performance. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Bill Tracey Sent: Sunday, December 11, 2005 3:21 PM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Spurs on 10 meters How sure are folks that grunge they are seeing and hearing at 28.500 MHz and thereabouts are DDS spurs? I did a little playing with this with different DDS frequencies and listening with another radio to the same frequency and have a feeling I'm hearing my computer. What I'm hearing is dependent on what is on my computer display, and can be heard on another radio with the SDR 1000 powered off. Some screenshots of various DDS tuning options and the spurs generated in the neighborhood of 28.500 are at: http://ewjt.com/kd5tfd/sdr1k-notebook/spurs/index.html Better Radio thru Software Regards, Bill ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
[Flexradio] Spurs on 10 meters
While tuning around 10 meters today I came across the worst case of spurs I have ever seen on any radio. From 28.580 to 28.585 is nothing but spurs. Turning off the spur reduction makes it even worse. This 5khz is not usable for me. Its totally destroyed by the spurs. Anyone else seeing this or have I got a problem with this radio. Stan AH6JR
Re: [Flexradio] Spurs on 10 meters
Same here, Stan. I'm sure it's not your specific system. Gary AI4IN -- Original message -- From: Stan [EMAIL PROTECTED] While tuning around 10 meters today I came across the worst case of spurs I have ever seen on any radio. From 28.580 to 28.585 is nothing but spurs. Turning off the spur reduction makes it even worse. This 5khz is not usable for me. Its totally destroyed by the spurs. Anyone else seeing this or have I got a problem with this radio. Stan AH6JR ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Spurs on 10 meters
Stan, Same here too with 1.4.5p7. Turning off Spur reduction shifts my spurs down a little. Having the frequency on 28.581 with SR off is the worst. -Tim --- Tim Ellison ( [EMAIL PROTECTED] ) Integrated Technical Services ( http://www.itsco.com ) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Stan Sent: Saturday, December 10, 2005 9:02 PM To: FlexRadio@flex-radio.biz Subject: [Flexradio] Spurs on 10 meters While tuning around 10 meters today I came across the worst case of spurs I have ever seen on any radio. From 28.580 to 28.585 is nothing but spurs. Turning off the spur reduction makes it even worse. This 5khz is not usable for me. Its totally destroyed by the spurs. Anyone else seeing this or have I got a problem with this radio. Stan AH6JR ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
