Another Prop Pitch Rotator Direction Indicator Prototype

For a long time the ugliest presence on my operating desk has been the controller for the two prop pitch rotators. When I say ugly, I mean really ugly. Have and look and see what you think. It's sitting on top of an Icom 7610, which makes for quite a contrast.

The controller is home brew and very old. The repurposed CDR direction meter failed over a year ago. As an interim(!) measure I installed a pair of op amp circuits on a prototype board feeding an outboard milliammeter pulled from my junk box. A rotary switch was installed to select the motor and direction, and also select which rotator direction to display. 

Despite its deplorable appearance it works quite well. Just don't breathe hard when you get close to it! I never did get around to putting the circuits on a PCB. My intent was to gut the innards of a couple of orphan Hy-Gain rotator controllers to serve as the prop pitch controllers. Then I had second thoughts. I put off doing anything with it until I was certain of what I wanted for a permanent solution.

Earlier this year I decided to set aside the orphan controllers that I picked up at local flea markets and took an entirely different approach. So I built a new prototype. It's been languishing on the operating desk due to family issues, thus adding to the ugliness for months. I recently made an effort to move the project forward. 

I have all the parts and a plan to complete the controller. The first version will only display the direction of the rotators. Turning the motors will, for the time being, continue with the ugly controller. One reason is that, in the midst of this project, the power supply developed serious problems and needs repair or replacement. Troubleshooting has been difficult with the fragile prototype board perched on top of the transformer and filter capacitor.

Although not assembled, even in its first version, enough has been done to be worth an article. Another will follow when it is done, and perhaps another when the rotation activation features are added. After that it will require refinement, which will be easier since the work should be almost entirely in the software.

Design objectives & features

I had a variety of objectives in mind for the controller, some critical and others for convenience or personal interest. They are listed below, but not in any particular order. I developed the list organically as I considered options to replace the existing controller and as I formed opinions on functionality as I proceeded.

• Compact size: I want it to fit well and look good on the operating desk
• Remote power supply: The 24 VDC power supply for the motor is fairly large and does not need to take up space on the operating desk
• Future PC integration: Integrate rotator control with my station automation system to provide easy access from each operating position (multi-op contests) and, possibly, for remote operation
• Software: Ease of modification and extension
• Support a variety of direction pot methods, and possibly other direction indicators
• Over 360° rotation: Handy in a pinch, but with strict limits to avoid coax damage
• Digital display and control: No mechanical meters or user-activated switches for motor power
• Front panel calibration: No need to open it up or to climb the tower

There are commercial products that can do most of what I want. However, regular readers will have learned by now that I prefer to design and build what I can. This project is well within my abilities. Indeed, it should be within the abilities of many hams. It's an opportunity to learn and to have the satisfaction of building station equipment that will be used every day.

Architecture

This version of the controller requires that the direction potentiometer on the tower be 10:1 and 10 kΩ. The manufacturer is Bourn and they are available from most large component suppliers. There are knock offs available on other sites that are not the same quality but are cheap and work pretty well. They need to be well protected from moisture. You can see one in the picture below being used to emulate the tower pot.

An op-amp differential amplifier compares the tower pot to a 10 kΩ zeroing pot in the controller and feeds that to an Arduino analogue (ADC) GPIO pin via a linear protection circuit. The op-amp circuit is very similar to that in the prototype sitting on the old controller. The differences are described in the next section.

Software measures the voltage and converts that to a bearing. In the present implementation, north is at the centre of rotation and over-360° rotation is supported. This is the most useful arrangement for HF propagation in this part of the world. Any centre can be set in the software, as can rotation limits.

The display is a 2×16 LCD (1602A). These are very common and cheap. A friend made a few bezels for the display on his 3D printer from designs available online. We haven't yet settled on which one to use.

The controller is powered from a 12 VDC (13.8 VDC) external supply. Onboard converters and regulators provide ±15 volts for the op-amp circuits and external pots and 5 VDC for the Arduino and LCD. The prototype is driven by a pair of 9 VDC batteries which, as we'll see, is insufficient.

