Significant Other Power Supply

Initially, I hadn’t given the power supply for the Significant Other project too much thought: I was more focused on the microcontroller, relays, and so on. After going for maximum efficiency with these components, though, it began to annoy me that it would be very wasteful to use an LM7805 regulator to bring lead acid battery voltage (13.8V) down to something that all the chips and relays could use (5V). The LM7805 tosses out the difference in heat, and while at the low currents that I need that doesn’t amount to much power — certainly, not enough to require heat sinks — it goes against the grain of QRP. If you have to haul a battery up a mountain, you’d like it to last as long as it can.

So, I started looking at more efficient (and lighter) means of powering the unit. The design I selected allows for two options. First, two AA batteries will fit inside the unit. Building them into the case assures that I can’t forget them. One of the goals of the SO project is to avoid unpleasant surprises while setting up the station in some remote location.  Since the unit draws so little current, I’d hope that a pair of AA batteries would last quite a while in field use.

Since radios are made to work from 13.8V sources, this is the other acceptable power input. The unit will be built with dual powerpole connectors, so that even if the battery has a single powerpole, it can be plugged into the unit, which effectively replicates the plug, so the radio can also be plugged into the unit. Even if the radio is greedy and pulls power from the battery causing the voltage to sag, the power regulator should cope with anything down to about 7.5V. If the lead acid battery gets that low, it’s probably toast anyhow.

Getting 5V from a 3V source requires a switching power supply, which could be a problem for a radio project since the switching happens at frequencies in the hundreds of kilohertz range. The LT1302-5 chip that I used in this project does not oscillate at a specific frequency, but is variable, and has the potential to produce RFI over a broad range of frequencies.

I followed the datasheet for the 1302 and built a “typical” supply using available parts. Layout is fairly critical, and I did my best to port their suggested PC board layout to manhattan construction. I didn’t have a 20k resistor, so I went with a 22k. I didn’t have any particularly low ESR electrolytics, so I used ones regular ones, etc. It seemed to work anyhow.

For testing purposes, I ran the power supply with a small load next to my FT-187nd, which was connected to a dummy load with cable that was unshielded for several centimeters. Within the ham bands, the only places I heard hash were on 160m and 80m, and even there, it only seemed to be around a couple frequencies. I had originally built the supply with a 10uH commercial inductor wound on a solid core. To limit EMI, I tried replacing this with an equivalent value hand-wound toroid (45 turns of 28Ga on a T50-2). This brought the noise level way down, and I couldn’t hear it when the antenna run was a couple cm away from the toroid. I suppose I could put the power supply in its own metal compartment, but it’s probably enough to just keep the RF path away from it in the layout.

Getting the right combination of bypass and charge-holding capacitors and discharge resistors is a bit empiric, and I’m not sure I did an optimal job, but I got out the voltage that I wanted. When connected to the oscilloscope, I noticed a periodic ~50mV spike that I thought could be a problem down the line for the microprocessor, so I borrowed a low pass filter from a similar project, the power supply in the Norcal 2030. I again had to substitute a bit — I think the filter inductors came out of an old TV. With that filter in place, the voltage is completely smooth as far as I can measure.

The two power supplies are connected by wire “OR”ing them together. The LT1302 senses 5V distal to a Schottky diode, but putting a diode after the higher power supply means that the voltage prior to its diode must be about 5.3 volts. To get that value, I used an LM317 and selected specific resistor values for its feedback network. The LM317 needs a small load to stabilize, so for the prototype, I threw in an indicator LED that lets me know when the high voltage supply is in use.

When the high power supply is active, it pulls up the LT1302 shutdown pin, which turns off the up-conversion. Without all that switching action, the voltage on the toroid side of the diode should be that of the AA batteries. This means that with the higher power supply active, the diode in the lower power supply is reverse biased and no current flows through it. This should mean that the unit can hot-switch between onboard and external power.

The prototype was a little smooshed because I had originally intended to only build the LT1302 circuit on that piece of copper clad board, and then I added the filter, and finally the 13.8V supply.

