The Final Touches

 At last, my paraset is complete, albeit with a few hiccups. First, I couldn't get the switching configuration quite correct. It seemed that every time I tried soldering in the crystals, the switch would begin to melt. Too hot I guess! Other than that, my paraset kit works excellent. Now all that's left is a field test...

So what am I left with since the switching configuration didn't work like I had hoped? There's still the option of putting in a crystal socket, which would make switching out crystals easier. You only need a SIP socket like this. Cut it to where you only have 3 pins, like this.

The only drawback is that you would have to remove the faceplate every time you want to switch frequencies. The pro is that you can use both crystals and resonators as frequency references.

Another option is to bite the bullet and make the switching unit. Unfortunately I don't have very much time when it comes to free time, so until I better my soldering skills, I think that this option is nothing but impossible. Maybe later on down the road it will be possible, but until then I'll have to wait and see.

I have seen many posts and projects that would allow the Pixie to change bands. All that needs replaced are C3, C5, L2, and C6. C3 is in the oscillator circuit, and C5, L2, and C6 are part of the LPF circuitry. There are many crystals that come in frequencies which are close to both CW and Feld Hell portions of the bands, such as 10.140 (10.143 is the Feld Hell frequency), 14.060 (14.063 is Feld Hell), and many more. As stated in the last post, using a variable capacitor between 100 and 300 pF will bend the crystal by 2 - 3 kHz, but results may vary by crystal size. It will also bend a resonator roughly 100 kHz. Adding an inductor within the circuit may also increase frequency range. A value like 5.6uH will suffice.

Whatever I decide, I am overall very happy with the outcome. I can't wait to start learning CW and send some Feld Hell. I think that it will be possible to make more of these easily, but I might have to settle with space constraints. In this project, I used a 4 x 6 metal recipe card box, but 3 x 5 boxes are more commonly available, especially in metal. This project has taught me a lot about craftsmanship, how to get creative, and use what you have available to you. In total, I think this project cost less than $20, well below my budget constraint. Even if you can't get the switching circuit to work correctly, you can still enjoy the Pixie by adding some frequency agility.

As the snow begins to thaw and it starts to get warm out, I have a few locations that I'd like to try my paraset kit at, mainly at the university that I attend. There are so many spaces that will definitely fit a 40m simple wire dipole that are almost or completely unobstructed.

Here are some troubleshooting tips that I have after this building experience:

• No sound - Check the battery voltage, check soldering joints
• Buzzer/sidetone constantly on or faint - Check that the variable capacitor is not touching the faceplate or anything metal. Check the oscillator stage.
• RIT is intermittent or not working - Check solder joints

The list is small, but these were the common problems that I ran into. Of course, these aren't all of the possible problems. The most important thing in any troubleshooting is to go back and retrace your steps. Are your soldering joints good? Are there any loose connections? Are components in the right spot, or have they gone bad? 

I am not an expert and I have no professional testing equipment like an oscilloscope. If you are still having problems, talk to someone who knows how to help or even ask your Elmer, if you have one.

Although this has been a simple modification, the sky is the limit when it comes to the Pixie. For instance, here are some ideas I'd like to try:

• Try replacing the transistors with power transistors to get more power output
• Make the Pixie into an AM transmitter, or better yet, an AM transceiver
• Make a propagation beacon or QRSS beacon
• Add some filtering circuitry to filter and narrow the audio to about 700 Hz
• Try experimenting with different antennas

There is so much more to this list that you can do with a Pixie. Because it is QRP, calling CQ may take a while. If your wrist gets tired, try sending Feld Hell. One advantage of Feld Hell is that it uses less of your transmitter's or transceiver's duty cycle. There is also a multitude of free software that allows Feld Hell operation, such as fldigi. If you have a Raspberry Pi, which can run off of a portable charger, you can take your ops to the field easily. 

Now that I think about it, because I have already drilled a hole for the switch, I could use that hole to put in a power switch. As I mentioned before, when I get better at soldering, I plan on doing the crystal switch. For now, I just want to fill the extra space, so I think a power switch is a great idea. 

To wrap things up, I think that this project has shown me just how simple a transceiver can be. With simple modifications, a rock-bound QRP radio can be as frequency agile as a commercial transceiver, while still being field serviceable. Truly, this project has been a success out of a small failure.

Until next time...

Paraset Pixie

 If you know me, you'd know that I'm a huge fan of homebrewing equipment. I feel that it brings out the true side of ham radio operators. While a nice Kenwood or Yaesu 100W rig is good to have, there's just the feeling of satisfaction in building your own equipment, whether it's built from a kit or from scratch. I don't know why, but I'm obsessed with the Pixie QRP kits. Coming in at a price of near $5 all the way up to $10, it's a reasonable build for anyone who wants to understand how simple a transceiver can actually be. Plus, it can be used for on air operation!

There are many drawbacks to the Pixie, including its wideband receiver and its vulnerability to broadcast band overload. However, in these flaws there is room for improvement. One such improvement is making it frequency agile, with no more than a switch, a crystal, a ceramic resonator, and a variable capacitor. Recently, I have been working to make the Pixie kit into a full-blown mini paraset kit, like the ones used by spies and soldiers alike during the WWII days. It is small enough to fit into a recipe card box, measuring about 4" x 6". Complete with a metal faceplate, a 12VDC receptacle, a BNC antenna connector, and a 50K potentiometer for RIT, this will hopefully be well worth the time and money.

