Rx Antenna Controller

Rx Antenna Controller is QRV.

I started building this unit a couple of months ago. I called it the Beverage Controller, because my motivation was to select amoung the three Beverage antennas I had erected. Yes, I've managed to erect three 500 foot Beverages, one to the NE, SE and NW.

Performance of these antennas is convincing -- 1-2 S-units lower noise than the inverted-L or dipole antennas I use on 160 and 80m, respectively, plus a directional signal boost if the beverage is pointed in the right direction.

I discussed my design issues with this unit in the previous article. Debugging the serial port took another month.

Serial Port Debugging

The reason I had chosen the PIC16F18426 for this design was because of the built-in EUSART. Receiving worked just fine. I could send commands to the controller and it would act on the commands. But it sent no response. 

I had configured the PIC to use RC5 (pin 5) for the EUSART receive input, and RA5 (pin 2) for the EUSART transmit output. After a bit of troubleshooting, I found no action on RA5. It remained at 4.5 V the entire time. Was this a wiring problem, or a programming problem?

I ended up writing another PIC project and setting up a chip on a solder less breadboard to solve this. This project simply sent "Hello World!" at 300 baud every 5 seconds. It also drive two LEDS on the C port pins. The LEDs which alternate during a 1-second startup. When transmitting, the second LED would light up. 

My serial test project worked perfectly. LED 2 flashed for about 1/2 second every five seconds, just as expected. So, why didn't the beverage controller project work?

I modified the beverage controller project to also send "Hello World!" every 5 seconds. Except it didn't work. I traced the wiring in the controller head. RA5 was connected to the MAX232E pin 11. It was the MAX232E that was driving the pin to 4.5 V. With the MAX232E out of the circuit, RA5 stayed at 0 V all the time. It was like the software had configured RA5 as an input, not an output.

I got to the point that I could test both projects on the solder less breadboard. I even programmed the same chip with the serial test project -- and it worked. Programmed the same chip with the beverage controller project -- and it didn't. This was definitely a programming problem.

I tried several modifications of the configuration, eventually applying the serial test project configurations to the beverage controller project. At some point, it started working. I still don't understand what I changed to make it work.

Putting It Together

Remote relay box

After such a struggle, I was happy to finish. I re-programmed the chips to send and receive at 9600 baud. This is plenty fast enough for this purpose.

The controller supports one Kenwood/Elecraft-style command, which takes two forms - a Get and a Set operation:

• Get - &AR; -- responds with &ARn; where n is 1 through 5
• Set - &ARn; where n is 1 through 5 -- selects the antenna specified by n, responds with &ARn;

With the serial port transmit working, I could remotely interrogate the controller to determine which receiving antenna was currently selected. And selecting an antenna would respond to ensure that the controller had received my command.

The controller mounts nicely on the equipment shelf. I used some temporary stick-on labels until I find my computerized label-maker. 

What's Next

The current firmware sends an &ARn; response when a button is tapped. I probably need to make that configurable with a serial command.

I've also thought about adding a scanning feature. The controller could automatically switch antennas after a few seconds. Holding a button could add/remove that antenna from the scan.

However, after a couple of months of using the controller, I've found a glaring deficiency in my design. The Rx Antenna Controller only selects one antenna for the RX ANT port. I use a broadband splitter to also connect to the AUX port for diversity reception. But this only permits diversity reception of one receiving antenna against the transmit antenna. I can't do diversity reception between two receiving antennas. 

What would be nice is to have the remote relay box select the antenna for the RX ANT and AUX port. This would require twice as many relays and a way to control them individually. Doing this requires a re-design of both the remote relay box and the controller box. 

Beverage Controller

Remote and controller boxes laid 
out for wiring.

With these Beverage antennas, I needed a way to switch between them quickly and easily. 

Taking a cue from the K9AY Controller, I didn't want to just hook up a rotary switch. I wanted a push-button controller. Plus, a lot of the time I'm remotely operating my station on FT8 from the house, I wanted that capability as well. 