The real test of this supply will be whether it makes the other components happy.

Sky House: Arrival

view south towards the Pacific oceanThe Nerkspedition to Sky House is underway. We arrived in LA a couple days ago and drove up the 101 to around San Luis Obispo yesterday. The final road to Sky House is a long, winding dirt road that hairpins its way up a mountain to a fabulous house that overlooks neighboring mountains, Morro Bay, and the Pacific Ocean. Most of the first day was spent getting everyone unpacked and settled.

Earlier today, I set up the FT817 for local repeaters in San Luis Obispo and Los Osos. No problem hitting them with full quieting from the top of the mountain, but not a lot of activity on them.

Even though this is the IARU World Championship weekend, I didn’t bother setting up for HF today given the solar activity: strong wake from a CME and an intensely south vectoring magnetic field. By report, the bands were pretty dead earlier except for sporadic E on 6m later in the day.

I’m hoping tomorrow will be better, so I tossed the 40m half wave dipole antenna into the trees at the top of the mountain. The wire comes down near a comfy chair next to the pool, and if conditions are better on Monday or Tuesday, I’ll give HF a try.

slt plus board with a missing L1 toroidImmediately before leaving for California, I noticed that both my winkeyer and SLT+ antenna tuner had developed rattles. I have to assume that this happened during my last flight back, which had involved a bumpy segment on a regional jet from Reno to LAX. Either that, or the TSA got more curious than usual and looked inside them. The winkeyer was missing a screw and the rest of the screws were loose, but there was no internal damage. For the SLT+, however, L1 had fallen off the pc board. I rewound the toroid and soldered it in while I was packing my bags for this trip and as an extra measure tacked all the coils down with hot glue.

Field Day CW Totals

We’re still assembling the total number of contacts from FD 2012 because the SSB and CW stations were not networked, but here are the totals for the two CW stations. I’d say we hit our goals and then some.

 

The 80/20/10 station

Mhz Contacts
3.5 279
7 304
21 15
Total 599

The 40/15 station

Mhz Contacts
7 430
21 115
28 4
50 1
Total 550

So, our CW total for the event was 1159 contacts. The results from the SSB, VHF/satellite, and GOTA stations and all bonus points should be out soon.

RAC Canada Day 2012

While the emphasis is on working stations in Canada (10 points), other stations do count (2 points), and this year there was more of an “everyone works everyone” flavor to the event. I worked stations from BC to the maritimes, but also a few French, one Netherlands, and one Romanian station. I heard a Brazilian station calling, but he couldn’t hear me.

In addition to working this contest for fun, it was also a test that the outside vertical had survived the storm. Right after the storm, the antenna had more slack in it than usual because the counter weight was resting on the ground. Apparently, a few branches that the antenna had once draped over are no more. I tightened up the support rope and the vertical seems no worse for the wear.

Field Day 2012

Ray, K2HYD at the operating position of the 80/20/10 tent. Hap, K7HAP is at the second position on the laptop, and Byron, W4SSY, supervises

To make everyone’s life easier, we stuck mostly to the plan developed for last year’s event, although I made some effort to simplify the set up where possible. This year, the main rig was a TenTec Omni VII, a radio with clearly marked controls and big tuning knob. Most people could sit down at this rig and be on the air in a matter of minutes without reference to reading material, nifty or otherwise. Instead of three antennas, we went with two: a moxon for westward gain on 20 meters, and a G5RV for all band coverage. The Omni had no difficulty tuning the G5RV for any band that we tried (10, 15, 20, 40, 80).

One major difference from last year is that we did not shut down in the wee morning hours. Both of the CW stations pounded brass for the entire 24 hour period of the contest. We had more operators than the previous year and divided the shifts carefully to assure that at least one person would be at the key all the time. It also helped that several of us brought our own tents this year for quick cat naps. We were all a bit punchy by Sunday morning, but after several cups of coffee, we powered through the rest of the event.

