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.

Signal Mountain Activated

some rocks
The peak of signal mountain. Photo taken from our operating position, looking north.

Our visit to Signal Mountain, Virginia was successful, and summit W4/SH-049 has been activated for the first time (and perhaps the only time for the forseeable future).  We made a total of 19 QSOs, which we thought was reasonable for our first  SOTA activiation (and not really knowing what we were doing).

On the morning of April 14, 2012, I met up with Ian N0IMB and we drove out to the site. A Google Map query for “Signal Mountain, Virginia” puts an arrow right on the summit, and there is a road all the way to the top. That road is silky smooth, but the residential road that leads to it is a couple miles of gravel and dust.  We drove in and parked about just after the sharp bend in the road. According to the terrain feature on Google Maps, this put us a couple hundred feet from the summit.

I unpacked Dolly, who in this case was not a cloned sheep, but an old furniture dolly that I have used since college every time I change dwellings. Most of the equipment went into a milk crate that was bungeed to Dolly. Given the road access, we didn’t pack particularly lightly — folding camp chairs, some folding TV tables to work on, and a couple bags of equipment and snacks. As peaks go, this was a pleasure cruise.

I led Dolly up the slope, pulling on her leash, and Ian lugged the rest of the equipment. The road continues past the peak to a fenced government facility, but we stopped at the peak and headed eastward up a gentle slope into the woods. When we got to the actual stony peak, Ian found a nice place to erect the buddipole tripod, and I set up the radios.

The buddy pole went up quickly, and we played with the counterpoise until we arrived at a 1:1 SWR on 20m (Ian made me take a picture of the MFJ tuner as evidence!). We tuned around on 20m and quickly came to the realization that our stated operating frequency was just wishful thinking. The band was humming from one end to the other with QSO Party activity. We tried working a few of the NM QSOP stations, but although they were thundering in, they could not hear the 5W the Yaesu 817d was putting out. CW was a bit better, but the stock filtering on the 817d was relatively wide.

We decided that before we really set up shop, it would make more sense to put the antenna on 17m and see if we couldn’t get out better without all the background chatter. The buddipole retuned quickly, and we were soon on the air. Our first contact was Mike KE5AKL from NM, which is quite fitting since he was the first station that I had worked as a chaser, the day before.

After that, we worked a succession of stations, some with callsigns that I recognized. The TenTec 1320 sitting next to me in my bag had, for instance, been modified according to instructions that I had found on the website of our third contact, Scott W5ESE. Two contacts, Bob WB4KLJ and John AF4PD, were from our local club, the Vienna Wireless Society, and must have been working us direct from 25 miles to the east.   Jonathan AK4NL was also a very close contact, being located on Bull Run Mountain. Our stateside contacts on 17m included VA, CO, ID, NM, TX and OR.

We were very glad to make contacts with England (G4OBK), Scotland (MM0USU), and Germany (DJ5AV).  We are particularly grateful to Phil G4OBK, who stayed on frequency after working us, followed us up frequency when we had QRM, and warned off a station who was about to transmit on top of us. The other station likely could not hear our puny signal, but could copy the solid transmission coming from across the pond.

Around three in the afternoon, we switched to 40m. It was a little more involved to move the buddipole to 40m, but we finally got a reasonable match.  Predictably, on daytime 40m, we worked primarily the US east coast: PA, VA, MA, NJ, and NY.

We had intended to work until about 6 pm, but stopped early, because we were informed that the access road was being closed up at 4 pm. In talking with some guys from the facility, who turned out to be communications professionals, we learned that the facility houses some sensitive radio equipment. Although our signals did not cause any sort of interference, we agreed that we would recommend that others not work this summit, even at QRP levels.

We learned a number of lessons from our first activation, and here are the ones I can remember:

  • It is okay, indeed encouraged, to self-spot. We had so-so cellular connectivity, but in the future, getting the word out will include spotting on sotawatch, qrpspots, and via twitter.
  • Less equipment is better. We did not use the G5RV or the TenTec 1320; while there is some value in being prepared and having redundant equipment, if I had to carry the extra gear up a more challenging slope, I would not have been a happy camper.
  • The WARC bands are your friends. Ian and I both like 17 meters. If I had to pick one band, that would be it.
  • We had originally not planned to work 40m in the middle of the day, but the east coast US hams were grateful to hear us, so I’d factor that in next time, and try to split operation between local and more DX stations.
  • Our pre-posted operating frequencies went right out the window. Also, we had too many of them. It probably isn’t practical to work more than a couple bands on a given activation.
  • 5W on voice is difficult, but still worth it – when we did connect wth other stations, most of the time we received fairly good reports, and on our end, the other stations were loud.
  • For CW, I’d prefer a radio with better filtering (or maybe a modded 817).


SOTA: Signal Mountain, April 14

A snow-covered mountainIan, N0IMB, and I will attempt to activate Signal Mountain, Virginia as a Summit On The Air (SOTA)  on Saturday, April 14, 2012. Signal Mountain is less than an hour’s drive from my house, and with a name like Signal Mountain, it seems the natural choice. Strangely, for being so close to a metropolitan center, according to the SOTA database,  this “peak”  has never been activated.

