North Carolina QSO Party 2010!

This past weekend (Sunday afternoon, to be exact) I participated in my first North Carolina QSO Party.

I was prepared to “be the pileup” as I live in Orange County, North Carolina and surely many folks would be trying to work me to increase their county count. I laid out my equipment the night before: my Yaesu FT-817D, my PAC-12 vertical antenna, my LP-100A wattmeter, and all the relevant cables and wires. The next morning I headed down to the green space at the end of the townhouses where I live and began to put it all together. The PAC-12 tuned up wonderfully on 20m for SSB and I was easily putting out 5W for all to hear.

I tried calling CQ a few times near the recommended frequency of 14.260MHz, but didn’t receive a call back at all. The bands were full and surely someone could hear me. After an hour or so of freezing under the shade of the gazebo, I decided to run back to my house and grab my HF Packer Amp to boost my signal a bit on SSB.

The extra power out did the trick, and I was soon making contact with folks across the Western hemisphere. My first contact was 9Z4AM in Trinidad at 20:16UTC before a long drought as I tried to call CQ again for the NCQP. I heard a fellow in Kansas finishing up a QSO with another ham and soon put K0KUD in the log at 20:53UTC. Soon after that, I was able to claim two more DX entities in Nicaragua (YN4SU) and Venezuela (YV1RDX) before shutting down the station for the afternoon.

All in all, I was disappointed with my performance in the contest and the weather (a chilly 50F with frequent strong breezes from the North), but I think I learned a bit from the experience. The next morning I spoke with N1LN on the W4UNC repeater and he told me of how 20m “went long” early in the day and that he and his wife made most of their daytime QSOs on 40m instead. I considered it, but didn’t change bands. I was comfortable on 20m and was hearing some fine signals. I was sorry that I didn’t have a chance to work some of the signals I heard (the Balearic Islands as well as a few other eastern European stations), but I’m sure there will be other times for that.

Now I have to get the QSLs in the mail as well as the green stamps so I can claim my rewards!

projects still on hold

It’s already Thursday and another weekend looms in front of me. I didn’t get a chance to warm up the soldering iron last weekend, as expected, but I guess that’s why ham radio is a hobby and not my profession or life’s work. Lately it just seems that the busy-ness of life has gotten the best of me.

I’ve gone back and forth (in my mind) between completing the Elecraft K2 or completing the PSK-20. I’d have to say that I’m about at the same point in both kits–a few more parts to stuff and  then an alignment stage. I suppose, time-wise, the PSK-20 kit is much closer to being complete; however, since I’m using a larger enclosure which is not pre-drilled, I will have to create a template and drill out the enclosure before calling that project done.

The feeling of satisfaction from completing a project still eludes me, but hopefully that will change and it will be a reality soon. Stay tuned!

a short trip north

This past week work led me to Rockville, Maryland for a few days. As always, I had my trusty Yaesu FT-7800R with me in the car to help keep me company on the drive. While my other coworkers elected to fly, I chose to drive so that I could have some flexibility to visit friends and family who I have in the metro DC area.

As far as radio goes–I didn’t make time to program any of the area repeaters in my radio before I left, so I left the rig stuck on 146.52 MHz simplex throughout my trip. Three times over the past three days I was able to make simplex contacts. I sent out QSL cards today to these folks: WA4KEB, W5JMC, and KI4XH. The terrain around Washington, DC is not exactly conducive to long simplex rag chews, unfortunately. Quick chats with WA4KEB and W5JMC were all I could muster, but I had a nice, long chat with Fred KI4XH.

Fred and I made contact on my way to Ham Radio Outlet in Woodbridge, Virginia, where I was headed for some window shopping and to purchase some 15A PowerPoles. We chatted a bit about my travels to Rockville as well as other future work trips I have planned for the spring to Chicago, Anchorage, and rural Pennsylvania. It turns out that he has had extensive travel experiences in Alaska and would be happy to offer suggestions for places to eat and things to do during my time there. What a fruitful QSO!

