Re: [Flexradio] USB3 USB3 USB3
I was looking at the available 2.5 cases for laptop drives at Fry's last week and noticed that a large number of them now allow for USB3. It is about time! I have been using ESATA to get fast backup from my desk computer to my external 2 TB drives, and USB3 seems to enable even faster transfer. None of the 2.5 drive cases at Fry's had firewire as an option, which is what I was actually looking for. My wife's Alienware M11x laptop has firewire, but not USB3. - Dan, N7VE -Original Message- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz] On Behalf Of Alan NV8A Sent: Tuesday, September 14, 2010 1:41 PM To: flexradio@flex-radio.biz Subject: Re: [Flexradio] USB3 USB3 USB3 I have read that Intel is betting on an optical-fiber technology that is claimed to be faster and more flexible (physically) than USB3. The only USB3 devices of which I am aware are the Seagate GoFlex external drives. They come with a USB2 interface, but that can be replaced by any one of a number of optional interfaces, including USB3. I have also read that even USB2 device will transfer data faster when connected to a USB3 port. 73 Alan NV8A On 09/14/10 03:52 pm, Neal Campbell wrote: Not quite true! I would say 40% of the motherboards out have a model that supports USB3 and the addon cards for it are about the same price as the usb2 add on cards. I haven't seen any products yet that do USB3 but the computer side is there and waiting. FYI, Intel has dropped support for PCI moving forward so better learn to love pcie! 73 Neal Campbell Abroham Neal Software www.abrohamnealsoftware.com (540) 645 5394 NEW PHONE NUMBER Amateur Radio: K3NC Blog: http://www.abrohamnealsoftware.com/blog/ DXBase bug reports: email to ca...@dxbase.fogbugz.com Abroham Neal forums: http:/www.abrohamnealsoftware.com/community/ On Tue, Sep 14, 2010 at 10:20 AM, Clay W7CEw...@curtiss.net wrote: I wouldn't get too excited about USB3 yet. Intel does not support USB3 in any of their chip sets yet and is not expected to until sometime in the middle of 2011. Until Intel jumps on the bandwagon (which they will), there will be too many computers without USB3 for it to be a serious contender. Even then, it will take a couple of years before most computers support it. A company like FlexRadio should not even consider USB3 before 2012. 73, Clay W7CE On 9/13/2010 7:10 PM, Eddie DeYoung wrote: I just couldn't keep quiet now that a new kid has entered the fray of connectivity! USB3... is now creeping onto most new home and laptop PC's... and IEE1394a is disappearing from all but the 'top end' laptops. ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/
Re: [Flexradio] Flex 1500 on 10 GHz weak signal
My wife is getting an Alienware M11x (Dell) tomorrow. It has an 11 display (1366 x 768 resolution), dual core i7 processor, build in firewire port, and a reasonable battery life. It seems like it might make a real nice portable SDR package for the folks that want to do this. - Dan, N7VE -Original Message- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz] On Behalf Of David McKenzie Sent: Thursday, July 15, 2010 5:38 AM To: Clay W7CE Cc: flexradio@flex-radio.biz Subject: Re: [Flexradio] Flex 1500 on 10 GHz weak signal Hi Paul, I may be interested as well. Thanks for your hard work in this field. Also, I think with the release of the Flex-1500 and the prevalence of netbooks, FRS should look at resizing the PowerSDR display to a minimum of 1024x600 instead of 1024x768. What's 168 pixels among friends? Regards, David K1FSY On Wed, Jul 14, 2010 at 10:17 PM, Clay W7CE w...@curtiss.net wrote: Paul, Sign me up for one. 73, Clay W7CE - Original Message - From: Paul Wade W1GHZ w1...@comcast.net To: flexradio@flex-radio.biz Sent: Wednesday, July 14, 2010 6:56 PM Subject: [Flexradio] Flex 1500 on 10 GHz weak signal got a chance to try out my new Flex 1500 on 10 GHz last Saturday. the N.E.W.S. Group was running MDS (Minimum Discernable Signal) testing on 10 GHz. (you can read more details in August QST - Microwavelengths) basically, a distant signal is reduced in 1 dB steps with each station recording the level where it is no longer audible. then it is moved in frequency a few KHz, and the level increased in 1 dB steps with folks trying to find it again. with the Flex, I lost the signal 2 or 3 dB before the best stations, but I found it again at the same level, using the waterfall display. the other stations, by ear, needed about 5 dB more signal to find it coming up out of the noise - a typical difference. I could not hear any signal when it first appeared in the waterfall. this should be great for portable operation. I was running this on a Netbook, making a nice portable package. the only problem is that the PowerSDR display is bigger than the Netbook screen in the vertical direction. any way to make display size an option? now for the two meter transverter for the microwave IF. I dug out my Miniverter (www.w1ghz.org/miniverter.zip) and am considering updating it to mate with the Flex 1500. any interest? 73 paul ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] Automatic Gain Control Threshold AGC-T versusreality
Sounds like a SDR could possibly automatically compute a best AGC-T setting by looking at an average of the 1% lowest signal content frequency bins across the band. - Dan, N7VE -Original Message- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz] On Behalf Of Lee A Crocker Sent: Monday, June 29, 2009 10:00 AM To: Flexradio Subject: Re: [Flexradio] Automatic Gain Control Threshold AGC-T versusreality The AGC threshold is basically the threshold where the AGC starts to reduce gain. That threshold is in no way set and forget. It is based on the band noise, and it should be set for each band/antenna combination. What AGC does is reduce gain. If you are trying to hear a very weak station at the level of the noise the LAST thing you want is your gain to be reduced. Being able to control this level therefore can be the difference between copy and no copy. It also is what makes the receiver so quiet. If you set the AGC-T correctly you can hear every signal on the band but you are not attaked by the constant drone of noise. The way AGC-T is set is to find a clear place on the band and set the AGC-T to where the noise is barely perceptible. You may need to increase the value the Audio to compensate. This maneuver sets up gain distribution across the stages of the radio, and it is set up correctly and remembered for each band, and for each season. Summer time static in a properly set up F5K or F3K melts into the background, while in the winter when the static is gone you may well want to run the receiver in a different position because the noise is so much less. The point being if static is S-9 you are not going to hear anyone that is S-1. If noise is close to S-0 then a S-1 signal is Q5. Alternatively you would never want to run the radio set up for S-0 conditions with S-9 static. This is exactly why it is not set and forget and needs to be adjusted for each band according to the noise that exists on each band. Legacy radios are clueless when it comes to this understanding of how to distribute gain. They are clueless largely because their gains are set in stone and can not be adjusted, AND thier AGC loops are a hodgepodge of non linear gain and distortion. This is the exact reason most legacy radios are not linear across the S meter reading. What you see on the S meter is merely a error voltage that tells you how much AGC is being employed. The Flex gives you a linear response across the dynamic range, so in a properly adjusted Flex the radio hears super strong stations with the same ability as it does stations virtually under the noise. If you are not experiencing this then it is likely you have not set up the radio correctly. 73 W9OY ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] Sensitivity
When I make measurements on my homebrew receivers in the -136 dBm range (using an HP8640B), I definitely notice a time of day sensitivity variation. I have chalk this up to external atmospheric noise (20m/30m) bleeding through the coax. I understand coax shielding is only good for ~30 db of attenuation. I just say this to affirm that making sensitivity measurements on very sensitive receivers with out a shielded cage can be a bit difficult. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Lux, James P Sent: Wednesday, December 10, 2008 11:26 AM To: Jon Maguire; FlexRadio Reflector Subject: Re: [Flexradio] Sensitivity Sensitivity measurements are a canard, anyway, at least for HF. Atmospheric noise is going to dominate receiver noise for the most part. What you REALLY want to know is the instantaneous dynamic range (how big a signal next to my signal can I tolerate). Not only that, but making quality measurements at -140dBm or -150dBm is non-trivial. (we do this at work for space radios) How do you know that you're not getting wideband hash from the computer in the next room leaking into your test set? What's the precision of your attenuator that's giving you your test signal? You might have a precision 0dBm source, and the signal generator has 10dB steps, but I'll bet that the 140dB step has a pretty big uncertainty. (just from packaging issues) (Agilent E8663B which goes down to -135dBm, only has level accuracies to -80dBm, where it's +/-0.8dB) (Agilent E4418B power meter with the 8481D head (which goes down to -70dBm) is good to 1-2%) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jon Maguire Sent: Wednesday, December 10, 2008 9:21 AM To: FlexRadio Reflector Subject: [Flexradio] Sensitivity Hello fellow Flexers. This was posted on the IC7700 Yahoo group the other day. Some comments would be interesting. Thank you. 73... Jon W1MNK Wow, that surprises me.. I thought the IC-7700 would have better noise floor figures when signal sensitivy is equal with the Pro 3. When you're into the -140 dBm MDS range, I would expect some sampling variance from rig-to-rig. The ARRL lab engineers are testing one unit, not a large sample. So, on any given day, they may end up with a unit that measures slightly better or worse than another production unit. Now compare MDS in the QST Product Reviews at 14 50 MHz across a range of transceivers from competing manufacturers. Generally, the Icom rigs are far and away more sensitive than their competition. For example, look at the MDS for the new SDR product like the Flex-5000A. ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] The inelegant Keying solution
