Is there anywhere that I can get a thorough explanation of the technology behind the Flex 6000 Serie

Roy Laufer

Hello,

I was chatting on the radio the other night with a guy that I have a great deal of respect for. He has been an Electrical Engineer, mostly focused upon antenna design for more than 50 years. He has been a Ham for even longer, and has been published numerous times in QST.

He seems a bit dubious of some of my claims for my 6700. When I mentioned its panadapter's bandwidth, it was his opinion that it used a local oscillator somewhere, and if it was using silicon alone, my machine would be close to melting from the heat and probably have the price of a military project.

I told him that it was direct conversion (which he called a zero IF frequency), and I only wish that I had more facts at my finger tips for the discussion.

I am not an Electrical Engineer, all that I have learned about electronics and Amateur Radio have pretty much been self taught.

I have read the brochures and the short reviews of the technology and of the 6000 series itself. Is there anything more extensive and detailed about the workings of the 6000 series?

I realize there are a few books on SDRs in general, but I really would like to be able to explain how my beautiful 6700 really works to a guy with an Electrical Engineering degree (if possible).

Any thoughts? Any ideas? Any source for more than the usual PDF files???

Thanks!

73,
Roy AC2GS

Walt - KZ1F

Well, I suspect it is fair to say you are not experiencing China Syndrome so the total meltdown is not terribly accurate. I think the term you likely wanted to use is direct sampling. Somewhere on the Flex site they have a diagram of the basic circuitry. Look for ' How to make a quiet shack' by Ky6LA, references to it will be on this site. The second half of it goes into the history and advancement of SDR technology. essentialy the 6000 series can 'digest' 14MHz of spectrum in one gulp. From there you can focus on small segments of it down to the given freq of interest with the given bandwidth of interest. So there are no intermediate mixers involved which means you'll have a signal free from mixer artifacts.. Look for the profile of Ky6LA and in that list of conversations will be a reference to his pdf.


https://community.flexradio.com/flexradio/topics/how-to-build-a-quiet-station

Mark Erbaugh

Roy, Here's my simplistic understanding of the operation of the 6000 series. These radios directly sample the incoming RF with no frequency conversion . The 6300 samples at about 128 million sample per second while the 6500 and 6700 sample at twice that. Based on the theory that you can capture frequencies up to half the sample rate, that means the 6300 is sampling everything from DC to over 60 MHz. The Flex radios use a FPGA as a super number cruncher to process all that data as that amount of data is too much for a typical microprocessor to handle. The operation your friend describes is more like the older Flex series. In those, the incoming RF was mixed down to few hundred kHz and that was the signal that was sampled at a much lower rate. At that rate the data can be processed by a microprocessor alone. 73, Mark

Roy Laufer

When I told him the panadapter's dynamic range, I think he thought I wasn't quite sane.

When I tried to explain my ability to watch 14 MHz of the 70cm and the entire 2 Meter band at the same time he also found this difficult to believe. He kept asking me about the "delay" of the display and if the display was "continuous" or multiplexed. I tried to explain that this is all rendered in the digital domain using packet protocols, so that the whole thing was multiplexed and not "real time" (what is?) but that the delay was small and synchronized with the audio to be imperceptible.

I've seen Howard's great presentation before, and I will look thru it again. I was just looking for some Flex 6000 Series more technical discussions.

I think if I showed him my 6700 he would think that it might be a magic trick (but then everyone here knows about Arthur C. Clarke's comment about the difference of those two things).

Jim Jerzycke

I'll be following this and reading the references, as I, too, have friends that don't really understand what "SDR" is, and apply the acronymn to anything with a DSP module hung on it.

And although I understand that there's a highly variable dividing line between what is, and isn't, true SDR, an awful lot of people out there don't, and they seem to throw the term around so they sound like they're "in the know"....

73, Jim  KQ6EA

Roy Laufer

I'm there with you with the simple explanation, but he's an Electrical Engineer, so the conversation veered on the capture of both I and Q information, and I believe there's a little bit more magic to get the 6700 up to 2 Meters (that's why one real receiver can work at 2 meters, but the other defaults to below 70MHz). Then there is decimation to be considered...

The devil is in the details.

I've seen some more technical articles of the theory in general, where the math started to make my ears bleed...

Simple is very nice, but Electrical Engineers usually don't like the simple explanation in the long run...

Roy Laufer

I get that from both ends, where anything that uses a DSP or even a computer program for remote control is called an SDR, as well as the other end of the "spectrum"!

I had another conversion, with another smart guy (what can I say, I don't suffer fools gladly<g>), who quoted the IEEE that SDR, by their definition, can only be direct conversion or direct sampling. According to him, the IEEE does not recognize the older Flexs as "true" SDRs either!??

Walt - KZ1F

What you can do Roy is look through the profile of Steve, N5AC as likely in the before time (shortly after the 6000 series was announced he likely did descriptions mere mortals could comprehend.

FB on the ear bleed thing. Too funnny  hi hi.

Also, Steve's done some pretty comprehendible YouTube vids that might be helpful.