Signal Mountain, SOTA designator W4/SH-049,  is a 416 m tall peak located at Long -77.7033 by  Lat 38.8816 degrees.  Conveniently, judging by a google map view of the site, a road runs up to the top, although by SOTA rules, we’ll park some ways down the road and lug the equipment to the top. We don’t have mules, but we do have a hand-truck and/or a furniture dolly, so we plan not to break our backs carting the equipment up the hill. While this may not sound very adventurous for more experienced SOTA enthusiasts, this is our first activation, so we are trying to keep it simple. One side benefit is that we’ll have a stronger signal: one item we are lugging will be a gas-powered generator, and we will be transmitting at 100W. [edited: Correction – it was pointed out by a more experienced SOTA-er that this would violate SOTA guidelines – no fossil fuel generators. Well, that’s fine with us, too. We’ll use storage cells, perhaps supplemented with a bit of solar if we can put our hands on the right equipment quickly enough. This means we will not be transmitting at 100W, or at least not for long stretches. Most of my gear is QRP already, so this isn’t a big adjustment. We’ll just talk louder :-)]  Rigs will be a Yaesu FT-817 and a TenTec 1320.

Operating Plan:

We will be operating under the call sign N0IMB from 16:00Z to 22:00Z on 14 April 2012. In local time, that is noon to 6 pm. Local sunset is 7:45 pm, so we should would like to pack up while we can see what we are doing.

We will operate voice from the top of each hour to forty-five minutes past, and then switch to CW for the last fifteen minutes. Typically, we will exchange a signal report, the name of the operator, and the SOTA designator.

Generally, we’ll stick to the following center frequencies. If these frequencies are busy, look for us up or down a bit:

Band CW Freq SSB Freq
40 7.027 7.187
30 10.127 cw only
20 14.027 14.277
17 18.077 18.127
15  21.027 21.287
12  24.897 24.947
10 28.027 28.487

We picked these frequencies after looking over the operating plans for other events on the same day (such as the various state QSO parties, the QCWA QSO party, etc.) as well as international band allocations. We may try 40m early in the day before strong absorbtion sets in, but then we’ll move to the higher frequencies. We are likely to spend the lionshare of the activation on 17 and 20m. In the last couple hours, we may try 30m. We will not be operation above 50Mhz for this event. [Note: Another update – to accomodate the US band plan, we have tweaked the center frequencies from the original posting, the three affected voice frequencies are highlighted in red.]

If anyone hears use, we’d sure appreciate being spotted so other people can find us! I think we will have cellular connectivity from the site, so we will also post our band changes via twitter (@dhakajack, with the hash tag #signalmt). My twitter account feeds to this website (, so the tweets will be visible in the right column in the desktop view. We will not post via twitter or SMS to qrpspots since we will be working barefoot for most of the event.

March contesting

I had a great run in the March NAQCC sprint, a two hour QRP CW sprint that encourages the use of straight keys.  I am surprised (but pleased) to see that I took the top position in the W4 division for simple wire antennas. I think this speaks to good conditions where I was operating, luck in hitting so many multipliers, and the absence of other stations that typically score very well (K4ORD and others).  I know that several of the contestors, e.g., K4BAI, were already preparing for their CQ WW WPX runs,  so that might explain the absence of some of the regulars.

Speaking of CQ WW WPX…

S line station, tuner, swr meter, paper log
Upper book: antenna tuner settings; lower book: the contest log.

With a 100W station and a couple fixed antennas in my attic, I’m not much of a threat to the CQ WW WPX establishment, but I thought I’d give it an “old school” try this time.  Instead of working the contest with my workhorse Kenwood TS-450, I fired up the Collins S-line station. With the recently acquired Heathkit SA-2040 antenna tuner and the TenTec 1225 SWR meter to keep an eye on things, I had enough flexibility to work all the bands.

I had a number of other things to do over the weekend, so I put in about four hours in the contest. I went full manual — not even computer logging, just some sheets of graph paper. I worked 136 contacts, three of which were dupes (the paper-only method leaves something to be desired in terms of real time dupe checking).

According to my log, I worked the following DXCC entitites: Aland Island (Finland), Asiatic Russia, Belarus, Belgium, Bonaire, Curacao, Bosnia-Herzegovina, Brazil, Bulgaria, Canada,Canary Islands, Croatia, Cuba, Cyprus, Czech Republic, Dominican Republic, England, Estonia, France, Germany, Hungary, Italy, Latvia, Lithuania, Luxembourg, Madeira Island, Montenegro, Morocco, Netherlands, Norway, Poland, Portugal, Serbia, Slovak Republic, Slovenia, Spain, Sweden, Switzerland, Ukraine, the USA, Virgin Islands, and Wales.

The rigs worked flawlessly, and the warm sound was pleasant. I did a lot of repeating, and surely my signal was not very strong compared to most, but it got the job done.