The CW tent is near a busy intersection and more accessible to other parts of the park, so we had a number of visitors drop by the 80/20 tent.  Some of these visitors turned out to be hams eager to put their hands on the paddles, and a few of them racked up an impressive list of contacts and we made sure to invite them back for next year. The more operators we have, the more pleasant staffing becomes. We might even be able to put someone on VHF CW for part of field day next year.

The 20 meter moxon (left) and G5RV (right) supported by a 40 foot military push-up mast, guyed at 3 levels.

Our computer wasn’t fully networked in at the start of the contest, so I don’t know how all the stations did. I have fuzzy recollection that we had around three hundred contacts on 20m and another 300 or so on 80m. We also worked on 15m for a while on Saturday evening, when the 40/15 station had gone to 40m and our 20m operation had been interfering with the SSB 20m station. I’m eager to see the final numbers after all the logs are merged.

One item to consider for next year — is it time to bring an SDR radio to field day? Would a graphic view of the whole band give us an advantage? Would a Flex radio (or other similar radio) play well with the other radios? I like the feel of a big tuning knob and I am used to zipping up and down the band by ear, but that’s all a matter of habit, and if there is better technology, we should consider it. Maybe it would be worth a test drive at some other event before field day 2013.

June mW Sprint

The view west towards mount roseI was sent on fairly short notice to attend a meeting at Lake Tahoe, which is just south of Reno along the California/Nevada border. I had one free evening before the conference, and it just happened to fall on the date of an NAQCC Sprint. I gave serious thought to throwing a wire out the hotel window, but the surrounding mountains called to me. This was not the usual monthly sprint, but the milliwatt version, so I figured that I needed all the help I could get and wanted to take advantage of the elevation.

After some quality time with Google Maps, it looked like Mount Rose was the highest accessible peak in the area. There is a parking lot near the trails that lead to the top of the mountain, but I didn’t think a business suit and dress shoes would fair very well on the gravely slopes. Across the road from the park lot is a campground with picnic tables and tall trees: the ingredients for comfortable field operations. In principle, there is a trail that runs up from the campground to Mount Slide, which, like Mount Rose is a SOTA peak. Again, if I had the right clothing and gear I might have attempted it, but it just wasn’t going to happen this trip. I settled for the 9000+ foot elevation of the campsite.

The view North, down the slopeI tossed a water bottle with a string into a tree, fired up the FT817nd on internal batteries and tuned up with the Hendricks SLT tuner. Before the Sprint, I worked WW0SS in Minnesota on 2.5W. Everything went faster than I had planned, so I laid down on the picnic bench and basked for a while.

I started searching around just a bit before the sprint to get a sense of band conditions. When the sprint started, I alternated between searching and calling. A number of local signals masked the sprint stations for a while, particularly with the poor selectivity of the ft817 (without a filter). I heard quite a few, some of whom were operating at 5W, while others were true milliwatt (less than 1W) stations.

I kept the rig at 0.5W for the entire event, and although I had two small lead acid batteries in the radio bag, I never had to use them. The 817 was running on fumes by the end of the sprint, but I was glad to see that it could make it through two hours of minimal power operation that had included a lot of calling.

All in all, I had six qsos on 20 and 40m. I reported 5 on the NAQCC sprint page because I wasn’t sure the last qso was complete, but I heard afterwards by email from the other station and confirmed that he had, in fact, correctly copied by call at the end of the contest. I think we gave each others 339 for that contact, and I recall that we needed a lot of repeats due to a mixture of summer weather background sounds, QSB and neighboring signals.

I didn’t come close to winning the sprint or even my category, but I enjoyed the scenery and the chance to sign myself as AI4SV/7.

WV Double Whammy

A few days ago, a troublesome area of the sun rotated earthwards and belched forth a stream of plasma meant to make my weekend challenging. A second coronal mass ejection occurred shortly after, with a higher velocity stream in the direction of Earth. Both shockwaves arrived during the West Virginia QSO Party. This K-index histogram covers the period of the QSO Party up to the point that I returned home.

