Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1] 2 Next   Go Down
  Print  
Author Topic: Little SDR Project  (Read 24296 times)
NI0Z
Member

Posts: 562


WWW

Ignore
« on: July 23, 2012, 10:00:47 AM »

I don't know how I stumbled down the path I did googling earlier this morning, perhaps it was the product of a decent nights sleep.

Anyway, I got to thinking about the Raspberry Pi Linux computer for $35 and the FunCube Dongle SDR and began to explore the possibilities of a hombrew SDR receiver.

Keep in mind this is a On The Cheap project and so a high quality result is not very likely.  As usual though, I put this out there to a group to see where we can tweak and improve and maybe have a little fun building our own little SDR.  Of course there will be the why bother questions, and I have no answer for you other than because we can.

Now that the disclaimers are taken care of, here is our challenge if there is one.  An SDR Reciever with integrated computer, screen, self contained for under $150.

Can we do it?  Maybe!

Let's talk about a few basics here to get us rolling.

I am going to create a shell system for starting purposes and then we can rip that outline apart and retool as we go.

For the computer lets go with the Raspberry $35 Linux computer.  It's cheap, very functional and has enough power for us in a size that is hard to beat.  Let's put a 16GB SD card in for our OS.  We will worry about some sort of enclosure for all this last after we settle on everything else.  I am trying to keep it all small though.

http://www.raspberrypi.org/faqs

Alright, next up, we need a receiver that can work with Linux.  The Funcube while nice is expensive and blows our budget all by itself almost, so I was thinking either a soft rock kit or I found that the RealTek dongle that can work like an SDR and modded for 0-30khz.  I will warn in advance it is not as nice as the Funcube a d I think it's only 8 bits.   Perhaps you all have some other ideas, these can be had for under $30 though.

http://superkuh.com/gnuradio.html
http://sdr.osmocom.org/trac/wiki/rtl-sdr

Alright, so at this point we need an antenna solution and I have not thought that part out yet.  As a Reciever only though, the Raspberry Pi does have an audio out.  If we need audio in then we need a USB sound card.  The Soundblaster Play looks promising at $29. http://www.logilink.de/showproduct/UA0053.htm?seticlanguage=en

The last part I was looking at was a Linux compatible touch screen.  Maybe 5 or seven inches.  Keep in mind the Pi computer only has composite or HDMI output and it would be nice if our screen also served as our primary input when we were using the Reciever so we did not have to have a mouse and keyboard hanging off it unless we wanted to.  We could of course make those wireless I guess.

Any ways, Lilliput makes some USB touch screens that might work.

I thought to finish it all off that any USB dongle devices or hubs we buy we could take their casing off and mount in our case.  I was thinking a nice case fashioned with see through plexy glass would be cool and affordable.  I am guessing we would need two power supplies, one for the Pi computer and one for a powered USB hub since it would have to power the USB devices we add on.

Here is a link with all the known functioning USB peripherals that work with the PI, quite a lot to choose from.

USB Peripherals for Pi
http://elinux.org/RPi_VerifiedPeripherals

So we would run our radio on SDR GNU and I was thinking that a regular 0-30k Am antenna would work.

Minus the display we are within the $150 budget so far.

Thoughts, changes?

By the way, somewhere out there I saw a guy advertising that he was making a 5 watt Transmitter add on to his SDR dongle Reciever.  Who knows!  Smiley

Other links

http://www.dh1tw.de/sdr-resources
http://www.amazon.com/LD-1TR-5-Watt-Software-Defined-Transceiver-Amateurs/dp/B007OLK2B0/ref=pd_sim_sbs_e_3


« Last Edit: July 23, 2012, 10:22:21 AM by NI0Z » Logged

N9VV
Member

Posts: 14




Ignore
« Reply #1 on: July 23, 2012, 12:09:44 PM »

Here is a list of 61 QSD projects that are all supposed to be inexpensive
and improved from the traditional SoftRock. Some of them are Transceivers.

http://www.n9vv.com/collected-list-QSD-kits.html

GL de Ken N9VV
 
Logged
NI0Z
Member

Posts: 562


WWW

Ignore
« Reply #2 on: July 23, 2012, 12:31:07 PM »

For fun I have been looking at other alternative base computers and there are several options to choose from varying from $150 new to $300 new that include touch screen, audio in out, ect.

