SDR evolution

[W1AEX]

Looking back at the versions of the Flex software I've used with my SDR-1000... including the latest beta release 2.16... I'm wondering what new, useful features I have in release 2.16 (other than bug fixes and colorful new user interface choices) that I didn't have in release 1.14.

I sat down with my pencil to make a list Stu, but then realized your observation seems to be on target. Other than bug fixes and the ability to customize the interface, there's nothing to write! That being said, I can only say that I am having more fun with my Flex 5K than any other piece of equipment in the station. I guess that counts for something!

The enhancement list at the Flex feature request site is interesting to browse, with over 500 suggestions being made by owners. Many of them seem to be reasonable and possible, but time will tell how many come to life. Flex seems to be consumed at the moment with efforts to get the Flex 1500 and its balky USB driver to behave.

On a brighter note, some of the peripheral devices that are being adapted to the PowerSDR interface (independently by owners) are pure genius. This one involving the insertion of code to PowerSDR to allow mapping the PowerSDR Flex functions to the controls of a DJ mixing console has amused me to no end:

http://www.youtube.com/watch?v=NR-ZwUaffI8

I'm puzzled by the comments regarding perceived flaws with reception on AM using synchronous detection. It comes very close to my SP600 in the fidelity department, and with the ability to vary each sideband independently to eliminate "other mode" noise, it excels. I don't have a lot of RF noise here, but when my wife is using the paper shredder or other such domestic RF generators, NB1 or NB2 or both of them combined clean up the noise very nicely. The NR function appears to have the same effect that noise limiter diode circuits had with older receivers, so I don't bother with it. Flex does acknowledge that at some point in the revisions of PowerSDR its performance took at least one step backward.

At any rate, since the fun factor is high, I am pleased with what it does and if new functionality comes along, that's frosting on the cake.

Rob W1AEX

[K1JJ]

Rob,

I saw a post on the Flex? forum where you were involved with trying to iron out IMD or audio problems on a friend's Flex 5000.  The audio .mpg you posted did sound rough.  You also mentioned that opposite sideband suppression was poor. Was that ever resolved and what was causing it?

Yes, you have more fun with that rig than you should..   There's no doubt that the Flex 5K revitalizes interest in ham radio. There's something about that pan adapter and being able to ambush and jump on people with a click of the mouse, no?

T

[W1AEX]

Hi Tom,

My suspicion is that the RF driver stage or the PA stage were not properly biased. Unfortunately, he sold the rig before any attempt was made to correct it, so I can't say if it was ever resolved. There is diagnostic, calibration, and alignment functionality built into the PowerSDR software which would have made fixing that as easy as a few mouse clicks.

When I first used my Flex 5K I got reports that the alternate sideband suppression was horrendous. In my case, it turned out that several things were fouled up (by me). I was using a sampling rate that was too high for my computer to handle well, and buffers that were too small in the TX portion of the DSP. Fixing both took less than 30 seconds. I also never bothered to check to see how hard I was pounding the TX ALC (it was pegged all the way to the end of the meter) and after making a few adjustments, it was clean as a whistle.

I have found that its best to never mention that I have a real-time spectrum scope because the assumption could be that I might be a bandwidth Nazi! The truth is, I just like to talk (and listen)!

:O)

[K1JJ]

I have found that its best to never mention that I have a real-time spectrum scope because the assumption could be that I might be a bandwidth Nazi! The truth is, I just like to talk (and listen)!
:O)

heheheh -  There are certain thangs we learn - to evade the land mines of ham radio...

OK on the bias.  Also the computer set up causing the other problems.   The state of SDR technology reminds me of the first transistor with leads hanging out everywhere.  Eventually they put thousands on the head of a pin.

I saw a tiny SDR transceiver on the web called "The Cube" IIRC.  It used no extenal computer and could be held in your hand. Digital readout and a mini spec display.   It would be nice to see a big version of that someday.  I have decided against getting a Flex 5K.  I'll use my FT-1000D and SoftRock spec/rx for now.