I think your basic problem with your solutions has been you are trying to minimize the current load to the keyer. This small current shorting to ground is the true source of your problem. The real solution is to increase to current. Moving to a relay does exactly that, but a mechanical solution like a relay will have contacts that will eventually have the same low current contact problem. Someone else posted the same contact problems on a receive only application (no current drain) that could be fixed only by using mercury wetted contact relays. I suggest instead returning to one of your earlier buffering experiments and greatly **increasing** the current through the contacts to perhaps 20 to 50 mA. Experiment with what current it takes to be reliable. I would suggest a simple 2n7000 with a gate pull up resistor to +12v such as 470 ohms (~25 ma). The paddle grounds the gate, drawing 25 mA through the paddle contacts. Since this is an inverter stage, a second stage is needed to get a non-inverted signal. Use a drain resistor of ~10K on this first MOSFET, and drive a second 2N7000 whose gate is connected to the drain of the first 2N7000. Bypass both gates with a 0.01 uf cap to ground for RF bypass. For both sides of the paddles, that is four 2N7000s, four resistors (2 10K, 2 470), and four caps, a rather minimal circuit. Alternatively, you could possibly look at the keyer input of the SDR5000/SDR1000 and add pull up resistors right there at the jack to either +5v or +12 depending on what the input circuit needs to see as a high voltage using a resistor mounted internally that sets the current to a high enough value. The higher contact current should keep the contacts from oxidizing and make things more reliable. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Lee A Crocker Sent: Thursday, July 03, 2008 8:38 PM To: Flexradio Subject: [Flexradio] The inelegant Keying solution I normally run my F5K with an external keyer through the serial port, which is a hold over from the SDR-1000 days. It made for an easy way to switch the keyer between 3 radios, by merely opening up PSDR SETUP and turning on the correct serial port to the radio I wanted to key. I tried using the internal PSDR/F5K internal keyer using my Begali paddles and found some intermittent trouble with the keying, dropped elements or the keyer would hang on a string of dits or dahs and would not turn off till I hit the paddle again. I have been working on different solutions to this keying issue with the internal keyer. I have built various circuits, trying to find a simple solution. I have a Begali Graciella paddle and it has gold contacts. I have a Begali Simplex Mono which has non gold contacts, and neither are they coin silver. The problem appears to be that the amount of current pulled from the KEY input at the nominal 3 volt voltage on the Key port makes my Begalli keys behave as an incompletely forward biased diode and not a conductor, and that signal appears to be ambigious to whatever is sensing it inside the radio. I tried using such things as PNP transistor buffers on the KEY input on the F5K to no avail. The junction of the transistor behaved the same as the paddle itself. I tried fooling around with a NE556 to act as a signal conditioner/debouncer and didn't like the result of that either. I wired up a couple of 12v reed relays and this seems so far to have cured the problem. I measured about 5ma current drawn through the relay coil using a 9V battery and at that current level the Begali operates in an unambitious way to the relay coil, and the relays thus far have keyed the KEY input flawlessly.. So this maybe a simple yet inelegant way to solve the keying issue. I used a couple of relays out of the junk box, but Radio Shack does sell some 12V reed relays that should work fine. The circuit is basically V+ or the + of the battery goes to the top of each relay coil and then each coil goes to either the dit or the dah of the paddle and then the ground of the paddle goes to the - side of the battery or ground. One side of each relay switch goes to ground. The other side of each relay switch either goes to DIT on the KEY jack or DAH on the key jack. For the relays I used polarity is not an issue, but some relays have built in protection so you may have to watch that. The battery only draws current when the contact is closed, so that part is elegant, and it will cost under 10 bux to build, which beats the hell out of some 40 dollar micro-pic solution. Eventually I will hook it up to the station 12V supply and probably rebuild it inside a pill bottle with a 1/4 inch stereo phone plug but I wanted to make sure it was going to work before I went to that trouble. If you build it the way I describe, the 12V will be dropped through the coils and will be self protecting, so if you get a screw driver across the paddle contacts it wont be like shorting
Re: [Flexradio] Processor Affinity for PowerSDR
We are running quad core processors at work for simulation. For our single threaded simulations, a 2.6 GHz quad core is a bit slower than our 3 GHz Core 2 Duo machines. On the other hand, when we run four simulations at the same time on the quad core machines (as long as the simulations are not too big and we have the memory), the run time for four simulations just a tiny bit slower than the run time for one simulation. Multi processor cores only really shine when the software is set up to take advantage of the multiple processing units, which can be a painful thing to do well. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tim Ellison Sent: Saturday, March 29, 2008 7:28 PM To: [EMAIL PROTECTED]; flexradio@flex-radio.biz Subject: Re: [Flexradio] Processor Affinity for PowerSDR I have a Core 2 Duo machine running XP and I see no different in performance if PowerSDR is configured to run only on one core. If you get up to 4 and 8 way core CPUs, context switching may impart some additional latency, but I only have two cores to work with. Other people's mileage may vary. -Tim -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Saturday, March 29, 2008 7:27 PM To: flexradio@flex-radio.biz Subject: Re: [Flexradio] Processor Affinity for PowerSDR So we are better off with a fast, single processor CPU than a bit slower multiple one for the SDR apps if we are going to limit to one? N0UU ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kb.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kb.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kb.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] 2nd receiver option questions
Diversity reception reduces resistance to fades. For this, we try to space our cell site antenna 10 wavelengths apart in order to minimize the correlation of the fades between the two antennas. However, diversity is also deployed on a lot of cell phone handsets today and the antenna spacing they use is much closer than this. 7 of separation at 800 MHz is only about half a wavelength. Never-the-less we see large improvements in the throughput capabilities even with this close spacing. I guess all I am saying here is that when using diversity, it is best to spread the antenna apart quite a ways, but that even a half wavelength spacing provides benefits. I should note that the new generation of cell phone equipment is not only making use of receiver diversity (that is kind of old hat), but that it is now making use of transmit diversity also. Unfortunately, that does not work with CW or SSB since sending the same signal out both antennas causes beam forming. It only works with data modes that modify the data from the one antenna so that it is different from the same data from the second antenna (complex conjugate?) and requires the receiver on the other end to understand what is going on so that it can put the two back together. I think SDR is an exciting concept. One of things that we are doing for the next generation of cell phone equipment is to do beam forming using feedback from the other receiving end. We call this precoding. It seems feasible that a high tech SSB or cw QSO between a pair of diversity transmit equipped transceivers could run a separate, slow speed, intermittent data stream that could feedback to each other precoding data that would allow phased transmit antennas on both sides to automatically track and align the beam steered transmit signal to each other in an optimized fashion. It could take the form of a small blip of precoding data on the receive to transmit changeover. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim, W4ATK Sent: Thursday, October 11, 2007 6:41 AM To: Lee Mushel; [EMAIL PROTECTED]; FireBrick; FlexRadio List; Jim Lux Subject: Re: [Flexradio] 2nd receiver option questions AS I remember there is more to diversity reception than just two receivers. Back in the war (Korea) we used three rosettes of rhombics fairly widely seperated with our RCA Diversity receivers (Huge seven foot racks). Later in my career we used diversity across Lake Ponchatrain on 6GHz, the dishes were spaced several wavelengths apart vertically on the tower. I doubt that many hams would have the space or antenna farm to support such activity, but then again I may be wrong. After seeing the full sized 80M 5 element Yagi the gentleman is Japan had constructed, I guess all it takes is $$. Jim, W4ATK -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Lee Mushel Sent: Thursday, October 11, 2007 8:34 AM To: [EMAIL PROTECTED]; FireBrick; FlexRadio List; Jim Lux Subject: Re: [Flexradio] 2nd receiver option questions OK, Gerald, step up and explain to these kids what dual diversity is all about! Lee K9WRU - Original Message - From: Jim Lux [EMAIL PROTECTED] To: [EMAIL PROTECTED]; FireBrick [EMAIL PROTECTED]; FlexRadio List flexradio@flex-radio.biz Sent: Thursday, October 11, 2007 8:11 AM Subject: Re: [Flexradio] 2nd receiver option questions At 05:37 AM 10/11/2007, [EMAIL PROTECTED] wrote: I understood (Hope ??) that the receiver on the FLEX5k is independent of the transmitter. If so then splitband should be possible already, and is the software the bottleneck. Or I am to optimistic and is the hardware not able to cater for that. Other question Can the 2nd receiver be used on the sane frequency as the main receiver, BUT WITH EXACTLY THE SAME FREQUENCY AND PHASE? Then you can do nice experiments with 2 small loop arials, 90 degrees crossed. I believe that this came up in early discussions of the F5K design on the list. Here's my recollection. Yes, the LO to the two receivers is driven from the same reference oscillator, so setting to exactly the same frequency is trivial. The latch signal to the two DDSes can theoretically be asserted simultaneously, so the phase should be the same (but this detail is buried in the firmware of the F5K, perhaps a Flex rep can confirm), with perhaps a slight offset due to propagation delay in the wires which will inevitably be of different lengths, etc. So the real question is whether the audio interface brings the data across time aligned from all receivers. There's no reason why it wouldn't be so, assuming all the A/Ds are clocked at the same rate. Again, I suspect that this is under the control of the firmware inside the F5K, so Flex would need to confirm. SO all you're left with is the inevitable offsets because of the differences in electronics among the channels (the filters on the output of