Shopping in Brussels: Composants Electroniques et Jeux de Société

Overexposed picture showing conjunction of venus and jupiter above the grande place
Conjunction of Venus and Jupiter above the Grande Place

I had a couple hours on Friday to do a little shopping before meeting up with friends for dinner in Brussels. We had planned to eat near St. Catherine’s, so I took the metro there a bit early. My first goal was Elak’s electronics, which is one of the best hobby electronics stores on the planet, as far as I’m concerned. Part of the store is given over to computer components, but the rest of the store is discrete components: walls of switches, transformers, project boxes, batteries, etc. There is a center counter area where they maintain an impressive assortment of ICs as well. They carry the entire velleman kit line, plus related accessories.

The only drawback to the store is that it is in a corner of Brussels where the streets do not conform to any sort of rectilinear plan. I always get lost trying to find the store, and having a Google map in hand only makes things worse. It is like that part of Brussels does not obey the normal rules of time and space. Sometimes I try to get to it from the De Brokère metro, sometimes from Ste. Cathérine’s, but no matter what, I end up getting spun around and asking directions. When I get there and think about the path I took it all makes sense, but as soon as I leave, the store randomly pops up in some other universe.

External view of Elak ElectronicsAt least I can recognize the outside of the store when I do find it: the wall next to it has a mural with an elephant and a gorilla. The other place that has a reasonable selection of more common components is MB Tronics. When I last visited them, they had a storefront on Chausée de Louvain not far from the Meiser traffic circle, but I believe they’ve moved the store in the last year a couple blocks to the east. MB’s store hours are not quite as fixed as Elak’s, and the store does shut down during part of the summer for vacation, so Elak’s is always a safer bet.

I ended up buying a set of machine screws and a package of assorted ceramic disc capacitors. I’ve bought this screw set before, and had used them up making various projects. The screws are just the right size for most small projects, particularly the kind that you build in an altoids tin. The capacitor assortment is much better than you can find at Radio Shack. The Radio Shack bag-o-capacitors is full of unhelpfully small value components, whereas the Velleman-brand assortment has a full range (in searching the web, I note that they are also sold by Fry’s Electronics stateside). I am sure that these caps are not top-of-the-line low variance components, but they are great for prototyping.

External shot of Wonderland windowOn the way back to the restaurant, I stopped by a game shop, Wonderland, that is only a few minute walk from Elak’s. This store sells primarily  French language versions of “Euro” table top games: Settlers of Catan, Dominion, Carcassonne, etc.  I don’t think that I saw any Z-man or Rio Grande games, but that’s not a criticism as the store wouldn’t have had room for them. The games were predominantly board rather than card, and I wish I had had more time to look through their inventory. Next time I visit the store, I’ll make sure I have more time, and I will also be sure to have more room in my suitcase. They get extra credit for having zombie dice on the counter. While I’m certainly loyal to my local supplier (Area 42 Games), Wonderland may carry some games that haven’t made it over the Atlantic yet.

Winterfest 2012

SA-2040 tuner: two big capacitor knobs, one central roller inductor knob, a turn counter and a knob to select output

At the end of February, the Vienna Wireless Society held its annual hamfest, Winterfest, and this partially accounts for my absence of blog entries in recent months, as I was coordinator for the event. We had more than 100 vendors in our indoor area, another 40 in our tailgating space, and about 700 people were attracted to the event. I could go on at length about the event, and maybe I will at some point, but for now I’d like to post about the items that I picked up at the event. I’ve mentioned my acquisitions to a couple friends and want to show some pictures.

As soon as the event opened, my eyes landed on a Heathkit SA-2040 Tuner. I have an LDG AT100Pro automatic tuner and it does a great job, but for the Collins gear, I wanted a fully manual tuner. The automatic tuner makes excursions in and out of good match, and I just don’t want to subject the finals of the S-line equipment to variable and out-of-range vSWRs. I’d rather map out the setting for the band segments that I use and then manually adjust.

I had, in fact, been looking for a few months at several models of manual antenna tuner on ebay, eham, and the other usual places. The SA-2040 was high on my list. Typically they run over $100, plus shipping. When I found one at Winterfest, I was happy to see that it was less than $100, in good shape, and already had the modifications that I was considering — a knob with a thumb wheel on the roller inductor, a switch to select multiple coax outputs, and a switch that takes the input to ground. I had a lot of administrative work to do at Winterfest, so I bought it as soon as the event opened and stuck it in my car for the day.

An overhead shot of the internal workings of the SA-2040

When I got home, I took a look inside it. Truthfully, when I got home, I crashed on the couch for the day and didn’t get around to looking inside the tuner for a few days, but either way, I did look inside, and saw that it’s in fine shape. The roller inductor and capacitors are heavy duty and in pristine condition, with no evidence of arcing. The modifications look solid, and I couldn’t spot anything troubling. I screwed it back together and then started trying to figure out how I could possibly fit it on my bench.

