Author: Jack

SOTA: GM/SS-280, North Berwick Law

Entering North BerwickLast month, I spent about two weeks in the UK with my daughter Lara looking at universities. We put about 1800 miles on the rental car and visited schools in England, Scotland, and Wales. Originally, Scotland wasn’t on the itinerary due to time constraints, but we ended up not only visiting the University of Edinburgh, but activating a summit just north of Edinburgh in North Berwick.

Easter weekend was right in the middle of the trip, and I had picked that downtime to visit the Isle of Man. By that part of the itinerary, we had already gone north to U. Nottingham and then west to Bangor. Along the way, we routed through Macclesfield to visit SOTAbeams and picked up a ten meter fiberglass travel mast and some other kit.

From Bangor, it wasn’t too far to Liverpool to catch the ferry over the Isle of Man. Unfortunately, the ferry hit the pier in Douglas the night before our departure. When we got to the ferry terminal on Friday morning we were told that the ferry was temporarily out of commission. I spent the next half hour tapping away at my phone in the ferry terminal car park, calculating what other interest places we could reach and then booking a hotel in North Berwick. In the back of mind, I was hoping to get on the air as MM/AI4SV, but I didn’t have any SOTA peaks in mind.

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HMS Belfast – GB2RN

IMG_20160322_101315I’m just back from visiting the UK with my daughter, Lara, who will be applying to universities there this Autumn. In a two week tour, we put 1800 miles on our rental car. I had some chance to play radio along the way, but our itinerary was so packed that I’m just now putting the details on the blog. Let’s start with the visit to the HMS Belfast, which is anchored on the Thames between Tower and London Bridges.

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Variable Power Supply

boxedUpI’ve been focusing on power supplies and related equipment lately because I don’t have a lot of bench gear. On one hand, I would like to build equipment from scratch, but on the other, it would be crazy not to look at some of the building block modules available on eBay and other outlets. I could not beat these prices, even if I built just about entirely from scrap. Using modules rather than homebrewing down to the metal seems like cheating, but it not only saves time and money, but often yields better performance and miniaturization.

So, this project consists of building a bench top power supply from three modules: a switching power supply that puts out a constant voltage, a DC/DC converter, and a combined voltmeter/ammeter. The combination is based on a youtube video by GreatScott that made use of a cheap DC/DC converter based on the LTC3780 that is being sold by various vendors  at a bargain price on eBay. Some of the same vendors are also selling a red and blue volt/ammeter. There are a few variations of the meter, I selected one rated for 100V and 10A and which did not require an external shunt resistor for current measurement.

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ATX Supply

supplyFrontRemember that ATX power supply that I fried last year? I replaced it with another mail-ordered supply and then it sat on the shelf long enough for me to get around to fixing it: a new regulator, some MOVs, a cap and the fuse, and it was ready for action — except I had no computer to install it in. I kind of doubt that I’ll build another tower form-factor computer, so I turned it into a high current bench power supply.

It has to be more than ten years since I’ve done this, and I believe the last time I didn’t even have an ATX supply. At that time, supplies needed a hefty load to get going and remain stable. I recall using a car headlight. Literally: an old-style (maybe halogen?) automotive headlight. I reviewed a couple videos on the subject to see what people were doing with more recent supplies and found one that I liked and more or less followed.

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Soft latch

I liked the circuit so much I made two of them. Here's front and back.
I liked the circuit so much I made two of them. Here’s front and back. The one on the left has an extra electrolytic cap; its addition did not affect the switching circuit at all.

Catching up on the bench back catalog: here’s a useful little module – a soft latch that isn’t finicky, works when you first plug it in, draws effectively no power when not changing states, and operates over a relatively wide range of input voltages. What’s not to like?