There are several Linux open source handheld game controllers to choose form and then devices like the arches Internet table link below.

8GB can be made to run Linux.  Imagine you can get these cheap,cheap used.
http://www.archos.com/products/ta/archos_70it/index.html?lang=en
Built in sound on Archos products is usually pretty good.

http://en.wikipedia.org/wiki/GP2X_Wiz
Example of the handheld Linux game controller option.

My thought on these is that you could make a docking bay for them and dual boot them to run your SDR.  That way you get a nifty tablet to use that doubles as your SDR interface.

Logged

NI0Z
Member

Posts: 562


WWW

Ignore
« Reply #3 on: July 23, 2012, 01:19:03 PM »

Here is a list of 61 QSD projects that are all supposed to be inexpensive
and improved from the traditional SoftRock. Some of them are Transceivers.

http://www.n9vv.com/collected-list-QSD-kits.html

GL de Ken N9VV
 

Genesis has come a long ways!  I may have to take back what I said in the future thread about there not being a first class SDR available for the average ham.  Their two transceivers look really nice!
Logged

KE5JPP
Member

Posts: 0




Ignore
« Reply #4 on: July 24, 2012, 03:32:09 AM »

Anyway, I got to thinking about the Raspberry Pi Linux computer for $35 and the FunCube Dongle SDR and began to explore the possibilities of a hombrew SDR receiver.

You need to google around more.  People have already thought of using the Raspberry Pi with SDR.  The conclusion is it is way too underpowered to do the DSP that is required for SDR.  The Raspberry Pi is a dead end.

Also, its called GNURadio, not GNU SDR.

You will not get something like this accomplished as long as you have no understanding of the DSP requirements for SDR.

Gene
« Last Edit: July 24, 2012, 03:36:38 AM by KE5JPP » Logged
NI0Z
Member

Posts: 562


WWW

Ignore
« Reply #5 on: July 24, 2012, 05:55:34 AM »

Anyway, I got to thinking about the Raspberry Pi Linux computer for $35 and the FunCube Dongle SDR and began to explore the possibilities of a hombrew SDR receiver.

You need to google around more.  People have already thought of using the Raspberry Pi with SDR.  The conclusion is it is way too underpowered to do the DSP that is required for SDR.  The Raspberry Pi is a dead end.

Also, its called GNURadio, not GNU SDR.

You will not get something like this accomplished as long as you have no understanding of the DSP requirements for SDR.

Gene

Hi Gene,

If you go to http://www.gnu.org/software/gnuradio/doc/exploring-gnuradio.html the requirements might just fit withing the Pi.

The idea here is really to build a cheap receiver which was stated up front.  Keep in mind, we are playing around theoretically here.

If you found an example where someone tried this and it did not work, please share it so we can learn from it.
Logged

KE5JPP
Member

Posts: 0




Ignore
« Reply #6 on: July 24, 2012, 06:04:36 AM »

Anyway, I got to thinking about the Raspberry Pi Linux computer for $35 and the FunCube Dongle SDR and began to explore the possibilities of a hombrew SDR receiver.

You need to google around more.  People have already thought of using the Raspberry Pi with SDR.  The conclusion is it is way too underpowered to do the DSP that is required for SDR.  The Raspberry Pi is a dead end.

Also, its called GNURadio, not GNU SDR.

You will not get something like this accomplished as long as you have no understanding of the DSP requirements for SDR.

Gene

Hi Gene,

If you go to http://www.gnu.org/software/gnuradio/doc/exploring-gnuradio.html the requirements might just fit withing the Pi.

The idea here is really to build a cheap receiver which was stated up front.  Keep in mind, we are playing around theoretically here.

If you found an example where someone tried this and it did not work, please share it so we can learn from it.