The WVQSOP runs over the whole weekend, but I was only able to join on Sunday. I knew about the CMEs, but figured that I’d still be able to make a least local contacts. I was also hopeful that as the day progressed, conditions would improve.

Since it was also father’s day, Lara decided to accompany me on my mad drive around WV. I had planned a course through three of the northeastern counties: Morgan, Hampshire and Hardy. Looking over reports from recent years, there were some Morgan entries, but not much for Hampshire and Hardy, which is suprising considering that both are near enough to the Baltimore/Washington corridor that it should be possible for hams from those areas to support the event.

My flight plan took me first to the Capacon Mountain Resort, a state park with some really nice facilities, but most importantly, a road that runs to the top of a 2500+ foot ridge. From the observation parking lot at the top, there is a clear shot east and west.

I set up the Tarheel screwdriver antenna and tuned around on 40m and 20m — I heard almost nothing. I know that the car station works okay — I worked Sardinia and the Virgin Islands last night on the way home from work, and I’ve had lots of DX success with the antenna. After about an hour and a half, I had one CW contact on 20m, and one very surprised voice contact on 40m. The voice contact was at least 58 from New York — he said I was the only station he heard on the air, and the feeling was mutual.

The operating location in Hampshire County wasn’t ideal, so I didn’t spend long there, and logged no contacts. I continued towards the VA border and stopped just short, on top of another ridge to get some contacts in for Hardy county. It was getting towards evening (7 pm local / 23:00Z) and 20m seemed to have some life. I worked two more stations on 40m cw, both in Indiana, and one in Kansas on 20m.  So, at the end of the day, what do I have to show for the effort? Five contacts.

Throughout the entire contest, I didn’t hear one other WV station. I had wondered why I had no logged contacts on LOTW, and only a couple that issued physical QSL cards. The low activity seems to be a combination of the number of hams in WV and their level of participation in this contest. Looking at the past logs, it looks like participants from states outside WV dominate the contest.

I’d  like to revisit the Capacon resort this summer for camping or perhaps for next year’s WV QSO Party. The one change I’d make would be a full size antenna. Even if I were to deploy from a car, I’d consider hanging some sort of wire antenna with a tree support and running the cable to the car. The screwdriver is a versatile antenna, but still physically very short.

For next year’s reference, and for anyone else who works the WV QSO Party, I’ve prepared a reference sheet of the counties in West Virginia in a more friendly format that is found on the event website.

 

New Trick: 6 meters

an old dogThis past weekend was the ARRL’s June VHF Contest, and for the first time, I got on 6 meters. None of the HF rigs in the house handle six meters. On Sunday morning, I did try plugging the Yaesu 817nd into my attic antennas, but I wasn’t able to get any of them to tune up (nor would I have wanted to try QRP through a long, mismatched feed line at 50Mhz).

Just for the heck of it, I tried the radio in my car, a headless version of the Kenwood TS-2000. I knew it would work 6m, but I was doubtful that I’d pick up much using my vertically oriented screwdriver antenna from the parking lot next to the house. That parking lot is surrounded by other houses and is line of sight to nowhere. I knew that weak signal modes use horizontal polarization on VHF, so I figured I’d have a pretty stiff cross-polarization penalty and be down 4-5 S units.

To my surprise, I heard a couple ssb conversations, right where they were supposed to be. Their grid locations were next to mine, but I was happy to hear anything. I cranked up to 100w and worked them without a problem. Next, I spun the dial down to 50.080 and started scanning for CW. I pounced on a few signals, got impatient, and ran a clear frequency for the next fifteen minutes, picking up ten additional contacts.

I had a few errands in the middle of the day, and got back into town around 6 pm. I couldn’t do much about the car antenna’s vertical polarization, but I was able to add some elevation by parking on top of the Fairfax Metro Station parking ramp. In principle, I had line of sight to mountains in the Appalachian chain. The car also has a 2m/70cm gain antenna, and I tuned around in the weak signal portion of those bands, picking up a few more ssb contacts, but no cw. I have a feeling that most people were on 6m and that the cross-polarization was a bigger issue at higher frequency.

