MODEL 5 MEPT

Well, I just couldn't stop. I gave up on model 4 in the middle of development and am now busy building MODEL 5. It is the brain child of Ross KB1KGA. His website is: http://www.theladderline.com/dds-60 and is chock full of the information to build a copy of his unit. He gives you the complete software program to be loaded into an Ardunio processor which is what he used to control the DDS-60. I put Mine on the air on May 21st and was spotted in Florida, Mass, Utah, Olkahoma, and a smidgin in Alaska. It was only running 160mW on 18,108,900 Hz which is the first time I have been able to operate on that band using QRSS FSKCW. (This thing allows you to work on any frequency from 1.8 Mhz to 60.0 Mhz. I have not tried it on the 136Khz bands but I was tempted. The picture at the left is my interpetation of Ross's schematic and the addition of my transistor transmitter and Multiband Output Filter board and Auxillary keyer modules. This picture has the new single transistor Output Amplifier from Diz's collection of RF Tookit modules: http://www.kitsandparts.com/rftoolkits.php This RF amplifier works very well in continous service giving me about 170mW of power output with 13.8VDC applied. The added heatsink is required for continous service. The PICAXE 08M keyer was built for the 80 second dits testing in October of 2010. I was able to be seen on W4HBK's grabber in Pensacola, FL, a distance of 1,163.7 miles away running an output powers of less that 1mW.
	This is another view showing the front panel with the readout displaying the frequency. The big knob on the right is the shaft encoder to change the frequency and the three green push button switches are the function switches that change the modes, provide an enter function, and control the frequency steps for the encoder. The toggle switch is the on/off power switch and the little green LED is the power indicator light. The readout display is also Lit when the unit is on so the little green LED is a bit of overkill. The readout I used was a Lumx Model LCM S01602DSR/B which I got at DigiKey Part# 67-1769ND for $11.38 each. I found no errors on Ross's schematic and I used the 3rd update schematic and software. I built the controller on the holed Hobby Board with the single solder circles around each hole and wired it with some left over wire wrap wire that I soldered to the terminals. I used an RBBB Ardunio Kit board from Modern Device and when I built the kit I made the pins point down. Then inserted them into SIP sockets and put them into the hobby board and soldered them. I used right angle pins on the LCD Readout and did the same thing. The DDS-60 which is also available as a kit from the American QRP Club was mounted the same way. Then I turned the board over and did the wiring. On one end I also made SIP plugs for the encoder and function push buttons. It came out as a nice, neat, and functional module.
The Filter board was built on the same type of Hobby board and the dip switches on either side select the different filters. I will try to supply a diagram of this in the near future. It also has a 50 ohm dummy load and a power monitor probe built in so it is easy to adjust the power output. A filter for 80/40/30/20/17/15/10&12 Meters are installed on the board. They were designed using SVC Filter Designer 2.11 from Tonne Software and was a bonus on the CDRom that came with my 2010 ARRL Handbook. The software worked very smoothly and every filter tested out to the same curves that I had printed out when I was using the software. I used some Monolithic Capacitors from JAMECO Electronics. (Only place I could find them in the values I needed)
	I have already modified this unit by changing the transmitter board to a single transistor RF amplifier Kit sold by : http://www.kitsandparts.com/rfamp1.1.php It is a one transistor wide band amplifier to which I added a heat sink to the transistor. I also use a pot to control the drive power to the little amplifier. I can get about 170mW at 13.8VDC which is more than enough to work the world on this mode. Not bad for $8 plus postage. It seems to handle continous key down service very well. I have not had one failure of this amplifier since I put it into service over 6 months ago.

Well, I wasn't satisfied with the frequency stability of the DDS-60 Synthesizer. Both of the ones that I built were drifting up and down in the band and the frequency accuracy of the readout could, at times, be quite far off. So, something had to be done. On my MEPT, I installed a GPS 10MHz Disciplined Oscillator, built a 10Mhz to 30Mhz tripler with a amplifier and fed that to my DDS-60 card in place of the 30 MHz crystal oscillator that came with the board. After recalibration, Mine is spot on frequency, No matter where I put it. But my buddy Perry didn't have a GPS Disciplined Oscillator. Thus the birth of the "Secondary Standard". W8DIZ sells a neat Frequency Standard kit for $12 at: http://www.kitsandparts.com/fref.php It works like a charm. I added my 10 to 30 MHz tripler and used it's output to drive the 30Mhz oscillator input to the DDS-60 synthesizer. It does very well at start up from a cold start and usually achieves stability in the first 15 minutes of operation. We are now testing for the long term effects of the temperature of Perry's Hamshack. It may need additional heaters, but for now it is working well. I have made up a file of the Frequency Standard schematic, Pictures from W4HBK's grabber of the Startup frequency drift, and a picture of the installation in Perry's MEPT. The .ZIP file can be copied from HERE: It might be best to SAVE TARGET AS to download it to your computer. I did this so the schematics would be clear and easy to use.