Go read the archives of the GNURadio mailing list as well as the openHPSDR mailing list.  If DttSP (the DSP code used in PowerSDR and other SDR software) cannot run on the Raspberry Pi, GNURadio sure won't.   GNURadio's CPU requirements are much higher than DttSP.

Example http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/2012-June/017462.html
« Last Edit: July 24, 2012, 06:07:26 AM by KE5JPP » Logged
NI0Z
Member

Posts: 562


WWW

Ignore
« Reply #7 on: July 24, 2012, 07:01:09 AM »

See his update, he is making progress.

http://g0orx.blogspot.com/

Keep in mind here were are talking about an hpsdr verses an 8bit dongle with a max of 192k bandwidth.  That's a big difference in CPU requirements in my mind.

Also, I am not settled on a Pi either, hence posting some of the game controller hardware, they have more horsepower and have built in controls that might be leveraged.

Another thought that came to mind is that there are several ARM dell laptops out there that have better than 1ghz CPUs in them that could be bought cheap and their hardware could be hijacked and setup into a new case and layout.

This is all theoretical discussion as I don't really intend to build one physically.

I respect your right to be critical and cynical about this so no offense taken and no worries on my part.

It's my guess that if someone really wanted to work at it, like the guy in the link above, a really cheap lowed self contained SDR could be created.  Heck, might even be able to get some knobs on it!

Check out this link and the entry on Funcube and Pi
http://www.funcubedongle.com/

Here is another link with the Pi being used for ham radio...
http://www.uk.amsat.org/8019

I think it's only a matter of time before we see someone have something working.
« Last Edit: July 24, 2012, 07:08:29 AM by NI0Z » Logged

KE5JPP
Member

Posts: 0




Ignore
« Reply #8 on: July 24, 2012, 08:32:48 AM »

See his update, he is making progress.

http://g0orx.blogspot.com/

Keep in mind here were are talking about an hpsdr verses an 8bit dongle with a max of 192k bandwidth.  That's a big difference in CPU requirements in my mind.

Also, I am not settled on a Pi either, hence posting some of the game controller hardware, they have more horsepower and have built in controls that might be leveraged.

Another thought that came to mind is that there are several ARM dell laptops out there that have better than 1ghz CPUs in them that could be bought cheap and their hardware could be hijacked and setup into a new case and layout.

This is all theoretical discussion as I don't really intend to build one physically.

I respect your right to be critical and cynical about this so no offense taken and no worries on my part.

It's my guess that if someone really wanted to work at it, like the guy in the link above, a really cheap lowed self contained SDR could be created.  Heck, might even be able to get some knobs on it!

Check out this link and the entry on Funcube and Pi
http://www.funcubedongle.com/

Here is another link with the Pi being used for ham radio...
http://www.uk.amsat.org/8019

I think it's only a matter of time before we see someone have something working.

Why anyone would waste their time on the Funcube is beyond me.  The dynamic range is terrible and unusable if it was possible to tune it on HF.   As I recall, it only goes down to 60 MHz anyhow.   I have one and it is barely usable on VHF.

Gene
Logged
NI0Z
Member

Posts: 562


WWW

Ignore
« Reply #9 on: July 24, 2012, 08:37:14 AM »

Gene, Funcube is too expensive for what it does, so I don't know why people are using them, I am not advocating it.

See this link here.
 http://www.raspberrypi.org/phpBB3/viewtopic.php?f=9&t=1450

The RealTek 2832U can easily be modded for AM 0-30khz.

That said Gene, are you just opposed to the whole try to find a way to build a tiny self contained cheap SDR concept, or do you have some constructive suggestions on what could be used?  If you would have read my original post and taken a constructive approach to the conversation you would either have left this thread alone or would have chimed in with some suggestions.

If your just opposed to it all and believe it can't and shouldn't be done, then your point has been made, thanks for your contribution.

Ideas often start small and very wrong and when we collaborate we can develop better concepts and ideas. 

