Visiting with Swedish Hams

Continuing the visit to Sweden from the previous post

Saturday morning, Kjell pulled his car up to the hotel, and we took off towards the village of Dalarö. Along the way, he showed me his mobile set-up, which included a Kenwood mobile rig set up for ARPS and an associated GPS unit.  As we drove, he gave me a brief run down of the history of the area and what was going on in terms of ham radio activity.

A scan of a business card from the restaurant SaltskutanAfter about fifteen minutes, we arrived at quiet village on the water (I realize “on the water” may not be very informative when it comes to an archipelago). Kjell mentioned that this particular village is popular among the well-off who maintain summer cottages there. One of the stops on our tour of this town was the tiny sea cabin that belonged to Anders Franzen, the archeologist who discovered the 17th Century wooden ship Vasa, preserved in the brackish waters of the Baltic.  For lunch, he took me to a restaurant in the building that at one time has served as the customs house (tullhuset) for ships bring in goods. The meal was very tasty and involved a meat similar to bacon, but thicker, served over what I think was a potato pancake.

A photographic qsl card for club station sk0qoAfter eating, we continued the trip towards the club station, SK0QO. The station is located on the Gålö peninsula, which until fairly recent times was an island. The station has been there for about a year, and the club owns the building, which is on the edge of some farm land. Driving up to the station, I noticed that they had a number of dipole antennas strung up, a vertical, and I think even a discone.

A number of hams were present at the station, some on the air, and others preparing for their annual hamfest, which will occur next week. I learned that the club is among the largest in Sweden, and that they frequently take part in contests.

The club house has a main room with a central table and a corner fireplace. One rig was set up on the table for QRP voice. I could hear some morse code sounds coming from behind the door to a side room. I peeked in a found a few operators on an IC-7000. It turns out that one of the operators was Jonas, with whom I had a CW QSO the previous day. He filled out a QSL card on the spot, and handed it to me, which is about the fastest turn around time I think I will ever have for a “dx” QSL. Afterwards, Kjell snapped a photo of some of us out in front of the station.

Photo with some Swedish hams in front of the SK0QO club stationJonas explained that on the previous day, by the time our qso took place, he had been operating for a few hours, mostly in English, and was relieved to hear a Swedish call — which turned out to be me.  I was relieved to learn that he had, in fact, sent to me in Swedish and that there wasn’t something wrong with my listening skills.

Also in the photo are Olaf, who oversees the station itself, and Carin, who is working on her sea captain’s license, and was also sending morse code that day.

After a nice time chatting with the hams at the stations (all of whom spoke excellent English), Kjell took me to visit his friend Sven, an extraordinary homebrew experimenter who definitely has “the knack”.

Sven is interested in monitoring the planet’s Schuman resonance, an extremely low frequency (i.e., 7 Hz fundamental) signal, and he has gone to extreme lengths to build his own equipment to do so. It is well worth reading Kjell’s excellent article on Sven’s efforts. What is amazing is that Sven has built equipment sensitive enough to isolate these tenuous signals, and that he does it in a populated area, where radiation from power lines, heating systems, and every other domestic electrical device complicates the situation.

This was no small task, and Sven is willing to put in an extreme effort. He has, for example, entirely cut AC power to the second floor of his house, where he has built a magnetic loop antenna the size of an upright piano. The coil itself is suspended by elastic supports and the ceiling and walls are covered in anechoic material to avoid acoustic vibration of the coil. He has gone so far as to “tune” the room itself, by positioning baffles to null out the room’s intrinsic acoustic resonances. No half measures there.

a map showing the route driven earlier in the day as reported by ARPSAfter all of this, I thanked Kjell for being an amazing host and for extending such a warm welcome to a visiting ham. We agreed to set up a sked at some point, and I hope we’re able to meet on the air in the future. Later that evening, Kjell sent me a link to our APRS tracked route from earlier in the day.

I was able to get on the air again that evening from the hotel room using a longwire thrown out my 8th floor window. Even with this very suboptimal antenna arrangement, I worked two stations on 20m, one in Wales, and one in the Czech Republic. For kicks, I did try the rockmite on 40m. I didn’t get any replies, but I did at least show up on a Netherlands reverse beacon monitoring station at 8dB above noise.

On Sunday, I again hiked into the woods behind the hotel, spent about two hours on the air, and worked eight stations (in Russia, Germany, Italy, Slovenia and England). I turns out that I was lucky, as not too long afterwards, a series of solar events disturbed the ionosphere for a few days. In all, I worked 14 stations and 9 DXCC entities with my 5w 20m transceiver.