Design

I planned for at least three Beverages, maybe more. Plus I had the K9AY loops. That's at least four antennas, having a fifth would give me a spare.

The buttons and indicators needed to be convenient to operate, up front in the station without being intrusive. 

The receiving antenna feed lines also needed to terminate at the Single Point Ground (SPG). Best option was a remote relay box to do the switching, and a small controller box containing the buttons and indicators.

Test positioning the Controller

Adding a serial port to the controller allowed the antenna selection to be interrogated and selected. I already the PIC16F18426 chips on hand. This 14-pin device has a built-in EUSART. A MAX232 would handle the RS-232 level conversion.

Construction

I found a small Bud box in my junk box for the remote. I ordered a die-cast aluminum box for the controller. It was small, but it fit very nicely up under the shelf supporting the P3. Convenient and unobtrusive.

Remote mounted on SPG

The remote has six RF connectors - four F-connectors for the Beverages, one BNC for the K9AY, and another BNC to connect to the K3. SPDT relays are used. When selected, the relay connects the antenna port to the K3 port. When unselected, an appropriate resistor connects across the antenna port. ( I used 82-ohm resistors for the F-connectors, 51-ohm for the BNC -- closest I had to 75 and 50 ohms, respectively )

I used 12 V relays. Unlike the KK1L 2x6 Antenna Switch, I didn't want to activate each relay with a separate line for +12 V. Instead, I sent +12 V to the remote box on a common conductor and then returned a signal for each relay to be grounded by the open drain pins on the PIC. 

This lead to a design problem. The PIC doesn't support true open drain outputs. Each pin is clamped to Vdd, which in this case is +5 V. That left about 6 or so volts across each relay, pulling them all in. 

To solve this, I added 2N3904 NPN transistors to the relay box as open collector drivers for each relay. A 3 K resistor connects the base of each transistor back to the PIC. Instead of a logic 0 activating the relay, a logic 1 does the same job.

The controller box is really tight. I borrowed five switches from the K1EL Keyer. The LEDs and switches barely fit. The controller itself is simple. Five RA port pins connect to the pushbuttons. Five RC port pins drive the LED indicators and NPN relay driver. One RA pin and one RC pin communicate with the serial port. 

Changing the sense of the relay switching required re-wiring of the LEDs. Before, they were tied to +12 with the cathode of each LED brought to ground by the PIC. Except that didn't work due to the design problem. Instead the cathodes went through a common 330 ohm resistor to ground, and the anodes were connected across the activation lines for each relay.

Debugging

I debugged this design in parts, starting with the controller box, then the relay box separately. Once I connected them together, I found the design problem that required much re-wiring. 

The button selection worked great. The serial port has been more of a problem. While the PIC receives commands correctly, it doesn't appear to transmit anything at all. It is a puzzlement. 

Beverage(s)

View 175 feet down NW Beverage.

My initial experience with the 2024 ARRL 160m contest demonstrated a serious noise issue on Ward Mountain. The Inverted-L showed an S4 noise level. I needed low-noise receiving antennas.

I'd had some success with the half-size K9AY loops at the Gwinnett station. But I could use something better.

At contest stations such as NQ4I or WW4LL, I've had the opportunity to use Beverage antennas. But  never at my home station.  I planned to change that. 

The Plan

Having a bit of acreage, there's room for several beverages.The key directions were to the NorthEast (NE), SouthEast (SE) and NorthWest (NW). 

For 160m Beverages, many recommend at least 550 feet of wire, minimum. This is just a bit over one wavelength long. ( Technically, using a velocity factor of 95%, one wavelength of wire should be 520 feet at 1.8 MHz ) Since they don't make spools of 550 or 520 feet of wire, a 500 foot spool should be sufficient. 

Wire is expensive. A 500 foot spool of stranded 14 gauge THHN wire is $78 at Home Depot. 