This weekend I hope to pull out the soldering iron again and work on some aspects of the PSK-20 project. While I was gone, the LP filter I had ordered from W8DIZ at PartsAndKits.com arrived. It should be a quick build as there are only a few through-hole parts and two toroidal inductors to wind. The LP filter will go between the frequency synthesizer and the PSK-20 PC board to transform the signal into a nice sine wave.

a lull in the action

On Monday, I attended the monthly meeting of my local radio club where I picked up a portable oscilloscope from Steve W3AHL to assist in testing the Si570 frequency synthesizer’s output voltage. The past few evenings have been busy with a couple college basketball games of interest to watch (Kentucky on Tuesday, Duke last night) so I haven’t had a chance to work on the PSK-20 project.

I may warm up the soldering iron this evening and fire up the oscilloscope which W3AHL has graciously allowed me to borrow in order to check the voltage from the frequency synthesizer. According to the specs, the SA612AN expects a 200-300 mV signal from the oscillator. The stock output is much higher than that. W3AHL had suggested that I use a Pi attenuator to reduce the voltage from the synthesizer. I followed his initial advice, but without an oscilloscope I wasn’t able to check the voltage. Before I had the chance to test it, I had received this message from him:

The only problem is the 10db attenuator is wrong.  Last night I realized we were measuring voltage — I calculated the attenuation needed based on power ratio, which is what I normally use for RF circuits.   So just to make sure I got it right this time I verified what was needed using the 8924C’s signal generator and a 30 dB attenuator I had.

So to take the 2.2 volt P-P signal (unterminated — it would be 1.1 volts if the PSK-20 board had a 50 ohm terminator resistor on its end of the coax) down to the desired 250mv. signal, requires an 18.9 dB attenuator.  This would require two 62.8 ohm resistors to ground and a 217 ohm resistor in series between them.   Or as close as you can get in standard values.

The current 10 dB attenuator should give 700 millivolts output — a tad too much.

Again, I’m glad to have the experience and expertise of folks like Steve W3AHL to help with projects like this one. I’ll post results when I have a chance to test them–hopefully this evening.

Yesterday I ordered a low pass filter kit from Dieter “Diz” W8DIZ, who runs an awesome site/store called KitsAndParts.com. I explained to him what I was trying to do, and he offered to help me create a low pass filter with a cut-off frequency just above the output of the frequency synthesizer (around 5.3 MHz) to help transform the square wave from the synthesizer to a sine wave (which is preferred by the SA612AN).

John,
I made you a custom LPF for 5.3 MHz
Need to calculate the turns on the T50-2 cores
Caps are 470p and 1000p
All packed and ready to ship tomorrow AM
-Diz

Diz has always been helpful and mindful of his customers’ needs. This can be clearly seen in his reviews on eHam. Hopefully the parts will be in by the weekend and the next phase of the project can be tackled before the beginning of the work week.

PSK-20 nearly complete and testing begins

This past weekend I was able to finish the basic PSK-20 kit (sans the 5.068 MHz oscillator circuit). Overall, this was a very easy build. It’s not a simple one-evening project, but it can definitely be completed in a 2-3 evenings of work with 2-3 hours each evening devoted to the task.

Steve W3AHL, a member of our local club, mentioned to me a few weeks ago at our regular monthly meeting that he had a ton of lab-grade test equipment at his house. Immediately, a light went off in my head, and I made a mental note to contact him whenever I was preparing to do the final checkouts on the PSK-20 project.

Yesterday, I headed down South to Chatham County to visit him (about a 15 minute drive from my home in Carrboro). We spent the better part of 3 hours with his spectrum analyzer and oscilloscope trying to figure out the answers to the following questions:

1. What is the exact frequency of my Si570 oscillator?
2. How far can I pull the 9 MHz LO down?
3. What additional adjustments are needed in order to use the Si570-based signal generator as the second LO?