 

 

SM0/AI4SV versus the TSA

Last week, I attended the European Cancer Organisation (ECCO) conference in Stockholm. Most of the time, I was either at the conference, or at side meetings that took place between meeting sessions. My schedule was pretty tight, but I packed my QRP bag in case I had some free time.

My plans almost ended at Dulles Airport. The United Airlines baggage clerk gleefully told me that my suitcase was about 500 grams over the limit, and that it would cost an extra $200 to ship it to Europe. I reached in, took out my QRP bag, and brought the suitcase weight back under the limit.  I had hoped to pack the QRP equipment in the checked luggage rather than to carry it through security, but having travelled many times with the same equipement, I wasn’t really worried about it. That was something of a mistake.

A TSA agent adjusts his light blue vinyl examination glovesWhen my QRP bag went through TSA screening, as expected, they wanted to hand-inspect it. They pulled the sealed lead battery out and said that it couldn’t go on the plane — they were unable to get a good image on their x-ray machine. I replied that this made some sense, it was, after all, a lead battery. I suggested they rescan it, rotating it 90 degrees in one axis or the other, so that the lead plates would be parallel to the beam. I got a puzzled expression. I explained that the exact same battery had gone through security many times, including at that same airport on other international flights, and had not been a problem. I wasn’t getting anywhere, though, so finally I let the issue drop, handed the battery to the TSA agent, and said he could keep it. I suppose they must have a nice collection of confiscated electronic gear by now, so they are probably in need of some batteries as well.

On the flight over, I wracked my brains trying to think where I might find a suitable power source, with limited times between meetings. I recalled that batteries were expensive in Belgium, and assumed that the cost would be similar across the EU, related primarily to ecological concerns about battery waste — in fact, I had guessed batteries would be even more costly considering exchange rates and Sweden’s reputation as a green country. One option I considered was visiting the hotel’s business center and borrowing the battery out of a UPS for a day or two, but I’m glad to say it didn’t come to that.

Right before jet lag caught up with me on the first day, Thursday, it occurred to me that no one would know better about where to find a battery than a local ham. A quick Google search led me to the blog of SM0FOB, Kjell Bergqvist. I strongly recommend reading through his blog entries — they’re interesting, even if you’re not headed for Sweden. Anyhow, I noticed that he lived very close to the town in which I was staying, so I shot off an email and turned in for the night.

Kjell's FB QSL card printed on glossy photo paperKjell wrote back the next day and identified two stores within a five minute walk from my hotel, both of which sold a variety of lead acid batteries and chargers. Kjell also suggested that I could just borrow an already charged battery from him, but since I had donated my last battery to the TSA, I thought it better to buy a replacement, plus a smaller charger. The cost was comparable to what I would have paid in the US, so I guess the cost of batteries in Belgium may have been driven more by local taxes or that lead acid batteries are considered more ecologically sound since they are rechargeable and in the end, somewhat recyclable.

Beyond giving me helpful advice about where to buy batteries, Kjell suggested that we go out for lunch on Saturday and visit a couple local hams and their club station. The timing couldn’t have been better, since my first meeting on Saturday was late in the afternoon, so we set a time to meet.

Friday morning, I visited the conference, caught up on email, and picked up a battery. The battery was fully charged when I received it, and since I had some time before an afternoon teleconference, I took my QRP bag and went for a hike.  The hotel is just east of the Handen commuter rail (pendeltåg) station, and just across the railway tracks is a park and a lake. I took a footbridge over the tracks and then followed some trails in the park. I assume that in the winter, these trails are for cross-country skiing. I followed the trail that looked like it led to the greatest elevation, and walked more or less parallel to the lake front. Eventually, I found a nice rocky area to one side of the path, and threw an antenna into a tree.

radio, tuner, earphones on a moss-covered rockThe location was perfect: a rock to sit on and a few other rocks at just the right distance to serve as a desk. The rocks were coated with moss, and the whole area was so undisturbed that I was a bit worried that perhaps people weren’t allowed off the trails. I tried not to bruise the moss and brushed pine needles over my footprints on the way out.

Once set up, I realized that I had not packed an RCA phono cable to go from the keyer to the rig. Luckily, I had some wire leads with alligator clips in the bag. I opened up  both the keyer and the rig and made the connection directly (that’s why the keyer is open in the photo). The rig was the usual — my TenTec 1320 and a longwire antenna tuned with a Hendricks SLT+.