T

[W1AEX]

There are lots of interesting SDR solutions. I like the hardware and software that Bruce KF1Z is using. It sounds great and looks very slick. A few days ago, while chatting with Nigel VE3ELQ, he told me about his RF Space SDR-IQ receiver, available from HRO for around 500 bucks:

http://www.hamradio.com/detail.cfm?pid=H0-009533

He is using SDR software written by Simon HB9DRV (the guy who has written much of the Ham Radio Deluxe software) and it's very slick. He took a screenshot of my signal as I altered my bandwidth and it picked it right up very neatly. It does mp3 recordings on the fly and will work with Virtual Audio Cable to decode DRM broadcasts using the Dream software. Not bad for a free piece of software!

http://sdr-radio.com/

Simon's software will also function with the SoftRock boards, so you might want to give it a shot just for the fun of it. I have not used it myself, but it would be interesting to see how well it functions on AM. Incidentally, for those who want to try SDR without purchasing any hardware, Simon's page has a java plug-in that allows you to connect by IP to about a dozen different receivers that users have made available around the world.

http://www.sdr-radio.com/OnAirServersFree/tabid/186/language/en-US/Default.aspx

Rob

[steve_qix]

I've been using the flex software for a while now, and I am also a software developer.  There are definitely some implementation bugs, but on the whole, it does a very good job.

The AGC has major problems on AM.  The AGC, when receiving AM, responds to the modulation - a BIG no-no for any AGC system for AM.

The filters ring to some extent.  You can somewhat mitigate this by reducing the receive buffer size, but it's not a perfect solution - it is tollerable, particularly if there is not a lot of atmospheric noise present.

That being said, I use the SDR all the time  - there is NO receiver I have EVER used that is as good at getting rid of interference, and making an otherwise uncopyable signal copyable as the SDR (Flex software with a softrock).

I have looked at the source code with an eye to make changes - it is COMPLICATED code.  I've written a lot of very complex code in my days, and it is a time consuming process.  If you're a software developer by day, you are probably dis-inclined to do more complex software development at night, particularly when you're not getting paid to do it.  But, I would like to solve the AGC problem with respect to AM, so at some point, I might take a shot at it! 

[steve_qix]

I've never been much interested in SDR because it seems like you usually have to have a Windows PC to run one and I don't want to blow hundreds of dollars on a Windows PC only to run a ham rig.  I also don't like depending on a PC to run a rig.  There are enough things to go wrong with the rig, even without a PC.   When the SDR 1000 had been out around a year a good friend got one and spent the following 24 months messing around with it fixing an unending stream of little issues.  When he was done he had spent around $2K on a fancy soundcard, a zillion ferrite cores, an after market TCXO, a newer dedicated PC just to run the rig, then there was the infamous flex radio 11 KHz spur on AM, and then it started blowing the IPA (I think or maybe the PA) repeatedly.   He doesn't have the Flex rig any more and I am extremely glad I never got one.    If I'm gg to fool with a computer I'll do it in my job where I'm getting paid to fool with it, and focus on boat anchors at home (mac user here at home).

Rob

Note to Rob - on some of what you said, I could not agree more.  There was NO WAY I was going to shell out big bucks for a high performance sound card or for the flex hardware for that matter.

But, you can get into SDR and the advantages of using it for almost 0 money, and still keep the BA receivers.  That's what I do here - usually use the BC-1004 for receiving, and the computer is off.  But, for those times when the 1004 can't cut it, it's sure nice to flip on the computer and the softrock, and abra-cadabra, a high performance receiver is at my fingertips!.

I'm using a 1.8gHz Pentium 4 that they were throwing out at my son's job (these machines are generally free or available for tiny money) and it does the job.  The secret is to run NO other software - a bare bones operating system (XP recommended even though Windows 2000 is more efficient).  The keyboard is on a slide, under the workbench so it doesn't take up any valuable bench space, and the computer is in a rack, behind the rack-mounted 19 inch monitor (19 inch flat screen monitors fit just about perfectly into 19 inch racks, and look pretty good too)!

Anyway, that's one way to go about it.  I *never never* have any trouble whatsoever with the computer because there's nothing on it to cause screw ups!

