Concepts

Identifiers

Some items in the configuration are identified by number. For example, each antenna is given a unique number. These numbers can be any positive number from 0 through 2,147,483,647. There is no need for these numbers to be contiguous – you can skip numbers, or number your 80 meter antenna 80 and your 40 meter antenna 40 etc.

In most cases the number does not matter. However when the server is looking for an antenna to select for a radio which has changed bands it looks from low to high numbers. So you would want to give the preferred antennas lower numbers than the secondary antennas.

Numbers must be unique for each type of item. In other words, there cannot be two antennas with ID 0 but there can be an antenna with ID 0, an antenna system with ID 0, a rotator with ID 0, a station with ID 0 etc.

Stations and Radios

Each physical radio is given a station number and a radio number. Typically a station represents a computer. So if you had two radios set up for SO2R you might call them “station 1 radio 1” and “station 1 radio 2”. If you had two radios each connected to a computer for multi-single you might call them “station 1 radio 1” and “station 2 radio 1”.

The Android client is designed for SO2R and can show two radios on one station. It expects them to be numbered as radio 1 and radio 2.

The configuration file describes which station and radio are connected to which amplifier keying and inhibit connectors on the switch.

Antennas and Systems

To the MOAS II, an antenna is anything that has a unique set of relays. An antenna system is two or more antennas that are related.

Consider the following antennas, which are part of an SO2R station. The stack of three yagis is connected to an Array Solutions Stack Match or similar, with the top antenna on port 3, the middle on port 2, and the bottom on port 1. The Stack Match is connected to port 4 on the 2x6 switch.

The twelve relays in the 2x6 are connected to relay outputs 0-11 on the MOAS II switch. Relays 1-4 on the Stack Match are connected to outputs 16-19 on the MOAS II switch.

flowchart LR
    R1[Radio 1]
    R2[Radio 2]
    2X6[2x6 Switch]
    SM[StackMatch]
    ANT1@{ img: "../icons/antenna.svg", label: "Antenna", h: 48 }
    ANT2@{ img: "../icons/antenna.svg", label: "Antenna", h: 48 }
    ANT3@{ img: "../icons/antenna.svg", label: "Antenna", h: 48 }

    R1 --- 2X6
    R2 --- 2X6
    2X6 --- SM
    SM --- ANT1
    SM --- ANT2
    SM --- ANT3

    style ANT1 fill:transparent,stroke:transparent
    style ANT2 fill:transparent,stroke:transparent
    style ANT3 fill:transparent,stroke:transparent

To the MOAS II this is seven antennas:

ID	Name	Station 1 Relays	Station 2 Relays
0	Top	3, 18, 19	9, 18, 19
1	Mid	3, 17, 19	9, 17, 19
2	Bot	3, 16, 19	9, 16, 19
3	Top Mid	3, 18	9, 18
4	Top Bot	3, 17	9, 17
5	Mid Bot	3, 16	9, 16
6	All	3	9

The 2x6 relay selection is straightforward. Ports 1-6 for radio 1 are selected by outputs 0-5. For radio 2 they are selected by outputs 6-11. The relay selection for each combination of antennas is not obvious. It is necessary to read the Stack Switch manual and schematic to figure it out.

The seven selections could be seven switch positions on a rotary switch. This is what Array Solutions built for their mechanical controller:

flowchart LR
    IMG@{ img: "../icons/radial_exclusive.svg" }

    style IMG fill:transparent,stroke:transparent

This scheme shows exclusive antennas. Each position selects an exclusive combination of antennas. (There are several positions which select all antennas because the switch they used had 12 positions).

There is another way this could be controlled. Three switches could be used, one for each yagi.

flowchart

    S1[Switch<br>Antenna 1]
    S2[Switch<br>Antenna 2]
    S3[Switch<br>Antenna 3]

This scheme shows additive antennas. With all of the switches up, all of the antennas are connected. Move a switch down and that antenna will be removed from the stack.

The relay table above shows that there is no straightforward way to figure out which relays must be selected for each additive combination. The server solves this by finding the exclusive antenna which has the correct antennas. This requires some additional information:

ID	Name	Station 1 Relays	Station 2 Relays	Components
0	Top	3, 18, 19	9, 18, 19
1	Mid	3, 17, 19	9, 17, 19
2	Bot	3, 16, 19	9, 16, 19
3	Top Mid	3, 18	9, 18 0, 1
4	Top Bot	3, 17	9, 17 0, 2
5	Mid Bot	3, 16	9, 16 1, 2
6	All	3	9	0, 1, 2

The new components column lists which single antennas are parts of which combinations. The server can use this information to find the exclusive antenna which is the combination of the additive antennas.