Re: [Flexradio] Noise floor, specifying
I like the way that PowerSDR allows you to make relatively precise noise floor measurements for either the receiver or for the current band conditions. The RX meter tends to bounce around a lot on noise, making it hard to determine a good average. However, if your receiver has been calibrated, you can switch the RX meter from Signal to Sig Ave and get a much longer term average reading of the noise. I like to average over a longer time that used for the defaults, which can be changed by going to Setup, selecting the Display tab, looking for the Multimeter section in the lower right corner, and changing Average Time to something in the 5000 (5 sec) range. Hit Apply when done. This feature gives an average that settles down gradually (converges?) to within 0.1 db over 20 to 30 seconds. In my mind this is an extremely useful feature. MDS (Minimum Discernable Signal) is often defined as injecting enough signal to make the output increase by 3 db. Increasing the output by 3 db means that the noise power equals the injected signal power and the two of them add together to double the total power (a 3 db increase). Thus, at the 3 db point, the injected signal level is at the same level as the noise floor of the receiver. Receiver MDS measurements should be done using a 50 ohm load. With PowerSDR and the above averaging, we can measure the noise power directly, and thus know directly the MDS of the receiver (or the noise floor of the current band conditions) without the need of injecting an actual measurement signal. The receiver bandwidth must be specified for MDS to be meaningful, and 500 Hz one of the bandwidth standards that is often used for this specification. I think it is extremely useful to take note of the noise level of the band and to see how it changes over the course of the day. A note of caution: In my home measurements of MDS, I have seen time of day variations in MDS results. I have come to realize that because the shielding of coax is not perfect (30 dB of attenuation?), a noisy band can impact the measurement of receivers in the 130+ dbm MDS region. I don't have an isolation chamber, so I just have to deal with it. You know you are in trouble when you can weakly hear signals across the band when the dummy load is connected. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dave Haupt Sent: Friday, June 15, 2007 12:05 PM To: flexradio@flex-radio.biz Subject: Re: [Flexradio] Noise floor, specifying You're getting very close to instrumentation norms. Noise, by its very nature, varies in apparent strength by the bandwidth in which you measure it. When measuring truly random noise, the power (in watts) is in direct proportion to the bandwidth of the filter used in the measurement. Man-made noise often consists of thousands of semi-correlated carriers, and the noise power can grow faster than simply being proportional to BW. To be accurate, an engineer specifies noise either as dBm/Hz which means dBm measured in a one Hertz bandwidth or watts/hz or something like that. It would also be equivalent to say dBm measured using a 200Hz filter or something like that. Audio-frequency guys tend to measure amplitudes in volts, at which point a square root gets into the picture, and you will read things like nanovolts per root Hertz. Sine waves and noise are described using different mathematical terms and as an interesting result, to make a truly accurate spectrum analyzer, instrumentation manufacturers often use an algorithm to attempt to distinguish a sine wave from a noise function. Anybody who's used the digitally-enhanced analog spectrum analyzers by HP (8566/68, 8590 and 8560 series) has probably encountered the noise marker. The instruments are calibrated for accuracy with sine wave signals (or sums of sine waves - any repetitive waveform), and are in error, fundamentally, for noise. When you turn on the noise marker, the instrument makes additional calculations to make the readings accurate for random noise. When you get down to the nitty-gritty of noise, it's not at all a simple subject. 73, Dave W8NF From: Doug McCormack [EMAIL PROTECTED] Subject: Re: [Flexradio] Noise Floor S meter vs Panadapter Thanks everyone for the quick and detailed explanation. I now understand the S meter displays one sum across the entire width of the green filter, while the panadapter displays hundreds of sums across the width of each individual pixel. When I set the filter very narrow (approaching one pixel) the S metter reading approaches the panadapter reading. My old Kenwood was similar in that selecting the narrow CW filter caused a drop in S meter noise floor. This behavior makes perfect sense for any radio. I guess if someone asks about the noise floor, they need to specify at what filter width. 73, Doug, VE3EFC
Re: [Flexradio] Noise Floor S meter vs Panadapter
What you see on the display and what is on the meter are two different things. If you are sampling at 48 KHz, what you see on the panadapter is the noise per 11 Hz bin. What you see on your meter is the noise from all the 11 Hz bins within the receiver bandwidth you have selected, which is not at all the same thing. However, these two should be related. If you were operating with a 3.3 KHz bandwidth, the dB difference between one 11 Hz bin and enough bins to fill 3.3 KHz is 10*log(3300/11) or ~ 25 dB. If the noise floor is roughly -145, then the meter should read roughly -120 dB in a 3.3 KHz bandwidth. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Doug McCormack Sent: Thursday, June 14, 2007 8:30 AM To: flexradio@flex-radio.biz Subject: [Flexradio] Noise Floor S meter vs Panadapter I recently build the Elecraft kit to provide a reference signal for calibration of my SDR1000. With the 50 uV reference my S meter shows -73 dBm (S 9.0). At 1 uV reference, the meter shows -107 dBm ( S 3.3). These two numbers show the S meter is perfectly calibrated. When I remove the Elecraft unit and no antenna is connected, the meter shows a noise floor of -117 dBm (S1.3). But the panadapter shows -145 dB. I wonder why the panadapter does not agree with the S meter. Maybe I am should ground the antenna connector when measuring noise floor? When people ask me about the noise floor, do I say -117 or -145? I have always suspected my 5 year-old Dell 1.8 Ghz has high internal noise possibly on the PCI bus. Perhaps this Dell system noise is getting into my M44 sound card. I hope to have a new dual-core Intel computer later this week. 73, Doug VE3EFC -- next part -- An HTML attachment was scrubbed... URL: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/attachment s/20070614/d3f5da98/attachment.html ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/ ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
Re: [Flexradio] Video Cards
I just picked up a eVGA 8800 GTS card for my wife's computer. It is indeed a high end video card. This one does have two monitor outputs which she might use for her photography editing. Circuit City has it on for $299 plus a $20 rebate. My wife got them to price match Fry's electronic price for the same card with is $249 after rebate. It is kind of spendy, but it is cheaper than using two SLI compatible 7900 video cards. The new mother board I picked up (the old one died), a P5N-E, has two video card slots for a pair of SLI compatible video cards. I too am in the NVIDIA camp right now after having stability issues on my son's computer with the x1900 series and the latest games. For video games, a good card is must. These days, much of the game performance comes from the video card. For recent games, a good video game computer is almost 50-50 driven by CPU and Video card. You have to spend at least $200 to get decent game performance (at least a x1900 or 7900). Take a look at the 8800 GTS. There is a good reason for such massive heat sink housing. My understanding is that graphics processors these days have a lot more transistors than the CPU. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Charles Greene Sent: Friday, May 04, 2007 4:35 AM To: FireBrick; FlexRadio List Subject: Re: [Flexradio] Video Cards Firebrick, Tnx. I am aware of the two card approach. However, most motherboards today have only two PCI slots and two video cards means you have to use the on-board audio or else a USB audio card. I have a nice PCI audio card I wouldn't be able to use, but I have a USB audio card. So is there a single video card approach? Chas At 06:38 AM 5/4/2007, FireBrick wrote: I jumped on the 'dual monitors' when it was first introduced and have used up to 3 monitors at a time. I presently use NVidia GeForce 7900 which is actually 2 video cards (takes up two slots. Works great with fully customizeable monitor sizes, resolution etc. both dvi and analog connectors. I hear no noise attributable to the card in my receiver. On 5/4/2007 5:15:57 AM, [EMAIL PROTECTED] wrote: All, In my quest to buy a computer for the Flex 5K, I am haven't found a video card yet. I don't know enough about them. I want to use dual monitors, and I want a card that will support 3D video games. I have looked at the AMD site at the ATI x1600/1650 series, and the GeForce site at the NVIDA 6400 series. I am looking for one in the $100 price range. First, how do I find out if a card will support two monitors? How much video RAM do I need? How do I find out if a card will support a particular game? (Looking at the game box tells me very little, and certainly not which card will work). 73, Chas W1CG ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/ ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/ ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
Re: [Flexradio] Flex-5000 Blocking Dynamic Range?