Regards,

Steve

[K1JJ]

Steve, interesting on the AGC AM problem using the SoftRock and PowerSDR software. I'm surprised the guys on AM have not brought it up, at least that I've heard. I will look for it when I fire mine up this week.

Cool idea on putting the video monitor in the 19" rack.

I just did an indepth reading on the Elecraft K3. Lots of reviews from users.  From what I read, it's not a perfect radio either. The cost is prohibative to me... $4700 new and maybe  $3500 used.   I'll continue to look into the SoftRock and later the high end receiver boards like Perseus, WinRadio, etc.   Man, this stuff will make your head spin.

All in all, it almost makes me happy with what I have now...  

T

[WA1GFZ]

Steve, I suspect the guys who share this cool software do it as a day job so it isn't a lot of effort.
I bet a lot of the processing software is cookbook making the real work the GUI.

[K6JEK]

I've been using the flex software for a while now, and I am also a software developer.  There are definitely some implementation bugs, but on the whole, it does a very good job.

The AGC has major problems on AM.  The AGC, when receiving AM, responds to the modulation - a BIG no-no for any AGC system for AM.

The filters ring to some extent.  You can somewhat mitigate this by reducing the receive buffer size, but it's not a perfect solution - it is tollerable, particularly if there is not a lot of atmospheric noise present.

That being said, I use the SDR all the time  - there is NO receiver I have EVER used that is as good at getting rid of interference, and making an otherwise uncopyable signal copyable as the SDR (Flex software with a softrock).

I have looked at the source code with an eye to make changes - it is COMPLICATED code.  I've written a lot of very complex code in my days, and it is a time consuming process.  If you're a software developer by day, you are probably dis-inclined to do more complex software development at night, particularly when you're not getting paid to do it.  But, I would like to solve the AGC problem with respect to AM, so at some point, I might take a shot at it!  

When the going gets rough, I turn off the tubes and use the Flex for receive.
Steve, if you're serious about working on the Flex software, you might want to contact my buddy Jeff, K6JCA.   He's worked on it a lot.   Many of his changes have been incorporated in the standard software.  Early users might remember when his console was more popular than the standard software. He might have been WA6AHL back then.  Anyway, he's very picky about AGC and may have actually already taken a run at the AGC system, not to mention the sync detector and half a dozen other things.  Heck, Steve.  You probably met Jeff when you were out here all those years ago.  He's good in QRZ.

By the way, your comment about "software developer by day" sure hit a chord.  That's what I did for a living for a couple of decades before I went into manglement -- write system software, operating systems, compilers, file systems, networking code.  I just can't work up any enthusiasm for doing it as a hobby.

[WA1GFZ]

Jeff is a good guy. I owe him one.

[K6JEK]

I don't see Jeff's email address in QRZ but it is in his blog which is a fun read.  Flex stuff is way back, click "older posts" a bunch of times.

http://k6jca.blogspot.com/

[k6jca]

Jon 'JEK' just notified me of this thread regarding SDR AGC and AM...

First, yes, I met Steve at Jon's place a couple of years ago (hi, Steve).  And hi, Frank!

I've actually dug into the PowerSDR AGC code, but it was some time ago and I no longer recall much about it.  I just know that it was a pain to understand, but if you put in the effort, you can do it (and I'm speaking as a hardware guy, not someone who spends his days writing software).  Four or five years ago, when I first purchased my SDR-1000, the AGC had major problems -- turns out the code was truly broken.  I made some mods myself to fix it.  But since that time it's been rewritten and improved upon by the Flex team (and if I recall, even commented?), and seems to do the job now.

I did want to add, in my opinion, the Flex software really shines in synchronous AM (SAM) mode, and my Flex-5000 is my receiver of choice (of the many I have) when I operate AM.  I haven't experienced any noticeable AGC issues in SAM mode, but I usually keep my AGC set to a long decay (couldn't tell you which setting, as I'm not in the shack at the moment), so perhaps that's the reason why.  Steve, if you could give more detail regarding what you're experiencing, I could do some listening tests myself.

By the way, I know at least one ham who has used the Softrock and the PowerSDR code for reception when he's operating AM, and that's Mike, W6THW.  It's worked well for him, and I've purchased a Softrock myself to do the same thing one of these days.

