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Phase 2A (Build): Embedded MPET for IP and DV modes.

Here we have the continuation of my phased approach to what I call the Embedded MPET for IP and DV MPET Project, I outlined here

The goal here was to integrate the MPET inside the computer to enable different use cases.

Within the HP DC7600 computer ( on hand already), the only changes I made to the factory hardware include:

  • Using a Dremel tool to notch out one of the low profile rear plane slot covers to pass through a larger grommet that has the USB cord to pass through.

  • Cut off the Molex style connector from the power cable that feeds out to the CD ROM drive to isolate the +12V and GND and replace with a coaxial style connector.

  • Drilled one tiny hole under where the sliding tray comes out to pull the CD-ROM drive out in order to anchor my new bracket for the switches and antenna jack.

Total costs: ZERO, unless I count the connector for the coaxial power I already had on hand as well as the grommet and screw.

It took a lot more words to describe such simple changes. :smiley:

Upgrades to the hardware for the computer included:

  • Going with a 2.5in 128GB solid state drive which is quiet and energy efficient tcompared to a 3.5in HDD.

  • Adding a MU-MIMO Wi-Fi PCI-e card

Total Cost: SSD was too small for my laptop when I upgraded it, so no cost for me there. Wi-Fi card by TP-Link was under $20.

I fashioned a mounting bracket and isolation out of some plastic material I purchased at P & T Surplus

Here is the finished product:


  • The three switches on the front control different features.

    • Status: Turns power on to the MPET with a fuse inline for safety. Note: There are spade clips used for future expansion to control power remotely to the unit through use of a relay shield and Arduino ( A later project....). Power is supplied from the internal PC power supply and is fed to pin 6 on the MPET.

    • Power: Allows High or Low RF Output which is about 4.6W on high at 12.06V and 2.31W on low. Power is adjusted by grounding pin 5 on the MPET to give me low power.

    • Channels: All three switches I had on hand were SPST with center off position. Grounding MPET pin 1 gives me CH.7, pin 3 gives me CH.4. Leaving it is center off position gives me CH. 8 according to what the MPET can store in its EEPROM. So this gives me 3 channels which I currently have configured for a few different frequencies and tone configurations. NOTE: In the future, I will control Pin 1, 2 and 3 through an Arduino to change any of the 8 channels remotely but while still having a physical switch for a master over ride.

    A "secret" feature with how I wired up the "Power" switch is to use its remaining position (UP) is to use it as a Safety. If the Power switch is in this position, it will not allow the MPET to be turned on via the Status switch.

  • The simple sound card interface is the KF5INZ "Easy Digi" board found at most ham radio suppliers, including E-Bay:

    This was the easy way out rather than making my own board from scratch. I changed a few resistor values on the board on hand and added in the 4N25 opto-isolator since the Easy Digi Board I had was meant for use with a smart phone and did not have those components populated.

    The KF5INZ is great to have on hand for all sorts of uses from a PSK31 interface to use for Echolink or many other applications.

    I wired the unit up to the MPET through pin 7 ( Audio In), pin 8 (Audio Out), Pin 13 (COR) and pin 14 (PTT)

    Audio feeds into the USB sound card.

    I chose to not use pin 4 (Mic) in order to get flatter frequency response and use the in built high pass filter in Echolink to cut out anything under 300Hz

    The DTR RTS and GND go to the COM Port

  • Hot diggity! I like it!

  • Beautiful job Steve!

  • Impressive...thanks for documenting.

    How much time over how long a period did you invest?

    Priceless at any cost methinks.

    Any plans to go into mass production?

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