There will be connectors on the rear of the enclosure for the direction pots on the towers and to drive relays in the 24 VDC motor power supplies. I have two power supplies so that both motors can be run concurrently. The software will sequence the relays and, in a future version, detect motion faults to prevent damage to the motors and power supplies.

Op-amp circuit

The op-amp circuit is almost identical to that of the earlier prototype, the one that is currently in use. I reverted to this circuit after exploring alternative differential amplifier designs that never quite did what I wanted. I developed a simple spreadsheet to predict performance. The circuit has to be linear within the range the tower pot covers with predictable and adjustable gain and zeroing.

In the end, simplicity won out over perfection. I can live with a few quirks.

There is one important difference between this circuit and that of the earlier prototype. A physical meter responds to current while the analogue GPIO pin ADC responds to voltage. I set a fixed circuit gain (negative feedback) and used a pot as a voltage divider to lower the net gain of the circuit. The protection circuit protects the Arduino microprocessor from adjustment errors and voltage surges.

For ±15 VDC op-amp power, one turn of the 10:1 tower direction pot has a 3 volt range over 360° (10% of 30 volts). That corresponds to the motion of the direction pot on the 1:1 rotation of the chain-driven prop pitch motor. On the other tower, the belt drive for the pot has an approximate ratio of 2.5:1 for 360° rotation. The circuit supports both with the fixed resistor for negative feedback. All that's required is to set the level pot.

The protection circuit design is linear between 1.5 and 4.5 volts, which is a range of 3 volts. With the 10 kΩ feedback resistor the gain of the op-amp is above unity, so the direct drive motor will cause a range higher than 3 volts at the op-amp output. The gain isn't so high that the op-amp is pushed beyond its linear curve; that is, output voltage approaching either power rail. It is however recommended that the tower pot be roughly centred within its 10 turn rotation so that there is no risk of the inputs approaching the power rail voltages. The 741 data sheet specifies what is allowed.

The same spec sheet shows that the minimum supply voltage for the 741 is ±10 volts. The 9 volt batteries are not quite enough and I did see a few anomalies when I let the input voltages get too high. Consider that for a 3-turn rotation of the tower pot the input voltage range is 5.4 volts (30% of 18 volts), or 9 volts for ±15 volt supplies.

Because the voltage for counterclockwise south (180° bearing) is 1.5 volts and not 0 volts, adjustment of the gain (level pot) also changes the 1.5 volt value. This does not occur on the earlier prototype because there is a true zero volt point for the meter movement. This is an unfortunate quirk  but one I can live with. Both the zero and gain pots will be exposed to the operator for calibration. For a true zero point circuit the gain control can be a trim pot within the enclosure, calibrated to the the turns ratio driving the tower pot.

The circuit requires protection from RFI and surges (e.g. lightning) since the tower pots are permanently connected. Op-amps are sensitive devices and microprocessors are fragile. Modular connectors rather than barrier strips will allow rapid disconnection for added safety. RFC and capacitors will bypass RF to ground. GDT (gas discharge tubes) will shunt high voltages pulses to ground. These will depend on the RFC and capacitors to "slow" the rise time since the pots must be DC coupled. Component selection has not yet been decided.

Arduino hardware & software

Perhaps one of the most critical requirements of a processor for control applications is the number and type of GPIO (general purpose input output) pins. Despite its simplicity, quite a few are needed:

• LCD: 6
• Direction indicator: 1 analogue input per direction pot
• Rotation selection: 2 digital inputs per prop pitch motor
  
• Rotator activation: 2 digital outputs per prop pitch motor, and 1 more for power sequencing
• Rotation sensing: 1 or 2 analogue inputs per rotator
• Wi-Fi connectivity: if not integrated, at least 1 RX/TX pair is needed

For control of my two prop pitch motors, the initial version requires 18 GPIO pins, of which 2 are analogue. There are ways to reduce the GPIO requirement that I won't delve into in this article. I am keeping the design simple for the initial version of the project.