Oh, and by the way, my email address is on my blog.  If you have any questions regarding the Flex AGC code, I can look it over and see if I can answer them.

- Jeff, k6jca

[K5UJ]

Steve, tnx for the information.  Very useful and glad it is here where I can get it in the future.

Jeff,  what is the language of the powerSDR code?  I assume it is OO instead of top down but is it an interpreted language like Python or is it lower level like assembly?  What do they use for version control?  I've been learning to work with Git and am finding it is pretty cool.

tnx
rob

[Steve - K4HX]

Steve, interesting on the AGC AM problem using the SoftRock and PowerSDR software. I'm surprised the guys on AM have not brought it up, at least that I've heard. I will look for it when I fire mine up this week.

Most guys on AM wouldn't notice it since it would be no different from receivers they've used in the past. The AGC in many boatanchor RXs responds to lower frequency audio.

[k6jca]

Hi Rob,

The PowerSDR GUI (e.g. for the controls & panadapter) is written in C#  (c sharp) and requires a compiler.  All processing, such as the AGC, is in either C or C++ (I've forgotten which).

I'd done a few small things in C before for work, but I'd never seen C# (and I'd had zero experience with GUI code like this).  However, the syntax wasn't that difficult to understand once I got into the code and starting mucking around with it.

Revision control had been done using Tortoise SVN, but I think Flex might now keep their development efforts off-line.  Not sure about that, though, so for those interested it would be worthwhile doing more research.

- Jeff, k6jca
http://k6jca.blogspot.com/

[WA1GFZ]

Hi Jeff,
I agree long decay helps with distortion of pumping AGC. Alberto's AM sync mode used a longer loop time constant but was slower to lock and cleaner.
I suggested years ago wondering if the loop time constant cound be changed after lock. This would be a way to get the best of both worlds.
On another note. Nice 813 rig. About a year ago you came on here looking for some panel meters. I sent you a PM asking which ranges do you need? You never responded so figured you were all set. Anyway, if those are the same meters in the rig picture I have a few like that. If you still need any let me know what ranges and I will see if I can provide them.

[WB2EMS]

while chatting with Nigel VE3ELQ, he told me about his RF Space SDR-IQ receiver, available from HRO for around 500 bucks:

He is using SDR software written by Simon HB9DRV (the guy who has written much of the Ham Radio Deluxe software) and it's very slick. He took a screenshot of my signal as I altered my bandwidth and it picked it right up very neatly. It does mp3 recordings on the fly and will work with Virtual Audio Cable to decode DRM broadcasts using the Dream software. Not bad for a free piece of software!

http://sdr-radio.com/

I have been running that combination for over a year and am very pleased with it. I have it set up on an old laptop in the corner with the server software on it  connected to my house network via wireless and dozens of people a day log into it and use it. I have to log in to the laptop to boot them off to use it myself!  I've been very pleased with Simon's software, although I prefer the faster panadapter of the Spectravue software that came with the radio. But I never use it directly anymore, just over the net, even in the house.

You can use my radio via the net by downloading the software from Simon's site, look for the beta kits, and in the input source drop down menu there's a choice to use remote via web. When that window pops up, in the upper left corner is a browse the web option. It shows all the receivers currently online and registered with the site. Once you've connected to a receiver, it's IP address is stored in the menu of the pop up box and you can just go directly to that IP in the future. There were at least a half a dozen SDR-IQ units available last time I looked. Plus a bunch of softrocks.

The Flex 3000 now has 4.5 Khz audio bandwidth available in the 2.0.x versions of the software, or 9 khz total occupied bandwidth with both sidebands. I don't know why they restrict it.

I have greatly enjoyed the Flex for AM. After getting my feet wet with the SDR-IQ, I decided to get an SDR transceiver and found a used SDR-1000. I operated it for a year and enjoyed it so much I started looking for a used Flex 3000. Found a good deal on a F5K instead and took the plunge. I have to say that between the SDR-IQ and the Flex it's really invigorated my interest in ham radio. Operating without the panadapter makes me feel blind these days. 