Beverage antennas are pretty simple. The long piece of wire is fed against ground at both ends. The near end uses a matching transformer to adapt the nominal 500 ohm impedance of the Beverage to a feedline. The far end contains a terminating resistor. 

Beverage terminators (above) and
transformers with F-connectors (below)

Terminator Boxes

I built five Beverage terminator boxes using a 470 ohm 2W resistor (OY474KE Ceramic composition resistor) and a 75v gas discharge tube.

These parts fit snugly in a small plastic box. Thumbscrews make for easy connection to the antenna and ground rod.

Transformer Boxes

500:75 ohm transformer

Beverage transformers are wound on BN-73-202 cores. Primary is 3 turns using red wire-wrap wire. Secondary is 8 turns yellow wire-wrap wire. The primary and secondary are separated using cut off bits of plastic stirring straws. The 3:8 turns ratio is a good match for 75 ohm coaxial cable used to feed the antenna. 

Transformer assembly progression

Transformers are housed in the same small plastic boxes. An F connector jack supplies the transformer primary. Transformer secondary connects to thumbscrew posts with another 75 V gas discharge tube across them. There is no common ground connection between the primary and secondary -- this avoids noise pickup from the feedline. 

Thumbscrews connect to the antenna and ground rod at the feed point.

I built four transformers initially. The small plastic boxes work necessitated a bit of ingenuity to get everything in place. 

Erecting

Single wrap traps wire

Installed insulator

Being surrounded by forest, the Beverages are suspended from trees aligned with the reception path. Screw-in electric fence insulators are used to support the antenna about 8 feet off the ground. 

A rope around a tree supplies modest tension for the wire at each end. This leaves the ends relaxed to connect to the transformer or terminator boxes and ground rods. 

The technique for installing the beverages is straightforward, I start by locating the feed point transformer near a supporting tree and mounting an insulator there. Once the ground rod and tension rope are installed, it's a matter of going from tree to tree installing insulators and hooking the wire. This continues until you reach the end of the wire, where the ground rod, terminator box and tension rope are located. 

Terminator installed

Tension connection

At the transformer and terminator, the wire to the ground rod zig-zags a bit to take up the slack from the insulator. This keeps the plastic box from flapping around in the wind.

Every attempt is made to keep the Beverage straight toward the target heading. A bit of direction change to make supporting trees is tolerable. I used the iPhone Compass app to keep me on heading. 

At my location, the terrain slopes a bit. For the NW beverage, after the first 175 feet, the drop-off is quite gradual. 

The NE beverage is another story. Terrain drops about 10 feet in the first 200 feet, but the last 300 feet drops about 80 feet. The beverage terminator ended up in the bottom of a deep ravine. Navigating the slope was quite difficult. Rocks, branches and other debris on the forest floor made for tricky footing. Be careful out there.

Feed Line

I caught a deal on some RG-6. I found 700 feet on a spool for less than $20 at the Dalton, GA hamfest. RG-6 is cheaper than stranded wire. A 500 foot spool is $50 at Home Depot. This 75-ohm coax makes for a good receive antenna feedline. It's cheap, low-loss and easy to match.

Performance

Only have a little experience with these antennas. NE Beverage has been up a month, and the NW Beverage a week. 

Performance is amazing. 

On the 160m Inverted-L, there's typically S4-5 noise. Noise level on the Beverage antennas varies depending on the time of night, but is typically 1-2 S-units lower. 

More importantly, signal levels are stronger. If I watch the Elecraft P3 panadapter, switching from the Inverted-L to one of the Beverages, the noise level drops somewhat, but the signals rise above even more. Sometimes, when there are no visible signals on the Inverted-L, many are Q5 copy on a Beverage.

Further, switching from one Beverage to the other can have a dramatic effect on signals. Sometimes, signals that are strong on one are inaudible on another. Other times, signals are about the same.