I the IP3 dynamic range and the blocking dynamic range are two different things. I agree that the IP3 and blocking dynamic range will be roughly the same throughput the coverage range of the SDR5000 by design. In my experiments with the same detector that Flex is using, I get 107 db of IP3DR (NC2030) and 145 db of blocking dynamic range. Ideally, there ought to be ~20 db of difference between the two. However, I think the linearity of the detector may have a ~ 105 db IP3DR wall that keeps that IP3 performance from matching what might be expected from the blocking performance. Still, 105 db IP3DR is pretty darn good. On the other hand, the current sound card that we have been using stink. The biggest gripe that I have is that the ADCs themselves have a differential max input of roughly 2.5v pk-pk, but that the sound card manufacturers place approximately 15 db of attenuation in front of that so that it is capable of ~12v or more pk-pk. This kills sensitivity and means that the receiver front end has to have excess gain to overcome this loss in order to get reasonable sensitivity. The use of excess gain hurts receiver performance. I think that moving to a SDR optimized sound card is a very good thing since it eliminates this excess attenuation. In addition, Flex is kind of hinting that they went with a very good ADC. If it is the AKA5394A, they may have picked up at 11 to 15 db of sensitivity improvement. This means that if they keep the receiver sensitivity the same as the SDR1000, the amplification they have to use to achieve that will go down by 11 to 15 db, which means the blocking dynamic range should improve quite a bit. I took a stab at estimating what the AKA5394A might be capable of doing in terms of blocking dynamic (2.5v pk-pk max input, 123 db of DR, 13 db additional noise penalty under max signal conditions, 3 db receiver front end loss (less using only LPFs), two channel (I-Q) 3 db noise channel enhancement, 20 db 48 KHz to 500 bandwidth noise gain), and it seems that the blocking dynamic range could be in the 130's given the number on the spec sheets. Of course there can be a big difference between what the spec sheet implies and what you can get in reality. It just seems to me that the SDR5000 may see a good bump in the blocking dynamic range compared to the SDR1000 primarily due to the gain reductions made possible by an improved sound card that has been optimized for SDR applications. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of k5nwa Sent: Monday, April 30, 2007 7:02 AM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Flex-5000 Blocking Dynamic Range? Unless I'm mistaken, a highly possible thing, the 20KHz dynamic blocking specification is the same -105 dB and at 50KHz it's -105 dB also. Until D/A's get a couple more bits of resolution that is the limit, close or far away it's the same number. You end up with not so good numbers far away but awesome numbers up close. If you must correct me, do so gently, I'm in a very good mood this morning and would like to keep it that way. At 07:27 AM 4/30/2007, you wrote: The reported Flex-5000 2-kHz 105-dB IM3 figures are very impressive and would land at #2 on W8JI's rx performance chart if tested by Tom and assuming the figures hold: http://w8ji.com/receiver%20IM3%20sorted.htm A figure I don't see reported for the Flex-5000 is wide or narrow Blocking Dynamic Range. According to the ON4UN Low-Band DXing book this ought to be 120-dB for serious low band DXing and contesting. W8JI reports 10-kHz BDR numbers and the Sherwood tests rated several current hi-perf rigs 130 dB 100-kHz BDR with Orion at 137-dB and the IC-7800 at 135-dB. http://www.sherweng.com/table.html Surprised that the SDR-1000 was never tested by Sherwood, hope the Flex-5000 will make it to this lab. Most of the contesters/serious DXers I know respect the Sherwood (and W8JI) tests and pay closer attention to these tests than the ARRL lab reports which seem aimed at a more general ham audience. 73, Bill NT1Y ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/ Cecil KD5NWA www.qrpradio.com www.hpsdr.com Blessed are the cracked, for they shall let in the light. ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/ ___ FlexRadio mailing list FlexRadio@flex-radio.biz
Re: [Flexradio] CPU Percentage question
When my wife picked up a new laptop, I looked specifically for one that had a separate graphics card. It is relatively easy to identify these laptops. In most laps, the memory will not be 1 Gbyte, but something smaller like 900 Mbyte. This is because the video memory is shred with the processor, slowing things down a lot, and the computer makers do not count the memory dedicated to graphics. Almost all the laptops (98%?) were like this. We ended up buying a Fijitsu that had a dedicated graphics subsystem (6200? 6250? graphics processor) that was on clearance. Much faster than the Gateway that we had before. This graphics subsystem is not the latest and greatest, but much, much better than the run of the mill shared CPU/video subsystems of the typical laptop. The very fastest graphics chips eat a lot of power. The laptops with the highest end graphics chips are very expensive $3K and really are not designed to be run off of batteries except for a very short time. Think of them more as overpriced portable desktop units. A system like the one we got is a good compromise for a SDR system. - Dan, N7VE ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/
[Flexradio] Noise floor driven, threshold based AGC?
I was listening to a homebrew SDR receiver last night and it stuck me how noisy it was compared to my analog, narrow band NC2030. As I thought about this for a bit, I think the reason that the NC2030 is so quiet (besides close attention of audio chain details), is that it has no AGC. Thus, I can turn the volume down to where the background noise is not that high, and tune around the band for signals, and signals tend to jump out of the (relative) silence and thus tend to stand out against the background a lot better. Given the fact that we have complete flexibility over the AGC in software, I was wondering if we could do something similar, but better. Suppose the receiver does an average noise level calculation over the sampled bandwidth (min function?) and then set an AGC threshold above that point (10 db?). If the signal falls into the range of the noise level up to the new AGC threshold, the signal comes through linearly amplified. If the signal is higher than the threshold, AGC is applied to keep it from blasting and or distorting away. This might give the best of both worlds where the noise floor is not needlessly amplified, producing a quiet receiver, but where AGC kicks in when needed to keep large signals under control. This could produce audio that is much more listenable than the current AGC amplified situation and more controllable than the AGC OFF alternative. - Dan, N7VE ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/
Re: [Flexradio] Noise floor driven, threshold based AGC?