I dug into my junk box and pulled out the clone Arduino Uno that you can see above. It is barely sufficient in this application since almost every GPIO pin will need to be used. Something like an Arduino Mega would be needed to support more than two prop pitch rotators. Processor speed and memory are unimportant in this application.

The display is a bottleneck so it's helpful that not a lot is needed in this application. An LCD with two lines of 16 characters, with each character a 5×8 matrix (like dot-matrix printer of the past) is good enough. Above you can see that the top line is for labels and the second is for the direction information. There is a limited character set native to these cheap and ubiquitous displays (a few dollars each) but it is easy to create custom characters. I created characters for the degree symbol (shown), arrows for rotation direction and alert symbols for faults and warnings.

The trim pot on the left side of the protoboard sets the display contrast. It is very sensitive to the voltage, with the required value in the vicinity of 1 volt. There are pins for powering the backlight, and that's mandatory for almost all environments. Visibility of the display is better than it appears in the picture. 

Although the dimensions are almost an industry standard, not every LCD of this type is identical. When you 3D print a bezel be sure it's the correct size and that there is a way to tighten it to the enclosure front panel. Our first few attempts were deficient. I am eagerly awaiting the latest print since it appears to be what I need.

The replacement of physical with digital direction indication requires smoothing. The signal from the tower pot is constantly changing, whether the motor is running or not. The mast rocks back and forth and the pot has imperfections and glitches, especially as it ages. Physical meter movements naturally smooth brief glitches (perhaps up to 100 ms) but we want to see all real motion of the mast. With a readout precision of 1° and Arduino cycle times that are quite short, the displayed direction is constantly changing. Active smoothing is desirable.

Smoothing can be done in hardware or software, or both. A time constant circuit (T = RC) easily takes care of brief glitches. For example, a 20 μF capacitor across the 10 kΩ level pot has a time constant of about 200 ms. Glitches will be smoothed but not normal rotation, which includes rocking in the wind. The same can be accomplished in software with a moving average. A simple example is to display the average of the last 5 measurements, where the loop interval is 50 ms. Software can do even better by identifying glitches -- unexpected and impossible changes between successive measurements -- and discard or modify them. 

With these methods it is possible to keep the bearing display sane. However, if the pot has degraded to the point that glitches are common or the voltage is unreliable it will have to be replaced. Software can't solve every problem.

Glitches are common with buttons and will have to be dealt with in a similar fashion when, in the next version, they are used to turn the rotators. Again, both hardware and software measures can be used. In this case, the term for the process is debouncing.

Notice in the picture above that the right hand bearing is "---°". This is done in software when the signal at the analogue GPIO pin (ADC) is out of range. In this case the pin has been grounded (not used for now). If it is not grounded the display might show a value, and that value would be related to that present on the operational pin for the bearing on the left. This is necessary since the Arduino multiplexes the analogue GPIO pins into a single ADC circuit and continuously scans each input. 

Due to the high input impedance and stray capacitance, an open but used analogue GPIO pin will measure the residual voltage stored in the stray capacitance. When the pin is in service the phantom reading vanishes. Unused inputs for disconnected tower pots may have to be grounded or pulled high to avoid this phenomenon. It can be done by modifying the software but that can be inconvenient.

Next steps

Circumstances to which I previously alluded are serious enough to keep me away from contests and most station work, and the blog. I've climbed towers only thrice in the intervening two months and two of those weren't mine. The list of station work to be done is growing. This will be a busy year.

At least the prop pitch controller can be worked on indoors and during evenings which gives me more opportunity to get it done. I have the enclosure, the power supplies and other components to box up the controller. Aspects of those details are interesting and well worth another article. Time permitting, that will come later in May.

12 VDC Prop Pitch Motor

The aviation electrical power standard has been 24 VDC for a very long time. Since this also holds for US military aircraft, prop pitch motors require a 24 VDC power source even though their design dates all the way back to WW II. It turns out, much to my surprise, that there exist 12 VDC prop pitch motors. I first learned of their existence several years ago when a friend purchased one at a flea market. 

