Softrock V9.0 (with electronically switched BPF)

A Softrock V9.0 RX with isolated antenna input and sound card outputs (using 600 ohm isolation transformers). There is no BPF fitted in this image. The BPF that goes with this build I include a couple of close up images of it, I placed it on a £20 note so you can get an idea about the scale involved. This particular electronically switched BPF is made up for 80m-10m and 6m. The final one Simon has now is for 160m to 10m.

Simon Brown (HB9DRV) of Ham Radio Deluxe fame asked me a while back if I'd help with building a Softrock v9.0 RX for him with an electronically switched BPF. This I did for him prior to the RSGB 2009 Convention where he gave a presentation on his new SDR software using a £50 radio, which is the one that I built for him. The software is so new that today (12th October 2009) he is only 6 weeks into developing it. I provided him with a WAV capture file for him using this very Softrock radio, in the presentation he used the RF Space IQ radio with the 20m beam live and a couple of the prerecorded WAV file including the one I recorded of the SSB segment of 80m during the last RSGB Club Contest 10th September. He now has the radio and has said will be using it to write support for the Softrock and will be adding remote support where he will provide a facility for a console/server situation where the Softrock can be operated remotely and will also have integration with another transceiver with CAT support. So the Softrock SDR can be the fisrt or second RX.

You can follow the new software developments here:

http://www.sdr-radio.com/

As I mentioned to one or two after the presentation, I had not expected Simon to advise it was me that had built it for him, but I will be happy to build and test one of these for others as I had for Simon at a small charge in addition to the cost of the kit and parts.

These are answers to questions I have had and in the hope I don't get repeats I answer them here as part of the post instead:

I am not developing Simon's SDR software he is.

I do have access to test builds and yes I have a SoftRock V9.0 working with it in my shack.

Although I am in contact with Simon if you have requests about the software ask him not me.

The ONLY source for Softrocks is Tony Parks, himself and THE source for kits is http://www.kb9yig.com/ Yes some others have them but they will utimately get them from him. You will find any supply problems are probably due to availability of suitable Si570 chips.

From time to time I may have some kits that I will build for others but I will never sell an unbuilt kit.

To my knowledge you cannot make/buy a PCB and build it yourself cheaper in ones and twos so buy a kit.

No I do not have the PCB masks, Tony does.

The isolation transformers are 600 ohm 1:1 with a frequency response able to cope with signals above 5KHz without large attenuation. Some cut off at 5KHz that are fine for PSK and digital modes, these were better than that. I cannot recall what they were but cost c£5 each. You can get very very good audio isolation transformers that cost a lot more than that.

The I and Q audio connectors are gold plated and isolated from the chassis.

The RF connector is isolated from the chassis.

The PCB is isolated from the chassis.

The chassis is a dicast Hammond Box.

The main image is for the TOP of the board so you see the C and R and the voltage regulator... you have to look underneath to see the the SMD components. I did not include that image I will later. These were three images Simon Brown (HB9DRV the Ham Radio Deluxe guy) used in his RSGB 2009 Convention talk on SDR and a £50 radio as I built the one in the photos for him.

To answer the question is it difficult to built is not so easy....

The answer is yes and no....I find it easy to build.

What are the challanges:

The BPF toroids are T25 and T30 so they are smaller than most will be used to (T37 or T50), if you can wind a T25 or T30 with SWG 30 wire then those are not a problem. I check the L values with a meter (mine from N6BM.. think I blogged my homebrew build not sure)

The BPF has two SOIC i.e. SMD IC on the base (see images). You can solder the pins using a 'flood' technique where is doesn't matter if you bridge the pins as you wick the excess off with desolder braid (or a length of clean briad from RG213 or RG58 (I never throw old lengths away just in case!). That is the lazy/easy way to do it but the chip 100% must be on the board accurately, so tack two opposite pins first.

The main PCB... top side you should have no problems.

The main PCB bottom... well three SOIC IC and the two large ones are 14 and 16 pin devices the mixer and divider, the 8 pin one is even smaller.

The L and C are all 0603 so small, so you need a steady hand, illumination and a magnifying lens. There is a tiny and I do mean tiny 5 pin regulator chip I don't know if these will be easy enough for everyone or not, I doubt it.

The Si570 chip has no legs and is pad soldered as long as you have a fine soldering iron tip that is clean and fine cored solder and patience and do not take too long/heat the chip or the others up too much should be fine.

Some use spray on flux with SMD components to make it easier to solder.

Some use binocular travelling microscopes.

Some have had sucess with solder paste and heat, never done it myself.

I use a 1mm or 0.5mm soldering iron tip on a temp controlled soldering iron, lots of light, normal flux cored 26swg solder and my own eyes.

I have built a few SMD projects for others.....but it is not a business.