For a more modest investment, a used Flex 3000 seems like it gives you most of the flex experience in a compact package. You give up some transmit bandwidth (I rarely run more than 4khz I find) and some of the front end receiver specs and the ability to do diversity receive, but for most use I think it would be fine. The SDR 1000 worked well, but the F3K and F5K get rid of all the extra wiring with the external audio box.

There may be higher performance hardware out there, I have some local friends who are into the Gnu radio development and were pushing me towards various kits, but they were complicated and in flux and just were hard to get good info on. In the end I decided that a semi turn key solution from Flex fit my needs at this time better. YMMV. Certainly a softrock on the IF of a good receiver run with PowerSDR will give you most of the receive advantages we are enjoying.
 

[W1AEX]

The AGC has major problems on AM.  The AGC, when receiving AM, responds to the modulation - a BIG no-no for any AGC system for AM.

Steve, when listening in the AM mode how does this issue manifest itself? I have definitely noticed some kind of peak distortion in AM mode on heavily modulated signals with every version of PSDR I have used, both with the Flex 5K and my 455kc down converter and wonder if that is what you are referring to.

It has never been a serious issue for me since I always use the synchronous detector when operating AM, and SAM seems to receive everything very cleanly.

Rob

[k6jca]

Hi Jeff,
I agree long decay helps with distortion of pumping AGC. Alberto's AM sync mode used a longer loop time constant but was slower to lock and cleaner.
I suggested years ago wondering if the loop time constant cound be changed after lock. This would be a way to get the best of both worlds.
On another note. Nice 813 rig. About a year ago you came on here looking for some panel meters. I sent you a PM asking which ranges do you need? You never responded so figured you were all set. Anyway, if those are the same meters in the rig picture I have a few like that. If you still need any let me know what ranges and I will see if I can provide them.

Thanks, Frank.  I didn't see your PM until last night when I logged onto AMFone after a very long absence.  Many thanks for your offer, but nothing needed at the moment.

The SAM demodulator in early versions of the PowerSDR code took a noticeably long time to lockup if the carrier frequency changed by a significant amount, and I found this to be a big problem when operating a boatanchor net in which no one was on the same frequency (figure +/- 3 KHz from the designated frequency).  I got around this problem by adding what I called my "SAM Lock" code to my version of PowerSDR.  Essentially, it'd look for a the strongest signal within a user-defined frequency window, and if that signal was there long enough, it would zero-beat the VFO to that frequency.  And because of the long lock (and, more importantly, unlock) time of the SAM demodulator, the phase-lock loop would regain lock quite quickly because, essentially, every new signal was zero-beated, and the phase-lock loop didn't have time to drift too far away.  Kind of an inelegant, brute-force method, but it actually worked pretty well.

I believe Flex has improved their SAM demodulator phase-lock loop.  Or I should say I haven't really had a need to add my "SAM Lock" code to the later consoles.

- Jeff, k6jca
http://k6jca.blogspot.com/

[WB2EMS]

Steve, when listening in the AM mode how does this issue manifest itself? I have definitely noticed some kind of peak distortion in AM mode on heavily modulated signals with every version of PSDR I have used, both with the Flex 5K and my 455kc down converter and wonder if that is what you are referring to.

I see this too, on most AM signals when in AM mode, on the voice peaks. I've wondered about it too, as it seems to be too sensitive to the peaks compared to other receivers on the same signals.

It has never been a serious issue for me since I always use the synchronous detector when operating AM, and SAM seems to receive everything very cleanly.

Agreed. Although it doesn't seem to like Tim's SBE very much.  Had to revert to straight AM when listening to that yesterday.

[W1AEX]

Agreed. Although it doesn't seem to like Tim's SBE very much.  Had to revert to straight AM when listening to that yesterday.

Yes indeed, Tim's SBE signal seems to defy the SAM's ability to lock onto it. Of course this is what happens whenever an unstoppable force meets an immovable object!

Incidentally, I did see your call in the list of available IP receivers while browsing Simon's site. I'll be trying to login shortly! Thanks for making your resources available!

:O)

[K1JJ]

I just received an email back from Greg at Flex answering some of the issues we are talking about here.  I sent him an email axing for his permission to post it here. More later.

