Push It To The Limit

New England Code Talker by AA1TJ
New England Code Talker by AA1TJ

Although there are many days when I can barely stand the level of rudeness on QRP-L (and increasingly on qrp-l.org), I am sometimes reminded why I maintain my membership. Some recent events there have helped to boost up the numerator in the signal/noise ratio, and correspondingly, my interest.

In case you haven't followed much of what has happened on the list in the last few years or haven't listened to SolderSmoke, there's a fellow by the name of Michael Rainey AA1TJ, who could be considered the mad genius of the QRP world. He has created what has to be considered some of the most unique and inventive minimalist QRP circuits that our hobby has ever seen. Take a look at his website to get an idea of what I'm talking about. I've also attached a YouTube video below showing you how AA1TJ has to operate this very unique transmitter.

AA1TJ trying for transatlantic QSO
AA1TJ trying for transatlantic QSO

His latest flight of fancy is his New England Code Talker voice powered CW transmitter. Yes, you heard correctly; the transmitter is powered 100% by voice sound pressure energy (about 15 mW RF output). AA1TJ has already made numerous successful QSOs with the transmitter, proving that the concept actually works. Recently he, AA1MY and W1PID met at the beach front cottage of W1REX to attempt the world's first voice powered transatlantic QSO, as well as what was claimed to be the world's first transatlantic QRP QSO on 160 meters (I think I misunderstood that. It's supposed to be AA1MY's first 160 meter transatlantic QRP QSO), both very amazing feats. I won't spoil the story, so get yourself over to W1PID's website to read the details of how this expedition turned out. I must salute all of you gentlemen for pushing the boundaries of our wonderful hobby and trying something never done before. Well done!

Update: Here's the "Rexpedition2009" report about the event from W1REX (PDF format).

Update 2: A great video from W1REX showing the transatlantic 160 meter QRP QSO:

Field Day 2009

2009 Field Day logoDisclaimer: For those who don't know, I'm an employee of Buddipole, and I do speak quite a bit of my positive experiences with some Buddipole products in this post.

Yes hams, it's that time of the year again. Field Day, the Super Bowl of the ham radio world. I haven't had the best track record of participating in Field Day over the years, due to a few different factors. The largest stumbling block is the nasty allergies that I get during late spring, which usually end up peaking in intensity right around the end of June. The other problem is that I've never been a big fan of the big-time organized local clubs. I won't go in to the reasons for that (you can dig back in the blog if you are really interested), other than to say that in my experience they are not the kind of places that I find interesting.

Now that I own a house with a proper backyard, I feel like I now have the option to participate in Field Day by setting up out back, so that I can duck inside if my allergies get too out of control. It also helped that I recently started taking some new meds, which have helped to control the allergies quite a bit better than anything else so far. So I was more than happy to give FD a go this year, even though it wasn't going to be more than a backyard adventure.

Station Setup

Field Day 2009 - Backyard
Field Day 2009 - Backyard

Given the recent development of my employment with Buddipole, and the demise of my main station random wire antenna in a recent spring storm, it only made sense to deploy the Buddipole. I could have dragged out the IC-718 sitting idle in the shack and paired it with my very heavy 35 Ah gel cell, but I was feeling up for a bit of a challenge. I settled on using the FT-817, and considered pairing it with my recently constructed 20 watt linear amp, but I realized that running 20 watts would give me the same power multiplier as running 100 watts would. So I figured, why not take the dive and go QRP for the entire event? Not only that, but why not make SSB the main mode of operation? This was appealing to me not only because I am a QRPer at heart, but also because it would push my limits, and give me something new to try.

I've run into my share of hams who think that QRP is the devil's handiwork, and that anyone running less than 100 watts is inflicting undue hardship on the poor receiving station. While I know that a QRP signal does have a more difficult time being heard (especially SSB), I also know that there have been plenty of times when the receiving station would have had no idea that I was running QRP unless I told them (and many times, I won't tell them). The fact is, if you can hear me well enough, you'll answer me. If not, you won't. Yes, I get less contacts running QRP. But if the conditions are too painful for the other station, they will just not answer me or will politely cut it short. I especially feel absolved of any guilt running QRP SSB on Field Day because of the whole nature of the event. The concept is to test how well we do under less-than-ideal conditions. Quoth the rules (emphasis mine):

2. Object: To work as many stations as possible on any and all amateur bands (excluding the 60, 30, 17, and 12-meter bands) and in doing so to learn to operate in abnormal situations in less than optimal conditions. A premium is placed on developing skills to meet the challenges of emergency preparedness as well as to acquaint the general public with the capabilities of Amateur Radio.

