Solar CDX

Return to Lamb’s Knoll

Three years ago, I paid a visit to Lamb’s Knoll Summit in Maryland (as detailed on this very blog). At that time, I went up the Appalachian Trail to the summit with a handheld to test my VX8GR handheld and a 70cm hand-held yagi. I verified that I could hit the VWS 2 meter and 70 cm repeaters in Virginia even with the Comet SRH320A antenna, a short whip. I also checked out possible operating positions and access paths with the intent of returning at some point for a SOTA activation. I also verified that from the summit I had good cellular connectivity and could hit a bunch of APRS digipeaters. Today I returned with my FT817 and activated the peak, W3/WE-007.

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QRV USA

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Field Day 2015. The 40m CW tent and its plastic cocoon. In the background: a ground-hugging hexbeam awaiting better weather for extension.

I’m back in the US for about a month, part vacation, part work. Stop one was field day with the Vienna Wireless Society at Burke Lake Park in Virginia. After that, I joined the family first in New Jersey and now in Montauk, New York. I’ll be in Montauk through around July 12th and then back and forth a bit to Washington, DC. I have a week of work, from July 20 to July 27 in Bethesda, and then the last few days in Indianapolis to attend GenCon.

Field Day was as always enjoyable, but this year particularly wet. I arrived less than 48 hours before the event, so I was still on Madagascar time, which helped with the late night operating. On the Thursday before field day, I was driving all over the place to catch up on shopping, including a visit to Ham Radio Outlet in Woodbridge, VA. On the way back, I passed the field day site and noted that a huge tree had been chopped down. This tree is right in the middle of the field day site and was traditionally used for antennas in the past. It had a number of dead branches last year (I’m not blaming RF) and the park authorities decided that it represented a hazard. Consequently, the antenna plan needed some rearrangement.

On the Friday of field day weekend, I showed up around noon to Lee’s (KD4RE) house to see if I could help with antennas. He was in charge of both food and antennas, but had simulated some designs in the previous week, so I followed his drawings and put together wire and PVC spreaders for a 20 meter and 40 meter vertically polarized delta loop. In the past, we’ve had some issues with interstation interference, so the idea was to cross polarize the various antennas where possible. The 40m was used by the 40m SSB station and the 20m by the GOTA.

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Oh noes. That was the antenna tree.

Antenna deployment was slowed by heavy rains on Friday. In areas near the park, roads flooded, rivers overflowed, and our simulated deployment came nearer and nearer to being an actual deployment. We got most of the antennas in place including a huge 40m moxon, but left the hex beam and spider beams just above ground level because we were worried about wind. Additionally, we were liberal in the use of plastic sheeting to supplement the weatherproofing of our tents, particularly the network operations tent, which already had equipment in it on Friday.

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A LeeCAD rendering of the 20m delta loop.

The next morning was sunnier, but the fields (and our shoes) were saturated with water. The antennas went up, with extra care to secure ground guys to either very large stakes or other fixed objects that would hold in the muddy soil. By the start of the event, 14.00h, the four HF stations were ready to go. In addition, we had the GOTA, a VHF/UHF and a satellite station in the field. GOTA attendance was somewhat down due to weather, which cut down on foot traffic through the park. We did not succeed in the satellite contact; we heard the ISS APRS beacon, but no one was operating from the station. Otherwise, the timing of the couple of operational FM birds was not favorable. Almost all of the contacts made were HF, although we did get in a little 6m activity at the end.

Field Day was successful in a number of ways: as always, a large club turn out despite the weather. There were many new (to me) faces at this year’s event, so that bodes well for the general health of the club. At least one CW and one SSB station stayed on the air around the clock. Finally, the club maintained its tradition of gourmet food — amazing steak, pulled pork, chicken, beans, potato salad, hamburgers, hot dogs, eggs, sausages. No one went hungry and the calorie/QSO ratio remained strongly positive.

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The girls on vacation. AI4SV/MM.

After FD, I drove up to Montauk, threw a rope in the trees and set up shop on an elevated porch with my FT817. I tested the set up in the Canada Day event on July 1st. In an about three hour period, I logged 51 QSOs, mostly CW, but seven were SSB. For provinces, I got ON, QC, MB, BC, SK, NL, NB, and NS. Since everyone can work everyone in the event, I also picked up a few stations from even further over the pole: Belarus, Ukraine, Czech Republic and Slovenia. A 5Ah battery lasted the whole operating period, as I was mostly S&P, although I did get a handful of replies to CQs.