It was nothing special. Just a simple SDR receiver; front end, detector, and audio preamplifier. I just threw something together to work with a 40m transmitter I was working on. It just struck me how noisy it sounded running with AGC turned on compared to my other NC2030 type phased narrow band rigs. The AGC just brings the band noise up when no other signal is present. - Dan, N7VE From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Sunday, January 21, 2007 3:35 PM To: Tayloe Dan-P26412; flexradio@flex-radio.biz Subject: RE: [Flexradio] Noise floor driven, threshold based AGC? Hi Dan, I wonder what homebrew this was, and what soundcard was used. My experience is that the SDR1000 can be very quite when you set the RF gain. I like to know what is happening in the homebrew situation (more than curious) 73 peter pa0pvn groeten Peter petervn(a)hetnet.nl mailto:[EMAIL PROTECTED] ; pa0pvn(a)hetnet.nl mailto:[EMAIL PROTECTED] ; pa0pvn(a)gmail.com ; pa0pvn(a)amsat.org . Van: [EMAIL PROTECTED] namens Tayloe Dan-P26412 Verzonden: zo 21-1-2007 21:54 Aan: flexradio@flex-radio.biz Onderwerp: [Flexradio] Noise floor driven, threshold based AGC? I was listening to a homebrew SDR receiver last night and it stuck me how noisy it was compared to my analog, narrow band NC2030. As I thought about this for a bit, I think the reason that the NC2030 is so quiet (besides close attention of audio chain details), is that it has no AGC. Thus, I can turn the volume down to where the background noise is not that high, and tune around the band for signals, and signals tend to jump out of the (relative) silence and thus tend to stand out against the background a lot better. Given the fact that we have complete flexibility over the AGC in software, I was wondering if we could do something similar, but better. Suppose the receiver does an average noise level calculation over the sampled bandwidth (min function?) and then set an AGC threshold above that point (10 db?). If the signal falls into the range of the noise level up to the new AGC threshold, the signal comes through linearly amplified. If the signal is higher than the threshold, AGC is applied to keep it from blasting and or distorting away. This might give the best of both worlds where the noise floor is not needlessly amplified, producing a quiet receiver, but where AGC kicks in when needed to keep large signals under control. This could produce audio that is much more listenable than the current AGC amplified situation and more controllable than the AGC OFF alternative. - Dan, N7VE ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ -- next part -- An HTML attachment was scrubbed... URL: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/attachments/20070121/0804bf8a/attachment.html ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/
Re: [Flexradio] Higher sampling rates yeilds improved sensitivity?
Ok. So when the sampling rate is increased 4x, the FFT uses the same number of points, so we just end up doing FFTs four times more often, with each bin being 4x wider than they were before. 4x wider ought to mean a 6 db increase in noise power. However, the fact that this is being produced 4x more often should mean that we get some of this back (all of it back?) due to the now larger sampling rate. A generator is not needed to measure this. Just turn off the receiver so that the sound card is connected to nothing by quiet, powered-down electronics, and use PowerSDR to look at the resulting noise from the sound card input. You ought to be able to look at the change in the apparent noise floor in a fixed bandwidth such as 500 Hz as the sampling rate is changed. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Robert McGwier Sent: Wednesday, January 10, 2007 6:26 AM To: James Courtier-Dutton Cc: flexradio@flex-radio.biz Subject: Re: [Flexradio] Higher sampling rates yeilds improved sensitivity? James Courtier-Dutton wrote: Robert McGwier wrote: James Courtier-Dutton wrote: Joe - AB1DO wrote: Dan, just out of curiosity I performed the following experiment: Using PowerSDR1.9.0 SVN821 Scound card is a Delta-44 Disconnected the Delta-44 cable at the break-out box, thus disconnecting the hardware Preamp set to Med Measured the noise floor in a 500Hz filter. To stabilize the digital signal meter, I set it to average over a period of 3 seconds. Result: At a sample rate of 48kB/s, the noise floor measured -130.5dBm At a sample rate of 96kB/s the noise floor measured -132.5dBm That would indicate an improvement of around 2dB in sensitivity, though not quite the 3dB you predicted. I cannot test 192kB/s (yet). Hope this helps, 73 de Joe - AB1DO You might not be measuring what you think you are measuring. The results you get are a result of the fft algorithm. The fft algorithm indicates power present in each bin. At 48kHz, lets say you get noise power in the 500Hz bin with 10 units of noise (bogus scale just to demonstrate a point) At 96kHz, this bin gets broken into 2. One of these bins will have the 500Hz signal, the other will not. So, on average, the 500Hz bin will now have 5 units of noise, with the other 5 units in the next door bin. One therefore has the apparent reduction in noise at 96kHz over 48kHz. This analysis is incorrect. The FFT size remains constant. That is, the same number of points are used in the power spectrum calculation. The size of the bin DOUBLES. I have not thought through the rest of the implications of Joe's measurements. I will try to duplicate them here if I get a chance. You are correct.When twice as many samples are used as input to the FFT function, the bin size doubles (samples per bin calculation), and so does the amount of bins double, so as the noise power is spread across more bins, less noise power will be present in each bin. (In my over simplification, I added confusion.) Also, as one has more samples as input, the less error will be present on the output, that is true of any statistics calculation. But in this case, we always use the exact same FFT. It is not even rebuilt as we change sample rates. The number of bins do not go up so the amount of bins do not they remain constant, so the noise power per bin should go UP. We always use a 4096 point FFT for the panadapter, spectral displays. If this phenomenon that Joe is pointing out is correct, it is interesting. Again, I am just swamped so though the generator is down in the lab, I haven't the time to go get it to hook it up. James Bob N4HY -- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair If you board the wrong train, it is no use running along the corridor in the other direction. - Dietrich Bonhoeffer ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/
[Flexradio] Higher sampling rates yeilds improved sensitivity?
I was thinking about the coding gain that we are currently using when we sample at 48K samples per second, but only use a 500 Hz bandwidth. This reduction in bandwidth results in (I think) ~ 20 db of gain, which is essentially a sensitivity improvement. The question that I was wondering was if increasing the sampling rate from 48K to 192K gives me another 6 db of sound card sensitivity improvement. Moving to 4x more over sampling of the desired signal (48K - 192K) is should give the same result as adding bits to the A/D converter. This is the basis that Phil is using in his very fast RF A/D converter receiver. The effective 15 bits of his A/D converter gives 90 db of dynamic range (20*log(2^15)), while moving from a sampling rate of 65 (?) MHz down to 3 KHz gives a coding gain of 43 db (10*log(65e6/3000)). For a total of 133 db of dynamic range. I guess that since there needs to be at least two samples for the highest frequency, the coding gain is really 3 db less (10*log((65e6/2)/3000)) for 130 db of gain. Has anyone noticed this sensitivity gain on your faster sound cards? With the sound card connected to your SDR receiver, but with the SDR receiver hardware turned off, you ought to be able to measure the noise floor of your sound card and see if that noise floor decreases as the sampling rate is increased from 48K to 96K to 192K. I have not seen anyone comment on this, so I was wondering if any of you see it happen in practice. I know that as the sampling rate of an A/D converter is raised, the internally generated digital noise also increases, and that this effect can offset the gains to some degree. If true, it seems like another good excuse to go to a faster converter. - Dan, N7VE ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/
Re: [Flexradio] RX Meter Setup
Thanks. That did it. I did not realize I had to change the meter to signal average. - Dan, N7VE From: stewart haag [mailto:[EMAIL PROTECTED] Sent: Thursday, November 16, 2006 5:49 AM To: Tayloe Dan-P26412 Subject: RX Meter Setup Hi Dan Go to SETUP DISPLAY TAB Refresh Rates Meter Delay [ ms ] mine set to 500 On Rx Meter select Sig Avg mine stays very steady Hope this helps Vy 73 Stew W4MO -- next part -- An HTML attachment was scrubbed... URL: /pipermail/flexradio_flex-radio.biz/attachments/20061116/00aba681/attachment.html ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
[Flexradio] Longer term RSSI average?
I finally got a chance to recheck this. The adjustments to the RX meter do not seem to do anything. No effect at all. I tried changing the multimeter section from an average time of 1000 msec to 9000 msec. No change. I changed the digital peak hold time from 500 msec to 999 msec. No change. Am I changing the wrong parameters? The digital RSSI meter seems just as jumpy. - Dan, N7VE If you're talking about the signal selection in the RX Meter, you can set it to Signal Avg and set the averaging time on the Setup Form - Display Tab. Eric Wachsmann Tayloe Dan-P26412 wrote: I want to make MDS measurements and the RSSI measurement jumps around so much that it is hard to estimate a good average. Are there any setting that can be changed to get a longer term average out of the RSSI digital output? ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
[Flexradio] Longer term RSSI average?