They seem to be quite rare. It is difficult to identify them from the outside. At the very least it is necessary to remove the motor cover and read the print on the motor. You don't even need to do that since the external appearance is quite different. I had occasion recently to become more familiar with these motors when the motor developed a fault and I offered to inspect and hopefully repair my friend's motor. The loss of any rotator is an inconvenience. Luckily he has enough antennas that the temporary loss could be tolerated.

Those of you with an interest in prop pitch motors and, like me, have never seen a 12 volt motor, this tear down and repair should be welcome. I had no information about them and I could not find any. All I had from a friend was confirmation that they exist. He was happy to receive the pictures I sent him since he had none in his files.

Separating the motor and gearbox (reduction drive)

In my workshop I carefully began disassembly. Although I have experience working on prop pitch motors, this one was a novelty. There was minor damage on the outside due to mishandling in the distant past. I filed down metal spurs on the motor body and motor retaining nut. The method for mounting the after-market rotating reed switch magnet was poor and did some damage to the exterior of the top motor bearing. I put that aside while I worked on the motor.

Pulling the motor off the gearbox was more difficult than I expected. It uses the same large threaded nut that is found on many of the small size prop pitch motors. I was surprised that the motor did not come free when the nut was removed. I carefully pried up the motor with a large gear puller to discover the reason for the resistance. 

It turns out that there are no electrical contact pins on the motor and the drive side of the gearbox. The motor wires are directly threaded through holes in the gearbox housing. Once I realized that, I removed the connectors crimped onto the wires and pushed the bare wires through the holes while pulling up on the motor. The motor and gearbox were finally separated. 

It is a good idea to label the wires at this point so that they are correctly placed for reassembly. I had to puzzle it out during reassembly since I forgot to do so. Luckily the wire arrangement is the same as the 24 volt models. This one is a right hand motor.

Note: After K7NV passed, his web site full of prop pitch motor information went offline. I have an archive as do many others, but at the time of writing there are no reliable links to point you to due to copyright and other issues. In any case, he had nothing on the 12 volt motors. I will not publish his wiring diagrams in this article. Hopefully at a later date there will be a permanently accessible archive of his material.

The next surprise was that the drive side of the motor axle was loose. That is, there is only one bearing, and that is located at the top of the motor axle. The motor cannot be spun unless it is attached to the gearbox. I thought that was very odd. On the other hand, I suppose there's some benefit in having one less bearing to deal with!

Unlike the splines on the more common 24 volt motors, the coupling is done with a blade. There is a matching receptacle for the blade on the gearbox shaft. The fit is precise so that the axle doesn't wobble. I have heard that this alternative appears on some 24 volt motors but I have never seen one.

Gearbox

At this point I checked the gearbox for freedom of movement. After leaving it outside during a cold spell (it was too large for my usual freezer test!) there was evidence of a poor grease choice. I didn't open the gearbox but the owner told me that he'd previously opened and lubricated what he could access. Not all parts are accessible without disassembling the planetary gears. 

I didn't open the gearbox since there was no evidence of a problem other than perhaps a poor choice of grease. I set it aside for when the motor was ready to be reassembled. Although I was curious about the design of the gearbox, that wasn't a good enough reason to open it for an inspection. Perhaps another time.

This is a picture of the drive side of the gearbox. Notice the lack of provision for electrical contacts, just the holes through which the wires are threaded. In the usual design the contact receptacles slot into holes and are held there with retaining rings. With this motor, care is needed to avoid tugging the wires and abrading the insulation during assembly and reassembly.

Since the contacts, where they exist, are part of the gearbox housing, I wasn't surprised to see that the part number was different. Other than that the housing looks the same as for the 24 volt design. The motor base is the same, and there is the same key in the gearbox housing to secure the motor position when the motor is mounted. The motor axle has to be rotated during assembly until the blade aligns with the slot on the gearbox axle.

Note the key at the bottom. It has a mating notch on the flange at the base of the motor. Its importance during reassembly will become apparent towards the end of this article.

Inside the motor

With just one bearing, it was easy to knock out the axle and armature assembly. With an appropriately sized tube, the bearing was then knocked out from the inside. This was done carefully to avoid damaging the bearing. I should say, damage the bearing further, since I already suspected that it was damaged. 