In short, the Beverage receive much better than the Inverted-L. During the recent Stew Perry TBDC, I listened on the Beverages almost exclusively. 

They work.

New Modes for the Auto Antenna Selector

Automatic Antenna Selector in use

I wrote previously about debugging selection modes for the Auto Antenna Selector. With that working, I wondered if I could do more. 

Originally, I thought that modes should swap the selections on the A and B ports. With Standard Mode, I was missing that. But how to allow more modes?

Flip-Flop Mode

I don't need Test Mode that often. Holding down the mode button could be divided into a short and long hold. A long hold -- 1 second or more -- would invoke Test Mode. A short hold -- 1/4 of a second, could invoke something else. 

Flip-Flop mode was born. With a short hold, the selections for Port A and B are swapped. This works both in single-radio and two-radio configurations.

The selector signals Flip-Flop mode by blinking the mode LED on and off over 1/2 second. As coded, it actually pulses for 1/2 second, then is off for 1/2 second. Not what I intended, but distinctive. I decided I didn't need to "fix" it.

Testing

Unlike the last code changes, these worked the first time. I found Flip-Flop mode helpful with the single radio when trying to use a different antenna with the AL-80A amplifier. Since it is only connected to the antenna on Port A, this mode makes this possible.

At the moment, tapping the mode button in Flip-Flop Mode doesn't do anything, still thinking about that.

Debugging the Automatic Antenna Selector

When I last wrote about the Automatic Antenna Selector, I mentioned adding modes to select more antenna options. Getting that to work took some doing.

Test Mode

Holding down the mode button invokes test mode. When entered, it selects port A0. Tapping the mode button advances to port A1, A2, to A5, then it goes to B0, B1, to B5, then back to A0. In this way, all antenna / port combinations can be selected. This allows new antennas or conducting tests or experiments before a new configuration can be programmed. 

The unit signals Test Mode with the mode LED being on continuously. Holding down the mode button again goes back to Standard Mode. 

Standard Mode

Standard mode determines antenna selections according to the connected K3 BAND0-3 signals. When only one radio is connected, both ports are based on the current band for that radio. The first port is the primary, the second part gets the secondary selection. Tapping the mode button cycles through the secondary port selections, the primary port being unchanged. 

When two radios are connected, port selections are based on the K3 BAND0-3 signal for both radios. Radio A gets the primary selection. Radio B gets its primary selection, unless that port conflicts with Radio A. It then gets the secondary selection (unless that also conflicts). Tapping the mode button cycles through the Radio B selections. 

The unit signal Standard Mode with a mostly dark LED. Off completely for the primary selection, pulsing twice for secondary, three times for tertiary. At the moment, there are only three stages. Adding a fourth would be easy.

Easy in concept, but after the code changes, it didn't all work.

Test mode worked great. Entering and exiting were reliable, and each tap selected the correct port.

Standard mode, however, didn't seem to do anything. The LED indication showed the mode selected, but the port selection did not change. I had only implemented the single radio logic, since I couldn't find a second cable to connect a K3.

Debugging

Debugging this over the last couple of weeks was driving me mad. No matter what changes I made to the code, the behavior did not change. Further, I noticed that when the K3 was on 6m, port B was also selecting a dipole antenna. That was unexpected, as it wasn't a valid antenna for 6m.

Eventually, it dawned on me that this was not single-radio mode. For some reason, the selector believed there were two radios connected.

That was a revelation. I knew there was a problem when the K3 powered down. When no K3s are connected, the selector was supposed to deselect all relays. Instead, it had two dipoles selected. 

This was connected with how Elecraft encoded the bands on the BAND0-3 pins. 60m is represented as all zeros. Even with the weak pull-ups enabled on the PIC, it wasn't enough to overcome the loading of the connected but powered-down K3.

The same problem was evident on the disconnected port -- it was registering 60m, which selected the dipole. 

Fixing

The first fix was hardware. I added 2.2k pull-up resistors to the BAND0-3 pins on both ports. After that, the relays deactivated when the K3 was powered down. But, I still saw the dipole selecting coming up on 6m when switching models. 