I spent about an hour there and worked four stations: two in Russia, and one each in Bosnia-Herzegovina and Sweden. I didn’t realize that the final station, SK0QO, was Swedish at first. I thought the SK prefix was in Eastern Europe. After a while, I realized that the station was sending to me in Swedish, though, assuming from my “SM0” prefix that I was a Swedish operator. I copied the name of the operator, Jonas, wished him a vy 73, and figured I would look it up when I got back to the hotel room.

When I got back, I did search it on qrz.com, and realized that SK0QO is the same station that Kjell had mentioned in his blog, and that we would be visiting the following day. While I was at the computer, I checked the reverse beacon network, which showed that my 5w signal had made it as far as Canada.

More on that and the rest of the Swedish QRP adventure in the next entry

Chicago, Boxen, and Heil

A view out the window of the Marriott Courtyard downtown hotel. In the foreground: a tentec 1320, straight key, and Hendricks SLT+ longwire tuner
A view towards the lake

This week as the American Society of Clinical Oncology’s annual meeting in Chicago, and I spent five days just north of the river, at the Marriott on S. Ontario Street. When I arrived, I was quite excited to see that my 23rd floor window opened ever so slightly, meaning I could get an antenna out. For the next several days, though, I was busy around the clock, and only on the final day did I get a chance to try to operate from the hotel. As seems to be a trend with these hotel operations, it failed miserably.

The rig was the TenTec 1320, so I was looking at day time operation, but I had a slight problem – the side of the hotel was white and my antenna wire was black. I wasn’t so much worried about someone noticing my antenna from the street level, after all, 30 feet of black wire up about 200+ feet is pretty difficult to see, but I was worried about neighbors hearing something tapping at their window and then seeing the black, insulated wire dangling. One good pull, and various pieces of my station would be headed towards the pavement.

There is a Radio Shack on Michigan, just south of the river, and as Ben informed me, they are unusually competent. I walked in, asked for antenna wire, and they knew where it was!

When I got back to the room, I figured that since I was so high up, I might as well put up as long a wire as possible. I doubled the 31.5′ length recommended by the SLT+ tuner manual to make a full wave longwire. It would have been nice to have had a tape measure, but I was able to work it out in multiples of 8.5 and 11 inches, which was doable with what I had on hand. I weighted the far end down with a ring from a keychain. I ran the counterpoise wire along the floor of the hotel room, and yes, tripped over it several times.

I looked around for something to protect and insulate the wire as it passed through the window sash, and decided that one of the throw-away ASCO newspapers could be rolled into a tube, and would help get the wire a little bit away from the building.

Not far enough, though. Although I had two of the elements of the magical formula for antennas (lots of wire, high up), I think the wire’s proximity to the building killed it. I was able to tune the antenna to fully extinguish the LED on the SLT+ tuner, indicating a good match, but being near the metal structure of the building effectively shielded the antenna. I heard few cw conversations on 20m in the morning. Granted, it was a weekday, but even so, the signals were not loud. I tried calling CQ for a while, but no responses. Now that I’m back in Virginia, I’ll need to double check the radio to make sure it is transmitting correctly, but I’m pretty sure it was the antenna and not the radio.

two large cardboard boxes awaiting unpacking
Total weight: 50 kilos.

I got back late Tuesday night, and had two large boxes waiting for me when I walked in — the equipment that I had shipped out to Operation Sizzling Pork. Tymme had shipped it two days before. Score one for UPS Ground service (and Tymme’s professional-grade packing skillz).

Not really related to any of this travel, but still along the lines of amateur radio, on the way to work yesterday, I noticed that Bob Heil had produced three episodes of the “Ham Nation” podcast. I had enjoyed his interview with Leo Laporte on Triangulation a couple months ago, and I had heard in subsequent weeks that they would be working on a ham radio-specific show for the Twit network.

As much as I appreciate the effort, I can’t say that the first few shows have, pardon the expression, resonated with me. The show may need some time to find itself, but I think it needs more structure. I wonder if it wouldn’t work better to have two hosts, one of whom is not an expert and could ask the questions that might be occurring to the audience. The show also needs to figure out what audience it wants to address. The other shows on Twit presume a sophisticated audience with knowledge of the field (e.g., Security Now), but there is something of a proselytizing aspect to Ham Nation. There is a huge audience of people worldwide who are already hams, and these are the people who most likely have sought out the show (and, from a commercial aspect down the road, probably the best target audience for ham-related ads).

Two contests, one rock

A night time cartoon of a tent and camp fire
Camping

I could say that we selected Rocky Gap State Park (78.65061 W, 39.71315 N) for Memorial Day camping because I knew I would be running a rock-bound transceiver in a QRP contest, but the truth is that as usual we waited until the last minute to make camping reservations, and there weren’t many choices for state parks within a three hours drive of Washington, DC. Despite the  last minute preparations, the camping went off without a hitch (literally, since we shoved everything in the back of one car).