The answer to the first question was fairly easy to determine. After applying power to the Si570 frequency generator kit and allowing it to sit for 20 minutes or so, the output frequency was 9,999,992 Hz. Its nominal frequency is 10 MHz, so that’s not bad. Saving this value to memory space “000″ in the menu allows the kit to generate more accurate frequencies than if you work with the assumption that the nominal frequency is equal to the actual frequency.

The answer to the second question is important because that will determine if the crystal I have will allow me to operate on USB rather than the LSB (which the kit is designed to operate on). This odd configuration may be overcome in some software packages. At the end of the day, I’d like to be able to operate on USB (the traditional sideband on 20m); however, if this ends up being a costly choice (dollars-and-cents-wise) I may bypass it. Measuring the frequency of the 9 MHz LO while adjusting the trimmer capacitor C38 helped me determine that the lowest frequency of the oscillator is 9.021 MHz. This is definitely not as low as I’d prefer for the generation of the USB signal. Inrad sells USB crystals for the frequency of 8998.5 kHz, but their cost is $12 plus whatever shipping and handling may be involved. Not exactly the least expensive solution. So, the solution for now is to accept LSB as my sideband of operation on 20m digital modes until such point that I feel like spending what will amount to at least $20 to obtain this new crystal.

The final question to be answered of the day was how to incorporate the Si570 frequency synthesizer into the kit as the second LO. Previously, I had thought about using high-side injection at 23 MHz (instead of 5 MHz) “just for fun” and because other folks on QRP-L had suggested it might be a cleaner signal. After speaking with Steve KZ1X I decided that it might be best to stick with the low-side injection method since using high-side injection may require additional changes to the circuit which I may not want to tackle at this point in my learning.

Going with this thought, Steve W3AHL fired up his oscilloscope and began measuring the voltage output of the synthesizer and comparing it to the voltage required by the SA612AN Gilbert cell mixer. It turns out that the peak-to-peak voltage is much higher than what is needed/tolerated by the SA612AN. Steve W3AHL helped design a 10:1 Pi attenuator using commonly found resistors from Radio Shack. In a perfect world (at least, according to the calculator he used), I would have a pair of 96 ohm resistors and a single 71 ohm resistor in the circuit; however, Radio Shack’s selection of resistors is limited to 100 ohm (for the 96 ohm) and 68 ohm (for the 71 ohm). Not a bad compromise at all!

The neat thing about this attenuator circuit is that it will fit on the PC board very easily. Recall that I did not install any of the 5.068 MHz oscillator parts. This has left open C43, C44, R47, R48, and R49 (as well as a few other pads). The Clock + (in the circuit) and Clock – (to ground) from the Si570 kit were fed using RG-174 coax at C44 and a wire jumper was added at C43 to make the connection between C44 and R47. The Pi attenuator was created by adding one 100 ohm resistor at R47 and at R49 and one 68 ohm resistor at R48. I haven’t had a chance to test this yet, but it should provide the correct amount of voltage for the SA612AN (200-300 mV). It still may be the case that I need to add a LP filter to create a sine wave from the square wave the Si570 creates, but I’m going to see what happens when I power it all up before I go that route.

Our regular monthly club meeting is this evening. I’m planning on bringing the kit to the meeting for a little intermediate show-and-tell and eventually giving a full presentation of my project to the club in February or March.

PSK-20 build

This past week has been long on building and short on writing, but I’m okay with that.

As of today, I have completed all but the last two steps in the assembly of the kit. The manual is broken down into “group builds” (e.g., Group 1 assembly installs the DC power circuitry, Group 2 assembly installs the Transmit/Receive switching circuitry, etc.) which help the kit builder have a sense of the purpose of each set of capacitors, resistors, transistors, and the like. Unlike Elecraft kits, which usually have an alignment or “check out” after each step of assembly, there are no such resistance or voltage checks for this kit. So, you must go on faith alone that there are no cold solder joints, misplaced parts, or nonfunctional devices until after assembly is complete. The first “smoke test” is truly that.