I want make MDS measurements and the RSSI measurement jumps around so much that it is hard to estimate a good average. Are there any setting that can be changed to get a longer term average out of the RSSI digital output? - Dan, N7VE ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] USB Interface on the Horizon?
It would sure be great as an initial start to simply provide this portion of the project as a gang busters audio card though. I for one am disappointed with the current state of the art in sound cards such as my Firebox. It requires entirely too much gain to get the best sensitivity out of the thing, probably because of attenuators on the line inputs. It would be really, really nice to have the sound card inputs optimized for SDR use. Between the 10 db improved A/D noise floor and a non-attenuated line input, I could probably see another 15 db of blocking range out of a 5v SDR pre-amp compared to what I have now. That would allow a lot more freedom in the blocking vs. sensitivity SDR trade space. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Cecilio Bayona Sent: Tuesday, September 26, 2006 10:09 AM To: FlexRadio Subject: Re: [Flexradio] USB Interface on the Horizon? Ken - N9VV wrote: There are, of course, many 12VDC computer systems on the market. They are especially popular with the Car computer for gaming crowd. May I suggest these resources for info: Embedded computer examples (pictures) http://www.linuxdevices.com/articles/AT8498487406.html http://www.linuxdevices.com/articles/AT9547755813.html 12VDC computers in all sizes http://www.logicsupply.com/index.php/cPath/50 http://www.mini-box.com/s.nl/sc.8/category.94/.f - The HPSDR group already has a full USB interface figured out and coded by Bill KD5TFD for the PowerSDR software. At first Phil VK6APH and Bill used the Xylo USB interface, but now I believe it is fully implemented on the Ozymandias board (http://hpsdr.org/ozy.html) on the Atlas backplane in an FPGA. de ken n9vv It must be noted that it's not just another audio card, the specs on it beats the pants off anything out there that is affordable. It's way better than a Delta-44 or any of the Firewire cards now supported. -- Cecil KD5NWA www.qrpradio.com www.hpsdr.com Sacred Cows make the best Hamburger! Don Seglio Batuna ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
[Flexradio] New SDR transciever kit announced
A new kit has been introduced by Hendricks QRP Kits that integrates a single band softrock style SDR receiver with a 2.5w VXO controlled cw transmitter. http://www.qrpkits.com/ http://www.qrpkits.com/firefly.html - Dan, N7VE ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] IK3MAC moonbounce file
There are actually two moon bounce signals in that file not far from each other in that file. Amazing! - Dan -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim, W4ATK Sent: Thursday, August 17, 2006 3:23 AM To: Flex-radio Reflector Subject: [Flexradio] IK3MAC moonbounce file My apologies for not sharing the location of the files ftp://flex-radio-friends.net/upload/W0VB/ The moonbounce file is IK3MAC CQ High Noise 12-5-2004. W0VB had his antenna pointed at the horizon and was recording. As I understand it, some time later he was listening to the recording and discovered he had capture the IK3MAC CQ. You will immediately see the CQ if you will select AVG for the panadapter display. Then turn on NB and NB2. Ehe signal will leap from the noise at you. Is this a great radio or what? Put the playback in LOOP and have fun. 73 Jim ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] Laptop Firewire + FireBox Recommendation
I found an inexpensive $26 card at CompUSA that seems to work fine. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Eric Wachsmann - FlexRadio Sent: Tuesday, March 07, 2006 9:50 AM To: FlexRadio@flex-radio.biz Subject: [Flexradio] Laptop Firewire + FireBox Recommendation We have had several customers that have had trouble finding a PCMCIA firewire interface for use with the PreSonus FireBox on a laptop. Does anyone have a FireBox working on one of these that could recommend the brand/model? I am using a PCI interface on my desktop made by Stor (model number not listed on the box). The first card I tried ($10) did not work at all with the FireBox. This card (~$20) has worked fine. Both purchased at Fry's Electronics here in Austin. Eric Wachsmann FlexRadio Systems ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] Laptop Firewire + FireBox Recommendation
Sorry. It was a generic CompUSA model. Firewire ports only. - Dan, N7VE -Original Message- From: Eric Wachsmann - FlexRadio [mailto:[EMAIL PROTECTED] Sent: Tuesday, March 07, 2006 10:21 AM To: Tayloe Dan-P26412; FlexRadio@flex-radio.biz Subject: RE: [Flexradio] Laptop Firewire + FireBox Recommendation Brand/Model? Eric Wachsmann FlexRadio Systems -Original Message- From: Tayloe Dan-P26412 [mailto:[EMAIL PROTECTED] Sent: Tuesday, March 07, 2006 11:00 AM To: [EMAIL PROTECTED]; FlexRadio@flex-radio.biz Subject: RE: [Flexradio] Laptop Firewire + FireBox Recommendation I found an inexpensive $26 card at CompUSA that seems to work fine. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Eric Wachsmann - FlexRadio Sent: Tuesday, March 07, 2006 9:50 AM To: FlexRadio@flex-radio.biz Subject: [Flexradio] Laptop Firewire + FireBox Recommendation We have had several customers that have had trouble finding a PCMCIA firewire interface for use with the PreSonus FireBox on a laptop. Does anyone have a FireBox working on one of these that could recommend the brand/model? I am using a PCI interface on my desktop made by Stor (model number not listed on the box). The first card I tried ($10) did not work at all with the FireBox. This card (~$20) has worked fine. Both purchased at Fry's Electronics here in Austin. Eric Wachsmann FlexRadio Systems ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
Re: [Flexradio] SDR-1000 for MW DXing - 9 kHz Channels
The third harmonic response of the detector is approximately 10 db down. You will need to decide how much third harmonic attenuation you need based on that. Ideally, you would like it to be 130 db down, but that may be difficult to achieve. The amount of attenuation you need will be a function of the difference in signal strength of the signal you want to hear and the strength of the third order harmonic undesired stations you don't want to hear less 10 db (the 3rd harmonic detector response) plus what ever margin you want to have between the desired and undesired signals. For example, if the signals you want to get rid of are -50 dbm, and the signals you want are -110 dbm, that is a 60 db difference, less 10 db for the detector response is 50 db, plus perhaps a 20 db margin between desired and undesired signals, back up to 70 db. I am sure this is readily achievable. - Dan, N7VE From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Guy AtkinsSent: Sunday, November 20, 2005 11:19 PMTo: FlexRadio@flex-radio.bizSubject: [Flexradio] SDR-1000 for MW DXing - 9 kHz Channels Hi guys, Greetings from a lurker! I've been mostly reading the mail here, and have learned a lot about the SDR-1000 and it's cooperative development on many fronts. My DXing "specialty" since 1990 has more and more been trans-Pacific MW DX from the Pacific Northwest USA. I participate in Beverage expeditions (DXpeditions to the WA coast four or more times per year to chase mediumwave broadcasters from across the Pacific and into Asia. I also pursue Asian mediumwave DX from my inland location east of Tacoma, WA.My home is about 120 miles inland from the coast (300 degrees bearing, and over a mountain range) so the reception definitely isn't enhanced by the coastal effect as on the DXpeditions, hi! Despite the obstacle of not being on the coast, and living near an RF-jungle where the mediumwave dial is packed with S9 + 50db signals from Tacoma/Seattle, I still manage to log MW stations from Japan, China, Korea, Tahiti, Malaysia, and other countries from home. A few weeks ago, trans-Atlantic MW DX was heard for a few evenings, too, especially by my friends to the north in Victoria, BC. Antennas here are a NW-oriented Beverage antenna, and a broadband, nonresonant loop antenna at the moment. I've also used switched EWE antennas at this location. Anyway, I'm using an IC-756Pro as the main receiver right now, but the SDR-1000 appears to be an even better choice for the type of DXing I do. Chasing the trans-Pacific DX on the 9-kHz "splits" has a lot in common with ham radio contesting, as both require radios capable of hearing a weak DX station adjacent to a powerful signal in a band chock-full of powerhouses. However, I understand that MW DXing with the SDR-1000 requires a lowpass filter to reduce the susceptibility to 3rd harmonic energy. My questions are-- 1. what amount of attenuation is required for the lowpass filter? 2. will a custom-configured LP filter for the SDR-1000's bandpass filter bank be sufficient? 3. would an external (antenna in-line) lowpass filter be better? I've been considering building a couple of 5th-order lowpass filters, one with a 1100 kHz cut-off frequency and another with a 1700 kHz cut-off, and switch between them depending on what frequency I was DXing in the MW band. 4. would the Palstar MW-550P preselector be a better choice in place of a lowpass filter? It offers 20 db of attenuation just 10 kHz removed from the tuned frequency, and up to 50 db attenuation further out. Use of this device would reduce energy on the band above *and* below the frequency of interest, perhaps reducing RF blocking effects and improving the chance of the DX to be heard (often just one or two kHz away from a local 50 kw station on the North American 10 kHz channel spacing). A friend of mine in Oregon, 30 miles from the nearest MW broadcaster, finds the MW-550P to improve the performance of his receivers and rendering the DX stronger and with less noise. If it can help in his rural environment, I'd think it could be of real benefit here in suburbia, even with the sturdy "frontend" of the SDR-1000. Thanks for any comments or advice relating to the SDR-1000, potentiallyas a premier mediumwave DXing rig. Guy Atkins Puyallup, WA USA
Re: [Flexradio] Firebox max input signal?