Since then, I’ve operated sporadically, both CW and voice. I had forgotten how useful 40m is, since that band is next to useless at my QTH in Madagascar due both to noise and lack of close-in stations. In the last few nights, though, I’ve had very clear contacts to the west coast on 40m.

 

 

Reading a rotary encoder with ATmega328

There are a bewildering number of examples, libraries, and opinions about how to write routines to read values from a rotary encoder. I found one that that looked particularly elegant and easy to generalize, so adapted it to the Atmega328 that I’m using for my current project. I used a pretty popular rotary encoder, Adafruit #377, although I think the demo code would work with other quadrature encoders.

Most of the work in done in a relatively light interrupt service routine that receives information from both directional pins on the rotary encoder. I did not do any addition software or hardware debouncing and I didn’t notice any jitter or erratic behavior.

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The Antananarivoduino

Blue LEDs make everything more spiffy.

Blue LEDs make everything more spiffy.

With wintertime (and remember, it is winter where I am) comes soldering – I can spend more than ten minutes in the garage without being drenched in sweat. I have a three week travel break before going on summer leave, so I’m trying to wrap up various projects. I have one project breadboarded and wired up to my arduino duemilanove, but I needed another arduino to work on another project in parallel, so I built one up on perf board: the Antananarivoduino.

The Antananrivoduino is about a simple as I could make it: an ATmega328, 16Mhz crystal oscillator, and 5V power. The one frill I added was a 28-pin ZIF socket that I’ve had kicking around for a couple years. The socket lets me seat a chip, program it, and eject it. It’s ideal for cranking out copies of a project or a burning a final chip that will go into an embedded project and won’t need any more programming.

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Solder Fan

IMG_20150528_144840 IMG_20150529_201936 IMG_20150529_201958 IMG_20150529_202007This project arose from a sudden desire to stop inhaling solder smoke. I just got back from about three weeks of constant travel around Africa with a bad head cold, cough and sore throat. After being away, I was itching to solder up something, but didn’t want to push myself any closer to bronchitis. The solution: a fan to waft away the solder smoke.

I had a bunch of waffle fans removed from computers, but some of them proved very wimpy. One in particular was super-quiet and drew about 200 mA, but was barely able to move air. Since more is always better, I dug into the junque box and pulled out a bunch of fans that I have removed from a commercial server. They were small, but powerful. Alone, each drew about a half amp and when plugged in a 12V battery (or tapped into the bench’s 12V supply), would vibrate themselves around the table. If one fan is good… four is even better.

I created a wood frame with some channels made from angle aluminum. Since the metal impeller blades are like little razors, I stapled metal mesh over both sides. After assembling the whole thing, it occurred to me that all the fans should face the same direction. Luckily, the wood glue hadn’t set by that point, and I was able to disassemble part of the frame, flip around a couple fans, and screw the whole thing back together.

With four fans running full speed, this thing is loud and produces almost enough thrust to take off. So, the interesting part of this project is not the fan itself, but the fan controller. Any sort of rheostat or linear device that would ramp up or down the drive voltage would be very inefficient and produce a lot of waste heat, so I went with a variable pulse width modulator. Rather than reinvent the wheel, I used a design described on the PC Silencio website. Two sections of the quad op amp create a triangle wave, another serves as buffer for a voltage divider, and the final section serves as a comparator to slice off the triangle wave at the level set by the voltage divider. The threshold determines the duty cycle of the generated square wave, which drives the motor at full voltage.

I didn’t have a LM324 in DIP14 layout, so I substituted a TLC271 op amp, which worked fine. For the n-channel MOSFET driving the motors, I went with an STP16NF06 (my old standby, used in previous projects such as the TEAPOT and Texas Topper Amplifier). Regardless of setting, the mosfet remains cool since it’s essentially either on or off and not hanging out in the linear range at all.

In practice, running the fans at near the lowest setting works fine for pulling away smoke from routine soldering. Since the question will inevitably arise — I should mention that in order to solder together the fan, I used a breadboarded version of the PWM circuit to run the fans so I could solder them together — thus getting around this bootstrapping issue.

Internet backup power

About the time I am wrapping up in the office, the sun has risen and people are getting into work on the East Coast of the United States. I leave early enough to get home so I can make teleconferences that start at 9 Eastern. I’d have quite a phone bill if I dialed direct, but fortunately, I can make most of these calls over the internet. Although Madagascar is a developing country, we have fiber to the house. The upstream connection isn’t entirely stable, but it is up most of the time, and throughput is surprisingly high. However, I still run into problems when the power blinks off.