Even more questions overnight, rather than moderate all the comments and respond here are the answers all in one place:

Please note I did not design the Softrock and I make no claim to have done so otherwise, Tony Parks KB9YIG is the designer. If you want to suggest changes contact him, or make them yourself and experiment. After all as I am sure Tony has stated before these are SDR samplers.

Numerous questions about the build

Q: The two electrical components in the picture near the bottom of the box, I assume those are the isolation transformers.

A: Yes, I have a box, literally of these, of various types bought from all sorts of rallies and electronics places. To test them, yes you need to test them! I put a mic on one side and the other connected to a DC-100kHz noise source (some PIC project and scanned the audio frequency. The input feed into an audio spectrum analyser (Google for a free one). I ignored the spec sheets as some are not that accurate. What I was looking for is those that DONT attenuate the frequency until about 25KHz. The ones that do and below are fine for PSK and SSB recording but IMHO crap for SDR, unless you don't mind loosing bits of the ends of the frequency response. The reason you may want/need these is to remove the LO signal, the S9+ big peak in the middle of the SDR frequency spectrum... if it isn't there then don't bother and save yourself the expense. The reason is ground loops are NOT your friend with SDR radios.
Q:How did you mount the isolation transformers to the box? It looks like there two lines of tape involved, any comments?

A: Double sided 'elephant strength' tape. Not a brand name just not weak craft rubbish. I think it is the sort that DIY guys use to fix mirrors to bathroom cabinets and wardrobe doors.
Q:The diecast Hammond box, which part number did you use?

A: No idea. Use what fits. I have a 'junk box' of these as a while ago asked what presents were good and I said tins and enclosures and that is what I often get from relatives now! The comment was meant more for it is metal and solid than some specific box. And as those in the presentation will remember Simon wanted something large and not black. You could get away with making one from double sided PCB... in fact sure that is what I did first time.
Q: On the temperature controlled soldering iron, what temperature setting were you using or would you recommend?

A: I use leaded solder so hot enough to melt the solder. On the small parts up it a bit as you want the time on the component to be short. If never done it before practice on some SOIC-16 pin devices on some junk electronics.
Q:What parts did you use for your antenna connection?

A: Insulated BNC. IS what it says... the chassis does not connect to the RF ground and there is a teflon(?) insulator. The reason is ground loops and the Socftrocks don't like them... they will work but you really want to use a balanced antenna. I would go with insulated 4mm banana plugs to keep costs down. Simon wanted a BNC/SO239.
Q: What parts did you use for your I and Q audio connections? (I realize they were gold plated)

A: Any decent phone connector that is insulated from chassis will do. Lots of different options. The ones I used were expensive and used similar teflon insulation, you can buy plates with two phone sockets on the plate is plastic... that would work.
Q:What parts did you use for your chassis isolation standoffs?

A: hihi... the Softrock V9.0 comes with them. Look at the corner holes on the PCB, now REALLY look at them, they are insulated from the PCB ground plane... So use the fixings you were sent, I fixed the bolt coming up through the bottom, then the FAT washer, PCB then thin washer then nut.. If does not then sort out something else, you should be able to lift the copper off the pcb corners with a fine blade. Otherwise use a Nyon bolt and nut.
Q:What is the switch for?

A:To turn the DC on and off. (too obvious?)

Q:Is the DC connector insulated from chassis?

A:Yes, I used a connector that usually shorts the chassis and barel but when the barrel is inserted it is isolated from chassis.

Q:How long did it take to build?

A:About 2 1/2 hours, including putting it into the box and taking phots for Simon. I had to redo the BPF for Simon swapping band 0 on the BPF back from 6m to 160m on the evening before the presentation and that meant changing the L and C values on band 0 and 1 so thet took an extra 40 minutes.

Q:How did you test it?

A:Follow the DC voltage values, I used an audio spectrum analyser on the isolation transformers, an insulation tester on the connector/chassis connections (the PCB was not in place), you could use a DVM that reads to Mohms to make sure the insulation really is insulated. I measured the BPF L values with a homebrew LC meter N6BM and the frequency response with a VNA. Don't just follow the winding numbers blindly they can be out, check your build! You test the BPF with +5V control signals and check the switching is occuring. Use the USB/Si570 test applications that exist to make sre the LO signals were working and the control signals for the BPF were as expected. (I used a frequency counter and an oscilloscope). Lastly put it on air and made sure it worked.

Q:Where is all the software available for the USB/AVR/Si570 used with the Softrock

A:See http://www.kb9yig.com/ and http://www.sdr-radio.com/ and http://www.softrockradio.org/ and join http://groups.yahoo.com/group/softrock40/

Q:Will you build one for others / do you sell these

A:Tony Parks sells the kits, in the past I have built softrocks (even as far back as the V4.0) and other rigs for those that cannot do it themselves and would do it again, I enjoy building projects. If you are interested then email me about it (use qrz.com for my contact details).