In the Group 3 build (the 9.000MHz and 5.068MHz oscillators and related components) I left out all components connected to pin 6 of U7 (SA612AN) since I plan on connecting the signal generator there in lieu of the 5.068MHz crystal. It may be the case that I will need to add some of those components once I determine their necessity, but there is plenty of physical real estate on the board for these parts to be installed at a later time. In face, Dave Benson states that “real men” can install in whichever order they wish, ignoring the “group build” guide laid out in the manual.

The last two portions of the construction include stuffing and soldering the transmitter bandpass filter and driver stages as well as the transmitter final amplifier to the PC board. I hope to finish those either tonight or tomorrow and then take the final product to fellow OCRA member Steve W3AHL’s home to tune the sideband generating circuitry and obtain an accurate measure of my particular Si570 part two days from now. After that, I should be ready to place the kit in an enclosure and start playing around with it on the air!

Once I complete the build, I’ll upload some photos of the board after each “group build” for viewing.

build of the Si570 Controller and Frequency Generator Kit #2

The first step towards completing my January 2010 project was to construct the Si570 Controller and Frequency Generator Kit #2 by K5BCQ. This fairly simple kit, which is composed of mostly surface mount technology (SMT) parts, will generate a square-wave signal from the Silicon Labs Si570 oscillator, has a LCD display, and a rotary/push-button encoder.

Despite my best efforts to botch the assembly and initialization of the device, I successfully completed it over the weekend. Partly due to me breaking one of the rules of kit-building (i.e., no building kits when you are sleepy or tired), I soldered the V+ and ground from the power supply to the output locations. During check out, the unit wouldn’t power up. A quick email to Kees K5BCQ asked me to check the voltage on the regulator–which led to my realization that the V+ and ground weren’t connected to the regulator. <sigh> Lucky for me, the location of a few capacitors kept me from frying any ICs. Once I connected the power to the correct points, and performed the initialization steps (holding down the push-button while applying power), everything is working as expected.

The Si570 comes programmed with its initial frequency from Silicon Labs. I requested 10 MHz initial frequencies. The initial frequency of the Si570 is set in the menu of the kit in menu item 000. While 10,000,000 Hz should be fairly accurate, I’d like to measure the exact output at the indicated frequency to make sure that it is not off by a few hertz in either direction. The accuracy of the start-up frequency of the Si570 in the menu item affects the frequencies generated using the controller, so this is key to its operation.

The kit is flexible in the voltage required for its operation. I’m thinking about adding a 5V regulator from the main power jack and feeding the display/generator rather than having to drill another hole for a separate power supply for the device. Using a wire jumper (rather than a 1/4W resistor) near the voltage regulator, allows for the use of power less than 11V.

In addition to the printed instructions provided with the kit, I followed the instructions on Clifton Laboratories’ site which were very helpful. Thanks for providing this excellent resource, Jack!

Next–on to building the PSK-20!

New Year; new project

This past year I have finally come very close to completing my Elecraft K2 (and most of its options), which has been a learning experience. While soldering the multitude of parts to the PC boards can be mind-numbing, the steps involving check-out of the rig help teach a bit of theory. Earning an Extra Class license requires an understanding of the theory involved; however, actually applying it to a project helps cement the concepts in the mind.

In 2010 I will be traveling a bit for my job and may find myself in lonely hotel rooms at night. Rather than spend the evenings flipping through channels on the television, I would prefer to get on the air and make some contacts. Given the fact that I travel with a laptop computer and often travel light, I thought it would make the most sense to try and bring along a transceiver which would allow me to get on the air and operate some of the digital modes. Dave Benson’s PSK-xx kits fit the bill.