T

[K5UJ]

The PowerSDR GUI (e.g. for the controls & panadapter) is written in C#  (c sharp) and requires a compiler.  All processing, such as the AGC, is in either C or C++ (I've forgotten which).

Revision control had been done using Tortoise SVN, but I think Flex might now keep their development efforts off-line.  Not sure about that, though, so for those interested it would be worthwhile doing more research.

jeff tnx.  i have no experience with C#; vy little with the other C flavors.   too bad they still use SVN.  Git has some advantages for example everyone has the complete repository so it is possible to work without a network connection.  more here:  http://progit.org/book/ch1-1.html  and finished work commits can be put here: http://github.com  I figured that since the code has to execute in close to real time it would probably be compiled.  There was some sort of panic when MS started moving beyond XP to 7 or Vista--I think it was Vista that came next because the Flex seemed tied to XP.  That has probably been resolved along with some driver issues but it made me leery of it.   There are no OS or  driver issues with your 813 rig I bet   

rob

[K1JJ]

Received from Greg Jurrens at Flex, posted below (with his permission) is the response to a few of my questions… I am happy with the careful attention he paid to everything asked.

BTW, current Flex owners – notice the way to connect your own spec-monitored transmitted signal to the FINAL outboard linear amplifier. They are now connected to the 100w Flex output itself and show nothing what the final linear amp is doing, if used. This is an important feature to have if you want to know the real story. The other way is to use a separate, outboard softrock monitor on the final stage linear, etc.

T
-------------------------------------------------------


Tom:

Sorry for the delayed response.  Just catching up from the holidays....

I will have more stock on the FLEX-5000A with RX2 later this week.  I completely sold out during the Holidays.  We will be shipping again by weeks end.

Your data is partially correct regarding some inconsistencies with the Noise Blanker and Noise Reduction code: During the development of our Version 2.0 software, we managed to disturb the DSP code that supports NR, NB1/NB2, and ANF functionality.  We are actively working a solution now and will hold final release of V2.0 until we fix this.  Our current STABLE release 1.18.6 is fine. 

For the FLEX-5000, our Monitor function is a direct TAP from our 100w PA chain.  I agree it would be useful to be able to monitor the amplified signal to ensure signal purity etc.  One method to do this would be to use the RX2 second receiver and enable reception on RX2 while transmitting.  You would feed RX2 the HPA's tapped signal using a directional coupler with at least 80db but preferably 100db of attenuation.  For example:  2KW = +63db - 100db attenuation = -37db Full scale.  This would give you an S9+36 signal on the input to RX2.  BIG... but not damaging and well inside the linear region of the receiver.   Please note we have not done this specifically at this power level but routinely do this with a 100w signal and don't expect you would have any issues.

For me to answer your "Diversity" question with softrocks, I have to define the term:  In the purest sense, receiver diversity means any 2 receivers on the same frequency with separate audio outputs.  Using 2 FLEX-5000s or 2 anything receivers would accomplish that.  What FlexRadio has done is go "Beyond Diversity(tm)" by creating 2 completely phase synchronous receivers.  This allows us to do both magnitude and phase correlation on the received signal.  The resultant signal can then be null-formed or beam-steered to the operator's advantage.  To our knowledge, the FLEX-5000 with the RX2 is the only amateur product that can accomplish the Beyond Diversity function.


PowerSDR will not currently handle 2 sound cards for RX1 and RX2.  In our FLEX-5000, the sound subsystem is integrated so we do it by a different method.  Your softrock solution would require someone to program that functionality in.  If you you are interested, most of PowerSDR is released under the GNU Public License.  You can request a "tarball" of the source by sending an email to gpl@flex-radio.com . 


Tom, I hope that answers your questions.  Please let me know if I can support you further in your evaluation. Let me know what else I can answer for you.  It's clear you are a very active ham.  I'd love to make you a FlexRadio convert.



73,
Greg - K5GJ

Greg Jurrens - K5GJ
VP, Sales and Marketing
FlexRadio Systems Inc.
T: 512-535-5266 x203
E: greg@flexradio.com
SKYPE: WD0ACD
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