The SA-2040 does not have an SWR meter, so I needed one. Luckily, I had ordered one several months ago from Ten-Tec as a kit: the 1225 SWR/Wattmeter. I had a good experience putting together the model 1320 QRP transceiver from Ten-Tec, and it has held up well as I’ve lugged it all over the world making contacts. The SWR kit was also a first-class affair — packed well, parts grouped meaningfully in several bags, all parts present with appropriate excess on wire, and a great manual. The wattmeter consists of a metal cabinet, a large cross-needle display, a range switch, and the option of average or peak-reading for both forward and reverse power.

Front view of the TenTec 1225 wattmeter, with meter illuminated in blue

The organization of the manual was excellent, with the usual check it and then check it again double column for checking off completed steps. There was no ambiguity in the instructions, all the landmarks were obvious, and I didn’t need to do any sort of clever interpretation or fall back on the internet to find exceptions, modifications, etc.

Calibration requires no equipment beyond a digital VOM. One trimmer pot controls internal reference voltage, and other pots are used to set the forward/reverse fudge factors for each power range. Having built the WM-2 QRP watt meter, I’d say that this one was slightly easier to calibrate. This SWR meter was a more complex build with more parts and more mechanical connections, but that is commensurate with its additional features (and I’m certainly keeping the WM-2 as well).

So, the 1225 Wattmeter was assembled over the last week and is now inserted inline between whatever rig I’m using (the first coax switch) and whatever antenna is selected (second coax switch). One fun feature of the 1225 is the RGB backlight, which can be adjusted to any color with trimmer pots. I’ve set mine to a dark blue.

TRS-80 model 100 and manualThe other item I bought was not radio equipment. Near the end of the hamfest, I walked by a table and saw a TRS80-Model 100 “laptop” computer. I’ve always thought this computer was way ahead of its time, and that it represented an important milestone in engineering, so when I saw one marked down to $50, I bought it.

This computer is powered either by wall wart or four AA batteries, has a full keyboard, boots instantly, and has a number of I/O ports including an RS-232 and the venerable S100 bus. I verified that this one is fully operational. I’m not sure exactly what I’ll do with it, but I think it was a good purchase.


Contests 2011

It’s still barely the first week in January, so I’m going to do a little retrospective on contests entered in 2011. Some contests I just hear on the air and jump into (particularly QSO parties), others I obsessively prepare for over several months (like the Indiana QSO Party, Operation Sizzling Pork). Usually, though, I don’t think much about them when they are over.

Not included in my retrospective are some of the contests that I participated in as a member of VWS, e.g., Field Day, and the NAQP SSB and CW.

Except for some of the QRP sprints, most contests take at least a few months to turn around results, which is somewhat puzzling considering that log submission is almost universally electronic. So, here’s the run down, based  on a quick scan of outgoing emails with logs attached. Unless otherwise stated, I entered as single operator, low power, CW only:

MN QSOP 1st VA station in category
BC QSOP Hey — I was one of only 20 outside BC in the contest
CQ WW WPX RTTY No way I was going to do well in this contest, but I made some contacts at least
2011 ARRL International DX CW I gave up trying to find the results on the ARRL website
VA QSOP I worked part of this contest with the VWS club, but them went home in the evening. I ended up getting a certificate as 1st place station in Fairfax, County, Virginia. Not bad for a half day’s work.
FL QSOP I recall this one — I was on the back porch with a QRP rig and only worked a couple, but had fun.
IN QSOP Well, I’ve certainly written enough about Operation Sizzling Pork on this blog, but it was the highlight of the year for me. I had fun preparing, during the contest, and even afterwards in compiling the scores. We placed second in the category of multioperator, multistation. Our station ran low power and worked both CW and SSB.
CQ WW WPX CW I think I was camping an entered this one QRP. A bit frustrating because only one out ten heard me, but after a few hours, I had a decent number of international contacts on 5W with an improvised antenna
REF The French amateur radio league contest. I placed 20th among US operators – pas mal.
HA DX I always enjoy the Hungarian contest. I came in at #278, but I still like the way they run this contest, communicate with log submitters, post the results, etc.
RAC Canada Day The RAC contest is also a favorite, although the results are not broken down geographically.
IARU HF The International Amateur Radio Union contest was fun in that I made contact with a number of headquarters stations and added a few new countries to my list. The results have not been posted yet.
The MARAC US Country QSO Party I had just installed the rig in my car and I made exactly one SSB QSO in this contest, but one is better than none. I’d like to try this again next year, but working CW.
Maryland/DC QSOP I worked this one with the NIH Amateur Radio Club, so it wasn’t an individual effort. We ranked second as club station in Maryland.
TN QSO Party I always seem to have great propagation in TN, so I worked this one QRP. I came in as the #3 out of state QRP operator, so I was very happy.
Arkansas QSO Party Luckily, they break the scores down by state, and as not many others from Virginia entered, I was the top VA station. It’s always worth sending in a score.
WAE SSB Again, I don’t have a chance in this sort of contest, but I did finally figure out how the whole QTC thing works.
OSPOTA I heard a random call for the Ohio State Parks on the Air Contest and dialed around to catch a few more. I came in #10 for stations outside Ohio.
Arizona QSO Party I had one QRP CW contact while I was in Montreal for a conference. Results aren’t up, but looking at logs received, I can guarantee that I was the only VE2 entrant!
NY QSO Party I usually have good connections to New York during the QRP sprints, so I also worked this contest QRP. I think I did pretty well, because I recall crossing a bunch of counties off my list, but results are not yet posted.
IL QSO Party I came in 49th in this short contest
ARCI Hoot Owl I worked this contest in the dark with a 20m rockmite, a longwire antenna and some mosquito spray. I had a great time and my score was roughly in the middle of the range, largely thanks to the bonus for working portable. I’d like to do more ARCI events this year.
NAQCC Sprint Hands down my favorite sprint. I have slowly worked my way up, both in terms of operating skill and antennas. I look forward to this every month, but schedules don’t always work out.
Spartan Sprint I also enjoy the SS, and have been working on trimming the station down from a chubby to a skinny. I can now operate pretty skinny, but only on one band at a time.

