One Of Two SO2R Operating Positions In Our Shack (AB1OC)

As some of our readers probably know, it has been part of our plan from the beginning to setup our station for multi-SO2R operation . We took the first step in this direction some time back with the installation of a microHAM MK2R+ SO2R Controller (the box one top of the left radio in the picture above) at one of our two operating positions. The MK2R+ is a full-featured and powerful SO2R controller. It provides many capabilities across the two radios at its operating position. Some of its capabilities include:

• Sharing  a single microphone, set of CW paddles, speakers and headset between two radios
• A built-in sound card interface for both radios
• Integrated voice and CW keyer capability
• Dual-foot pedal control for keying each radio in the SO2R setup
• Sharing of SteppIR antenna control between two radios

MK2R+ Audio Routing

One of the most powerful capabilities of the MK2R+ is its sophisticated audio routing capabilities which are configurable via microHAM’s USB Device Router. The picture above shows the audio routing configuration options for the MK2R+. The operator can do things like listen to a mix of 4 VFOs from two radios at the same time. Hear one radio’s audio in one ear  and the other radio’s audio in the other ear. The routing of audio can be automatically changed based upon which radio is selected for transmit, foot pedal presses, etc. These capabilities are very useful when operating in an SO2R configuration during contests.

MK2R+ Control Ports

The microHAM USB Router software runs on the PC controlling the associated SO2R operating position/MK2R+ and provides a unified set of interfaces to both radios in the SO2R setup via a set of virtual COM ports. The picture above shows how this is configured for my operating position. In addition to a full set of ports to control each radio, there are common interfaces for the integrated WinKey CW Keyer and for controlling the MK2R+ itself. Loggers like N1MM know the microHAM control protocol and can automatically switch audio, sound cards, the radio which has focus for Tx, etc. based upon what the operator does inside N1MM. Again, this is very useful when operating SO2R or SO2V in a contest.

Current Antenna Control Stack

The MK2R+ alone works great for a shack with a single SO2R position but it leaves the operator to manually control antenna switching, rotators, and other antenna-related functions. Up to now, we have managed our antennas via the stack of antenna and rotator control boxes shown above. Manual operation of this type is fine for DX’ing or for one person operating alone in a contest.

Current Manual Antenna Switching System

The problem of switching and controlling antennas becomes more complex in a multi-operator station like ours (we have two separate SO2R positions in our shack with a total of 4 radios). We currently use the custom-built manual antenna switching system shown above to assign our available transmit antennas to one of our 4 radios and to select which antenna a given radio is connected to. We must  manually handle control of antenna rotators as well as manually setting the operating frequency of our three SteppIR antennas when they are not connected to the first of our two SO2R operating positions. This sort of manual operation works OK for DX’ing and casual operating with one person in the shack at a time. It is highly error prone with two operators working at once so we decided to expand our microHAM system to fully automate the control of our antennas and associated equipment.

microHAM Station Master Deluxe Antenna Controller

We are using microHAM’s Station Master Deluxe (SMD) antenna controllers to automate the control of our antenna systems.  We are installing an SMD with each of our 4 radios in the shack. The SMD provides a number of antenna control automation capabilities including:

• Band and frequency specific selection and configuration of available antennas
• Routing of frequency and other control data to our two SteppIR DB36 Yagis and our SteppIR BigIR Vertical based upon which radio has selected these antennas
• Control and routing of our two rotators on our tower based upon the radio which has an associated antenna selected. For example, if one position selects  our upper DB36 Yagi and another selects the lower DB36 Yagi on our tower, each SMD will independently control the rotator associated with its selected antenna. If one radio has both antennas selected as a stack, then that radio’s SMD will control both rotators together.
• Sharing and control of our 8-Circle Directional Receive Array including creating a “virtual rotator” for it which allows its direction to be set via the SMD’s rotary encoder or via a COM port by an external rotator control program or logger. We have also created a “scan” feature for this antenna which switches its direction clockwise by 45 degrees every few seconds. This is useful when one hears a weak station and needs to  determine where to point the receive array for best reception.
• Automatic transmit/receive antenna switching for each of the four radios in the setup. For example, a radio can transmit on one antenna and receive on a different one. When the associated radio is keyed, the controlling SMD automatically switches the radio between the selected transmit and receive antennas.
• Automatic control of the four Switchable Bandpass Filters associated with our radios. These are essential for operating multiple transmitters in the station on different bands at the same time.
• Automatic control of our power amplifiers
• Automatic same band lockout between the radios in our shack.
• Enforcement and sequencing of antennas to avoid simultaneous Tx/Rx on closely spaced antennas from different radios.