Some antenna systems are only exclusive. For example, a 4-square has four exclusive directions, NE, SE, SW, and NW. There is no additive antenna scheme which makes sense in this case. It is not even necessary to configure a 4-square as an antenna system in most cases.

The server can also handle antenna systems which include antenna systems. The Multi- Multi 20 Configuration example shows this.

Frequencies

The MOAS II does not know anything about ham bands. All antenna ranges are specified by frequency.

Antennas have a lower and upper frequency range, expressed in KHz. The maximum frequency which can be specified is about 2 THz. An antenna can cover multiple frequency ranges and each frequency range can select different relays.

A tribander would have three frequency ranges. If it is connected through a switched bandpass filter the relays for the three ranges might be different because it is selecting a different filter for each range.

A 160 meter vertical might have two frequency ranges. The lower frequency segment might specify an extra relay which adds an inductor. This change would be invisible to the operator.

If an antenna covers multiple frequency ranges it is usually best to list them all rather than one large frequency range which covers all of them, even if the relays are the same for all cases. For example, it is better to list 14000-14350, 21000-21450, and 28000-29700 instead of 14000-29700. This is because the server uses the frequency ranges to decide if two stations are on the same band. When it makes these comparisons it only uses the frequency range that the radio is operating in (it also checks contiguous frequency ranges if there are any).

Conflicts

It is possible that one radio using an antenna precludes another radio from using a different antenna. In the following example radio 1 cannot use the 15 meter beam when radio 2 is using the 10 meter beam. These two antennas have a conflict. In this case Radio 1 will show the 15 meter beam as unavailable and the operator will not be able to select it.

flowchart LR
    R1[Radio 1]
    R2[Radio 2]
    2X6[2x6 Switch]
    RELAY[Relay]
    ANT10@{ img: "../icons/antenna.svg", label: "Antenna - 10M", h: 48 }
    ANT15@{ img: "../icons/antenna.svg", label: "Antenna - 15M", h: 48 }

    R1 --- 2X6
    R2 --- 2X6
    2X6 --- RELAY

    RELAY-- NC ---ANT10
    RELAY-- NO ---ANT15

    style ANT10 fill:transparent,stroke:transparent
    style ANT15 fill:transparent,stroke:transparent

In the earlier example with the stack of three yagis there are seven antennas, none of which can be used when the others are in use. For that case antennas 0-6 have conflicts with antenna 0-6.

Override

If antennas conflict (including an antenna conflicting with itself) only one radio can use these antennas. Normally the antennas will not be available to other radios. However the antennas can be configured to override the selection. If this is done, the antenna is available, and if it is selected the station using the antennas in conflict will be assigned to different antennas.

Fast and Slow Transitions

If the relays that must be switched when changing between two antennas are fast enough that they can be changed between the time the amplifier keying line closes and the time RF comes out of the radio then one of the antennas can be used for transmit and the other for receive.

In the case above with three yagis, if the relays in the Stack Match are fast enough the station can transmit on some of the stack antennas and receive on different stack antennas. The speed of the relays in the 2x6 does not matter for this case because they do not change when switching between the stack antennas. If the relays are fast enough then antennas 0-6 have fast transitions with antennas 0-6.

Persistent Relays

If an antenna system has internal relays, such as those used to select direction in a 4-square or to select individual antennas in a stack, and the antenna system is used for transmit and not receive or vice-versa, the internal relays will be selected and deselected each time the radio switches between transmit and receive. If the internal relays are slow this will prevent using the antenna system for only transmit or receive. It also can cause the relays to wear out sooner.

This can be avoided by declaring the internal relays to be persistent. The persistent relays will not be changed between transmit and receive, provided that the other antenna being used is part of a different antenna system. For example if you transmit on the 4-square and receive on a beverage the 4-square internal relays would not switch when changing between transmit and receive. However if you transmit on the 4-square northeast and listen on the 4-square southeast the internal relays will switch because the transmit and receive antennas are part of the same system.