Field Day 2009 - Buddipole
Field Day 2009 - Buddipole

The great thing about using the Buddipole was the ability for me to use it in conjunction with the frequency agility of the FT-817 to hop around the bands. Yes, it does take a bit of time to change bands, which is not quite as fast as using a multiband doublet with a tuner. However, with just a bit of practice, you get to know what setting sare needed to resonate your antenna on any band and can reconfigure and tune it in a matter of a few minutes. Given that I decided to run QRP SSB, I needed every bit of power I could get, so I was glad to not have a lossy tuner in the way.

Given the somewhat last minute nature of my decision to play in Field Day, I didn't have a way to power a notebook PC with a battery, so I settled on the old standby of paper logging. Since I decided to stay strictly search & pounce, it wasn't a big deal to paper log. The biggest pain is in dealing with dupe avoidance, but I figured that I wouldn't have to worry about that too much since I would be racking up huge QSO counts.

Field Day 2009 - A123 Battery Pack
Field Day 2009 - A123 Battery Pack

The only thing left to nail down at this point was power. I knew that I wanted to try out our brand new A123 lithium nanophospate battery technology that we are ramping up at Buddipole. If you don't know about this battery technology yet, prepare to be blown away when we officially roll these out. This technology has been used in the R/C hobby for a few years, and is just now making it's way into amateur radio use. It also happens to be the same technology used in the upcoming(?) Chevy Volt plug-in hybrid vehicle. It would take too long to list all of the advantages of this technology here, but the amazing flat discharge curve, long life, very quick charge time, and incredible safety are all reasons why I'm confident that this will be the dominant battery technology in the portable/pedestrian mobile ham circles within the next few years. The particular pack that I was using is a 3S1P configuration, which means 3 cells in series, one parallel set (we also have 4S1P and 4S2P packs). Each cell is 3.3 V nominal, so this pack is rated at 9.9 volts, which is perfect for use with the FT-817. A **1P pack has a capacity of 2.3 Ah, which I figured would give me at least a few hours of operating time.

Field Day 2009 - Solar Power
Field Day 2009 - Solar Power

Being at a bit of a disadvantage in the "contest", I wanted to pick up some extra bonus points, so I remembered the 5 watt Harbor Freight solar panel that I had gathering dust in the closet. Using that in conjunction with my half-depleted 7 Ah gel-cell, my power strategy was fully formed in my mind. During the sunny part of the day (my backyard is on the north side of the house and is fairly narrow, so it doesn't get a ton of sunlight) I would use the solar panel/gel cell combo, then switch to the A123 pack when there wasn't anymore sunlight to be had at the station.

Given the set up that I described, it looked like I would fall into the 1E class for the event. Given a very strict reading of the rules, it seemed like I might have been able to claim 1B Battery, but in the spirit of the event, 1E was the appropriate choice.

Operating

I wasn't able to start operating right at 1800 UTC due to some chores that needed to be completed first before play time. When I did get going, I started on 20 meters with the Buddipole in vertical dipole configuration and quickly started to get QSOs in the log. As I mentioned earlier, my strategy was strictly search & pounce, choosing only the loudest stations to try to work. For the most part, it was a successful strategy. I was able to work just about everyone that I heard at a S5 - S7 signal level or better.

Once the afternoon wore on and 20 meters started heating up, the pileups started to heat up as well. I found that it was getting harder and harder to be heard as I was the little fish in the big pileup. So by mid-afternoon, I started working my way up the bands. By jumping to 15 meters (then 10, and eventually 6) was the band was starting to open, I was able to stay ahead of the really competitive pileups. One of the coolest things about the operating was the feeling of riding the QSB like a wave up and down; waiting for a crest in the propagation to strike fast with my callsign. It could have all been in my mind, but it did seem to help to operate like this.

As the sun started to set behind the neighborhood houses, a good sporadic E opening hit the West Coast and I was able to get some nice 6 meter and 10 meter QSOs out to about 1000 miles or so. I had big plans for staying up late after dark to operate, but by the time that dusk fell on Beaverton, I was totally exhausted. So I laid down on the sofa and set the alarm on my iPhone to wake me in a few hours. Not surprisingly, I must have turned off the alarm in my sleep, because the next thing I remember is that it was 5 AM the next morning.