Besides, there is not a whole lot else going on here in the way of conversations, so if nothing else I have offered up some SDR fodder until something better comes along.  Ignore is always an option. Smiley

« Last Edit: July 24, 2012, 08:58:15 AM by NI0Z » Logged

KE5JPP
Member

Posts: 0




Ignore
« Reply #10 on: July 24, 2012, 10:04:30 AM »

Gene, Funcube is too expensive for what it does, so I don't know why people are using them, I am not advocating it.

See this link here.
 http://www.raspberrypi.org/phpBB3/viewtopic.php?f=9&t=1450

The RealTek 2832U can easily be modded for AM 0-30khz.

That said Gene, are you just opposed to the whole try to find a way to build a tiny self contained cheap SDR concept, or do you have some constructive suggestions on what could be used?  If you would have read my original post and taken a constructive approach to the conversation you would either have left this thread alone or would have chimed in with some suggestions.

If your just opposed to it all and believe it can't and shouldn't be done, then your point has been made, thanks for your contribution.

Ideas often start small and very wrong and when we collaborate we can develop better concepts and ideas.  

Besides, there is not a whole lot else going on here in the way of conversations, so if nothing else I have offered up some SDR fodder until something better comes along.  Ignore is always an option. Smiley



If you want to admit that this is just some mental masturbation on your part, I can understand.  What I find funny is your general lack of understanding of what it would require to build a "cheap" self contained SDR.    I am not opposed to ideas for a new SDR.  I do own multiple SDRs that work very well and I am satisfied with.

Yes, you might be able to mentally masturbate up a cute little imaginary "toy" SDR in that price range, but who would really take it seriously?  First you are posting about a SDR with a backplane and plug in modules that obviously would cost way more than most guys would be ever willing to pay for it, and now you are talking about some "toy" SDR that costs under $150.  You are all over the place on this and it is hard to take you seriously because of this.  Roll Eyes

Gene
« Last Edit: July 24, 2012, 10:07:48 AM by KE5JPP » Logged
NI0Z
Member

Posts: 562


WWW

Ignore
« Reply #11 on: July 24, 2012, 10:28:12 AM »

Gene,

In my observations here, you seem to like to put people down very quickly.  Perhaps it's not me that has an issue here.  I have made several posts of several other people trying to do exactly the same thing.  They all must be so called mental masturbators as well?  Lol

Ok Gene, I have your answer now, laden with insult.  You simply object to the idea, and that's all you really had to say wasn't it?

Most hams I have come across are helpful, kind and try to help newer hams that come along rather than lambast them and try to put them down.

What's up man, are you angry at the world or something?  Did you lookup my license?  Did you see I haven't even been a ham a year? 

It's my opinion that if we want to see this past time thrive we should encourage and not discourage the new people getting involved.

You know Gene, I was driving home and on 2M yesterday and learned several things from a long time ham, he was patient and explained a few things to me about 6M and I was grateful for his wisdom and experience and let him know it as well.  I was able to go home and immediately leverage his advice about 6M. 

You could be such a tremendous asset here if you were more patient with folks.

I hope I will be wrong in believing that you'll likely look to trounce on any post I ever make here forward.  Congrats on probably chasing another newbie ham away whose asking questions, and seeking answers.  You know, that doesn't just deprive me from learning, it deprives everyone else who wants to learn and is afraid to ask.

Is that what you want?

73's Gene, I'll just avoid you if you want to be condescending.
Logged

KE5JPP
Member

Posts: 0




Ignore
« Reply #12 on: July 24, 2012, 10:47:24 AM »

Gene,

In my observations here, you seem to like to put people down very quickly.  Perhaps it's not me that has an issue here.  I have made several posts of several other people trying to do exactly the same thing.  They all must be so called mental masturbators as well?  Lol

Ok Gene, I have your answer now, laden with insult.  You simply object to the idea, and that's all you really had to say wasn't it?

Most hams I have come across are helpful, kind and try to help newer hams that come along rather than lambast them and try to put them down.

What's up man, are you angry at the world or something?  Did you lookup my license?  Did you see I haven't even been a ham a year?  

It's my opinion that if we want to see this past time thrive we should encourage and not discourage the new people getting involved.