The two pictures of the armature show the axle and commutator. I later cleaned the carbon from the commutator and saw that it was in good condition. The bearing seats on the shaft up against the top washer. When disassembling prop pitch motors it is critical to take note of where the washers and shims came from so that they are put back in the same place during reassembly. A mistake can damage the motor when it is run.

In the 12 volt motor the brushes are at the top of the motor; they are at the bottom (drive side) in the 24 volt motors. You can see how the wires are routed to the field coils and brushes. The brushes appeared to be in good condition so I cleaned the interior as well as I could and set it aside. I filed down metal spurs on the exterior that may have been caused by rough handling in the past. That was done mostly for aesthetics and to avoid skin damage during handling. It also made it easier to slip the motor cover on and off.

Motor bearing

My attention next focused on the motor bearing. The symptom when it was on the tower and not turning was excess resistance to manual rotation of the motor axle. An application of modest force freed the axle and the motor worked again. When it happened again my friend brought it to the ground. This is not the first time I've dealt with bearing trouble in a prop pitch motor so I proceeded with the confidence of experience.

Since there was no sign of mechanical scraping or other damage on the armature or field coils the problem had to be in the motor bearing or the gearbox. A bearing or gear failure in the gearbox typically doesn't result in locking the motor axle. The reason is the high reduction ratio. It usually takes several rotations of the gearbox axle to take up play in the many gears before it locks up. Since the gearbox axle turned smoothly, even after the low temperature test mention earlier, the bearing was the primary suspect.

Turning the bearing by hand was smooth. At least it was at first. Eventually I noticed an intermittent roughness. I tossed the bearing in the freezer. When I retrieved it an hour later, he imperfection was pronounced. There was also a small amount of play between the inner and outer sections that indicated worn balls.

I found a compatible modern bearing for the "201" shielded bearing by perusing my catalogues. It is the same as the top bearing for the 24 volt motor. The old 201 has shallow concave races that do not support axial loads; that is, it works best as a thrust bearing. The 6201 double sealed replacement is a deep groove bearing that is suitable for high axial and radial loads at speeds greater than that of the motor. I ordered two so that I can replace the ancient top bearing on one of my 24 volt motors.

You can see the difference between them in the picture above. The larger surface of the inner section is handy for firmly securing the aluminum arm that contains the magnet for a reed switch. My friend has a Green Heron controller for his other prop pitch motor that supports this arrangement, but for direction indication with this motor he uses a 4O3A compass on the antenna. 

I use 10:1 potentiometers for my chain drive and upside down prop pitch motors. There are many ways to accomplish direction indication for prop pitch motor rotators. There are both commercial and home brew solutions.

Reassembly

Installation of the bearing highlighted a curious aspect of the design. Since it is installed from the top there is no resistance to axial force pushes it upward. Normally this shouldn't be a problem since the bearing should only experience radial loads. 

The method by which the direction indicator bar and magnet (parts visible at the lower right) were mounted on the axle prevented vertical migration of the bearing. In the 24 volt motor, both motor bearings are pressed in from the inside so they cannot move. 

After pressing in the bearing I pushed the axle and the attached armature into it from the open bottom end of the motor housing, taking care to have it seated against the axle washers. There is a flange on the axle that seats the washers and bearing in their correct positions. 

I had difficulty aligning the blade on the motor with the socket on the gearbox. It isn't as easy as one might expect because there are two pairs of items to align: the axle blade and socket, and the key on the gearbox body with the notch in the motor flange. What makes the task particularly difficult is the near press fit of the motor into the gearbox housing and lining up those two mechanisms must be done blind; all are invisible when the motor is pressed into the gearbox housing. Another complication is that the wires have to be inserted through the gearbox holes during this procedure, and they can't be twisted far while pushing on the motor and axle into their respective slots. Needle nose pliers come in handy.