This was a software problem. One of the internal variables was initialized incorrect, which was the source of the 60m selection. When initialized correctly, single-radio Standard Mode selections worked as they should. 

With that working, I'm full of new ideas for improving mode selections. Once I figure out which ideas are best, hopefully it will be a small matter of code changes....

Bell & Howell IMD-202-2 (Heathkit IM-1212 In Disguise)

Bell & Howell IMD-202-2 in place at workbench.

When my Systron-Donner digital multimeter was damaged by lightning in June of 1992, I looked for a replacement. Somewhere along the line, I found a Bell & Howell IMD-202-2 at a hamfest. This was at least twenty years ago -- I have a email message from January 2005 asking about it.

Somewhere along the line, this meter refused to measure anything. When I moved it to Ward Mountain, it was time to fix it. 

The sticker of the multimeter says "Heathkit IMD-202-2", but it's not a Heathkit number. In twenty years, there's apparently more information available. I found that it's a Heathkit IM-1212 with a Bell & Howell label. They sold this unit in the late 1970s as part of an electronics instruction course.

While I couldn't find an assembly manual, I did find a schematic and a calibration procedure. The unit is a simple and straightforward design. Opening it up, there's a single circuit board, plus a bit of wiring around the function and range switches. 

Stepping through the calibration procedure, I couldn't find anything amiss. I had difficulty using a frequency counter to set the counter oscillator. Even with an oscilloscope, I couldn't find a clear signal to measure -- yet the unit was working. I decided to use the calibration without a frequency counter.

When performing the DC and AC voltage calibration, I backed up these measurements using a modern portable digital multimeter. In the twenty years or so since I obtained the Bell & Howell, I've purchased four of these gems. 

The calibration went smoothly, and the Bell & Howell now has an honored place on my workbench. 

Measuring 1k resistor.

Compared to modern instruments, it's not impressive. It sports 2 1/2 digits -- the first digit is just a neon lamp that signals a leading "1". A second neon lamp lights a "OVER" indicator. By comparison, my modern portable digital multimeters have 3 1/2 digits, and at least one of them is auto-ranging. Accuracy isn't great -- perhaps 2% when freshly calibrated.

Still, it's sufficient to be tied to the workbench. The problem with the modern portable digital multimeters is the "portable" part. I leave them all over, and can't find one when I need it. Plus, the nixie tubes are cool.

At least until I can fix the Systron-Donner, which is a much nicer instrument. I have full manuals for the Systron-Donner. Last I looked, it had a problem with fried comparator using a LM301AH with matched FET input amplifiers. Yes, that's a TO-8 style integrated circuit, something you haven't really seen since the early 1970s. And the matched FETs are in a common plastic case with six leads -- a rather uncommon part. I intend to remove the damaged parts and install new parts with socket pins. 

Automatic Antenna Selector Project

Auto Antenna Selector under test.

Some projects are years in the making. October 2020, I ordered the KK1L 2x6 Antenna Switch board. I assembled it and by December I rigged up a manual antenna selection switch. Two years later, I mounted the KK1L to an aluminum panel to create a Single Point Ground (SPG). While all that work was beneficial from a bonding and grounding standpoint, antennas were selected manually. If I changed bands and forgot to change the antenna selection, trouble could ensue.

The purpose in buying the KK1L 2x6 Antenna Switch was fully automatic antenna selection. I needed a controller that could communicate with the Elecraft K3 and select the right antenna. 

A PIC microcontroller seemed suitable. I'd had success using one of these chips to build a K9AY Controller. For that project I had used a PIC16F1503. After that, I picked up the PIC16F18426 and PIC16F18446 chips -- these offered more features than the '1503, including a serial port and way more program memory. The Microchip tools were free, and I had a PICkit3 programmer.

I sketched out three designs.

