I've started work on my ComboStar HF DSP based radio. Overall with a few hard to find parts, it's a great project to build. Assembly has been easy with a large selection of alternate parts on on the board. The BOM and schematic kept confusion thus far to a minimum. Big thanks to W4ZCB and SP5TAA for sending critical parts (Crystals and EEPROM). Mouser does sell a 16.67mhz but not in the package provided on the board. Thus far I have the DSP booting and awaiting more parts to complete the build. I completing my build with 805 size parts and hot air aides in getting everything straight. There are a few 603 exceptions such as LED's and in a few places I used 603's with parts I had laying around.
I've done about 98% of the board using mouser for parts sourcing. RFParts has the filter. Several members of homebrewradio provided critical crystals and EEPROM. Kitsandparts has magnetics and wire. The only items that were hard to come by seems to be the mini-circuits parts. I found a close match that pulse manufactures that I will try in place of the MCL 4:1 part (This likely won't work and W4ZCB was kind enough to send me an alternate). I was able to locate the amp on Ebay in small quantities. I've been assembling as parts arrive and testing voltage prior to setting any major components. So far so good and only a few mistakes that were easy fixes with hot air assistance.
DSP Testing the ComboStar. This is the first step in testing and be sure to check voltages prior to placing anything expensive. Also on the DSP be very careful as the pins are fragile. The technique I used was flux first, then tack a pad placing the part where you want it. You have to use very light pressure with iron to prevent bending pins. Ensure you have no burrs on the tip prior. If you evenly apply solder as you go down each row of pins you won't have to wick any excess. I've found that a continuous motion leading a bead of solder over the work does well with no or little cleanup.
More progress and DSP section is loading with Blinking LED. Just as a note for troubleshooting - No LED check LED orientation (You should have check voltages prior to DSP soldering). Solid LED - Check pF on crystal. Likely not enough capacitance = lazy clock. I used 22pF. Also for clarification to power DSP attach to DSP section and install jumper.
The OCXO section was tested and a nice clean output is seen. Any OCXO could be used in theory. The DDS input reference is 400mhz max and the IC has a 4x-20x multiplier. The schematics are for a 3.3v OCXO but this could easily be modified to work with several units. Assembly was straightforward but a heat-sink had to be made to fit in the board space. I drilled and tapped a hole to allow the heat-sink to sit off the board to stay clear of the components for the regulator underneath. A heat-sink is required as this part gets very hot. With the heat-sink shown the temps get warm to the touch but dissipation is well within the 317's spec.
Various Photos during the build.
Here a few screenshots of an IOS application I've been working on to allow IOS devices to communicate with external CAD systems. This particular integration is with TicketsCAD.
I've been working on several stepper controller boards for other projects and I needed something small to do testing. The MendelMax 1.5 was a good option so I've started construction. These take a considerable amount of time to source all the parts and I purchased the majority from McMasterCarr and misumi. Both have excellent service, website, and very fast shipping.
I purchased a HP 5328a counter off ebay for a decent price. It arrived a few days later and I'd say cosmetically its a 9.9/10. After putting it on the bench and turning on the unit I released it didn't have the oven based oscillator. It did have channel C option and GPIB interface. After checking channel A I was really glad to see that things were working correctly. I moved over to test channel C. All was well I thought until I noticed that the connector on channel C seems to work intermittanly. After pulling the cover off I was pleased to see the unit was very clean inside. I removed the channel C card by taking a single screw out from the rear to remove the top cover. Removing the BNC was just a simple process of removing the nut. After taking the connector apart it was tarnished quite a bit. Some cleaning and I did apply a bit of pressure. After assembly the C channel was working perfectly.
I've got a ton of emails about the adapter for the Kenwood TM-D710A. The microphone on this unit uses a digital pulse counter based on 4017 logic IC's to determine, over a single wire, which key is pressed. This same principle can be use in other projects to read a keypad, control LED's etc with on a pin or two from a microcontroller. For reference below, are the articles on the TM-710A Adapter and associated projects.
http://www.shaneburrell.com/?p=688 - Keyboard Adapter itself - This board is line powered from the microphone cable. It effectively sits between the Kenwood radio unit and Microphone. It allows you to place a keyboard in between the two to allow functionality that Kenwood never intended per say.