Alternate Paths

It is possible to create an antenna system where more than one combination of relays will connect an antenna to a radio. For example in the following diagram radio 1 can be connected to the 15 meter beam through either coax 1 or coax 2. If radio 2 is using the 20 meter beam radio 1 must use coax 1 and if radio 2 is using the 10 meter beam radio 1 must use coax 2.

flowchart LR

    R1[Radio 1]
    R2[Radio 2]
    2X6[2×6 Switch]
    RELAY1[Relay 1]
    RELAY2[Relay 2]
    T((T))

    ANT10@{ img: "../icons/antenna.svg", label: "Antenna - 10M", h: 48 }
    ANT15@{ img: "../icons/antenna.svg", label: "Antenna - 15M", h: 48 }
    ANT20@{ img: "../icons/antenna.svg", label: "Antenna - 20M", h: 48 }

    R1 --- 2X6
    R2 --- 2X6

    2X6 --- RELAY1
    2X6 --- RELAY2

    RELAY1 ---|NC| ANT10
    RELAY1 ---|NO| T

    RELAY2 ---|NO| T
    RELAY2 ---|NC| ANT20

    T --- ANT15

    style ANT10 fill:transparent,stroke:transparent
    style ANT15 fill:transparent,stroke:transparent
    style ANT20 fill:transparent,stroke:transparent

Since the two paths to the 15 meter antenna use different relays the MOAS server considers them to be different antennas. The configuration file specifies that they are alternates for each other and the server will automatically switch the 15 meter antenna path as necessary.

Alternate Antennas

This feature is designed for cases where there might be a problem, such as a damaged receiver front end, if a station transmits on an antenna while another station is listening on another nearby antenna.

The configuration file for this case specifies a set of conditions – frequency, transmitting antenna or antennas, receive antennas, and an alternate antenna. If another station transmits on the specified antennas the switch will select the alternate antenna for the receiving station. If the alternate antenna is not available it will select no antenna for the receiving station.

Shared Antenna Systems

A shared antenna system is a system with multiple antennas which can be used simultaneously by more than one station. Examples are a 9-circle receive array or a set of switched Beverage antennas. If each station can select a different beverage it is not a shared system but two systems using shared antennas. Another example of a shared system is a stack of tribanders with a triplexer.

The main feature of a shared antenna system is that changes affect all radios which are using the system. For example if the 80M operator changes a shared beverage system from northeast to south it changes the direction the 160M operator is listening to.

Because of this the shared antenna acts a bit oddly in one case. If a radio is using the shared antenna and another radio is switched to it, it will be connected but the shared antenna will not change. Once the radio is using the shared antenna the direction or the members of the shared antenna can be changed.

For example, suppose the 80M operator is listening on the northeast Beverage and the 160M operator is listening on his transmit antenna. The 160 operator selects a beverage. No matter which beverage he selects he will be connected to the northeast beverage. After he is connected to the beverage, if he selects the south beverage both 160 and 80 will be switched to the south beverage.

Inhibits

The inhibit capability is very flexible and can be configured in several ways.

It can be set up to be symmetric (radio A inhibits radio B and radio B inhibits radio A). With this configuration whichever radio transmits first will block the other. This can be used for SO2R or for two stations on a band.

It can be set up to be asymmetric (radio B inhibits radio A but radio A does not inhibit radio B). With this configuration radio A will block radio B whenever it transmits. This could be used for two stations on a band where station A runs and station B chases multipliers. It can also be used in CQ WW multi-2 where a station uses band changes to work multipliers on another band.

It can be set up for three or more radios, either in symmetric or asymmetric configurations.

These capabilities cannot be used with radios which do not have an inhibit input or where the switch is not connected to the inhibit input unless an external method such as an antenna relay is used to provide the inhibit function.

Each radio has two lists of which other radios will inhibit it from transmitting when they are transmitting. One list is for other radios which always inhibit, and one is for radios which only inhibit when they are on the same band. The latter is useful if a station has the ability to put two radios on the same band - when they are on the same band they can be automatically interlocked so only one can transmit.

There are also inhibit buses. A radio can be associated with one or more inhibit buses. All radios on the same bus will inhibit each other.

Shared Transmit Antennas

Normally two radios cannot select antennas which conflict. However if the radios use inhibits so that only one can transmit at a time and the switching between them is fast then they can.