AKA Interface Considerations

A couple months ago, Ben, NN9S, suggested developing a morse code keyer that would run on android devices (see his write up and video). Since then, we’ve been designing hardware and software to get the job done. The software lives in a repository on the Google Code site, and is moderately functional, but far short of ready for general release. On the hardware side, we’re still batting around ideas. Here is a brief history of the ground we’ve covered with regard to hardware design, and some idea of what’s coming next.

Phone, AKA, paddles and a transmitter - the most common configuration.

We considered all sorts of options such as having the device’s left and right channels run into a standard keyer, using the USB port directly, and some other more exotic alternatives (bluetooth anyone?), but we eventually settled on the idea of having the android device output a sound, which could be used directly to modulate a signal, or could drive a switch of some sort.  The simplest configuration would be the device plugged into the androidomatic keying adapter (AKA), and the AKA plugged into the radio’s key  jack. Presumably, most people would want to be able to also key their rig using a straight key, paddle, or bug, so we assumed that the AKA and some other sending device would connect to the key jack via a Y adapter of some sort.

Android devices encompass a gamut of hardware platforms including phones, pads, netbooks, and dishwashers. Well, soon. At home, my only android devices were a Nexus S phone and an Optimus T phone, so that’s where I started in terms of characterizing the platform. Two essential tools were the android app “FuncGen” and the multiplatform audio editor “Audacity“. FuncGen runs on the android device and can generate various waveforms with all sorts of parameters, whereas Audacity test files (e.g., *.wav files) can be generated on a desktop computer and transferred to the android device for playback using apps like media player or winamp. The phone’s output can also be recorded via Audacity to analyze fine timing events (for those of us without fancier equipment).

Using FuncGen at full media volume to generate a 1000hz sine wave, the Nexus S put out about 1.85V peak-to-peak (654 mVrms) into a 20-100k load, and the Optimus T put out 1.9V peak-to-peak (671 mVrms). The output impedance of the Nexus S was about 14 ohms, and the Optimus T was near 17 ohms. I calculated the maximum power transfer at around 7.9mW per channel for the Nexus S, and 6.4 mW for the Optimus T.

Output voltage at maximum volume into a fixed (20k) load was flat for the Nexus S from 20Hz to 3000 Hz, with only slight attenuation (down less than half a decibel) at 10kHz, and down almost 2 dB at 20kHz. The Optimus was more sensitive to frequency and was ideally flat from 300-3000 kHz, with more marked attenuation at 10kHz (less than 1 dB) and 20 kHz (down almost 5 dB). Both phones demonstrated a log-linear relationship between the number of clicks on the media volume scrollbar and the rms voltage output (e.g., for the Nexus, if full volume was 707 mV, one detent down was 477 mV, the next was 317 mV, 224, 150, 100, 70, etc.) — meaning that the voltage drops off fairly quickly to relatively low levels.

The first hardware design considered was literally a VOX keyer circuit. A quick websearch turned up a nice design by N1HFX. This straightforward circuit is based on a 1458 op amp, which is essentially two 741C op op amps in one package. The circuit was meant to work from very low voltages generated by a microphone, so the first op amp acts as an inverting amplifier, and the second as a comparator. The 741C op amp is a dual voltage op amp, so to run this from a battery, the positive input of the first amplifier is raised to half Vcc by a voltage divider; likewise, the set point for the negative input is a bit above half Vcc. The output from the second amplifier will be a square wave at the same frequency as the input wave, and ranging from about 1V to (Vcc-1V). Since this drive would only be half-duty cycle, some smoothing is necessary before driving a transistor. A simple RC circuit sets the degree of smoothing, and a diode prevents back-discharge of the capacitor into the amplifier. Since the circuit was designed for voice, the RC values were chosen for a relatively long time constant; however for purposes of keying a rig for fast CW or even Hellscreiber transmission, a low time constant is preferable.