The basic idea is that mechanical switches, even simple toggles, are much more expensive than push buttons. It would be nice to be able to push a cheap push button and have it turn devices on and off. Some bad ways to do this would be to have the circuit twiddling its fingers, burning power, waiting for button presses – for example, having a microprocessor down stream of a voltage regulator idling until it detects a change in state on the pin connected to the push button. Sure, the microprocessor could be throttled down in some energy-saving mode and might only consume microamps, but the upstream voltage regulator would be consuming power, certainly true for linear regulators, and to a lesser extent for switchers.

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Back to the bench: 7 segment display

Three 4-digit displays: red, yellow, and green.
Three 4-digit displays: red, yellow, and green. Ew, shiny pads!

Since the SOTA genie escaped the bottle, the blog has leaned towards operation rather than bench work, but rest assured that projects have been percolating in the background. Here’s an update on a few of them: a custom LED display, a soft latch circuit, and a high-current converted ATX power supply. Let’s start with the LED Display.

For an upcoming project (actually, one that was moth-balled last June, stuck in a butter-cookie tin, and just recently again saw the light of day, followed by several days of pouring over notes and head scratching to remember where I had left off), I needed an LED display that would show voltage, amps, and power. Sure, you could figure the power out from the amps and volts, but I wanted it to change in real time to give me feedback while I make adjustments.

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SOTA W7A/WA-010: Mingus Mountain

Sorry, Amateur TV folks, you are out of luck in this park.
Sorry, Amateur TV folks, you are out of luck in this park.

You would think that with a name like “Mingus”, it wouldn’t really be necessary to specify the SOTA designator — but you would be wrong, as there is also a Mount Mingus (W4T/SU-008) in the database. I’d assert that my Mingus is the One True Mingus. I don’t know if there is any technical difference whether something is named Mountain versus Mount, but I would like to think there is, and that the one I climbed was the real deal: my first ten-point summit. We just don’t have mountains like this in the Mid-Atlantic region.

I had initially missed Mount Mingus because of a peculiarity of the Arizona association’s database. Initially, the state was divided into two regions, east and west. Mingus is in the west part. Later, they when more states were added, additional regions with tighter geographic scope were created like North and South Maricopa around Phoenix. I had wondered why some mountains appeared to be missing in the regional databases. Now I know.

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SOTA: W7A/MS-065 Goat Hill

goatViewTowardsSuappoaGetting to the top of Mount Suappoa wasn’t too bad, since it’s mostly a matter of following a paved road. For the same two activator points, Goat Hill was much more of a climb. As mentioned, both peaks are in South Mountain Park to the South of Phoenix. In fact, in the picture at right, you can see antennas on Suappoa.

The aptly named Summit Road winds through the park and cuts across Ranger Trail which leads up to Goat Hill. It looks like Ranger Trail is used by both hikers and those on horses, and that some begin lower down on the trail.

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SOTA W7A/MS-048 Mount Suappoa

suappoaTowersSince I was only in Arizona for a short time on this trip, I didn’t attempt to acclimate to the local time zone, I just let me biological clock freewheel. The night before this outing, I had gone to bed at 6:30 in the evening, which seemed just fine to me. The flip side of this was then waking up around 3 am. Instead of forcing myself back to sleep, I just started my day. I got some work email out of the way and then began looking through peak information. I found two peaks that had been previously activated, seemed like reasonable climbs, and which were near each other, both in South Mountain Park.

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SOTA W7A/MS-050: The road not taken

lookoutMt-sideI have a few more SOTA adventures to report, the most recent from a brief trip to Arizona. During that trip I visited three peaks, but I wanted first to write about Lookout Mountain, W7A/MS-050. I had reviewed summits on the SOTA database before the trip and thought that this peak was a good candidate, particularly since it has never been activated.

When I flew into Phoneix it was early in the day — too early to check in, so I pointed the rental car towards the mountain. I took 16th Street south of East Greenway up to a parking lot at the base of the mountain; this is the start of Trailhead #308. There is a sign there with some topographic maps and information about environmental hazards.

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