There are several cases where this can be useful. If a station has two antennas which are pointed in different directions and has two radios it can be configured so that both radios transmit on both antennas but each radio listens on one antenna. It is also useful if a station has one transmit antenna and several receive antennas. Several radios can share the transmit antenna and each listen on a different receive antenna.

Partner Radios

If two radios are inhibited so that only one can transmit at a time, they can share transmit antennas. Normally if a radio is receiving on a transmit antenna it will be disconnected when another radio transmits on it. If the stations are partners and certain conditions are met, the radio will instead be connected to the partner’s receive antenna.

The conditions are:

• There are two stations using the shared transmit antenna. This is not available if more than two radios are using the antenna.
• The radios are set to be partners.
• One partner has an antenna which cannot be used for receive when the other is transmitting.
• The other partner has an antenna which can be used. It must be able to be connected to the partner and it must be fast.

Wait and Interrupt Mode

If a radio is transmitting and an operator selects a different transmit antenna, the behaviour depends on whether the switch is configured to wait or to interrupt.

If the switch is configured to wait the radio will continue to use the old antenna until it stops transmitting. The next transmission will be on the newly selected antenna.

If the switch is configured to interrupt the transmission then it will inhibit the radio, wait a few milliseconds, change the antenna, wait a few more milliseconds, and uninhibit the radio.

This may sound useless but the entire time for this operation is typically less than 100 milliseconds, so very little is actually lost.

Interrupt versus wait mode is configured per-radio. Interrupt mode should not be configured for radios which do not have an inhibit input or where the switch is not connected to the inhibit input.

The delays for interrupt mode can be set in the configuration. The time is in milliseconds. The default is zero, which means the antenna will start to switch as soon as the inhibit line is set.

If an operator changes transmit antennas while he is transmitting another operator may see his old antenna as available and could try to use it. The switch recognizes this and will not switch the second radio to the antenna until the first radio finishes transmitting.

Scenarios

A scenario contains a group of antennas. When a scenario is active the antennas in that scenario are available. Scenarios may have conflicts with other scenarios. In that case when the scenario is made active scenarios which are in conflict will become inactive.

An antenna in one scenario might be an alternate path for an antenna in another scenario. For example, two scenarios might connect the same antenna to the radio but through different amplifiers.

Scenarios can be selected based on whether two radios are on the same or different bands. There may be more than one scenario for radios on the same band and the selection can depend on which one changed bands last. Scenarios can also be selected by a function.

Relay Groups

A relay group contains one or more antennas which are not used for antenna switching. They may be used for purposes such as turning an amplifier on or off. A relay group may be unavailable, available, or selected. Different relays may be selected for each state, and for transmitting or receiving when the group is selected.

Relay group available can be controlled by a station being within a specified frequency range or having a specific transmit or receive antenna, and by a scenario being active, and different relays can be selected depending on why the relay group is available.

Rotators

The server is designed to be able to control antenna rotators.

An antenna can be specified as being fixed or as having a rotator. If it has a rotator the client can change the direction. The configuration can include the offset of the antenna on the mast in case some antennas are at right angles, and it can include the clockwise and counterclockwise limits in case a rotator has limited travel.

An antenna system such as a 4-square can be electronically rotated. If the antenna is configured as having an electronic rotator then when a direction is selected the antenna selection having the closest direction will be used.

Button Clients

One way to display antenna selections is as an array of buttons. The buttons display antennas which could be selected and indicate whether an antenna is unavailable, available, or selected graphically. Pressing a button can select or deselect it. Buttons can also activate functions.

The number of rows and columns of buttons is dependent on the client. The Windows MOAS II client is configurable and can show multiple windows each with a different number of rows and columns if desired. The Android client rows and columns can be changed through a setup menu. The number can be different depending on whether the phone or tablet is horizontal or vertical. Buttons are also available for selecting rotators.

The layout of the buttons is in the server configuration file. The client gets the information when it starts or when the information changes. The layout describes which antenna each button should show. The lists of buttons are specified by frequency range. The range 7000-7300 would show 40 meter antennas, the range 3500-4000 would show 80 meter antennas etc.

There can be multiple layouts for different numbers of rows and columns of buttons. The client requests a list for the number of rows and columns it will display and the server selects the closest match from the configuration file.

When a button for an exclusive antenna is pressed that antenna becomes selected and all others are deselected.