Based on the N1HFX design, we prototyped a similar circuit, with the following exceptions – for cost/availability, we used an RC 4558 op amp, which is a workalike to the 1458. Because the phone’s volume is adjustable, and the output is relatively high, we used a fixed resistance ratio for the comparator set point. The smaller RC values used were just large enough to smoothen output wave. We added some bells and whistles including a power indicator LED, and another LED to indicate when the keying circuit was closed. It was probably overkill, but to further protect the phone, we stuck an optoisolator between the rig and the rest of the circuitry. In retrospect, all of these LEDs are nice looking, but consume many orders of magnitude more power than the keying circuit itself, and they might as well be omitted — in our final designs, we just key the rig from the switching transistor.

Another design that we considered was based on a circuit described by Robots Everywhere in their implementation of an earphone jack-based serial port on android devices. Their write up made us wonder if android phones could put out digital levels through the ear phone port — boy, that would certainly make our job easy. As it turns out, some can and some cannot.  The Nexus S can sustain a very flat positive or negative voltage without breaking a sweat: at 20Hz, the output waveform is very square, at 1000Hz, there is some ringing. The Optimus T, however, looks like it’s output is capacitively coupled. At low frequencies, it’s not very square at all — the output capacitor bleeds voltage until the next half cycle. The take home is that around 1000Hz and above, both phones can generate some semblance of a square wave.

The Robots Everywhere design centered on an LM324 single voltage source quad op amp, but used only two of the four op amp subunits. Our next design was aimed at getting away from timing issues related to signal rectification and need for a “filler” capacitor prior to the switching transistor.

Since the phone can generate a stereo output, our next circuit used the left and right channel to generate square waves180 degrees out of phase — effectively get a halfwave rectifier for free by doing it in the software. These waveforms were fed into op amps like in the first design, with amplification occurring in the first stage and inversion in the second stage for each channel. When the positive portions of two channels are then brought together through diodes, the result is just about a flat positive voltage, about about 1V under Vcc (due to the diode drop). This voltage is applied to the gate of a 2N7000 enhancement mode N-channel FET, which has a threshold voltage of just under 3V. The gate capacitance itself further smooths the small defect at the edges of the two square waves. The 2N7000 could be directly connected to the rig, but we again used an optoisolator, since the design required the use of a battery anyhow.

Both the dual and quad op amp designs resulted in some prolongation of tone sent out the phone’s earphone port. The best we got with the dual was about 4-5ms, and the quad op amp design yielded around 3ms extra duration. We could compensate in software, ending the signal earlier, but it would be preferable to avoid that complication. For morse code, this extra delay would probably be unremarkable, as a single code element at 30 wpm is 40 milliseconds, so +/- 10% is probably tolerable. At fast code, it becomes significant, though — at 60 wpm, a single element is 20 milliseconds. Since we had plans to implement Hellscreiber keying as well, with a minimal on-time of 8.163 milliseconds, this delay was not acceptable.

In addition to the timing issue, we realized that it would be preferable to not require a power source for the adapter. Luckily, one solution address both problems — using a transformer to step up the voltage enough to directly bias a switching transistor. This approach was inspired by the interesting work done by the “HiJack” team exploring power harvesting from the iPhone’s earphone port. They designed a miniature power supply using the AC from the iPhone’s audio output as driving voltage. A similar approach was taken by Wolphi, in connecting the iPhone to microphone input for his excellent PSK31 appplication for android. His circuit was, in turn, based on a circuit proposed by KH6TY.  Similar solutions have also occurred to hams in the past developing interfaces for sound-based keying of Hellscreiber, including a design by K9JRI that includes a voltage doubler.

In considering transformers for stepping up voltage, we did try the nearly microscopic one employed by the HiJack team. Unfortunately, it was too far off in terms of impedance matching to function well. We ended up going for the most accessible transformer, a 8:1000 ohm audio transformer from Radio Shack. This transformer gives about an 11-fold voltage step-up, so some losses in rectification are tolerable. In principle, germanium diodes or even synchronous rectification could reduce these losses, but there is enough head room to not worry about it. The currents involves are minuscule, so there is no problem is using tiny (read: cheap and available) signal diodes like a 1n914. A 0.01 uF capacitor does not entirely smooth the wave, but it ensures that the voltage is never below about five volts, and the 2n2222a transistor remains saturated when the transformer is energized. The additional duration introduced by this circuit is around 300 microseconds. I tried adding a voltage doubler per the K9JRI circuit mentioned above; the voltage was marginally increased and the duration increased slightly as well to around 1 millisecond. Since the extra complexity did not add much, I’ve opted to stick to the simpler design, which can be built from easily obtained parts for less than ten dollars (much less, if you mail order and/or buy in bulk).

The transformer-based designs have the benefit of providing galvanic isolation between the android device and the the keying circuit and rig. One downside to transformer-based designs is that they need relatively high volume output from the phone. The design above required that media volume be set within three clicks of maximum on the Nexus S. The dual op amp design worked down to 9 clicks below max, and the quad op amp design worked down to 12 clicks below max.  Both devices tested put out about the same voltage and power, and hopefully most android devices are in the same ballpark, but if there were a particularly underpowered device, or if this circuit was used in some other context where lower output were available, a design with active components might be necessary. The other drawback to

We are now trying to figure out ways to miniaturize the design, and of course, the most limiting factor is the transformer. If anyone spots a suitable transformer let me know. I guess the idea one would be 16 ohm on the primary, and 2000 on the secondary (or 4000 on the secondary, with a center tap — allowing us to get rid of two diodes).