A bit disappointed, but feeling renewed, I put on a pot of coffee and decided on my strategy for the morning. It seemed obvious to give the lower bands a shot, since the propagation was bound to be best there and I hadn't worked them the day before. So the Buddipole was reconfigured as a Versatee Vertical with the low band coil, and the power was supplied by the A123 pack. Once I got going again around 7 AM, I was shocked at how well I was doing on 75 meters. The puny 5 watt signal from the FT-817 into the Buddipole had some good mojo, as I got multiple unsolicited "great signal" reports from the stations that I contacted (many of them VE7s). In my QSOs on the previous day, it was obvious that I was a QRP station, often needing multiple calls to bust a small pileup and sometimes needing a repeat or two. But both 75 meters and 40 meters were working remarkably well for me. The call got through on the first try nearly every time, and almost no fills were necessary. It truly felt like I was running 100 watts.

After a morning of fun, I had to go QRT for the day in order to complete some other chores that I had put off for far too long. It was a bit tough to tear myself from the station, but responsibility trumps fun, even if you try to put it off for as long as you can.

Results

Before I started operating, I thought that 50 QSOs would probably be a reasonable goal to shoot for as a QRP SSB station. As it turns out, I got really close; with a final tally of 49 QSOs, all of them SSB. Twelve of those QSOs were on solar power, so I qualified for the 100 point alternate power bonus. Since I was on emergency power the entire time, I also got 100 points for that. Given my 5 watt power limit and 100% emergency power status, I qualified for a power multiplier of 5. I also managed to copy the special W1AW bulletin for 100 points, and plan to submit my log via the web for another 50 points. If I did the arithmetic correctly, that should give me a final score of 595 points.

I also want to make note of the performance of the A123 battery pack. I started the event by charging the pack to a full charge with my Cellpro Multi4 charger. Although I did the majority of my operation timewise on the solar panel, by far I had the most QSOs with the A123 pack. According to my rough log calculations, I used the A123 pack for over 3 hours of operating time and logged 37 QSOs with it. When I returned the pack to the charger after Field Day, the charger reported 19% of the charge was left (the voltage display of the FT-817 never dipped below 9.6 V the entire time I was operating with the A123 pack). The next charge only took 38 minutes to get me back to 100%, and ready to go again. The 3S1P pack only weighs about 8 oz. and gave me a ton of operation time, much more than I expected. It sure blows away the much heavier and bulkier 5 Ah gel cell that I usually use with the FT-817. Ask the Goathiker, he'll tell you how great these things are.

I could wax poetic about the event, but I think you get my feelings about the thing by now. I'll just end by saying that this was my best Field Day by far, and that I had more fun with QRP SSB than I thought possible. I have a great appreciation for the excellent ops that put up with my peanut whistle, and learned a lot more about how capable a QRP SSB station can be.

New Homebrewing Finds on the Web

I got a few pleasant surprises this weekend regarding ham homebrewing websites. First off, I received a very nice e-mail from Jonathan, KB1KIX. He stumbled upon my documentation for the Willamette transceiver (AKA the qrp-l.org Group Project), and took the time to do a very nice write-up about it on his blog. There's a lot of excellent content on his blog, so I've added it to the blogroll. I hightly recommend that you stop by and take a look for yourself.

The other item that I found was the home of the projects of David Forsman, WA7JHZ. I had seen some of David's projects highlighted on other sites (QRP Homebuilder, SolderSmoke, etc.), but I didn't realize that he had his own projects site until I came across it randomly this weekend. It's not strictly QRP (in fact most of the projects are not QRP), but there is a lot of emphasis on lower-power voice rigs (both SSB and AM). There's a lot of great content to peruse, so get thyself over there right away and start browsing!

Back from the Bunker

Well, I've pretty much put the finishing touches on my secret QRP project for a well-known QRP club. The beta testers are currently working on building it, and hopefully the club can make an announcement about the kit fairly soon. It's not a very complicated circuit, but it's somewhat novel and has a bit of the "popcorn" factor. I think it will be a fun build for those who purchase it.