Design A - 1 radio, 1 set of relays

The most basic design - it does little more than replace the manual switch. A single DE-15 jack brings the BAND0-3 information from the K3 into the PIC. Three outputs drive a 74LS145 BCD decoder to select one of the six relays through a 2N3906 driver transistor. Two other outputs allow selection of the 160 or 80/75m shunt matching networks.

Total I/O required nine pins, which any of the three chips could provide.

Design B - 1 radio, 2 sets of relays

A limitation with Design A is that a K3 with the KAT3 has two antenna jacks, but the selector only chooses one antenna. Design B reads BAND0-3 from one radio, and selects the best antenna on port A of the switch, which is connected to ANT1, and the second best antenna on port B, which is connected to ANT2. The operator can then use the ANT button on the K3 to switch between the two antennas. 

This design retained the four inputs for the BAND0-3 information, plus six outputs feeding two separate 74LS145 BCD decoders, and two additional outputs for the 160 or 80/75m shunt matching network. 

That's exactly 12 pins -- still possible using any three of the chips.

Design C - 2 radios, 2 sets of relays

I liked Design B, but along the way I purchased a second Elecraft K3. If I were trying to use both radios, what would I need to switch the antennas?

Two DE-15 jacks facilitate the BAND0-3 data from each radio, requiring eight inputs. The selector could then choose the best antenna for both Radio A and Radio B, unless that choice caused a conflict, in which case Radio B would get the second-best choice.  Outputs were the same as in Design B. 

This required the 20-pin '18446, because the 14-pin controllers don't have enough I/O available. 

It occurred to me I might want to switch the antenna selection priority sometimes, so Radio B gets the best antenna in a conflict and Radio A gets second best. That required an input pin for a pushbutton and an output to light an LED. This used all the 18 pins available on the '18446. 

Design Choice - B/C - 1 or 2 radios, 2 sets of relays

First look with front panel assembled

The end design combines Design B and C features. Two DE-15 jacks are used, and the PIC software decides if a K3 is connected or not based on the pattern of BAND0-3. Unconnected pins are pulled up, so a value of all ones indicates no connection. If only one radio is connected, the software acts like Design B, if both radios are connected, it acts like Design C. 

The front panel has LEDs for the six relays on port A and B, so you can visually see which antenna is selected for each radio. An LED each for the 160 and 80/75m shunt selection, and a pushbutton and LED for the mode selection rounds out the front panel. A power switch and a switch to choose between the 80 and 75m shunt network round things out.

Power requirements are simple. A port relays take 88 mA, and B port relays require 44 mA. Selecting one relay for both ports is less than 140 mA. The 160m shunt relay requires 120 mA and 80m relay requires less. The power requirements of the PIC, 74LS145 and LEDs are negligible by comparison -- 300 mA covers everything. 

Construction

A look at the guts of the box. The relay
drive transistors dominate the board

I searched for a smart-looking cabinet for this project fitting the dimensions of the station. I found a reasonably priced enclosure on Amazon.com. I took lot of care drilling the front panel so that everything lined up correctly. I figured I might be staring at it for years. In retrospect, the rear panel doesn't look so pretty.

With the cabinet in hand, how to construct the hardware? I considered developing a PC board, but I was eager to build. I ended up using a bit of perfboard and some 3M Scotchflex prototyping sockets. The Scotchflex system is now obsolete, mainly because everything is surface mount, but I had most of this in the junk box. I had to engineer a 20-pin 0.3 inch socket -- which I accomplished with two 14-pin sockets back to back.

The downside to this approach is all the wiring required for the relay and LED driver transistors -- there are fourteen 2N3906s, three 2N3904s and a bunch of related resistors. A PC board would have taken more design work ahead of time, but the construction would have gone quickly and taken less space.

I worked on this project off and on in six different locations - Gwinnett county, Fulton county, Warren county, two locations in Gordon county and finally from Floyd county. For a while, I carried the whole project with me in a small cardboard box wherever I was.

