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Author Topic: Flex Site: "Imagine a transceiver that changes Ham Radio - Forever.."  (Read 27933 times)
N9RO
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« Reply #60 on: June 03, 2012, 08:42:02 PM »

Quote
Geez, either go back on your meds or resume your electroshock treatments please!

Zack
N8FNR

Making fun of those less fortunate does not win you any friends.  KNOW YOUR AUDIENCE!

Tim - N9RO
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Real techies don't use knobs.
WD5GWY
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Posts: 403




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« Reply #61 on: June 04, 2012, 04:51:56 PM »

Yeah, yeah, Flex makes the WORST radios in history according to you. In fact I bet that from your point of view that Flex makes MFJ look like mil-spec.

I know that I have been glad to learn the One Great Truth that you posess. Perhaps you could give seminars at TED next year and share your revelations with the world at large?

After reading your missives I have sold my Flex-5000 and replaced it with a Sugiyama F850 rated 1.3 on eham http://www.eham.net/reviews/detail/3633.  Are you happy now? Or does everyone need to sell all of their Flex rigs then you will shut up?

It would be nice if this forum could actually be about SDRs including Flex rather than being a forum for your personal vendetta.

Why not just move on with your life? It seems as if that this is all you live for.

Geez, either go back on your meds or resume your electroshock treatments please!

Zack
N8FNR


Hmmmm, was this directed at me? Shocked
I don't think I've trashed Flex like that at all. In fact, some here think
I am Flex Fanboy. I'm not, but, I do like the radios and what they do.
There are some here that do have something against Flex (the company)
and from reading their past experiences, I can see why they feel the way
they do. If you want a rah rah Flex forum, try one of their Yahoo groups.
I too get tired of some of the things here, but, at the same time, these people
do have a legitimate complaint. And if certain people's posts bother you, you
can always IGNORE them. There are still a lot of useful info that shows up here
concerning SDR radios. You just have to sift thru some stuff to get to the meat
sometimes!!
james
WD5GWY
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N0YXB
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Posts: 320




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« Reply #62 on: June 05, 2012, 01:30:53 PM »

I agree about the "rah rah forum" suggestion.  Although I don't own an SDR yet, I have learned a lot here and would hate to see discussion curtailed because of brand loyalty (or disloyalty).   Smiley   We should be able to discuss the good and the bad aspects of SDRs without it becoming too personal.
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K9IUQ
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Posts: 1955




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« Reply #63 on: June 05, 2012, 03:59:42 PM »

 We should be able to discuss the good and the bad aspects of SDRs without it becoming too personal.

The problem of course is the Flexers do take it personal.

I don't understand it myself. Flexradio are just radios. Personally I like to hear opinions that differ than mine. Many times I learn something. When someone does not agee with me, that is fine I do not take it personally - until hams start calling me names, especially profane names like was done last week before the SDR forum got locked down.

Stan K9IUQ
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WD5GWY
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Posts: 403




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« Reply #64 on: June 05, 2012, 05:21:54 PM »



The problem of course is the Flexers do take it personal.

I don't understand it myself. Flexradio are just radios. Personally I like to hear opinions that differ than mine. Many times I learn something. When someone does not agee with me, that is fine I do not take it personally - until hams start calling me names, especially profane names like was done last week before the SDR forum got locked down.

Stan K9IUQ
Yep, it's just another radio to use in the pursuit of the Amateur Radio hobby. Some like it and others don't. And luckily, there are a lot of alternatives as far as transceivers are concerned. That, to me, makes it fun.
   I think the name calling is simply childish and uncalled for. It's time for some folks to grow up and get a real life. It's a HOBBY not a lifestyle!!
  I for one, value your opinions Stan and am glad you have posted your experiences here. It is appreciated.
james
WD5GWY
 
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K9IUQ
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Posts: 1955




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« Reply #65 on: June 05, 2012, 06:00:28 PM »

I for one, value your opinions Stan and am glad you have posted your experiences here. It is appreciated.
james
WD5GWY
 

Few Flexradio owners have said that publicly. However I have more than a dozen private emails saying the same thing you just did. Many have thanked me for getting many of the Flexradio problems fixed.

Remember always - The squeaking wheel gets the grease. Go along with everybody else and ignore faults and you get what you deserve.