The AKM is one heck of a chip. As I was reminded earlier, the 120 db range is the wideband noise specification. If you want to know the range in a 500 Hz bandwidth, the noise (and dynamic range) reduces by 10*log(2/500) or 16 db for a 500 Hz dynamic range of 136 db. Since the max is 5v, this would represent a maximum signal of +18 dbm. With a 136 db dynamic range at 500 Hz, this implies the receiver sensitivity is -118 dbm. Thus connecting this A/D converter directly to the detector with no amplification would give an excellent high level blocking capabilities, but you might want 20 db of pre-amplification in order to get down to a more reasonable -135 to -138 dbm MDS sensitivity level, 500 Hz bandwidth. 136 db of blocking dynamic range capability would be quite interesting. - Dan, N7VE -Original Message- From: Ahti Aintila [mailto:[EMAIL PROTECTED] Sent: Tuesday, November 08, 2005 2:39 AM To: Tayloe Dan-P26412 Cc: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Firebox max input signal? Hi Dan, I was wondering the same specification of the PreSonus Firebox, but did not ask them. Thanks for doing that. Obviously Firebox has better dynamic range than Delta 44 (higher max level, lower noise?). However, the best specifications I have seen is with AKM chip set as given in your link below (123 dB dynamic range with +23 dBu maximum input signal ≈ 31 Vpk-pk). Since the Tayloe detector (QSD as Gerald says) can handle about 4 Vpk-pk and we optimally could use gain of 31/4 = 7.75 (+17.8 dB) between the best practically available sound card and the sampling detector. We should also find a better amplifier to replace INA163, because it is too noisy at these low gains. So far I have not found any pin to pin replacement, but I am experimenting with two OPA2227's as dual balanced output amplifiers assembled on a small circuit board. Naturally a minor surgery has to be done to the TRX board. I wonder, why TI suggests OPA2134 together with PCB11804? It has higher noise than OPA2227. By the way, my sound card is WT192X that has AKM chip inside and can take 31 Vpk-pk. 73, Ahti OH2RZ - Original Message - From: Tayloe Dan-P26412 [EMAIL PROTECTED] To: [EMAIL PROTECTED] Cc: FlexRadio@flex-radio.biz Sent: Tuesday, November 08, 2005 12:41 AM Subject: Re: [Flexradio] Firebox max input signal? Here is the information that I got about the PreSonus Firebox line inputs. It looks like it is good for +18 dBu or about 17.4v pk-pk maximum. In contrast the Delta 44 is rated to +14 dBu or about 11v pk-pk. - Dan, N7VE -- For Line inputs (0dBFS=+18dBu) , we are performing something very similar to the datasheet you refer to. We attenuate the signal by approximately 5.5x to fit into the converter. Best Regards, Jonathan Hillman [EMAIL PROTECTED] PreSonus Audio Electronics 225-216-7887 x. 117 From: Tayloe Dan-P26412 [mailto:[EMAIL PROTECTED] Sent: Monday, November 07, 2005 2:15 PM To: jonathan hillman Subject: RE: Maximum input to the Firebox? I have looked at the manufacturer (TI, Cirrus Logic, AKM etc) specifications of several of the best 24 bit A/D devices currently on the market. On of the things that I noticed is that although the A/D input is rated at 0-5v, the reference designs of the parts often show an input buffer that has a gain of less than 1 in order to allow the input to go to a level of greater than 0-5v (5v pk-pk). Example http://focus.ti.com/lit/ds/symlink/pcm1804.pdf figure 44 or http://www.asahi-kasei.co.jp/akm/en/product/ak5394a/ek5394a.pdf figure 13. The AKM figure 13 above shows an attenuation of about 5.3x (input R=3.3K, feedback = 620+91 ohms, gain of ~0.188x). I can see that this might be needed since line level devices such as a mixer board often are capable of relatively high outputs. A Heath-Allen mixer console (http://www.allen-heath.com/DL/ml4000ug_ap4314_4.pdf - see page 12) is rated at an output of +23 dBu, where 0 dBu is 0.775v RMS (1.096v pk or 2.192v pk-pk). Thus +23 dBu translates to ~ 31v pk-pk of audio. Thus, I might expect the line input buffer to the A/D converter to have attenuation rather than gain. I am simply trying to find out what the input buffer stage of the A/D converter looks like (gain and voltage limits) in order to best match my output to the line input of this box. - Dan Tayloe ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
[Flexradio] Firebox max input signal?
Anyone know what the specifications are on the D44 and the new Firebox audio interfaces? I thought I understood the D44 as being capable of up to 27v pk-pk input. I looked for the Firebox specifications, but none seem to be given. I assume the max input range is different for the microphone inputs than for the line inputs. If anybody has characterized the Firebox, it would sure be nice to know what the limits are. - Dan, N7VE
Re: [Flexradio] Turning off the AGC
It seems to me that if you use MDS measurements (3 db S+N/N audio shift) to measure the noise floor, the AGC will take care of itself. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of KD5NWA Sent: Thursday, October 27, 2005 10:50 AM To: Flex Radio Cc: [EMAIL PROTECTED] Subject: [Flexradio] Turning off the AGC I want to try to measure the noise floor of my SR-40 setup and will need to have the AGC completely turned off. If I turn off the AGC of the Flex software will it really completely turn off all forms of variable gain? Cecil Bayona KD5NWA www.qrpradio.com I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ... ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Audiocards, USB, etc.