We left early on Saturday morning, had tents up by around noon, and I then spent some time entertaining the neighbors by throwing soda bottles with strings into the high trees. In appreciation, they turned up their country music, which was much appreciated, but not by me.

This was the CQ WW WPX CW contest weekend, so I knew there would be a ton of activity, with a good chance to be heard internationally. For that contest, I brought the TenTec 1320, and ran its ~ 5W into a longwire antenna through my Hendricks SLT+ antenna matcher. That rig only tunes 20m (~14.003 to 14.073), so I was limited to daylight plus a bit. With other camping activities going on, I periodically sampled the band to see what propagation paths were open. I was using a straight key as I don’t have my keyers on hand, but it wasn’t too bad since I wasn’t calling CQ much with such a peashooter station. Logging was performed in the classic style: paper and pen, with a lot of page flipping to avoid dupes.

The late afternoon/early evening both days was my best time. I logged 31 contacts, with DX to Aruba, Canada, France, Germany, Italy, Martinique, Spain, and Venezuela.

The CQ contest was over at 20:00 local time on Sunday, just in time for the ARCI Hoot Owl Sprint to begin. I had brought the 40m rockmite for this contest, since the contest offers bonuses both for QRPp operation and field operation. With the large membership of the ARCI potentially listening, I thought I might have a chance to be heard by someone.

I started at 20:00 EDT (00:00 Z) and stayed at it for 3 and a half hours, before I decided to walk down to the lake and stare at the clear night sky for a while. The rockmite has a built-in picokeyer, so I was able to use my Bencher BY-1 paddles, which was a good thing since I was somewhat zombified that late in the evening after a good night’s sleep on hard ground the night before.

A giant mosquito attacks a running man
Rumors may have exaggerated somewhat

Not only did I log some radio contacts, but I also was visited by many species of insects, who were attracted to the coleman lantern providing light for the log book. In fact, one unlucky bug is a permanent addition to the logbook itself.

In all, I logged nine contacts in six states (MI, NC, NJ, NY, OH, and VA). Five of these contacts were with ARCI members, who gave their member number in exchange, the rest sent me their power, some QRP, some not. I assume for the purposes of the contest in terms of my score, my power matters, but not theirs. Because I was operating on the rockmite at 500 mW output, my score got a 10x multiplier. Even more helpful, I got an additional 5000 points for operating portable (a bonus ~3x bigger than my score itself).

Operating with the Rockmite takes some patience, as the bandpass is large enough to hear many simultaneous conversations. When stations reply, it can be hard to tell if they are zero beat or not, particularly if they send just their call rather than “ai4sv de mycall mycall”.  Infrequently, I also had a touch of broadcast band interference, which faded in and out, and was always too tenuous to pick out specific spoken words.

Rocky Gap State Park was not chosen based on its potential as a contest location, but it worked well as one. The park elevation is about 1200 feet, and we were in site 182, which is at the far end of one loop, at the top of a hill, and surrounded by woods. Our site did not have electrical feeds, which further reduced the noise.  The entire site is in a valley, however, with taller hills to the east and west, so some low angle radiation may not have passed.

I would certainly consider Rocky Gap again for family camping, but I have my eye on some sites that are both closer and more elevated, for instance in West Viriginia, Black Water Falls (elevation 2897 feet) or Pipestem Resort (elevation 2690 feet, plus it has the word “Resort” in the name).

 

Upstairs with NAQCC

We interrupt coverage of Operation Sizzling Pork for this brief mention of last night’s NAQCC sprint, which turned out much better than I would have had any reason to expect. This is a monthly two-hour QRP sprint in which I have participated a half dozen times, usually netting only a few contacts. When I got home from work last night, I remembered the sprint, but was not very optimistic: both main rigs,  the antenna tuner, and my keyers are in Indiana, plus a thunderstorm was predicted for prime operating time that evening. However, by the end of the contest, I had made more QSOs than ever before.

an 80m dipole fed through a vinegar jug wrapped in coax
The Belgian Vinegar Antenna (BVA)

With the vintage Collins gear still out for repairs, I had two choices: my 40m rockmite (550 mW) or my ~4W TenTec 1320. The rockmite seemed a bit light for my purposes, so I went with the TenTec. There was one problem, though: the stealth vertical in the backyard is not resonant on 20m, the TenTec’s only band. As of last month, our attic has a newly installed floor, so I strung up a simple dipole from the rafters. I used the former “Belgian Vinegar” antenna, and shorted the radiating wires to sixteen feet, seven inches (calculated for resonance on 14.060). The BVA was basically a dipole center connector plus a gallon vinegar jug wrapped with coax to make an air-core current choke. I wasn’t worried about RF running down the cable in the current installation, so I uncoiled the coax and discarded the vinegar jug. I had used this antenna for two years in Belgium, and during one contest when I operated from Mount Vernon, NY.