I chose the PSK-20 because of the high activity on 20m PSK31 and because the other kits are for bands which would require an antenna of greater size than I would prefer to manage on business travel (PSK-30 on 30m, PSK-40 on 40m, The Warbler on 80m).

I’ve previously operated PSK31 on my Yaesu FT-817D with a Tigertronics SignaLink interface and been quite successful, earning the QRP-ARCI 1000 Miles Per Watt award (see post here about those adventures). Using a transceiver with a built-in interface would save space and weight when they are at a premium.

I ordered a PSK-20 rig in the summer of 2009 and finally received it in the fall, but have yet to begin the project. With increased confidence in my homebrewing abilities and greater understanding of theory, I have set out to modify the PSK-20 kit to tune the entire 20m band and allow me to reach the calling frequencies of digital sound card modes other than PSK31.

The PSK-20 rig itself is an interesting rig. It has a ~4KHz bandwidth centered around the PSK31 frequency for 20m (14.070MHz) and operates on the non-traditional lower sideband (LSB). The sideband is of no consequence for some variants of PSK31 (e.g., BPSK) but matters more for others (e.g., QPSK).

According to Dave’s documentation about the receiver…

U1 is fed with a 5.07 Mhz Local Oscillator (LO) signal and converts the incoming 14.07 Mhz received signal to the 9.00 MHz Intermediate Frequency (IF).

and

Product detector U2 receives the 9 Mhz IF filter output and multiplies (mixes) it with a ~ 9 Mhz LO signal.

Also (for the transmitter side of things)…

Single-sideband filtering is performed by a second filter comprising Y7-Y10 and related capacitors. After passing through the transmit IF filter comprising Y7-Y10 and related components, the signal has been reduced to a 9 MHz SSB signal. Its output drives 2nd mixer U7. This mixer is also driven by a signal from the 5.07 MHz LO, Colpitts oscillator Q9 and associated components.

The output of this mixer consists primarily of both the sum (14.07 MHz) and difference (3.93 Mhz) frequencies applied to the mixer. Q7 is an emitter follower used to buffer the high-impedance output of the mixer. U8 is a Monolithic Microwave IC (MMIC) and provides approximately 12 dB of gain.

My plan, as it currently stands:

1. Pull the 9.0MHz local oscillator LSB signal to USB by adding a level of inductance in line with the trimmer capacitor already on the board
2. Replace the 5.068MHz crystal and its supporting circuit with a frequency-agile signal generator
3. Mount the entire rig, including a digital frequency readout, in a Ten-Tec enclosure (the enclosure that Small Wonder Labs provides for the PSK-xx rigs is not large enough to accommodate the size of the digital frequency readout and dial)

In order to make this a fully portable digital station, I’ll need to bring along an antenna (I’m thinking either a 1/2 wave wire antenna cut for 20m) and perhaps an antenna tuner. The tuner, should I need it, will be filled by my Elecraft T1. It offers small size and excellent performance that will be appreciated when packing my bags for my business trips.

Should be an exciting few weeks. My first trip will occur in the third week of January, and I hope to take the rig along with me. First, to construct the signal generator of choice–the Si570 Controller and Frequency Generator Kit #2 by K5BCQ and K5JHF.

greetings from Poland

What a nice Christmas gift! Just got back from vacation to Kentucky to visit my parents and among the other Christmas cards, catalogs, and magazines was this card from SP3CFM in Poland. Zbigniew said he would QSL without the need for me to send return postage, and he did. I’d already received his Logbook of the World QSL, but this was the one I was really hoping for.

The contact was made in early October 2009 on 20m PSK31 with less than 5W from my FT-817D.

obverse

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North to Alaska

I received the QSL card from KL8DX a few weeks after sending him mine as well as a SASE. Nice to have this one in the collection.

This QSO qualified me for the QRP-ARCI’s 1000 Miles Per Watt award, as I mentioned in a previous post.

Not only does Alaska qualify you for such awards as the ARRL’s WAS, it also counts as a DX entity. Go figure!

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