SMD Rotator Control Ports

The Antenna Rotator management capabilities of the SMD are very useful for switching and sharing antennas on rotators. Each SMD has a pair of Virtual COM Ports which are automatically associated with the active rotator for the currently selected Transmit and Receive antennas. This allows loggers and other software running on the host PC to control the direction of the current selected antennas no matter which antennas are in use. The SMDs can also create a COM port for the “Virtual Rotator” from devices that are steered via switches such as transmit and receive vertical arrays. These devices behave just like they had a conventional rotator when they are selected and can be controlled by software running on the host PC via the Rotator COM Ports for the controlling SMD.

Our HF-6m Antennas

The first step in this upgrade was to layout a complete design for the RF and control elements of our station. The picture above shows the Antenna switching and control elements of our design. The tan boxes are switches and other RF elements such as Low-Noise pre-Amplifiers (LNAs) that are part of our antenna system. The grey boxes are microHAM control boxes which provide relay or serial data interfaces to shared equipment in our station.

microHAM Control Boxes And Hub

The microHAM control boxes are all part of a shared serial bus (microHAM’s uLink bus) that interconnects all of the control boxes to the four SMDs in our shack. The picture above shows the uLink Hub where the four SMDs connect to the uLink bus (lower right), the serial control boxes (uLink DATA – upper row) which control our SteppIR antennas and Green Heron Rotator Controllers, and several uLink Relay control boxes (uLink RELAY 10 & RELAY 6 – lower row on the left side) which provide relay closures to control antenna switches, stack controllers and other equipment.

SteppIR DB36 w/80m Dipole and Stack Switching Design

The microHAM SMD system is quite flexible and one can control just about any RF device or antenna system that you can dream up. We have two challenging configuration situations our station. The first is a SteppIR DB36 Yagi antenna with the 80m Rotatable Dipole Option installed parallel to the boom. The Rotatable Dipole uses the same SteppIR SDA100 Controller as the associated DB36 Yagi but must be pointed with a 90 degree offset when its selected. I was able to configure this easily using a virtual switch and antenna combination that made the Dipole appear as an independent antenna which shares the SDA100 controller with its associated DB36 Yagi.

The second configuration challenge was related to my custom Stack Switch and Phasing System. I built this element around the DX Engineering ProStack PS-2B Stack Switch and added a custom-built Feedline Breakout Switch to allow us to pull the lower SteppIR DB36 Yagi out of the stack so it can be used independently by a second radio. This allows one operator to use one of the two SteppIR Yagis on one band while the other operator uses the other one on a different band. Again, the flexibility of the microHAM SMD system allowed me to control the combination of the DXE Switch and the Custom Breakout Switch as a Single Two into Two Stack switch with Both Out of Phase (BOP) capability.

Automated Antenna Switching Matrix

The next stage of the antenna switching system is a 10 x 4 antenna RF switching matrix which allows any of 10 antennas to be connected to any of the four radios in our shack. This part of the design is being executed using microHAM’s Ten Switches and 4+4 Switches as shown above. The 4 SMDs in the system all have access to this antenna switching matrix via the uLink bus and the associated uLink RELAY 10 control boxes so they can connect antennas to their radios. This matrix also provides switching between independent transmit and receive antennas for the 4 radios in our shack.

Operating Position Design (AB1OC)

The final element of the design is the two SO2R operating positions. The picture above shows my operating position. As you can see, the MK2R+ provides the interface to the two radios and exchanges radio frequency, PTT, inhibit and other information with the two SMDs associated with each to the radios at this position. The SMDs provide direct control of the Band-Pass Filters (BPFs) and amplifiers for their associated radios. They both interface to the uLink bus via the uLink Hub so that they can control all of the antennas and switches which are shared across the station as well as coordinate the utilization of shared resources between the four radios in the setup.

The microHAM system has tremendous flexibility and my early work with it has gone well. There is a learning curve involved but microHAM’s documentation is excellent and Jozef, OM7ZZ and Joe, W4TV at microHAM have been great about answering my questions and helping me to configure my system. There is also a microHAM Yahoo! group which has been quite helpful. Many stations will not have the complexity to warrant the installation of a full microHAM system such as ours. For simpler stations, the microHAM Keyers, USB Interfaces or an MK2R or MK2R+ can provide simplified sharing and control of equipment across two radios.

As you can probably tell, the construction of the antenna automation portion of our station is a significant project. I will cover the rest of the project and more about the configuration of the system in a series of future posts. Right now I have our uLink bus built and all of the control boxes installed and configured. Two of our four SMDs are installed and operating. The planned next steps include adding a second MK2R+ and a second pair of SMDs to integrate Anita’s operating position into the system, building the antenna switching matrix and beginning to cut over some of our antennas to the new system. You can read the other articles our series on station automation here:

• Station Automation Part 2 – Second Operating Position And Antenna Switching
• Station Automation Part 3 – Antenna Cutover And Final Integration
• Station Automation Follow-On Project – Software Defined Radio Integration

– Fred (AB1OC)