[Update 17 May 2016]

The androidomatic keyer has not had a lot of love lately; Ben and I have been busy with other projects and developing for android requires more sustained attention than we can afford for now. However, I’d still like to see this work preserved. When the GoogleCode repository blinked out of existence, I moved the software archive over to github, where it now resides:

Warming the shack

The power supply, receiver, transmitter and station monitor/phone patch, plus microphone and key
Collins S-Line Station

For several years, I have been putting together a Collins S-line station, and earlier this week, I fired it up for the first time.  This station was the top of the line, when it was produced in the 1960s, and although there have been plenty of technical innovations along the lines of improved frequency stability, image rejection and DSP, these units still sound great.  Now that winter is approaching and the basement is growing chilly, I was more motivated than ever to get this tube equipment on the air.

I have had these radios packed up for quite a few years, not really wanting to ship them all over the world as we moved. Last year, I started putting them back into order. I started by looking through the archive at the Collins Collectors Association and joining their email list. Between the archive and routine access to people who know these rigs inside and out, I came up to speed in no time.  I didn’t see anything too amiss on my inspection of the rigs, aside from some carbon residue near the rectifier tube in the power supply. This is a common defect in these supplies — some arcing occurs from the rectifier tube to the metal cabinet, so I wasn’t too worried about that, but realized that the rectifier socket would need to be replaced by a ceramic one down the road.

photo of the underside of the 32S-3 transmitter
I took a lot of photos during the survey phase to provide some insurance that I'd be able to reassemble the radio after working on it. The underside of the 32S-3 transmitter showing extensive point-to-point wiring. The "black beauty" capacitors are prominent. They and the surrounding silver-colored electrolytic capacitors were replaced.

The most likely items to fail in rigs of this age are the electrolytic capacitors, so I went through each unit and replaced all electrolytic capacitors, plus any paper capacitors and some of the less reliable “black beauty” oil-filled caps. There is some debate about whether it is better to replace preemptively or only when there is evidence of failure, but I leaned towards the preemptive side. While I want to preserve the original engineering, I also want these units to perform well and get some actual on-the-air use.  The other obvious thing that can fail are the tubes. Of course, I can’t just run down to the corner store anymore and use their tube tester. To put that statement in context, these radios are just slightly older than I am.

There are a lot of patch cords that run between the station components, some audio, some RF. These and the power plugs and control connectors had degraded to the point that I wanted to replace them. I rebuilt the connecting cords and power cords using the original plugs and sockets, but for everything else, I visited Joel at RF Connection in Gaithersburg, Maryland. Conveniently, his store is about five miles from where I work, and it is packed with every connector, cable and adapter known to man. He also stocks a lot of the materials used in restoring Collins equipment, including replacement feet. Yes, I replaced the little rubber feet, because they also had degraded over time.

photo of a capacitor deep within a metal slot
This was my favorite capacitor to replace -- deep down in a metal pocket that I couldn't disassemble. It was like soldering a ship in a bottle.

After inspecting the units, I took each out of its cabinet and to greater or lesser extent stripped them down. All the tubes came out and everything got a thorough cleaning. All the pots got a shot of deoxit, and other bits of mechanical tune up were performed. I replaced the burnt out panel lights with long life replacements from D.A. Buska Engineers, LLC.  These LED lamps should last just about forever, which is good because it is something of a hassle to replace bulbs. It involves my wrist bending in ways that seem unnatural. However, I would think twice about using the LED lights again if I did another restoration. Their light is harsher than the original incandescent lamps, and there is some barely perceptible flicker.

After putting everything together came the smoke test. Since these rigs had been off for more than two decades, I approached this cautiously. I tested each unit separately, bringing power up slowly using a variac (auto-transformer). The power supply came up to voltage and all the supply outputs tested nominal. The receiver also powered up, and when I hooked it up to an antenna, it seemed reasonably sensitive. The band calibrator seemed to work, and put the dial right on WWV. I flipped through the different bands, and could hear signals on all of them.

Photo of the upper deck of the transmitter, with the final amplifier cage in the foreground
The top side of the transmitter. The front of the radio and the main tuning dial are in the rear, the final amplifier cage is in the foreground. A bunch of the tubes have already been removed at this stage.

The transmitter was more complicated. When I got to about 80V on the variac, a thin wisp of grey smoke wafted upwards from the power amplifier section of the transmitter. I couldn’t find where the smoke was coming from, but the take home message was clear — I needed some professional help.

Even if I had not hit this snag, I would have sent the radios in for some professional servicing at this point. After such a long period on the shelf, they were in need of a laboratory realignment, which is beyond what I can do with my current equipment. I also wanted someone who really knew Collins equipment to look them over.