The ISP has adequate backup power to maintain the connection, at least for some time, so this is my problem in the house. The house too has a backup generator, but there’s a couple seconds to shift over from mains to generator and vice versa. In that time, the houses’s router goes down and takes a minute or so to reboot every time power switches over. What’s needed is a UPS, but the smallest computer UPS here runs around $150. Also, it seems like a UPS is massive overkill when the problem is just to keep a router happy for about a minute.

I have a good stash of small lead acid batteries for portable ham radio use, and it occurred to me that I could probably use a couple in backup power supply projects. At this point, I’ve come up with two designs built of materials squirreled away in my garage. Schematics are below the cut for anyone interested. Continue reading Internet backup power

Concours IF 2015: Sourire

15391458183_f602481b75_o“Sourire” s’agit d’une courte histoire racontée du point de vue d’une marionnette. Vingt-quatre commandes — 19 de spécifique et 5 juste pour passer le temps — suffissent pour atteindre la solution. Néanmoins, j’ai bloqué quelques fois et de temps en temps j’ai eu besoin de jeter un coup d’oeil au walkthrough.

C’est un imposant défi d’écrire une IF dans laquelle le jouer est littéralement pendu des fils et presque immobilisé. Le joueur apprend immédiatement que ce n’est pas possible de se déplacer dans les directions cardinaux. D’ailleurs, il n’y a beaucoup de voir est les objets vus sont hors de portés du joueur. Qu’est-ce qu’on doit faire? C’est un bon commencement, pourvu que le joueur ne devient pas frustré après quelques tentatives de faire avancer la scène.

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Visit to Zambia

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Flooding in Madagacar after the most recent cyclone.

This year’s cyclone season has been unusually severe – folks in Madagascar are telling me that it is the worst one since around 1959, particularly from the perspective of the central highlands. However, most of the precipitation has been on the coasts, where towns are literally underwater. Storm systems tend to form over Mozambique, intensify in crossing the channel, land forcefully on the west coast of the island, cut across it, and continue into the Indian ocean, either eastwards towards Réunion or shifting towards the south. Along the way, the storms dumped enough rain to entirely saturate the soil in the first month or two. Now, there is nowhere for the water to go, and it is overflowing dikes, bursting dams, and causing mudslides. Before the rainy season, the government was struggling to keep the wobbly national infrastructure working, but at this point, it is struggling to maintain basic services such as electricity and road maintenance. Continue reading Visit to Zambia

2015 ARRL CW DX

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If North America were a toroid, one could pass the windings through the Dakotas.

Having recently put up the G5RV, I gave the ARRL DX CW contest a shot this past weekend. The antenna is up only about 10m and is not resonant on 15m, but it has performed well on 10 and 20m in the past. On the first night, 10m was very quiet, but activity on 20m was brisk, particularly in the early morning hours when I was working two calls per minute.

In principle, 10m should have been open starting the in mid-afternoon on Sunday, but it was slow until around dinner time. Again, 20m was my main band, despite having mostly mined it out the previous day. I managed to get a few contacts on 15m, and even fewer on 40m, where local noise was a problem.

I didn’t stay in the chair the full time, even when I had favorable North American windows. I had to disconnect the antenna for some time due to thunderstorms on Saturday afternoon and on Sunday evening I had a guest in town and went out for dinner. Still, I am happy with the number of contacts I made given my conditions.

I worked a few states that I hadn’t such as Vermont, Rhode Island, Delaware, West Virginia, Nevada and Wyoming — hopefully, those stations will QSL via LOTW. I heard a North Dakota station, but barely, and he was drowning in a pile up. Maybe I’ll take another shot when Sweepstakes or some other convenient contest rolls around and I have the hexbeam up.

My final tally:

Band QSOs Mults
40m 7 4
20m 418 52
15m 18 13
10m 56 26

3A/AI4SV Reverse Dxpedition

Sunset in Nice.

Sunset in Nice.

Living in Madagascar, I have enjoyed operating from a sought after DXCC entity; little did I suspect the same would be true on my recent trip to Europe. I packed along the FT817 on a trip to Nice, France, where I attended a business meeting. I had picked a hotel with an open 8th floor deck and hoped to string up the end-fed to operate in the evening. On the way out the door, my wife asked me, “so I don’t suppose you’ll have any time to visit Monaco, while you’re there?”  I have to admit that I hadn’t really thought about it, but as soon as she mentioned it, the gears began turning. I had meetings in Nice and Lyon, but some free time on Saturday before flying out. On the way to the airport, I double checked that Monaco was a signatory to the CEPT convention.

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