This is an example of buttons for a 4-square:

flowchart LR

    NE[4-Square<br>NE]
    SE[4-Square<br>SE]
    SW[4-Square<br>SW]
    NW[4-Square<br>NW]

The order and position are set by the writer of the configuration. The 4-square could also be done this way:

flowchart

    NW[4-Square<br>NW] ~~~ SW[4-Square<br>SW]
    NE[4-Square<br>NE] ~~~ SE[4-Square<br>SE]

An antenna system which is additive offers more choices. For example, this is an exclusive set of buttons for a stack of three yagis:

flowchart

    TOP[&#160&#160&#160&#160Top]:::box ~~~ MID[&#160&#160&#160&#160Mid]:::box ~~~ BOT[&#160&#160&#160&#160Bot]:::box ~~~ ALL[&#160&#160&#160&#160All]:::box
    TOPMID[Top + Mid]:::box ~~~ TOPBOT[Top + Bot]:::box ~~~ MIDBOT[Mid + Bot]:::box
    classDef box width:123px,height:78px

This could also be a set of additive buttons. Pressing a button alternately adds an antenna to the stack or removes it.

flowchart

    TOP[&#160&#160&#160&#160Top]:::box ~~~ MID[&#160&#160&#160&#160Mid]:::box ~~~ BOT[&#160&#160&#160&#160Bot]:::box
    classDef box width:123px,height:78px

It is possible to mix additive and exclusive buttons. If the entire stack is used most of the time it could have a button to quickly select it:

flowchart

    ALL[&#160&#160&#160&#160All]:::box ~~~ TOP[&#160&#160&#160&#160Top]:::box ~~~ MID[&#160&#160&#160&#160Mid]:::box ~~~ BOT[&#160&#160&#160&#160Bot]:::box
    classDef box width:123px,height:78px

Pressing the All button will select the entire stack. Pressing the other buttons will add and remove them from the configuration.

Both the windows and Android clients have a quick way to exclusively select an additive antenna. If you double-click an additive antenna in the Windows client or press and hold it in the Android client all other antennas will be deselected.

Display Clients

A display shows the currently selected antenna for one or more stations. The Windows button and knob clients have them built in – they display below the title in the window.

Knob Clients

Some operators prefer to turn a knob to select antennas. The Windows knob client interfaces with a Phidgets knob. Everything is configured the same as for a button client except that the list is 1 row by 50 columns.

It is usually not a good idea to assign a large number of antennas to a knob, as the operator will need to turn it a long way. A 4-stack of yagis would be easy to set up as additive antennas on a button client, but with a knob client there would be 15 switch positions. The station designer should consider whether the knob client should select fifteen choices or if some should not be made available in order to simplify operation.

Relative Clients

Relative clients are designed to be used in logging programs and similar. The client does not need to know anything about the antennas. It can choose one antenna from a list or can choose the next or previous antenna in the list. For testing purposes there is a relative client built into the Windows button client. Click on the small icon in the upper left to access this client.

If there are more than a few antennas available on a band the relative client will be difficult to use. Normally only the most commonly used antennas would be set up for the relative client. The relative client’s antenna list is separate from the lists used for the button and knob clients.

Functions

The server can be configured to make functions available to the client. These are the currently available functions:

Extra

Sets an extra relay when a radio transmits.

Inhibit

Connects a radio to an inhibit bus.

Partner

Sets two radios as partners which can share a receive antenna if they are sharing transmit antennas.

Relay

Turn a relay on or off.

RX=TX

If the transmit and receive antennas are different, set the receive antenna to be the transmit antenna.

Share

This function constructs and deconstructs a shared antenna system.

An example would be a station with a stack of two tribanders and a triplexer. The stack could be shared or it could be split into two antennas each connected to a different radio.

This function is turned on and off by alternate button presses.

Store and Recall

These are two functions. Store stores the current antenna selection and Recall recalls it.

Swap

Swap exchanges the antennas of two radios. This is only available if both antennas cover the frequency of the other radio.

An example would be a station with SO2R capability using a tribander and a multiband vertical. The operator might be running on the tribander and searching for multipliers on the vertical. If he finds a weak multiplier he may need to swap the tribander onto the multiplier station briefly.

AltActive

Sets which radios cause a radio to switch to the alternate antenna when they transmit.