temporary station in the bedroom
Temporary Upstairs Station

I didn’t attempt to run coax down to the basement, but just down through the trap door and into the bed room, where I borrowed my wife’s computer desk. Her iMac was temporarily pushed to the side to make room for the station. I did not have an antenna analyzer or VNA, but I did have a power meter that measured forward/reverse power, so in the fifteen minutes before the event, I trimmed the antenna old school, calculating the vSWR. I got it down to about 1.8:1, and figured that was good enough. I was sweaty and itchy from fiberglass and didn’t want to mess anything up right before the contest, so I left well enough alone. With a 25 foot cable, I figured there wasn’t enough power loss to worry about, even at QRP.

Out the window, I could see lightning flashes, and under ordinary conditions, I would not have used the outdoor vertical. However, given that the dipole is indoors and lower than the various metal projections on my roof, I figured I was okay working through the storm. Loud static crashes interrupted work all evening. After each crash, the radio’s AGC would kick in and I’d be deaf for a couple of seconds as sensitivity recovered. Despite the QRN, reception was fantastic on 20m.

I worked eastern and central North American stations in the first half of the contest, as with the vertical antenna, Minnesota and Texas came in particularly well. Around 01:20Z, propagation went long, favoring western stations, particularly Oregon. I was pleased to work NAQCC members in both Canada (Saskatchewan) and Cuba during the contest.

In all, I had 17 QSOs, although I noted that the last one was a repeat, probably trying to be sure that I had copied him correctly on the earlier exchange, so I can say that I have 16 QSOs that count towards a score. All of my contacts were with members, so 2 points each, and made using a straight telegraph key, so a 2x multiplier. I think I did pretty well this week both in absolute score and likely in relative score since I presume that some of the heavy hitters were on the road to attend the Dayton Hamvention.

I was impressed by the performance of the attic dipole, which was refreshingly free of man made noise, versus my usual operation on the lower bands with the vertical antenna. Over the summer, I am hoping to refine the attic installation and make it permanent, routing the wires down to the station in the basement.

Next Year Jerusalem; this year Hungary

I had another go at the rockmite last night on 40 meters. I tuned the LDG tuner to 7.028 with the Kenwood B2000 and then substituted the rockmite for input; antenna was the 43 foot tree-slung vertical wire. The LDG has latching relays, so it stayed tuned even when the drive was removed. I started calling around 18:30 EDT (22:30 Z) and was answered by W2XB, Don in Lakeview, New York (a bit south of Hamburg, along the shore of Lake Erie). Don was using an Elecraft K3 and gave me a 349. His signal was weak but copiable (after I asked him to QRS down to around 15 wpm), so I gave him a 359. The rockmite is not very selective and there were signals up and down probably a khz, so most of the filtering was done  between yours truly’s ears. This contact went back and forth three times, and I can’t say that I copied every last letter, but the signal was quite stable. So, that is QSO number 3 for the rockmite, 282 miles (~450 km) on 550 mW.

After listening to the rockmite for a while more, my head was beginning to swim. I craved the narrow filtering… no, make that any filtering whatsoever, so I fired up the Kenwood and sent a QRL on 40m. I was answered immediately by a “?”, so I cq’d, and was surprised when HA3OD, Arpi, came back to me. I believe he said that he was operating at 30W from a location near Pecs, Hungary. So, about 4600 mi (7400 km) on 5W — even better than the rockmite.

I’m pretty happy with QRP performance last night. Propagation conditions were not particularly great (prediction for the band was “fair”), but noise was less of a problem than usual. I am considering building some sort of audio filter to narrow the rockmite experience. I know that there was a rockmite filter, but I don’t believe it is still available. I’ll have to look around a bit.

Rocky Road

Yesterday, my brain was mush, so I didn’t attempt anything at the workbench. I turned on the radio and tuned around the ten meter band, not expecting to hear much. However, I did hear considerable activity from South America, calling with “MM TEST”, which turned out to be the Manchester Mineira contest. Since the contest originated in Brazil, it wasn’t surprising to hear so many stations from that country. I had my first contacts with Peru and Ecuador, and logged a few with Columbia, Aruba, Cuba, Mexico and a few U.S. stations. I heard Chile and Panama, but didn’t manage to land them. I only caught the last couple hours of the contest and did not try running at any point.