I contacted Peter Wittenburg at Collins Rebuilders. He is located near Annapolis, Maryland, which is close enough that I could carefully pack the rigs in my car and drive them up. It was definitely the right call — the radios got the love and attention that they deserved from an expert. Peter swapped out the rectifier in the power supply, fixed a fairly major problem in the receiver’s permeability-tuned oscillator (not for the faint of heart), replaced a few tubes that had seen their day as well as a few other discrete components that were not up to spec.  He ran the rig through its paces and gave me a nice report, that shows by and large, the rigs were seaworthy.

An Astatic microphone
An Astatic D-104 microphone.

While he was performing his analysis and repairs, I picked up an Asiatic “lollipop” microphone with the proper Collins connector at a hamfest. I had previously borrowed a variac for testing, but decided to purchase one for fulltime use in the station. The Collins equipment was made for a time when the line voltage was lower than the present, and higher voltages will shorten component life. The whole station is now plugged into an isobar strip that itself is plugged into the variac, which maintains voltage at 117V RMS. The station is turned on/off with the isobar rather than each unit’s power knob, as those knobs are all but irreplaceable and are prone to mechanical wearing.

Over last weekend, I made sure that my attic antennas were tuned up, presenting less than a 2:1 vSWR across their useful ranges, as the tube equipment is not tolerant of (read: smokes when confronted with) less well-behaved loads. The ionosphere was revved up as high as it has been in the last decade or so, which boded well. I made my first contact on 40m with WB8PPH (“wb8-pumpkin-pie-headquarters”), who was running a special event station for the Circleville Ohio Pumpkin Festival. I had a few more contacts with PA, IA, and IL and then Sweden, England, Croatia and the Czech Republic on 20m, and Cuba, Honduras, Mexico and finally South Africa on 10m. The received sound quality was golden, and I received favorable reports concerning my audio quality as well.

schema of s-line wiring between different modules
Interconnections for transceiver operation.

The rigs can be run in transceiver mode, where the transmitter is slaved to the receiver’s VFO, or they can be run independently, with the both the receiver and transmitter VFOs in action; this is what you would have to do to operate split, for instance, as there is no other RIT/XIT function. Separate operation is also the way to go for CW operation. In transceiver mode, you would hear nothing when zero-beat to the incoming signal (naturally), and the offset in CW mode is 1.3 khz, which is impractically large. To operate CW, I picked a clear frequency and used the “cw-spot” function on the transmitter to send a low-level signal to the receiver, allowing me to adjust them to the same frequency. I did one round of calling (straight key, natch) and had an immediate reply from Northern Ireland and Bulgaria. I had a little difficulty getting the vox-balance right to accomodate semi-breakin operation (some hangtime after transmit so the relays aren’t constantly clicking, but not so much that I miss the reply). According to the overseas stations, there was no problem with key clicks or chirps, so I guess we’re okay on that front as well.

I’ve never been a big fan of sideband, but I got a big kick out of working stations with this rig, and I think I might be spending more time behind the mike this winter.

QRV à Montréal

Graffitied picnic table with Tentec 1320, Winkeyer, Palm Paddles, and wiresI’m up in Montreal for a conference on rare diseases and the agenda is pretty tight. However, after meetings ended this afternoon, I scampered northwards from the hotel, up past McGill University, heading for the high ground of Mont Royal Park. The downtown is a canyon of metal buildings, but ground slopes up as you head north, away from the river.  I actually didn’t climb to the top of Mont Royal — I stopped when I found a picnic table about half way up. The top of the hill sports a bunch of antennas, and I thought it best to keep some distance from other radiators (and the giant metal crucifix at the top of the hill. I’m not sure if it radiates, but I didn’t want to go near it either).

My picnic table was already decorated by the local artisans with their initials and names, so I knew it was something of which they were proud. Conveniently, but not too surprisingly, there was a tall maple tree nearby, and the antenna went up in one throw (because no one was looking). I set up the TenTec 1320, the Hendricks SLT+ tuner, and my Swedish lead-acid battery. I should mention that this time, TSA had no problem with lead acid batteries. I guess that was last week’s policy.

I was operating as “AI4SV/VE2”, which is a quite a mouth [fist] full. The first station I worked was Ivan, IZ4DLR, who gave me a 569. He was running 200W into a 3 element beam. I informed him that his beam was performing very well both coming and going. My next contact was with Stan, N7OC, who was also running 5W in Custer, Washington. I was pretty happy with the distances — Italy and Washington within a few minute of each other. I had a few more contacts, working Virginia, South Carolina, and even one station in the Arizona QSO Party. I hope I was a multiplier for him. I’ll have to think about what station category I’d be in that contest — Single op, single transmitter, single band, cw only, qrp, portable, Candian.

A basket of friesOn the way back, I stopped by a restaurant advertising itself as a transplanted Belgian fritérie. It was nice to see a place that served different sauces with their fries, but the fries themselves were a bit overcooked, and the sauce andalouse could have been a bit spicier. Nonetheless, their beer was good, and they had hockey on a big TV, so it was still worth the trip.