Spring boarding off of this project, I intend on extending some of the circuit elements that came about during the development of the secret project and using them to create something new. I don't want to say too much at this point, since I don't want to give any clues which could spoil the QRP club's kit announcement. At this point I'll just say that if I can pull this off, it will be a new take on a QRP classic. But I don't want to hype anything too much. I would rather underpromise and overdeliver. Plus, this thing hasn't even gotten off of the engineer's notepad yet. It should be a fun one to try to accomplish.

Watch This Space

Last week, I was informed that everyone in our company would be receiving a temporary (but indefinite) 10% reduction in pay. To make matters worse, it looks like we will be taking more mandatory shutdown days in the current quarter; we've got five coming up over the next few months. This is also another open-ended cost cutting measure; there is a possibility of more shutdown days in the upcoming quarters. As might be expected, my first reaction was anger and frustration, but I've cooled off a bit since then and let rationality replace emotion. The truth of the matter is that they economy sucks real bad, and only appears to be getting worse at the moment. I believe the company leaders when they say that this was done to avert more layoffs. Given the choice between a 10% reduction in pay and a 100% reduction in pay, it's pretty obvious what the best option is. I still can't say that I'm terribly thrilled, but this wasn't entirely unexpected either.

So now the belt needs to be tightened a bit more at our household. Given my personal theories about what's going on in the world, I seriously doubt that this is the worst that we will see. Let's just say that I will be extremely grateful if I still have this same job in a year from now. With that in mind, I have been giving serious consideration to getting into the kit-selling business. Not that I expect to ever get rich selling kits to hams, but I really enjoy design and it would be nice to at least be able to supplement my income now that it's taking a pretty big hit.

Along those lines, one of the reasons why the technical content has been light around here lately is that I have been working on a kit for a well-known QRP club. I don't know when I can spill the beans or how much I can say about it, but I think it should be an interesting and fun kit for a lot of builders. Keep an eye on the blog for more details about the kit when I'm able to release them.

Furthermore, I have some other kit ideas that sprang from this original design. Those are the ones that I would like to bring to market under my own banner, along with some other unique designs that aren't currently on the market. At best, it will still be months before you see anything commercial coming out of my lab, but I'm going to do my best to get the ball rolling very soon since I've now got a fire lit under my butt. I'm still going to post other technical content when I can, just don't be surprised if that category is a bit light for the next few months while things spin up over here.

Willamette AF Filter Mod

As I mentioned in a previous post, I did the calculations to change the AF filter in the Willamette from a low-pass filter with a 3.3 kHz cutoff to a peaked low-pass filter with a cutoff frequency nearer to 1 kHz. I finally got around to implementing the mod last night and got a chance to listen to it on the air today and take some measurements of the filter response.

First off, let's take a look at the filter response:

New Willamette AF Filter Response

If you compare this to the old response, it probably won't look drastically different, but it does cut off a bit eariler than the original filter. There is a bit of a peak as predicted, although it's a bit wider and shallower than expected.

However, the real proof is in the listening. I found (purely qualitatively) that the response of this filter was much tighter sounding than the original. Much of the high frequency interference is gone, and you can tell by tuning through a signal that it drops off much more quickly at the higher AF frequencies. You do lose some of the "crisp" direct conversion sound, but I feel like this is made up for in the utility of having greater filtering.

Here are the steps that you need to take in order to modify your own rig:

  • Replace R50, R51, R54, and R55 with 24 kΩ
  • Replace C55, C59 with 100 nF
  • Remove C56, C57 then place a 1 nF capacitor from Q12 base to ground (in the place where C56 was located)
  • Remove C60, C61 then place a 1 nF capacitor from Q13 base to ground (in the place where C60 was located)

One other small thing that you might want to do is replace C65 with a 1 uF capacitor. I noticed that when the AF gain control was set to maximum, that there would be an annoying popping during keying. This change helps to eliminate this problem.

I hope that you enjoy this modification to the rig. In hindsight, I'm not really sure why I designed such a wide open AF filter, although I suspect it was because I wanted to preserve the "DC" sound of the rig. However, I think that utility trumps a nicer sound in this case and will make the rig more usable overall.

W8DIZ 5 Watt CW Amplifier Analysis

I finally got the proper binocular ferrite cores that I needed to build the W8DIZ 5 watt amp correctly. You can see my previous post on this amplifier here. In my last post, I noted that I was seeing some strangeness in the drive level circuitry. I found that I had a very bad connection through my ammeter to the DC power supply, and once it was corrected the drive circuitry worked as it should.