Thanks James,

Stan K9IUQ
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N0YXB
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Posts: 320




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« Reply #66 on: June 06, 2012, 12:11:35 PM »

I for one, value your opinions Stan and am glad you have posted your experiences here. It is appreciated.
james
WD5GWY
 

Ditto, I have learned a lot from Stan, Gene, and Brian (but haven't seen any posts from him in a while). 
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K9IUQ
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Posts: 1955




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« Reply #67 on: June 06, 2012, 03:25:01 PM »


Ditto, I have learned a lot from Stan, Gene, and Brian (but haven't seen any posts from him in a while). 

I miss Brian, his views are very different from mine, but he is articulate, intelligent and interesting. Mostly I loved arguing with him. Rarely did he call me names, and when he did I just laughed.

Stan K9IUQ
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VE3WGO
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Posts: 7




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« Reply #68 on: June 09, 2012, 02:13:25 PM »

The Flex-6000 looks like a great architecture.  Digital Downconversion Receiver, Digital Upconversion Transmitter, GPS-disciplined LO, all-DSP audio.  It's going to be a fine performer.  One thing - it's using 16 bit words to process, and that is 90 dB dynamic range (throw away LSB. if not, it's 93 dB, but LSB is noise) - it's very good but not fabulous. 

What will it do better than current generation of Flex radios, or other high end fast DSP transceivers?  It's getting harder and harder to tell, though.  Same almost blank front panel though, and that's a shame....

My hope is that some future "Flex 7000" will join the ranks of "knob radios" and will have an optional control panel with knobs.  The smooth front panel looks cool, and using a PC gives the ham nice graphical interface, but it is very lacking in user control and quick, accurate adjustment.  An on-screen mouse clickable slider or thumbwheel is far less than ideal compared to a rotary knob.  Today's best "knobby" radios have scrollable menus, programmable knobs, detents, and all sorts of advanced and specialized tactile and visual feedback mechanisms to make the radio's settings fully programmable and easily adjusted.

Knobs are not old fashioned.  Unless you think humans are old-fashioned - well, I suppose we are actually, having been designed either a billion or at least a few thousand years ago, depending on which Book you believe in.

It's because rotary adjustment is what our forearms were actually designed for - our best hand/arm fine motor skill is rotary control  That's why we have rotary controls and wheels for for critical tasks like steering our vehicles, turning door knobs, key locks, and tuning dials, where we need accuracy and dexterity, as well as tactile feedback (feeling in our fingers).  And that's why the knob-festooned front panels of ham radios continue to be popular. 

So building an SDR is ok, but it need not make the front panel devoid of user control knobs.  There is no sensible connection between these two attributes.  So c'mon Flex... knobs.
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KE5JPP
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« Reply #69 on: June 09, 2012, 03:25:56 PM »

The Flex-6000 looks like a great architecture.  Digital Downconversion Receiver, Digital Upconversion Transmitter, GPS-disciplined LO, all-DSP audio.  It's going to be a fine performer.  One thing - it's using 16 bit words to process, and that is 90 dB dynamic range (throw away LSB. if not, it's 93 dB, but LSB is noise) - it's very good but not fabulous.

You really need to educate yourself on SDR architectures.   Look up process (or processing) gain and you will see that you are completely wrong about the 90 dB dynamic range.  You have failed to take decimation into account.  It will achieve at least 30 dB better than that (~120 dB or so).

Gene
« Last Edit: June 09, 2012, 03:28:23 PM by KE5JPP » Logged
VE3WGO
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Posts: 7




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« Reply #70 on: June 09, 2012, 08:29:42 PM »

Gene, perhaps my point wasn't clear.  So rather than educate myself further, I will explain the problem differently. It's real.  I wasn't referring to Rx ADC sample rate. No, I was referring to ADC sample width, which is 16 bits (according to Flex's 6000 specsheet).  I was therefore calculating full scale range of the ADC.  16 bits gives 93 dB.  You can try to actually make use of the LSB with dither techniques.  A DSP can make full use of that 93 dB, but you can't invent any more bits. 

