softrock

Fri May 31 01:13:40 CDT 2013

Hello Alex.
I don’t see which band your Softrock Rx is on, but for 40M, the crystal is 4 times the actual frequency.  For 20M, I believe he plays some games and uses a 4/3 or some such.  If your Softrock is 40M, you would need 28.2MHz or so for the output, I think Tony supplies a 28.224MHz rock.  Possible to drive it with an AD9850, but you will need some sort of amp on the DDS output.  In addition, what I have done is to bias the input to the first flip-flop to 1/2 VCC with a couple of resistors, such as 4.7K, and apply the amplified DDS output to that input via a coupling cap.  This allows the flip flop to switch back and forth with the DDS output signal.  I did this with some crystal controlled Softrocks and early DDS modules.  Most AD9850 modules have a 125MHz oscillator, so even 1/4 the clock is still over 30MHz.  But, the output level DOES drop off as the frequency increases in DDS units.  I have also put the DDS output right where the crystal plugs in, and used the oscillator transistor as an amp, but that’s a little trickier.

For Windows, the easiest SDR software to use is Rocky.  HIGHLY RECOMMENDED FOR STARTERS.  Go to www.dxatlas.com and download it.  As long as you are using a sound card with stereo inputs, it will be good enough to try out.  You may see some unwanted spurs, and a large spike at zero Hz, the center frequency, but at least you can play SDR with it!  You will also see an image float through the spectrum, until you do the image cancellation.  You can tell an image as it moves the opposite direction when you tune, and it will be of the opposite sideband.  For example, if you must use USB to listen to a 40M SSB QSO, it’s probably an image of the real signal.  For CW, you can’t really tell that way.

Turtle Beach sound cards were nice early on in SDR development (even Flex supported the Santa Cruz I think), but they have been long passed over.  I have a couple Turtle Beach cards, but don’t use them anymore.  Try whatever you get, as long as it has a stereo input, preferably line inputs.

Most SDR software only does the local onscreen spectrum display, and sound out of the sound card.  To do digital in the same computer, you need to either route that audio out back into another sound card through a cable (yech), or use something called “virtual audio cable”, or VAC.  It is a commercial software package from a guy in Russia, I think it costs about $30.  That’s what most people do.  There is a free version, but it has an embedded voice that duns on about buying it, and interferes with operation.  There have been a couple other versions of VAC software announced recently, I need to locate that info.

AS far as building SMT, I just put the chip down on the board and hold it in place with my fingernail while I tack solder opposite corners.  I then go back and solder each pin.  Solder wick is great for removing excess solder, and shorts between pins.  Use it carefully, don’t push down too hard with the iron, or move the wick around too much.  Get a really thin tip for your iron.  If you have the funds, look up an X-Tronic 4040 solder station.  For just over $120, it has both a really nice iron, with several tips included, and a hot-air soldering wand.  Great deal for the money.  As things get smaller, if you plan to keep building, you need tools like the 4040.  Also, when putting down SMT ICs, use a little flux like from a Kester #2331-ZX flux pen.  Put it on both the board pads and the IC pins.  It make all the difference in the world!  You won’t be fighting the soldering at all anymore.  The solder just flows where it’s supposed to!

All for now.
73, Terry, WB4JFI

From: Alex Fraser 
Sent: Friday, May 31, 2013 1:38 AM
To: tacos at amrad.org 
Subject: Re: softrock

    Very timely reply!  I just got the kit in the mail today.  I bought the Softrock Lite II RX to get my feet wet.  I hadn't realized there was some surface mount components on that tiny board.  I got the optics to see it, but I'll have to improve the way I hold the board.  Right now I'm using a small hand vice clamped in a larger vice.  I got some ideas how to do it, but of course I'll google some videos on the technique.  I'm still working on getting the Arduino/AD9850 VFO into a hard soldered version.  I will clear that project off the table first. I need the hand eye practice and can prototype some jigs and fixtures for holding the new small kit better.  I thought I might be able to use that VFO to replace the fixed   Softrock xtal, but I believe the AD9850 might not go high enough in frequency, I'm still reading how these things work, sampling rates and artifacts IIRC, Nyquist? 

    I stop by the local computer junk store (L&Y electronics) every Friday. Tomorrow I will start searching for sound cards.  There are a few other hams I see in there from time to time.   We often help each other rooting through the junk bins. Price will be a concern.   Turtle Beach cards were once talked about on this list, can't remember the context.  I'll do a search. 

    I haven't down loaded any SDR software yet.  I did download the one that works off the net connection, but none yet to control a local SDR.  I say this because once I download I might get an answer to this question, but as of now I have no ideal how you would decode the digital modes with an SDR?   Does the SDR software have that capability built in or do you pipe the audio to your regular software, like mixW?  Could you use and audio mixer?  

On 5/30/2013 6:45 PM, wb4jfi at knology.net wrote: 
  Hey Alex.
  I’m not sure what on-board sound chipsets are the best.  Generally, you get whatever that particular motherboard has, and if you don’t like it, you need to install a sound card.  The older USB sound card that people liked was the Creative EMU 0202.  I believe its replacement is not as good.

  Depending on how good your soldering sills are, either the Ensemble II receiver or the Ensemble RxTx are good choices if you are comfortable with SMT.  They both rely on the Si570 chip for he LO, which allows frequency agility – a huge benefit.  These are both HF kits.  The receiver covers all of HF, while the RxTx is a small transceiver that covers one band really well, and another band OK.  The crystal-based Softrock kits are much simpler to build, but are stuck on whatever freq the crystal is for.  For 40M, the main Softrock frequency is 7.056MHz, for example.

  Softrock Ensemble receiver ($67):
  http://fivedash.com/index.php?main_page=product_info&cPath=1&products_id=6&zenid=fc11d0c66aca3263e3f48f1e58894fb0
  Softrock Ensembe RxTx ($89):
  http://fivedash.com/index.php?main_page=product_info&cPath=1&products_id=7
  Softrock crystal receiver ($22):
  http://fivedash.com/index.php?main_page=product_info&cPath=1&products_id=5

  Fivedash (Tony Parks) used to run out of these kits all the time.  You may have to monitor the web site for in-stock opportunities.  There are also some Softrock-like kits out there as well. Lazy Dog is one company making a similar kit.  Bill Fenn has a crystal-controlled version that he purchased from Japan.

  Almost any computer over 1GHz will work somewhat with simpler SDR programs, such as Rocky.  Windows XP and higher are OK as well.  Higher speed computers and/or newer versions of Windows (or Linux) will provide additional benefits, such as a wider receive spectrum – assuming that your sound card allows it as well.  Most SDR apps are 32-bit, generally so that they can run on a 32-bit OS.  There have been driver issues with 64-bit Windows as well...  For Apple devices (iPad/iPhone/iPod) there is a free iSDR app for that.

  There’s a LOT of options in both hardware and software for SDR these days.

  You may have also asked about slices of spectrum are displayed.  From what I’ve seen so far, each slice has been displayed on a separate line (in PowerSDR).  There is talk in the HPSDR group about splicing adjacent spectrum slices together, but I think that’s more for a spectrum analyzer project.  The new Flex radios, and some others like our own Charleston SDR, can suck in wider spectrum data, and that data can be displayed directly as a wider swath.  But, this isn’t true for sound card-based SDRs.  This is another advantage of DDC-based (Direct Digital Conversion) SDRs versus the cheaper QSD-based SDRs, which rely on sound cards (the Flex 1500, 3000, and 5000 have internal sound card like interfaces).
  73, Terry, WB4JFI

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