Afterwards, I plugged in the 550 mW rockmite 40 and tried calling for a bit. The signal went through my LDG tuner and then my 43 foot vertical wire in the backyard. The band conditions were not great last night, but the activity level was relatively high.  I tried for about an hour, and stopped around midnight. I figured that I might have more luck the next morning, with fewer competing signals (but also fewer listeners awake). I started calling around 6:30 and went about 45 minutes. Local sunrise was 06:27 EDT / 10:27 Z, so 40m was fading towards the end of that period. I didn’t get any responses, but I was picked up at reasonable levels on the reverse beacon network, by stations from Massachusetts and Georgia.

reverse beacon network listing showing ai4sv picked up from 7 to 20 dB above noise

At one point this morning, my ears were nearly blasted off by a New York station operating on 7.031-something. I cranked the RF gain all the way down on the RM40, but it was still loud. The reverse beacon network registered the station at 51 dB above background in Illinois and Maryland — that’s about 10,000 times stronger than my 500mW signal, so I have to guess that the station was using either a linear amplifier or had one heck of an antenna. Even operating more than 3 khz away, he cooked me.

So, no cigar so far on the higher-power RM, but I am sure that the signal is getting out. Maybe I need to keep an eye on the QRPspot site.

Honey, I blew up the amplifier

Actually, let’s start on a bright note, and then we’ll get to the part involving smoke.

Inside view of the rockmite 40 installed in a mity box
The Rockmite 40

My main reason to build the amplifier was to get a bit more power out of the rockmite. Part of the problem in getting the amp working was also likely low driving power. The basic design of the rockmite uses the prototypical bipolar NPN for the “final” amplification — a 2N2222.  There are variants that use other transistors and get the power above a watt, and there are also some tricks to increase the drive, but the stock rockmite should yield a nominal half watt or so with no mods. So, I took off the cover of the rockmite and poked around, checking all the part values. I had already made one substitution: C8 was decreased in value from 0.1 uF to 0.01 uF to knock the side tone volume level down to something tolerable.

Sure enough, I saw the problem — I had used 47 pF (marked 47J) instead of 470 pF (marked 471) for C15 and C17, which are on the output side. Yes, the “1” and the “J” looked similar. I stuck the right value capacitors in, and power output using a 13.2V supply was 550 m. Not too bad.

Next, I plugged the RM into the Texas Topper. I didn’t power it right away, though, because I was interested to see what sort of insertional loss the Texas Topper introduced when it was not active. Power output was about 400 mW. This probably wasn’t an entirely fair test because the Tx Topper was still on the bench top, with tack-soldered connections to the BNC connectors.

Texas Topper before final install

I removed the extra N4148 from the amplifier, because I figured it probably had enough drive now to work without extra bias. Power output was measured as 2.2W, so about 6dB gain.  While I could live with that (and, in retrospect should have), I was curious what would happen if I bumped the bias back up a bit. The N4148 went back in, raising the bias voltage from about 2.05 to 2.75V. Power output was now 7.7W — 11dB gain. I measured roughly 7Vpp in, 20Vpp out, so roughly in agreement.  Part of the increase in gain might also have been due to switching from using alligator clips to apply power to using a thicker wire terminated on one end with a power pole connector and on the other end with a type N coaxial plug.

So, at this point, I was actually (hah) thinking of introducing a one or two dB attenuation pad, although the idea of burning off power in  a QRP rig feels inelegant. More inelegant, however, was trying to bend the FET forward so the heat sink would fit in the enclosure. When I pushed it forward (yes, with power applied), there was a bit of sizzle and then a bright flash from the LED. I don’t know if something arced before the LED toasted, but I was left with the acrid and no doubt carcinogenic aftertaste of stupidity wafting through the shack.

I inspected the board around the FET and couldn’t see an obvious short. The parts in that area do share some close quarters, and the heat sink is right next to both transformer coils. I took out the LED (shorted now) and yanked the FET. Good thing I had a bag of them on hand….as will soon be even more evident.

With a new FET, a new LED (not quite the same type, but close), and another diode, I was back in business. Everything was fine until I tried to stuff the heat sink into the enclosure. This time, not under power. The problem is, though, at some point, you have to apply power, or the whole thing is just a paperweight. Zot. Sizzle. Flash. Puff.

Yeah. So, at this point, I’m out of FETs and thinking that maybe I need to do something more creative regarding the strained relations between the heat sink and the enclosure. The heat sink should be applied right to the metal tab on the FET, which is the drain. The case is aluminum, and at ground potential, so that particular twain shouldn’t meet.