Oversampling can improve noise and quantization errors. But if an interferer clips the ADC at full scale, the desired signal is impaired.  So the ADC full scale range is a critical parameter.  AGC is the only way to deal with it if the interferer is luckily placed outside of an RF roofing filter's passband, and that needs to be a pre-ADC roofing filter.  Close-in interferers that clip the ADC are destructive.  Alternatively, the interferer can be dealt with in front of the ADC with some form of active canceller, and that interference cancelling technology will be the new secret sauce.  Flex say they are doing direct sampling for digital downconversion, and they are designing it to include the 144 MHz band, and their sample rate will be 245.76 Msps, which means they will also need to filter out aliases mirrored around Fs/2. And this sample rate also shows that they aren't oversampling to try to get more effective bits for higher SNR. 

So, 93 dB is all they'll get with their 16 bit converter.
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KE5JPP
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« Reply #71 on: June 10, 2012, 06:09:11 AM »

Gene, perhaps my point wasn't clear.  So rather than educate myself further, I will explain the problem differently. It's real.  I wasn't referring to Rx ADC sample rate. No, I was referring to ADC sample width, which is 16 bits (according to Flex's 6000 specsheet).  I was therefore calculating full scale range of the ADC.  16 bits gives 93 dB.  You can try to actually make use of the LSB with dither techniques.  A DSP can make full use of that 93 dB, but you can't invent any more bits.  

Oversampling can improve noise and quantization errors. But if an interferer clips the ADC at full scale, the desired signal is impaired.  So the ADC full scale range is a critical parameter.  AGC is the only way to deal with it if the interferer is luckily placed outside of an RF roofing filter's passband, and that needs to be a pre-ADC roofing filter.  Close-in interferers that clip the ADC are destructive.  Alternatively, the interferer can be dealt with in front of the ADC with some form of active canceller, and that interference cancelling technology will be the new secret sauce.  Flex say they are doing direct sampling for digital downconversion, and they are designing it to include the 144 MHz band, and their sample rate will be 245.76 Msps, which means they will also need to filter out aliases mirrored around Fs/2. And this sample rate also shows that they aren't oversampling to try to get more effective bits for higher SNR.  

So, 93 dB is all they'll get with their 16 bit converter.

Like I said, you need some serious education.  I am tired of going through this time and time again with guys who refuse to do so.  Roll Eyes  Roll Eyes Roll Eyes Maybe someone else in this forum will have the energy to do so.  You are talking about roofing filters as if it were a QSD type SDR, which direct sampling SDRs do not have... Sigh...  No one calculates dynamic range from the number of ADC bits because it means nothing.  High speed ADCs have a SFDR rating and a dBFs noise floor rating which are the important parameters.  The ADC clipping level can be placed where you like by amplification or attenuation.

And whether the ADC is oversampling or undersampling, it is the bandwidth reduction (decimation) in the following DDC that mostly determines the dynamic range of the receiver.  Like I said before, read up on processing gain as the result of decimation.

process gain = 10 * log10 ( Fs/ 2 * Ff ), where Fs is the 245.76 MSPS sampling rate and Ff is the final output sample rate.  

Just think about what you are implying for a minute.  If your 245.76 MSPS ADC clips at 0 dBm (almost S9+80!) then from your calculation of the ADC's 90 dB (or so) dynamic range, you're telling me you won't be able to hear signals below -90 dBm (about S6) when the DDC decimates the signal down to less that 100 kSPS?   Cheesy  Read up!

Gene
« Last Edit: June 10, 2012, 06:58:44 AM by KE5JPP » Logged
VE3WGO
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Posts: 7




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« Reply #72 on: June 10, 2012, 08:38:46 AM »

Of course roofing filters will be needed.  Did you invent some new technology that the rest of the world missed?

In the Flex 6000 architecture, ADC at at 245.76 Msps means Fs/2 is 122.88 MHz, so their two receive bands: 30 kHz-77 MHz falls into the 1st Nyquist zone, and 136-165 MHz falls into the 2nd Nyquist zone. 

The 30 kHz -77 MHz range will have an alias at 168.76-245.73 MHz.  It will need to be filtered out before the ADC to avoid corrupting sampled RF of the .03-77 MHz signals.  In fact, there would be aliases or image responses at every +/- n*FS/2 up to the maximum response of the RF front end, so they will use a LPF no doubt to reject everything above 77 MHz for the low band.  For the 135-165 band, aliases will be at 110.76-80.76 MHz, which unfortunately is the FM broadcast band, so let's see how well they handle that one with good filtering.  I'm guessing a good BRF ahead of any amplification for IMD, but also deep rejection ahead of the ADC to make sure FM band aliases are not going to fold into 2 meter sampled signals.