George KF2T

The FRS road show featured an excellent powerpoint on SDR, too. Not sure where it is kept, but it told the story well. Great points about what is and isn't SDR, because a lot of radios (amateur and not) use digital features to great benefit. Precious few use the full 6000 direct sampling treatment. And yes, your smart friend is right - it's a serious computational load. The radio server does a LOT of thinking in there!

Roy Laufer

I think the problem is that he hasn't kept completely up to date with what silicon can do these days. His statement of the excessive heat and exorbitant price point was quite true a few years before the 6000 Series.

It's difficult not to to fall a little bit behind the bleeding edge of all of technology!

In the 1800, they say, one man could learn EVERYTHING known at the time (I think that's rather apocryphal), lota luck trying to do that now!

Jim Jerzycke

Yep, I've seen people run a CAT program with a cable to their PC, and then described how they're now running an "SDR"!

And there are some "other" vendors out there (Brand "E" comes to mind), who use the term "Superhet SDR" just so they don't get left off the bandwagon.

By their definition my Kenwood TS-950SDX is a "Software Defined Radio".

Roy Laufer

It's a topsy turvy, wibbily wobbly timey wimey experience, trying to explain SDR technology to the poorly informed...

Jim Jerzycke

That it is.....

Burt Fisher

I tell my 5th graders when I was in 5th grade a computer was the size of the school, plus no keyboard, printer or monitor

Roy Laufer

Those few youngsters that know some anthropology think that all of us spent a great deal of time sharpening our flint head spears for "the hunt" <grin>...

Jay -- N0FB

You might find the 2 videos to have helpful information. https://youtu.be/UyXZn5ppYpk https://youtu.be/yj44qGVjikw

Burt Fisher

If you don't have an hour to watch, try this for 8 minutes

https://www.youtube.com/watch?v=s0bf5wdtL1Y

Roy Laufer

Thanks! I saw your great interview years ago and enjoyed it while I dreamed of owning one as I unsuccessfully dreamed of a Collins T/R when I was young and resource poor. This is a great discussion for " the man in the street". I'm looking for something that would prepare me for a deeper enquiry from a real smart guy with an Electrical Engineering degree.

Steve W6SDM

"... it was his opinion that it used a local oscillator somewhere, and if it was using silicon alone, my machine would be close to melting from the heat and probably have the price of a military project."

Explain to your friend that's why, in addition to an amateur radio license, all Flex operators are required to hold Level 1 certification issued by the Nuclear Regulatory Commission.  My Flex 6300 was the cost of a military project - it cost about what the Navy pays for a roll of toilet paper.

KY6LA_Howard

Here are links to a few of my presentations

How to build a Quiet Station  https://db.tt/xG8SOiRI

Modern Radio SDR-101  https://db.tt/0ALtyaj9

And still a bit rough

Four Generations of SDR  https://db.tt/U2PytP2Z

The last presentation attempts to explain the difference between true SDR and their different generations vs Superhet with DSP radios such as the K3 which incorrectly claim to be SDR's so as to be able to market to the uninformed....

Roy Laufer

Thanks a lot! I will review them tomorrow, although I am sure that I reviewed them when they were first released.

Going over the same material can be useful. For some reason I got Direct Conversion mixed up with Direct Sampling after the last time I researched the subject.

I ordered a more technical treatise on the subject, written last year, from Amazon. I just hope the engineering equations don't cause my ears to bleed too much!

Burt Fisher

Totally impressive presentations

EA4GLI

LOL

DrJ

I second the request for someone in the community and/or Flexradio corporate to direct us to this information or provide this type of information on their website. I wonder if the reason for the lack of information could be due to worry of patent infringement or some other business worry. I would guess that the technology is unique and likely registered and available in full detail in the patent office?

Glenn

HamRadioNow episode 220:  http://arvideonews.com/hrn/HRN_Episode_0220.html

Myth Buster!!!!   Steve from FlexRadio describes how things work.

Roy Laufer

I've seen it, I love it, but...

What can I say, I am greedy. I would REALLY like a full review of the technology from front end to audio output, in detail, that would satisfy an Electrical Engineer.

That is what I am seeking!

Roy Laufer

I don't think it's a trade secret, as much as FRS doesn't wish to use the time and resources for a "white paper" that will return very little in sales. Most of us are not Electrical Engineers, and no one lost money by underestimating the intellectual curiosity of the average consumer<grin>.

As for a patent search, I doubt FRS has one that outlines the full functionality of their 6700 series, and if you've ever read some patents, you'd see how many were "clear as mud"...

Bill -VA3WTB

It would be nice to see a good paper on this, I thought of doing a presentation to my ham club but finding good material is hard. I do like the info from Howard, he has lots covered there

M0GVZ

There are lots of videos of Flexradio engineering presentations done at various conferences on Ham Radio Now's Youtube channel. There are things on there described in way that'll probably go over the top of your friends head.

Ken - NM9P

Jim, part of this, I think, is that many Flexers and other SDR folks have gotten sidetracked in the "knobs vs. no-knobs" debate, which is not really the heart of the issue. That is merely a control surface issue. The real heart of SDR is the detection/modulation method.

Jim Jerzycke

I agree.