I tend to only order from Mouser when I get enough items on my “want” list to make the shipping work out, so it might be a bit before I replace the burnt out components, but I’m sure I will in the next couple weeks. The board has held up very well to my repeated soldering/unsoldering, and I really don’t have any complaints about the Texas Topper per se. This is more a mechanical issue at this point — all the electronic bits seem to do a fine job of amplifying. I may, in fact, order another one just to play on another band.

Even without the Texas Topper, doubling the output of the Rockmite should make it more usable. I’m looking forward to rolling both it and the TenTec 1320 out next week for the QRP to the Field Event.

Texas Topper QRP Amplifier

I seem to be doing well enough running the Kenwood B2000 at 5W or the TenTec 1320 at around 4 watts, but I haven’t made many contacts with my Rockmite, which on a good day puts out around 250+ mW, but less when the battery runs down a bit. A while back, I had ordered the Texas Topper (a.k.a. Tuna Topper) amplifier (nominally 5W out) from www.QRPme.com. For $25 it’s a good deal. The design lends itself to flexibility and experimentation, allowing the user to choose whether to use onboard/offboard options, a tuna-shaped round or altoids-shaped rectangular form factor, a range of input powers (using fixed or variable attenuator, if necessary), fast/slow switching, and transceiver or xmtr/rcvr configuration.A round Texas Topper printed circuit board, unpopulated

I put the kit together last week, made an enclosure, stuck it in, connected everything up, and … nothing. Well, not quite nothing. My WM-2 wattmeter read about 50mW output. Not good — the amplifier was doing something, but not in the direction that I had hoped.

The amplifier is well-documented on Chuck Carpenter’s website, which provides a parts list, pictures of the board, schematics and helpful advice. From the circuit diagram, it’s apparent that there are two halves to the pc board — one that controls switching through a relay, and the business end of the amplifier that centers on a MOSFET followed by a filter network.  As far as I could tell, nothing was shorted.  In the “receive” state, signals fed straight through from input to output connectors. When I keyed down the rockmite, I could hear the relay click in, and I was able to verify that the input signal was being appropriately routed over to a 4:1 transformer to feed to the MOSFET.A constructed Texas Topper on the bench top for troubleshooting

I checked DC voltages with a DVM, and verified that the bias voltage (determined by the forward voltage drop across an LED that conveniently also serves to let you know power is applied) was 2.05V. The voltage on the MOSFET’s metal tab (the drain) was about the same as battery voltage, as it should be.  Unfortunately, I didn’t have an RF probe on hand for tracing of RF voltages — the probe was lost in the last move. It would be easy enough to build one (see nice plans on W5ESE‘s site), but I didn’t have a suitable diode on hand and apparently Radio Shack no longer carries the 1N34 in stock. No problem — I have something better, although not quite as portable: an oscilloscope.

The incoming signal was about 8Vpp, and 4Vpp after the 4:1 input transformer. I expected to detect something on the drain of the MOSFET, but all I got was hum (maybe just background).  Probing beyond the MOSFET, I didn’t get much. I was stumped at this point, and starting wondering if I had done something wrong during construction.

It seemed to me that there were two likely places that I could have screwed up — in winding the two bifilar transformers (which, I recall I did while watching an episode of “No Ordinary Family”, so maybe I was distracted), or maybe in installing the MOSFET. I had placed a mouser order at the same time as the kit order, so I had a couple extra MOSFETs to play with. Using static-free everything (mat, wrist band, soldering tip, etc) and low heat, I replaced the MOSFET. No change. The kit comes with 22 and 26 gauge red magnet wire for winding toroids. To be extra careful, when I rewound the two bifilar transformers, I used on strand of red, and a strand of another color. Radio Shack does carry a magnet wire set, which conveniently includes 22, 26 and 30 Ga lacquered wire, and the 22 is gold and the 26 is green. The transformers look much better when wound with two color wire, and it’s easy to verify at a glance that the correct wires are tied together and that they all end up where they should. Again, though, no change.

I tried replacing the MOSFET one more time, as I thought that perhaps I had not had the right load on the amplifier when I tested it the first time, but again, no change.

The Texas Topper laid out for testing on the benchtopAfter  I looked at the data sheet for the FET and noted that the gate threshold voltage is listed as a minimum of 2v and max of 4v. The transfer function graph showed the drain current picking up sharply above 4v. My rockmite has lower output than most, and it occurred to me that I might be at the lower end of this amplifier’s design — not enough umph to drive the FET’s gate. To up the bias voltage, I stuck a 1N4148 diode between the stock LED and ground. This bumped the bias from about 2V up to 2.75V. Result: 1.5W output. On the oscilloscope, the waveform was a bit distorted on the FET’s drain, but smoothed out in the filter and was well formed at output.  Going from 250 mW to 1.5W is somewhere around 7dB gain — not quite the 10 dB gain typical for this amp, but a huge improvement over my rockmite’s usual output.