SD VA MD IA IL DC PA MN TX WI  QC AB SK

Around 7 pm, the 6-meter band seemed to improve, and I starting hearing Canadian stations. In the next hour or so, I worked three provinces (AB, SK, and QC) and ten US states out as far as MN and TX (see the map). I am sure some of these stations had elaborate antennas, and when they would pan away the signal would drop to nothing.

This experience has convinced me that there might be signs of intelligent life at and above 50 Mhz, and that this would be worth doing again, but with better antennas. One option would be to try this contest next time (June or December) from W3NIH, using the 2M/70cm AZ/EL rotatable antenna and the STEPPR for 6m.  Another option would be to head to the mountains and see if I can put together some yagis (maybe combine it with a SOTA activation?)

In other news, I’ve been travelling a lot for work, so I didn’t write up the CQ WPX CW. I hopped in for part of the second day of the contest and logged 273 contacts. Most were entities that I had worked before, although some were on new bands. I did notice a new entity in the LOTW right after the contest, though: Saba & St. Eustasius. I guess it makes sense that St. Eustatius hears well.

 

Scoping Out Lambs Knoll Summit

a topographic map showing APRS pings from Lambs KnollThere are a limited number of SOTA peaks within a short drive of Washington, DC, and most of them, particularly the ones with zero activations,  are on private property. After spending a little time with the SOTA database, I found one promising peak less than an hour’s drive away: Lambs Knoll,  W3/WE-007. The most attractive feature is that it is located on the Appalachian Trail, and as a plus, it is line of sight to the VWS repeater.

A Google Map view shows that the trail winds back and forth, with a road running up the middle of it towards a facility on the peak. Even in the aerial photo, it is clear that there are two large log periodic antennas on that site, which turns out to be an FAA facility. By some accounts, this facility started as a Cold War continuity of government site (designated Corkscrew), but presumably, it no longer performs that function.

I drove to Fox’s Gap, along Reno Monument Road. Just off the side of the road, there is a dirt parking lot. The monument to General Reno and some historic markers are also there. The road leading to the FAA site is marked “road may close without notice”, but the metal gate somewhat up the road does not look like it has moved in recent times. The Appalachian Trail crosses Reno Monument Road and runs through the parking lot and into the woods.

The white-blaze trail winds through the woods and eventually rises towards a clearing, where large high tension lines run down the hill. The trail then continues for some distance and forks, with a blue trail running level, and the white trail continuing upward. The path becomes increasingly steep and rocky. On the day that I went, I ran into a good number of hikers on this part of the trail. At one point, the trail crosses the road to the FAA facility and then continues upward. From here, the ascent is not so steep, though, and the trail wraps around the facility.

An aerial shot fo two log periodic antennas within the compound
Log Periodic Antennas from Google Maps

At the point that I thought I’d have line of sight to Tyson’s Corner, Virginia, I was successful in hitting the 70cm VWS repeater with my handheld at 5W using my Comet antenna. From that same position (the red dot on the above topopgraphic map), I was able to get acknowledgement to APRS squirts from three digipeaters.

After climbing back down, I drove the access road up to the facility. It is a nicely paved road and winds up the hill. At the point where the power lines cross the road, a fence runs along each side of the road, blocking access to the cleared strip of land under the lines. There are gates in the fences, but they are closed. The Appalachian Trail crosses the road higher up, with some minor signage to indicate the intersection.

At the top of the hill, the road splits with the main facility to the right and an emergency vehicle entrance straight ahead. I did not approach the main entrance, but it looks to be  a remotely-controlled electronic fence, probably with a card reader and some cameras. From the front of the facility, I could not see the log periodic or other recognizable antennas.

To reduce the climb time, one could probably drive up the road, drop operators off, and park the car back near the Reno Monument. Park the car along the side of the road is not a good option. The weakness of this plan is that whomever drove the car either has to wait in the parking lot for a “pick us up” call, or has to hike the whole trail — but it would allow the operators to get into position more quickly and have a longer operating day.