Don't ever again try to convince me or anyone else that pre-ADC anti-aliasing filters won't be needed.  Call them what you like, but they are in fact roofing filters, which is what RF front end designers need to define the RF bandwidth of the stages ahead of sampling or mixing and highly selective stages, be they analog, digital or whatever.  If you think I still need an education, go read up on sampling theory before you start pointing any more jabs at me please.

I've only ever known decimation and process gain to apply to noise limited systems, such as CDMA (IS-95 etc) or DSSS (spread spectrum systems, including old WiFi 802.11b) which an HF receiver is surely not.  An HF receiver is interference limited.

Let's see what dynamic range Flex eventually claims with 16 bits.   Their spec sheet currently says "TBD"

FWIW, Flex 5000 uses 24 bit low IF sampling rate ADCs, which allows their receivers to have dynamic range limited by RF front end performance rather than the ADC.

Ed
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NI0Z
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« Reply #73 on: June 10, 2012, 10:09:26 AM »

Say the specs and speculation turns out to be real, the question I have at that point is this.  How many people are going to have a shack and antenna system that is really going to be able to leverage those specs?
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KE5JPP
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« Reply #74 on: June 10, 2012, 02:04:05 PM »

Of course roofing filters will be needed.  Did you invent some new technology that the rest of the world missed?

In the Flex 6000 architecture, ADC at at 245.76 Msps means Fs/2 is 122.88 MHz, so their two receive bands: 30 kHz-77 MHz falls into the 1st Nyquist zone, and 136-165 MHz falls into the 2nd Nyquist zone.  

The 30 kHz -77 MHz range will have an alias at 168.76-245.73 MHz.  It will need to be filtered out before the ADC to avoid corrupting sampled RF of the .03-77 MHz signals.  In fact, there would be aliases or image responses at every +/- n*FS/2 up to the maximum response of the RF front end, so they will use a LPF no doubt to reject everything above 77 MHz for the low band.  For the 135-165 band, aliases will be at 110.76-80.76 MHz, which unfortunately is the FM broadcast band, so let's see how well they handle that one with good filtering.  I'm guessing a good BRF ahead of any amplification for IMD, but also deep rejection ahead of the ADC to make sure FM band aliases are not going to fold into 2 meter sampled signals.

Don't ever again try to convince me or anyone else that pre-ADC anti-aliasing filters won't be needed.  Call them what you like, but they are in fact roofing filters, which is what RF front end designers need to define the RF bandwidth of the stages ahead of sampling or mixing and highly selective stages, be they analog, digital or whatever.  If you think I still need an education, go read up on sampling theory before you start pointing any more jabs at me please.

I've only ever known decimation and process gain to apply to noise limited systems, such as CDMA (IS-95 etc) or DSSS (spread spectrum systems, including old WiFi 802.11b) which an HF receiver is surely not.  An HF receiver is interference limited.

Let's see what dynamic range Flex eventually claims with 16 bits.   Their spec sheet currently says "TBD"

FWIW, Flex 5000 uses 24 bit low IF sampling rate ADCs, which allows their receivers to have dynamic range limited by RF front end performance rather than the ADC.

Ed

Not only are you are lacking in the understanding of signal processing techniques, you also seem to be lacking the correct signal processing terminology. You seem to have problems with reading too.  Anti-alias filters are referred to as anti-alias filters, not "roofing filters".  The term "roofing filter" is used primarily in Ham radio circles and in ANALOG front end design for the filter that is generally found after the first analog mixer, not by professionals in the signal processing field and not related to a direct sampling receiver.  No where did I say that anti-alias filters were not required in a direct sampling receiver, so quit trying to twist the conversation into something I did not say.

You have not answered the question: If your 245.76 MSPS ADC clips at 0 dBm (almost S9+80!) then from your calculation of the ADC's 90 dB (or so) dynamic range, you're telling me you won't be able to hear signals below -90 dBm (about S6) when the DDC decimates the signal down to less that 100 kSPS?

Gene
 

« Last Edit: June 10, 2012, 02:10:10 PM by KE5JPP » Logged
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