Software Defined Radio/Remote Operating Gateway Part 1 – System Design And Hardware Installation


Flex-6700 Software Defined Radio Stack

Flex-6700 Software Defined Radio And Remote Operating Gateway

We’ve been planning to add a remote operating capability to our station for some time now. We also did some previous work with a FlexRadio Software Defined Radio (SDR) in our station and we felt that an SDR would be a good platform to build a remote operating project around. We decided to combine our remote operating goals with a next generation SDR upgrade (a FlexRadio-6700) for our station. This project has turned out to be somewhat involved so we will be providing a series of articles to explain what we did:

We will be tackling our goals of building a Remote Operating Gateway (GW) in two stages. Stage 1 will focus on operating our station from other rooms in our house (our Home Offices are prime locations for this). Stage 2 will involve operating our station “On The Go” from anywhere in the world that has sufficient Internet Access is available. We also want to enable full control of our station when operating remotely including:

  • Use of our Amplifier
  • Antenna Selection
  • Rotator Control
  • Equipment Power Monitoring and Management

We also use a microHAM station control system and contesting equipment and we want to fully integrate our new Flex-6700 SDR with this gear. Our Flex-6700 uses a dedicated Microphone to avoid some audio integration issues that we encountered between the Flex-6700 and the microHAM MK2R+ that we use in our station.

SDR/Remote Operating Gateway Architecture

Flex-6700 SDR/Remote Operating Gateway Architecture

The first step in this project was to develop a system design (pictured above). We opted for an architecture which uses the Flex SDR as a third radio in Anita’s Operating Position. Her position is now an SO2R setup with a Yaesu FTdx5000 as the primary radio and a choice of either an Icom IC-7600 or the Flex-6700 SDR as the second active radio.

Elecraft KPA500 Amplifier and KAT500 Auto Tuner

Elecraft KPA500 Amplifier and KAT500 Auto Tuner

Elecraft W2 Watt Meter

Elecraft W2 Watt Meter

FilterMax IV Automated Band Pass Filter

FilterMax IV Automated Band Pass Filter

The Flex-6700 SDR has an associated Elecraft KPA-500W Amplifier/KAT500 Auto Tuner combination, an Elecraft W2 Wattmeter, an automated band pass filtering via an Array Solutions FilterMax IV and a dedicated microHAM Station Master Deluxe (SMD) Antenna Controller. The Elecraft components are good choices for our remote operating project because they all have applications which enable them to be controlled and monitored over a network (more on this later in this series of articles).

Station Antenna System

Out Station’s Antenna System

The additional microHAM SMD allows the Flex-6700 SDR to have full access to and control over our entire antenna system and associated rotators.

K1EL WinKeyer

K1EL WinKeyer

Our setup also includes a K1EL WinKeyer to enable computer controlled CW keying of the Flex-6700 SDR. This device is relatively inexpensive in kit form and was fun to put together. We have a Bencher Iambic Paddle connected to the WinKeyer for in-shack CW operation.

SDR microHAM Integration

SDR microHAM Integration

The diagram above shows the details of the device interconnections which make up the SDR Radio System. The microHAM SMD Antenna Controller requires a serial CAT interface to its host Flex-6700 SDR to determine what band and frequency the SDR is on. The Flex-6700 SDR does not provide such an interface directly but it does create CAT control virtual ports on a host Personal Computer (PC).

DDUtil Setup - SDR Virtual CAT Access

DDUtil Setup – SDR Virtual CAT Access

DDUtil Setup - Bridging Physical Serial Port To SMD

DDUtil Setup – Bridging Physical Serial Port To SMD

To solve this problem, we used an application called DDUtil to bridge the derived CAT port associated with the SDR to a physical serial port on the PC. The PC’s physical port is then connected to the microHAM SMD associated with the Flex-6700 SDR. The pictures above show how DDUtil is set up to do this.

Station COM Port Configuration

Station COM Port Configuration

The microHAM gear, WinKeyer, Rotators, Radio CAT Interfaces, Amplifier/Auto Tuner Interfaces, etc. all use serial or COM ports on a host PC for control. It’s also true that many loggers have trouble with accessing serial ports above COM16. All of this requires a carefully developed COM port allocation plan for a complex station like ours. The figure above shows this part of our design.

A-B Switching Design For Radio Port 4

A-B Switching Design For Radio Port 4

microHAM Bus Expansion And Antenna Switching Gear

microHAM Bus Expansion And Antenna Switching Gear

The last part of the hardware puzzle required to integrate the SDR into our station was the installation of a second microHAM uLink Bus Hub, microHAM Relay 10 Control Box and an A/B antenna switch which is controlled by the microHAM SMDs. This allows the 4th radio port on our antenna switching matrix to be shared between the Icom IC-7600 and the Flex-6700 SDR.

microHAM Configuration For SDR Station Master Deluxe

microHAM Configuration For SDR Station Master Deluxe

The last step in the integration of the Flex-6700 SDR was to configure the microHAM system for the new equipment. This involves adding SMD #5 to the microHAM system and configuring it (and the rest of the system) to know about the Flex-6700 SDR, associated amplifier and its interconnections to the rest of the system.

SmartSDR Software

SmartSDR Software

The Flex-6700 SDR Hardware is controlled and operated via FlexRadio’s SmartSDR Application over a network. We have 1 Gbps wired and an 802.11 b/g/n Wireless Ethernet systems in our how and the SmartSDR/Flex-6700 SDR combination works well over either network. The software based approach used with most SDR allows new features to be added to the radio via software upgrades.

SmartSDR Setup - Tx Keying And Interlock

SmartSDR Setup – Tx Keying And Interlock

It is very important to prevent the Flex-6700 SDR and the associated Amplifier from keying up when the antennas in our station are being switched or are being tuned. The screenshot above shows the configuration of SmartSDR to enable the keying and interlock interfaces between the Flex-6700 SDR and its associated microHAM Station Master Deluxe Antenna Controller to implement these functions. This setup enables the Tx Keying and Tx Inhibit interfaces between the Flex-6700 SDR and the microHAM Station Master Deluxe to work properly to key all of the equipment in the setup (SDR, Amplifier, active Rx antennas, etc.) and to lock out keying when antennas are being switched or when one of our SteppIR antennas are tuning.

Flex-6700 SDR With CW Skimmer

We will cover some additional software and integration steps to realize our Remote Operating goals. For now, check out the above video to see how the system performs. This video was recorded using our Flex-6700 SDR and CW Skimmer during the 2015 ARRL CW Sweepstakes Contest. We are really enjoying operating in CW mode with the new SDR setup!

– Fred (AB1OC)

One thought on “Software Defined Radio/Remote Operating Gateway Part 1 – System Design And Hardware Installation

  1. We should note that the microHAM Station Master Deluxe is not a required component for integrating a FlexRadio SDR into a station with a single radio. Our station is a Muti-one setup with 5 radios that share all of our antennas. In this configuration, the microHAM Station Master Deluxe provides many advantages. Our readers can look at our series on the Design and Construction of Our Station for more on our use of the microHAM Station Master Deluxe and related equipment.

    – Fred (AB1OC)

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