There is no indicate of hours of operation along the trail — it is not a park that closes at night, but it is probably best to tackle it in the day time. There may be some sort of camping along the blue trail, although I’d just drive out for the day.

Sugarloaf & QRPTTF

French Bread Loaf, Copyright © 2004 David MonniauxThe weekend was the QRP TTF event, and this year’s rules favored stations that did double duty as SOTA (summits on the air) stations. The Vienna Wireless Society made its annual pilgrimage to Glyndon Park in Vienna, Virginia, and I was sorely tempted to hang out there and partake in the barbecuage. However, the SOTA bug still had its fangs in me, so I headed to Sugarloaf Mountain in Maryland, or in SOTA terms peak W3/CR-003.

Sugarloaf Mountain is in private hands, but the land owners have opened it up for public use. The lone peak rises prominently above the surrounding farmland. Access is not bad at all — there is a road that runs up the mountain, with three parking lots providing views to the West, East, and South (towards the Potomac River). I had downloaded a trail map from the Sugarloaf website and decided to approach the summit from the Western Overlook.

The path up is well maintained, and consists predominantly of stone stairs. There’s a handrail at the steepest parts. Little kids were running up and down the stairs, impatient for the adults. I took a few breathers on the way up, but it wasn’t too bad a climb, even with equipment.

When I got up there, I found a slanting rock at the very top and made it my base. Being on the edge of the Washington Metro area (and perhaps the Southern edge of the Baltimore region), there were lots of visitors, some who watched with amusement as I tossed soda bottles with strings into the trees, and others who asked me questions about the hobby.

I set up the 20m station first, a TenTec 1320, which I had built from a kit three years ago, plus a longwire antenna and the Hendricks SLT+ tuner. The usual. Later in the day, I put up a longer wire antenna and brought out the 40m Rockmite.

Once at the top, I checked into the club via the 2m repeater, but found that the 440 was quieter. I had brought along a homemade yagi that I had used on the FM sats last year; I’m not sure it helped that much. Ian, N0IMB spotted me on the SOTA site, and that led to a short flurry of contacts on 20m.

Shortly after the first contact, there was a brief hail storm with tiny pebbly hail. I covered everything in the plastic that I had brought along, but luckily the storm did not convert to rain, and weather remained cool but clear for the rest of the day.

I set up my VX-8GR hand held on the summit, and used it to post my current frequency and coordinates via APRS. I heard confirmation tones from at least three digipeaters, but I’m not sure if anyone actually used this information to find me on HF.

My first contact, W7CNL was nice enough to spot me on 20m, and later N4EX did the same on 40. I was pleased to work three members of the Vienna Wireless Society, including Kevin WB0POH, who was operating the club station K4HTA at Glyndon Park. He later told me that he was trying out Tom N4ZPT’s new KX3. The signal was paperthin and went in and out, but we managed to complete the call. Later, I had a clear QSO with Jake, N4UY who was using an attic antenna and putting out 2W on a GM20 transceiver.  Finally, I worked Ray Albers, K2HYD from his home in North Carolina on the Rockmite.

My longest distance contact was G4ELZ Jeff from the UK. The rest of the 20m contacts were west coast US, TX/OK, or Florida. The total for the day was 22 worked on 20m QRP, and four more on 40m QRPp.  Looking over the log, I worked the following states: NJ, OH, NC, PA, NY, AL, OK, TX, FL, MI, MD, VA, OR and ID. Florida was disproportionately represented in the log because I worked a few FQP stations. I also worked a number of QRPTTF stations, plus one summit-to-summit contact with AA5CK on W5/QA-008 in Oklahoma.

I was glad to get the rockmite out for some exercise. I’ve now worked about 30 station with it, corresponding to six states. It was a rough ride with the rockmite due to lack of selectivity, and I appreciate the work of the other stations in pullings its signal out.

I stopped working on 40m when the clouds grew dark, and on my way through the parking lot back to the car, the storm broke. I avoided getting drenched by about ten minutes.