I forgot to say that your measurements show that your sound card shows a 114 db dynamic range which is 5 to 6 db better than the specs guarantee them to be. Looks like there is some margin in the A/D converter specs. Sounds like someone need to push TI and Wolfson for better ADCs! - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ahti Aintila Sent: Saturday, September 24, 2005 7:47 AM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Audiocards, USB, etc. Thank you Dan and Jim for the good comments. Sure I noticed how difficult it is to measure the sound cards without proper instruments. The clipping (or compression) levels are easy, but the noise in the present computer environment and with signals approaching the thermal noise levels are challenging. Instead of measuring the audio card only I decided to continue with the whole SDR-1000 system. I recorded 1) the noise floor (dBm/500 Hz) with audio card input cable input connected to the radio and the antenna connector terminated to 50 ohm and then 2) with a signal to radio until clipping or compression was indicated at the line-in connector of the radio or at the SDR-1000 own measurement systems. The results were: Preamp Setting HIGH, -140 dBm/500 Hz, -26 dBm, INA163 out 25 Vpp Preamp Setting MED, -130 dBm/500 Hz, -16 dBm, INA163 out 25 Vpp Preamp Setting LOW, -130 dBm/500 Hz, -13 dBm, INA168 out 4.8 Vpp (1.4 dB compressed) My conclusion is that the QSD can take about 4 Vpp until it starts to saturate and my sound card can take 29 Vpp, so the amplifier after the QSD could have 17 dB voltage gain for optimal results. The front end gain need to be adjusted accordingly. Dan mentioned:... ideally 130 to 145 db to match the blocking performance of other rigs This should be our target and to achieve that we need audio cards handle signal from tens of nanovolts to tens of volts. I estimate, the accuracy of the above measurements is about 1 dB. The measurements were made with PowerSDR 1.4.5 console with unmodified RFE. These figures serve as the reference when comparing the results of the ECO-25 modifications. 73, Ahti OH2RZ - Original Message - From: Jim Lux [EMAIL PROTECTED] To: Tayloe Dan-P26412 [EMAIL PROTECTED]; Tayloe Dan-P26412 [EMAIL PROTECTED]; Ahti Aintila [EMAIL PROTECTED]; FlexRadio@flex-radio.biz Sent: Saturday, September 24, 2005 6:20 AM Subject: Re: [Flexradio] Audiocards, USB, etc. At 05:40 PM 9/23/2005, Tayloe Dan-P26412 wrote: I would think that on top of the audio blocking test we also want to run audio IP3 tests and audio IP2 dynamic range tests as well to make sure that the distortion characteristics are at least as good as the SDR1000 front end. - Dan, N7VE Such tests would be useful, but are quite challenging to make for high performance systems. You can take two general approaches: 1) Obssessively account for all the error sources, use very clean sources, etc. so you can truly know that what you've measured is just the unit under test, and not quirks of the experimental setup. 2) Measure it in a typical setup, in which case the performance will certainly measure out worse, but at least it's representative of what you'll really get. Consider that if you're looking for 140 dB relative levels, you're looking for signals of a 0.1 microvolt on a 1 volt signal. I've done DC measurements to 6 digits, and it's, frankly, an ordeal. You'd also need sources that are that good, which is no easy matter, especially if you want to cover the full frequency span of the device (several decades). For instance, the SRS DS360 claims -100dBc distortion from 10mHz to 20 kHz. It's not too pricey at about $3000. ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] Audiocards, USB, etc.
You might not be getting a true measure simply by checking sensitivity (noise floor) and clipping (largest signal). I think this measurement would be good only if the card is known not to change its internal gain between these two measurements types. Do audio cards do this? Do they have built in variable gain structures that automatically handle input signal overload? If so, what is then needed is an audio blocking test where a weakest detectable audio signal is injected, and a large signal neighbor is injected to the point the weak signal goes away (blocked). This test will truly show the usable dynamic range of an audio card. We would like to have this dynamic range very large, ideally 130 to 145 db to match the blocking performance of other rigs (I think not very practical), but we do want this as large as possible. - Dan, N7VE -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ahti Aintila Sent: Friday, September 23, 2005 4:09 PM To: FlexRadio@flex-radio.biz Subject: Re: [Flexradio] Audiocards, USB, etc. Hi Riho and Bob, If I am not mistaken, the dynamic range of the loopback measurement in this case may be limited by the DAC that happens to have noise about -106 dBA. Another limiting factor is the maximum signal before clipping. The important parameters for our SDR-1000 receivers are the noise and clipping levels of the ADC. Almost all ADC's in higher class audio cards with balanced input have reasonably low noise but the clipping level may be too low. According to my measurements with Waveterminal 192X the clipping level is +22 dBu and the noise at 24 kHz bandwidth is less than -103 dBu. The measurements have been made with carefully balanced input and isolating audio transformers at the input and output connections. Sorry, I don't have the A-weighing filter. Due to the home made signal generator and low noise instrumentation amplifier I cannot guarantee the correctness of my measurement values, but clearly the limitations seem to be on the SDR-1000 hardware side. 73, Ahti OH2RZ - Original Message - From: rihob., es7aaz [EMAIL PROTECTED] To: FlexRadio@flex-radio.biz Sent: Friday, September 23, 2005 7:15 PM Subject: Re: [Flexradio] Audiocards, USB, etc. Hi, Bob: Esi Juli unbalanced loopback @ 24-bit, 48 kHz mode: http://www.hot.ee/es7aaz/Juli.htm P.S. It was RMAA 5.4 when I did this measurement. Rgds, Riho, ES7AAZ. ___ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Re: [Flexradio] DDS discussion
Let me say that for the future AD9954 and AD9958 just look spectacular. I have ordered the development boards for both of them. Especially on the low bands, either of these would give spur performance where the spurs are below the noise floor at all but sub multiples of the clock. It is my understanding that the 9958 has made spectacular strides in this keeping the clock submultiples off the output. The very first thing you need to do when evaluating a new part is to read the spec sheet. Once again, the spec sheet for the new AD9958 device can be found at: http://www.analog.com/UploadedFiles/Data_Sheets/383477232AD9958_prd.pdf Read it. See what it says. Spec sheets are normally optimistic, not pessimistic. The real world results are rarely much better than what is in the spec sheet. The close-in spur results specs are given on page 42. The specs for 1.1 MHz are not significantly different than those for 15.1 MHz. The close in spurs at 1.1 MHz are 90 db down +/- 10 KHz, 88 db down +/- 50 KHz, very similar to the numbers that are shown for 15.1 MHz and the numbers at 40.1 MHz. These spurs would not be as much a problem if they were sparsely distributed. Again, the information is contained in the data sheet for us to get a handle on this. Page 12 shows the spur distribution for both 1.1 MHz (Figure 12) and 15.1 MHz (figure 15). In both cases, there are numerous spurs in the 80 to 90 db down region. What does this mean to the receiver? In the case of my NC2030, a very low power, high performance hardware SDR, the blocking dynamic range is 130 db at 10 KHz, and over 140 db at 20 KHz. On 20m, the sensitivity in a 500 Hz BW is -135 dbm. This means that a signal has to be over +5 dbm 20 KHz away to cause the receiver front end to go into compression, and -5 db when only 10 KHz away. If the LO has numerous spurs in the -80 to -90 db region and the sensitivity were -135 dbm, then signals 80 to 90 db higher than the receiver noise floor will get mixed on frequency. Thus, even though the receiver front end might be capable of rejecting signals up to +5 dbm 20 KHz away, a LO spur at 80 db down will cause a signal at only -55 dbm to appear on frequency as crud. This is not good. The LO limitations have now caused the receiver to give up 60 db of blocking dynamic range when this happens. It might not be so bad if we were only talking one close in spur, but from the sheets above, the spurs are numerous. In a contest weekend, we can have many signals mixed on frequency due to this effect, artificially raising the apparent noise floor of the band, and potentially masking the signals we want to hear. If you have a very clean signal generator such as an old HP8640B, you can go looking for these spurs yourself. Set the generator to a level 100 db above the noise floor of the signal and sweep it across a range 2 to 100 KHz away from the receiver center frequency. You should actually see spurs pop up and move around as you sweep the generator across this region. Try a couple of different bands and a couple of different center frequencies and see what kind of variation you get. You need to understand what DDS chips were designed for in the first place to understand their performance limitations. These chips were designed originally for cellular telephone base stations. These base stations have a performance requirement that is quite different than what hams need. A cellular telephone base station has a group of mobiles that are in the range of its coverage. A closed loop power control mechanism is used between the base station and the mobile phone to reduce the phones power such that its signal is just sufficient for good communications with the base station. In CDMA phones (Verizon, Sprint, Alltel), the speech data is sent in 20msec data packets, and it is typical to set the mobile received power at the base station such that there is a 2% packet erasure rate. The bottom line is that to a cellular base station receiver, * all mobiles arrive at about the same power level *. The base station does not have to typically worry about very strong signals adjacent to weak signals. In such an environment, spurs only 80 db down is perfectly fine. Likewise on transmit, the base stations need spectral purity of (I think) 70 db down. This is much more stringent than ham transmitters, but again, spurs 80 db down or more are ok. Thus DDSs work great for the intended application, cellular base stations. However, ham receivers do not face signals that are all uniform in strength. We have very weak signals right next to very strong ones. Thus ideally we would like to have high sensitivity in order to hear the weak ones combined with high adjacent signal rejection, thus blocking and IP3 specs. In my case, IP3 is more important than blocking specs. A receiver will distort 20+ db before it overloads. However, I do not have any big gun