Software

Like the K9AY controller, everything is interrupt-driven. The '18466 CPU is configured with a 500 kHz clock speed, and a timer interrupt occurring every 5 ms. 

During the interrupt, we sample the A and B ports from the radios, plus the mode button. All of these values go through debounce logic - the value must hold for 10 interrupts (50 ms) before taking action.

If either the A or B values change, or the mode selection changes, then the antenna selection logic is followed. If either port is all ones, it indicates a radio isn't connected, so the Design B rules are used to select the antenna. If neither port is all ones, we assume two radios are connected, and Design C rules are used to make the selection. 

Debugging

Unlike the K9AY controller, I had a bit of trouble getting the software working. Part of the struggle was knowing if a problem was a wiring problem or a software issue.

At first, nothing seemed to work. In the end, I wrote really simple firmware that just blinks the mode LED based on the timer. Nothing. Setting up the chip on a solderless protoboard, still nothing. After some experiments, I got the timer interrupt straightened out and had a blinking LED on the protoboard. 

Then came the wiring issues on mode LED. One issue was the transistor drivers for the LED didn't have proper pull-ups. Eventually, I settled on a one second startup routine that would blink the mode LED briefly once, then twice. After that, the chip would be looking at the input ports and selecting antennas.

In the next phase, I wrote an additional startup routine that selected the antenna for ports A and B. Every second or so, it selected a different relay, and hence light the LED. I coded it to go in a pattern so I could verify that each relay driver and LED worked correctly. Of course, it didn't work.

Several wiring problems became apparent. First, the 74LS145 chips weren't getting any +5 volt power, so they weren't doing anything. They had been wired, but one of the wires broke. Once fixed, the LEDs lit. Then it was apparent they were going in the wrong order. 

The wiring between the PIC16F18466 and the 74LS145 chips had two problems. First, the pins for the A port and B port had been reversed. Second, outputs from the 74LS145 were reversed. Putting out a value of 001 into the 74LS145 selected antenna 5, and a value of 110 selected antenna 0. Rather than doing a massive amount of re-wiring, it was easier to change the software and re-draw that part of the schematic. 

Then we finally come to the business end -- hooking up the K3 BAND0-3 inputs. That's when I found my last wiring error. Turns out, I had swapped the pins between rig A and rig B. Another problem solved with a software change.

It Works! Now What?

Even with the basic software running, I felt the need for change. I've disassembled my station in Gwinnett county, and the antenna configuration I programmed, even designed this Automatic Antenna Selector for no longer exists.

The antenna selection logic originally was a bunch of switch statements embedded inside if / else statements -- not very easy to change. I re-coded to use a short table of eleven rows and four columns. The rows represent each band, 160 through 10m, including 60m. The columns are the first, second, third and fourth choices of antennas. Much easier to understand and update.

I expanded on the idea about the Mode button. Originally, it was just primary / secondary. To allow for up to four antenna choices, perhaps there are more than two modes. How does one tell which mode you are in? The mode LED was programmed as just on or off. I could have it be off for primary, blink once for secondary, twice for tertiary, and three times for quaternary.

The last issue was how to test the relay action without having to program a new antenna configuration.  Currently, there's nothing programmed for relay position 4. If one wanted to hook an antenna there to test it, how do we do that without burning a new chip? 

Holding down the mode button could select a special mode that selects ports A0 ad B5. Then, each time you tap the mode button, it would switch: A1 and B4, A2 and B3, etc. In this way, each port can connect to each antenna. And the mode LED would indicate this with a solid on condition. Hiding the mode button again would switch back to the to the normal program.

How about using a radio other than the K3? Maybe I want to use the Novice Transmitter, or perhaps my trusty Elecraft K2/100. Perhaps we re-purpose the seven-position manual selection switch to encode K3 band values. A simple diode matrix would work, and I have a bunch of 1N270 diodes, 

This project is now working, but it is far from done.