One solution to the alignment problem is to mark the motor and gearbox and lining them up during assembly. That might work if the motor axle is simultaneously oriented correctly. After fussing with it for 10 minutes without success, I tried another method. I removed the armature and axle assembly, seated it on gearbox axle socket and then pushed on the motor housing. I did it with an aluminum tube that fit over the axle and rested on the bearing surface (not the rubber seal!) and tapped it downwith a rubber mallet. When the motor flange struck the key it was easy to slightly rotate the motor until the key fit into the slot since the axle blade and socket were already engaged.

In retrospect, it would be easier to put the bearing aside while the armature and motor housing are installed. That avoids dealing with the press fit of the bearing while simultaneously aligning the axle and key. The bearing can then be pressed in over the axle into the motor housing.

Test

The P and Q wires are to the right in the adjacent top view. One of those is common and other is not used. Which it is depends on whether the motor is right-handed or left-handed. The R and S wires are close together on the left side. One is for CW (clockwise) and the other for CCW (counter-clockwise) rotation. Only the slots for the R and S wires are imprinted on the gearbox housing.

My initial tests with Astron 13.8 VDC linear power supplies failed. The crowbar protection circuits of the 10 A and the 25 A supplies shut down the power due to the high starting current. The protection circuit acts too quickly to permit the motor time to start. I inserted a high power resister of a few ohms in series with one lead but that dropped the voltage too much to operate the motor. It wouldn't turn at all.

I tried the same setup with a 24 VDC power supply and the same thing occurred. I dispensed with the resistor and the motor came to life. I didn't leave it running for long since the higher voltage could stress the motor. DC motors can often run quite well at lower and higher voltages than specified, provided the motor will start (low voltage) and not run too hot and fast (high voltage). Hams in decades past used this "feature" to vary prop pitch motor speed with a 120 VAC auto-transformer (e.g. Variac) on the primary side of the power transformer

My small multi-meter didn't fare well on its 10 A scale during these tests. Something sparked but it still seems to work afterward. They're cheap to replace so I was not too concerned. As you can see on the meter, the clip leads themselves lower the voltage at the motor from the approximately 26 volts measured at the power supply. The wires get quite warm, more than on the 24 volt motors I've tested. That makes sense since P = EI and the power consumption of the 12 and 24 volt motors should be similar.

My friend uses narrow gauge wire up the tower to lower the voltage from his 24 VDC power supply. It also cheaper than larger conductors! I know that he measured the current as 7.5 A, but the voltage at the top of the tower is unknown and probably has never been measured.

Although my friend doesn't need it, I plan to remount the aluminum bar and magnet on the motor axle. I prefer to have it there for two reasons. It can be used as a handy lever to test freedom of motion of the motor and gearbox, which is how my friend used it to discover the intermittent bearing problem. The other reason is for insurance against the bearing working loose. Although the risk is low, it is easy to prevent. I will change the hardware since the lock washers previously used put uneven stress on the bearing. The bearing is strong but that is no reason to take an unnecessary risk.

Conclusion

The motor will likely be reinstalled on my friend's tower later in the spring. I'm hoping that it will now work well for him. He had pretty much given up on the motor before I offered to work on it.

I hope you enjoyed this tour of a rare variety of prop pitch motor. I doubt that I'll ever see another like it. If you come across one, you now have an idea of what to expect.

Eclipse Science & Amateur Radio

What is science?

Science is a process for understanding our natural world, encompassing fields as diverse as particle physics and biology. Science is memorizing or listing facts. Data (empiricism) is critical for developing and testing scientific theories. A robust scientific theory explains the data, makes testable predictions and is falsifiable.

Quite a lot of science will be done during the upcoming April 8 solar eclipse. A portion of what is planned to be done by amateur radio operators is science. There is overlap between the two which is quite interesting. Which is, measuring the change of the virtual height of HF reflections as the ionization density first declines and then recovers during the full 3 hour duration of the eclipse. Rockets will measure the ionization profile over a long vertical path while hams and professionals sound the ionosphere at various frequencies.

Almost everything else hams will be doing is not really science. That may sound unfair so I'll explain my position.