You know Gene, I was driving home and on 2M yesterday and learned several things from a long time ham, he was patient and explained a few things to me about 6M and I was grateful for his wisdom and experience and let him know it as well.  I was able to go home and immediately leverage his advice about 6M.  

You could be such a tremendous asset here if you were more patient with folks.

I hope I will be wrong in believing that you'll likely look to trounce on any post I ever make here forward.  Congrats on probably chasing another newbie ham away whose asking questions, and seeking answers.  You know, that doesn't just deprive me from learning, it deprives everyone else who wants to learn and is afraid to ask.

Is that what you want?

73's Gene, I'll just avoid you if you want to be condescending.


I think you are being a little too touchy here.  "Mental Masturbation" is just a colorful term for talking about something without really intending to pursue or built it.  Also, you have admitted that you are new to this stuff, so I don't think I was terribly off base when I said that you have a general lack of understanding of the nitty-gritty details of SDR.  None of that is meant to be an insult and should not be taken as so.  When I say that I cannot take these discussions seriously, I am trying to tell you that you seem to be jumping all over the place with these ideas without sticking to one and pursuing it seriously.

If you are going to post about these things on the forums, you'd better develop a thick skin fast.  
Gene
« Last Edit: July 24, 2012, 10:49:13 AM by KE5JPP » Logged
NI0Z
Member

Posts: 562


WWW

Ignore
« Reply #13 on: July 24, 2012, 11:12:54 AM »

Gene,

About the touchy part, if you noticed, all I did was ask you questions about what your motivation was and point out the consequences that negative responses can cause.  Trust me, I can handle myself in a Fourm. Smiley.  If I can't get people to conduct themselves like adults then I simply steer away from them. Life is too short to let some person I have never met and don't know ruin my day.  Enough on that.

I'd like to invite you to go back to the beginning and initial post.  It invites people to improve upon the initial offering.  It even offers up an initial goal of $150, also subject to discussion.

One way, certainly not the only way or even the best way, to innovate, is to toss something out there and let people pick at it and offer improvements on it.

So, if it wasn't clear then let me say that is the objective here.  Improve upon the initial base offering.  I see at least I lured you in to not like the initial offering.  In fact, I am not sure you support the idea at all.  While not likely, if we innovated the equivelant of a SDR-IP for $250 I don't think anyone would be upset right?

Isn't part of the heritage of Ham radio to do it yourself?  Low cost alternatives?

Let's take a time out for a moment.  If a poor kid came up to you and told you he needed a computer for school that he could write his papers on, we could tell him to go buy a Dell, drop his $300 and go about his business.  All is good right?  But what if he knew he could buy something for $50 that would do most of the same things and overall be workable?

So if we find the bottom line dirt cheap answer for an SDR then we can build up to something better that may or may not still represent a reasonable cost.  Example, commercial embedded Linux computer, $200... Pi, $35.  Ok, can the Pi do enough heavy lifting to get the job done or not.  Verdict isn't quite in yet on the cheap SDR.  Funcube dongle $150,  RealTek 2832 Dongle $30.. Both stink really at the end of the day.  What's is the middle ground answer on all these things?

I have learned that if you toss some thing out there, peoples dislike of it usually gets them to suggest something better to improve it.

Gene, any suggestions or do you just want to say forget it?  Again, you can choose not to interact in this thread.  Heck, I might even continue to just debate the merit of the whole thing if that's what you want to do, and then again, I might not.

Well?  Ball is in your court, you in or out of this conversation?
« Last Edit: July 24, 2012, 11:15:25 AM by NI0Z » Logged

KE5JPP
Member

Posts: 0




Ignore
« Reply #14 on: July 24, 2012, 12:18:53 PM »

Well?  Ball is in your court, you in or out of this conversation?

OK, if you want to seriously talk about building a stand alone low cost decently performing SDR that is not a toy, let's seriously talk about it.  We are talking about a small run of like 100 units, not producing one of these imaginary devices in the tens of thousands.