Originally, I had planned to put on a DDS VFO with an AD9850. Unfortunately, I felt that this would take up way too much space and would consume a fair amount of time. In addition to this, it would take away from the simplicity of the Pixie, and utterly ruin the effect of a field transceiver. What I opted for instead was a simpler solution, courtesy of Peter Parker, VK3YE. Below is one of the many videos that I've used along the way.

Once you have this mod completed, the operating trick is easy: find a frequency that is open, with little to no noise activity, and call CQ. One thing that VK3YE explains in another one of his videos is the problem with many QRP rigs. These rigs are frequency-locked, meaning that they are agile for only a few hundred hertz; whereas with this mod, the Pixie becomes operational from 2 - 3 KHz (crystal) all the way up to 100 KHz (resonator), a much-needed modification if you're going to use it on the air. On 40 meters, this is essential and helpful. Here is a rough prototype diagram of what the paraset will hopefully look like:

As you can see, the KEY socket can also be used to transmit Feld Hell. In my previous post, I mentioned a circuit that you can use on any CW transceiver to transmit Feld Hell via an optocoupler. It converts the AFSK signals from software like fldigi into OOK, which is what the Pixie uses to transmit Morse Code. One thing that I must point out is:

CW is a MODE, NOT just Morse Code

Feld Hell is a CW mode, as is Morse Code. I haven't found any other modes that fall into CW other than Feld Hell and Morse.

Now that that's clarified, let's get back on track. Below is an image of my partially-completed paraset.

As you can see, I have a "dummy Pixie." This Pixie doesn't work(?) as I accidentally soldered in the amplifier transistor backwards and, in the process of removing it, mutilated the PCB. The 12VDC socket and the 50K pot have both been installed on the faceplate. As I write this, the rest of the parts are on the way from Amazon, so hopefully I'll get a completed photo up here at the end of the week.

In my opinion, this is a worthwhile modification. Buy yourself a Pixie kit off of eBay or Amazon, get the SPDT switch and the variable capacitor, buy a crystal or two, and a ceramic resonator. The final cost of this project is well within the $20 - $30 range, a cost that is relatively within the budget of a ham who is on a budget, or who wants to get on HF fast.

I can't guarantee that you will be heard the first time, but that depends on your location, your antenna, and the power output. 9VDC will yield a lower power output (around 300 mW) than 12VDC (a bit under 1W). A 40m half-wave dipole performs great with this little radio.

One other thing I should mention: This radio doesn't only work on 40m. You can modify it to cover 160m - 6m with a change of LPF values. That information is below:

Notes: For 10 and 6 meters, replace the oscillator capacitors (C3, C4, and C7) with 47 pF capacitors. For 80 meters, add a 100 pF to C7 to jumpstart oscillation. You might also try experimenting with different transistors to see which one provides the most power output. A 2N2222 or a 2N5401 may give better results.

I know that this is still a work in progress, but I hope that by the end of the week or the beginning of next week, I can update this post with the completed project.

Stay tuned for an update soon to come!

Feld-Hellschrieber: What the Hell is that?

     Today I want to pick on a mode that is the German equivalent to an American's fax machine. Many of you ham operators have heard of Feld Hellschrieber, or simply called Hell. Feld Hell has its roots in the early days of WWII, and although its popularity has died off due to newer, reliable modes like FT8, many ham radio operators continue to use this mode.

    In 1929, Rudolf Hell created a facsimile/fax-like mode that would be integrated into the German army in WWII and going into the Cold War. Although it is not widely used commercially, it has been adopted into the amateur radio community. Many more Hell modes have come into existence, like Hell 105 and Slow Hell. There are many differences between these modes, such as OOK and FSK modulation, but they are all related in the fact that they are all Hell modes.

   

    After seeing my FT8 signals appear on PSKReporter, I figured I would try other modes, more specifically, Hell and RTTY. My RTTY signals were heard on the West Coast, but in checking other sites, I couldn't find my CQ calls sent in Feld Hell. That doesn't mean that I will give up though! I will keep pumping out signals until someone answers my CQ calls or I get spotted.

    I might try Hell on my Pixie kit, as Feld Hell is specifically modulated in OOK (On-Off Keying), just like other CW modes. Using an external switching circuit, I can manipulate the AFSK signals that come from my computer's fldigi software to key the little transceiver using an optocoupler. More information on that can be found in this PDF. In the future, I hope that this is possible.

    Because of my interest in Feld Hell, I decided to join the Feld Hell Club. I was recently accepted and was presented with my member certificate! So far, I have access to 40, 15, 12, 10, and 6 meters, but I'm hoping that I can get access to all of the HF bands, and I might have just the solution. I'm planning to add a DDS VFO to a Pixie so I can surf the bands and send CW or Feld Hell. I might throw on an amplifier in the future, but we'll see what I can do with QRP.

    In the end, is Feld Hell worth it? In a nutshell, yes. It is a fun mode that acts like fax, and it can easily be used on CW only transmitters or transceivers.