Imagine that, like Galileo, you roll balls down an inclined surface to measure the acceleration of objects due to Earth's gravity. This was fairly innovative at the time and he was able to generate data good enough to generate theories about gravitational action on bodies. The experiments were repeatable, the measurement error bars reasonably good, and the theory was falsifiable. That's science.

If you repeat these experiments today, are you doing science? In my opinion, no. Although that statement may seem to be inconsistent with what I said above, it really isn't. Many centuries have passed since those early experiments. The quantity and accuracy of data gathered from countless experiments over the centuries has generated increasingly excellent theories of gravitation and related field of physics. 

Should you perform Galileo's experiment now, the data gathered will be paltry and of woefully inadequate accuracy. You will discover nothing that is not already known, and any differences will be attributed to experimental error or large error bars.

Operating during the eclipse and observing propagation is very interesting and should be encouraged. However, other than for the very precise sounding experiments there will little of note added to the tome of science. The data collected will tell us very little or nothing that we don't already know. Just like redoing Galileo's experiments with rolling balls down an inclined surface.

If it isn't science, what is it? It's a combination of science education and perhaps entertainment. Considering the woeful lack of science awareness in our science-dependent civilization, public education has value. How much of that education makes it out of the relatively cloistered amateur radio circle into the public consciousness may be underwhelming. That would be unfortunate but hardly surprising. I can only hope that organizations like HamSci can raise public awareness. 

As for myself, my radios will be turned off. I live in the path of totality and the weather forecast is promising (as I write these words two days before the big day). Where I live the duration of totality will be a little less than 2 minutes. That increases to about 3 minutes directly south on the shore of the St. Lawrence River. I gain about 2 to 3 seconds of totality for every kilometer travelled south from my QTH. Crossing into the US isn't worth the trouble since travel to the shadow's centre only adds another 10 to 15 seconds.

I have friends planning to visit to view the eclipse. Since the zone of totality eclipse ends about 15 kilometers to the north, many people will drive south for the event. If plans change and they don't come over, I'll probably trek south to gain that extra minute. I know several obscure parking areas where I can do that without battling the massive crowds that are expected. The experience is better in a crowd but I don't want to waste the entire day since I'd have to leave early to find a place to park.

This is not my first solar eclipse. When I was a child there was one that passed through northern Manitoba. It was partial where our family lived in Winnipeg. My father smoked bits of broken window glass for us to look through. Yes, that's a terribly dangerous way to view a partial eclipse but what did we know. I just remember how wonderful it was. 

The experience left an indelible impression on me and kindled my lifelong interest in astronomy. I still wonder whether I ought to have made that first love my career. I'll never know. After that first eclipse I pored over astronomy books in the local library. I discovered that Winnipeg would be on the path of totality during an eclipse in 1979. What luck! But when you're 6 or 7 years old that's an incomprehensibly long way off. It was always in the back of mind as I grew into adulthood.

The years ground on and February 26, 1979 finally arrived. It was my final year of university in my home town of Winnipeg (VE4). The Canadian prairie gets a lot of sunny days during winter but it is very cold. The administration opened the roofs of many of the buildings on campus and that's how many of us viewed the eclipse. It was fun but cold: about -20° C with a mild breeze. As the Moon crept across the sun the temperature dropped. We'd duck inside occasionally to warm up.

It was an awesome experience that I've never forgotten during the following 45 years. That eclipse occurred near the peak of the solar cycle, and it was a big one so a lot was going on (on the sun and on 10 and 6 meters). During totality there was one very large prominence and a few smaller ones scattered around the solar disk. Many stars were visible as our eyes adapted to the dark. Totality lasted only a couple of minutes although I don't recall the exact duration where we were. It was long enough for a thoroughly amazing experience.

It is well worth the trouble to travel to view a total solar eclipse if none comes to you. I've found that most people who've never seen one don't appreciate what they're missing. Once you experience it you'll understand how worthwhile it is to make the effort.

I can only hope for clear skies and a prominence or two on April 8. I may update this article after the eclipse. Is viewing an eclipse science? No. It is educational and entertaining, and that's good enough for me. I'll put amateur radio aside for that one day. Hams not in totality's path may enjoy monitoring the bands to discover its effects.