First, you need to decide the architecture - direct sampling or QSD.  In the price range you are shooting for, direct sampling is pretty much out since high speed ADC chips are expensive.  You also need to implement a NCO and downsampler in a FPGA which pushes you over your budget.  There are DDC chips, such as the AD6620, that you could use instead of the FPGA, but they have only limited dynamic range.   The AD6620 is not cheap either, running around $30 in single quantities.  You'd be somewhere around about $26 for a smallish FPGA (something like what is used in the Perseus, for example).  The supporting chips for a direct sampling SDR associated with the ADC, FPGA or DDC, etc... is going to push you over budget.  So, you are left with a QSD type sampler (or a pair of mixers).

To cover 0 - 30 MHz with your QSD you need a local oscillator source. Cheap QSD SDRs typically use the si570 chip, but it is somewhat expensive too (the Elecraft KX3 uses the si570).  You could instead use a DDS chip or a PLL.  I would look at the new self contained PLL synthesizer chip from Analog due out soon, the ADF4351 which runs about $15 in single quantities.  The si570 runs around $25, but it has funky discontinuities in frequency output that has to be worked around while tuning to prevent "chuffing*".  The rest of the parts for the QSD are pretty cheap.  Now, you have to digitize the I/Q output of the QSD which requires a two channel audio ADC.  There are a lot of choices here depending on the dynamic range you are shooting for and the sampling rate.  To keep it under budget, let's constrain the design to 48 kHz sampling to reduce the DSP load we have to deal with.  We want to shoot for 24 bits per channel.  16 bits per channel seriously limits the dynamic range.  The effective number of bits (ENOB) for a 16 bit audio ADC is only around 12-13 at best.  The ENOB for the better 24 bit audio ADCs is probably around 18-20, which gives us satisfactory dynamic range.

Now we need to talk about the DSP processor.  We have the I/Q channels from the QSD digitized by the audio ADC, we need to process them using DSP.  Many SDRs use the PC to do this.  Since we want to be stand alone, we need to look at embedded DSP.  You could take the route that Elecraft did with the KX3 and use an Analog Devices SHARC DSP chip.  These chips cost about $35 in single quantities, but they require a $3000+ investment in the development tools to work with them.  The SHARC DSP and the supporting components needed are going to push you out of budget anyhow even when we do not take into account the cost of the development tools.  Something like the Raspberry Pi is way too underpowered for satisfactory use.  You could use something cheap like the Microchip dsPIC, but you won't be able to handle even the 48 kHz sampling rate with it.  The SDR Cube uses the dsPIC and it is really pushed to give you 8 kHz.  The dsPIC is also on the way out and severely limits the dynamic range.  The Microchip PIC32 running at 80 MHz is more capable and not too expensive.  Microchip has a decent DSP library for the PIC32.  I would seriously look at the PIC32 for the DSP processor which runs around $10 in single quantities.  

Next we need to do something for control and display.  We need to be able to read rotary encoders and buttons and generate a display output.  Again, I would look at the Microchip PIC32 for this.  You'd probably need a PIC32 for the DSP processing (it will be almost fully loaded in doing the DSP only) and another PIC32 for the control/display processing.  Microchip has some very nice libraries to support the PIC32 like USB, Ethernet, and VGA.  You could probably handle a relatively simple VGA display for output with the PIC32.

http://www.youtube.com/watch?v=TrNWv1q1b8o
http://www.youtube.com/watch?v=9vf2dAW3Uc4&feature=related
http://www.youtube.com/watch?v=0Ghb5m8NZb4
http://www.youtube.com/watch?v=Blp4396hik8
http://www.youtube.com/watch?v=tu6uNRyRtgo

Still, you are going to be really pushing your $150 budget in trying to get a stand alone SDR made with using even the cheapest components.  There is a lot more detail that needs to be discussed, but I am getting tired of typing for now.

Gene

*Chuff - A noisy puffing or explosive sound, such as one made by a locomotive.
« Last Edit: July 24, 2012, 12:34:43 PM by KE5JPP » Logged
Pages: [1] 2 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!