The theory of operation: The microprocessor in the radio head unit sends pulses to the microphone. On each pulse the line is pulled low which the microcontroller spies on via another pin attached to the pulse pin. On a scope, it's very easy to see the line being pulled low depending on the keypress. In hacking the pulses, its just a matter of seeing what key generates what pattern. In the TM-D710A adapter I used a AVR to talk to the microphone and read a standard keyboard. The One Signal Wire board design above was used to Emulate the mic controlled by the AVR.
Below is a video some Arduino code I initially developed to scan the microphone patterns driving the Kenwood Mic from the AVR. If you look at the scope this should give you a good idea how the pulse counter is working.
The TM-D710A keyboard hack was a really fun project and hit multiple stages of hack/design. The 4017 counter is a pretty neat way of reading/controlling things using on 2 pins from a micro-controller.
I've taken on yet another TS-430 and ran into an issue with whats coming off the PLL board. I traded a TS-430 I had purchased as non-working which I repaired/tuned for a unit in very nice shape cosmetically but not working. Another HAM back on the air, but now I have another TS-430 to figure out. I suspect this may be an issue with VCO signals coming to the PLL but after spending several hours getting to this point, I've put the project down for a bit to work on my workshop. Hopefully someone on a list somewhere has seen this before and I'll hear back from someone by the next time I pick this project up.
After a lengthy stretch of research on the EL 512x256 Planar display I finally gave up trying to get a datasheet for it. If you happen to have a datasheet I'd love to get a copy. Planar didn't have one or so I'm told by there rep. After a bit of reverse engineering I was able to figure out the output to the display. I prototyped it on a large FPGA dev board but then wondered if it would be possible to find a usable LCD to fit the frame and to use something a bit more practical to do the conversion. I have gotten a few responses back from other 8935 owners that they might be interested in a conversion kit of sorts based on what I have done so far. I also wonder if the E8285A has the same display. If somebody has a E8285A I'd like to know if it has the same display because that might make it worth putting together a kit. For now I just seem to take a step further and further towards a complete solution each time I power up my 8935 and struggle to tell what input is in the lower part of my screen.
Here is a photo in case you have something similar. (Note the pilot production tag)
I have a HP 8935 E6380A service monitor that had some pretty severe screen burn. After looking around for a replacement I wanted to see how hard it would be to adapt a current LCD to the 8935. Suprisingly it was fairly easy. I had a 10.5 inch display and after probing around a bit to see what signals/power were on the A1A1 connector (400 i think) I started playing with a FPGA dev board to convert signals to something I could see on the screen. It works but doesn't fill the entire screen and its not the right size hardware. Now that I have a PLAN B and I've found a 6.5"ish lcd I can readily buy cheap, I'll troll along with the burnt display till it fails or I can't stand it anymore. I'm hoping there is a lot of interest in this to other 8935 owners and its something I can justify doing in the near future.
Some things I played with while I had the 8935 apart and the 10.5" connected:
- Inversion to have some way of preventing screen burn.
- Adding some color (Changed boarder color, changed color of spectrum analyzer portions of the screen) This isn't something that can be done everywhere. If its simply which pixels get what color it's trivial.
- Added text to the parts of the screen not used going from 512x256 to 640x480. Could add ADC to show voltages etc as extra info.
-Centered screen and added border.
I recently discovered my B & K E200D would no longer modulate while working on a Kenwood TS-440AT. After getting inside the E200D nothing appeared to be unusual and I remember a site I had used before when searching for the switchcraft connector I needed to make a cable for this unit. http://www.freeinfostuff.com/E200D/E-200D.htm . After going thru the calibration procedure, everything was in calibration with the exception of the modulation level which once I adjusted the level the modulation meter was back in action. Easy quick fix and now I know that the unit is calibrated.
I've be looking at several platforms to do DSP work in relation to a SDR and digital modems. I have a xmos demo board and some AVR32 items laying around which I needed nice DAC/ADC to interface with. The TLV320AIC23 is a nice inexpensive codec. I built a small prototype board to use the chip in development products and later I'll turn this into a module that can just be plugged in to various projects. This board can be used with a small MCU 16-32 bit to do APRS, GSMK (DSTAR), P25 and various other digital demod/mod. The board breaks of all of the TLV320 channels for both input and output.