For this basic analysis of the amplifier, I took measurements of the RMS voltage of the amplifier output into a 50 Ω dummy load with a constant input amplitude of 0 dBm. I also measured the total current draw of the circuit, which allowed me to calculate the amplifier efficiency. Note that no low-pass filtering was used at the output of the amplifier. The output waveform was not sinusoidal, but my DSO is able to do a good job measuring RMS voltage.

Test Equipment

  • Tektronix TDS 1012 Digital Storage Oscilloscope (100 MHz bandwidth)
  • Tektronix SG 503 Leveled Sine Wave Generator
  • Tektronix DM 502A Digital Multimeter
  • Tektronix PS 503A Power Supply
  • M3 Electronix FPM-1 Frequency Counter/Power Meter

Test Conditions

The DC power supply to the amplifier was set to a loaded voltage of 13.5 VDC. The signal generator for the input signal was set to 0 dBm power output into 50 Ω, which was verified with the FPM-1 each time the frequency was changed. Two sets of measurements were taken, one with R6 set to minimum and the other with R6 set to maximum.

Measurements

Min Max
MHz VRMS (V) PO (W) IDC (mA) VRMS (V) PO (W) IDC (mA) Eff.
1.8 13.7 3.75 440 22.4 10.03 957 0.776
3.5 20.2 8.16 768 23.9 11.42 992 0.852
7.0 13.8 3.81 470 21.7 9.42 844 0.826
10.1 9.3 1.73 300 19.8 7.84 732 0.793
14.0 5.24 0.55 174 17.6 6.20 635 0.723
18.7 3.12 0.19 103 14.4 4.15 514 0.598
21.0 2.07 0.09 78 12.6 3.18 452 0.521
24.9 1.53 0.05 65 9.05 1.64 326 0.372
28.0 1.19 0.03 60 6.56 0.86 232 0.274

Conclusion

As Diz states in his original post, the efficiency of the amplifier is quite good. However, both the power output and the efficiency starts to droop a bit above 20 meters. It's my belief that this is a function of the gain-bandwidth product of the two PA transistors. According to the datasheet, the FT of a 2SC5739 is 180 MHz. Given the rule of thumb of having a FT at least 10 times the output frequency, it makes sense that the output starts to get a bit weak around 18 MHz. I do have some similar devices (2SC5954) with a slightly higher FT of 200 MHz that I will probably substitute in the circuit to see if I can improve the upper HF response a bit. There seems to be some kind of strangeness at 3.5 MHz, which doesn't allow me to get much power output range. I'll have to check with Diz about this. Regardless, this would still make a very fine QRP amplifier up to the 15 meter band. The amplifier is extremely stable and the PA transistors don't get very hot during long periods of use. I currently have the transistors floating freely, but a modest heat sink would probably be a good thing if running the amp at full power output. This kit will be a great addition to the RF Toolkits line.

W8DIZ 5 Watt CW Amplifier

W8DIZ 5 Watt CW Amplifier
W8DIZ 5 Watt CW Amp

A few days ago, W8DIZ made a post on qrp-l.org announcing a new addition to his RF Toolkits line. This one is a 5 watt CW amplifier using a push-pull 2SC5739 pair as the PA (my new favorite full QRP gallon transistor). I built my own version of the circuit using parts that I had on-hand. The only substitiutions that I had to make were the cores for T3 and T4 (the output transformers), but I have the correct cores on order from Diz. With an input signal level of 0 dBm (1 mW), I was able to get nearly 5 watts output into a 50 ohm dummy load from 160 to 30 meters. The power output started to droop above 20 meters, but I suspect that is because I used the wrong core types on the PA circuit. There is also a control to adjust the power output using a PIN diode bias control on the driver amp emitter. It seemed to work fairly well on some bands, but on others was not very well behaved. Once again, I'm going to wait for my correct cores to arrive before making any final judgements about this.  The great thing about using a PIN diode design like this is that you are using a DC bias to control the gain, which means you can run a long cable to a panel-mounted potentiometer. This looks like a great amp and I look forward to getting it built completely correctly once the parts get here. Stay tuned for another update with detailed measurements once that happens.