So, now I am playing around a little to see what happens when I run this system with a fully charged battery and play a bit with the bias voltage. Hopefully, I’ll have a chance to try out the rockmite-on-steroids this weekend.

 

 

No QSOs in Boca Raton

This started as more of an IF (interactive fiction — not intermediate frequency) blog, but it does make a lot of sense to consolidate other topics here as well, since most of the time when I have to list a “blog” or “web site” link, I list this one. So, consider the flood gates opened. That probably means a flurry of excited posts followed by intermittent (on a geological time scale) dry spells. Let’s face it: that’s just how I am about updating websites. Maybe postings will be more regular if I can broaden the scope of the posts to just about everything and if the blog posts are useful to me as a sort of lab notebook.

Along these lines, one topic I’d like to document is ham radio trips, which I will conveniently define as any time I am not at home and get to play radio. Since I take a lot of trips for work, and since I almost always take a radio along, there should be a bunch of these.  Very often, the conditions aren’t optimal, and I don’t have a lot of time on trips, so more often that not, I probably won’t make that many contacts, but it’s more the effort than the QSO count.

Rather than recount projects and outings to date, I’ll just start from here forward. This weekend, I spent a couple days in Boca Raton. Scratch that. That’s how it is listed on the map — it is actually Deerfield Beach, Florida.  It’s only a beach if you consider concrete to be beach-like. It’s inland a few miles, and the view was of route 95. The conference I was attending was held at a resort that actually *is* in Boca Raton and overlooks the the ocean, but  I’m travelling at government rate, and that only goes so far.

My room was on the third floor of the hotel, right near the front entrance, which made antenna placement challenging.  On the first evening, I bid my time until there were no cabs or cars in the oval driveway, and then lobbed a 65′ long wire over a palm tree. I had attached it to a water bottle, and A long wire antenna running from the window to a palm treecouldn’t see where it landed after I gave it a toss. There were a couple tense moments when I went looking for it outside and found it dangling 20′ above the driveway, over the heads of some oblivious guests. I managed to yank it back a bit and get it into the bushes. Later that night, after dark, I guyed it down more substantially. Most of the antennas was elevated at about 35′, with the distant end down lower. I ran a 35′ counterpoise around the room and tuned the whole thing with a Hendricks SLT+ tuner.

The rig du jour was the 40m Rockmite, with the 7028.0/7028.9 crystal, running from a 7.2 Ah absorbed glass fiber lead acid battery. A picokeyer was built into the rockmite, and morse code was generated by a Palm Paddle which was duct taped to the battery. Where the wire crossed the metal window frame, I wrapped some duct tape around the wire as padding and then closed the window snuggly. Luckily, the hotel cleaning crew didn’t mind wires sticking out the window, and left the whole thing intact while I was attending my meeting on Saturday.

So far, I have had two — count them, two — contacts on the rockmite, but considering that it only puts out 300mW, that’s not too bad. Both have been from home using my 43′ vertical antenna (which is nothing more than a vertical wire radiator slung into a tree plus a few ground radials). One contact was across town, the other was to Michigan.  In the Michigan case, I was responding to a CQ call, and it was a difficult QSO.

I had no problem hearing other stations calling on 7.028 plus or minus 1 khz. Powerful stations would cut across both of my frequencies, and I had to wait them out. I heard strong signals from Italy, Slovakia, Slovenia, Germany, Croatia, France, and around sunset, from Columbia. Some strong local signals (SC, GA) were zero beat, but I could not work them. I called for a few hours intermittently, but had no responses. Well, maybe some qrz’s, but I am not sure to whom they were replying.

This was the first I had tried out the SLT tuner with the rockmite. Interestingly, the rockmite is powerful enough to illuminate the LED that tells you when the system is resonant. I would have wondered if my signal were getting out at all, if I had not had some confirmation from the reverse beacon network. Apparently, I was just above noise for a few of the stations, but at times, my signal was pretty decent (also, though, taking into considerations that the receiving systems for some of these reporting stations have high gain antennas).

So, no bites, not even nibbles, but considering that the antenna was somewhat of a compromise, I’m not writing off the rockmite. I am, however, strongly considering finishing the Texas Topper amplifier, which would boost the signal nearer to 5W and give me a fighting chance when my antenna options are limited.