build

All posts tagged build

I got a slow start on the Fafnir build, though preparation work is quite important. The boat rests on a jig during construction, and that is what I put up yesterday.

Fafnir Jig

Fafnir Jig

I decided to have the boat plans digitized into CAD files. The first step was the jig verticals you can see above. The work is being done by my friend Erin Hood. The panels were cut by my friend Marc at Elite Woodwork in Sarasota. The advantage of having CAD files is that small errors on the plans can be fixed in the 3D model before any wood is cut. The precision of CNC cutting machines is amazing and everything should fit down to the millimeter. Erin and Marc did a great job and if Erin wasn’t familiar with boat building techniques, he certainly is now. I can’t wait to see the first bulkheads cut this way.

Fafnir 3D View

Fafnir 3D View

Those files will be made available to Fafnir builders who can prove that they paid for an original set of plans, assuming John Welsford has no objections.

The top of the jig verticals needed to be beveled. I used a file for the bottom of the notches and an electric orbital sander for the top edges. Filing by hand took some time but the sander was really fast, almost too fast for comfort.

My next step is to laminate the keelson in place, then the bottom plate. Making scarf joints will be a pain. I need to build some kind of a jig for my router to cut those planks at an angle. I’ll probably make a video of that, so stay tuned..

After my semi-success with the DC20B, I decided to tackle the Rock-Mite from Small Wonder Labs. I also got the Mighty Box. The kit is very small and has no toroids to wind. It does however have a surface-mounted integrated circuit. Winding toroids is actually very easy. I don’t know why people make such a big deal of it. Maybe they just haven’t tried. Soldering the SMT circuit, while not that hard, was stressful. That being out of the way, the rest of the kit was a breeze. Being fairly confident of my abilities, I installed the circuit board in the box without trying it first. This way, I could use all the connectors for testing. To my satisfaction, it worked the first time!

My goal with this Rock-Mite is two folds. First, it is a stepping stone to building an Elecraft K1, which I have just started, and second, it provides me with a small emergency radio for my bug-out bag.

I can’t really compare the DC20B to the RockMite as far as performance is concerned, but building the Rock-Mite is easier, and there is no tuning required. The circuit board is slightly smaller. I replaced q6 with a 2sc799. R18=2.2 ohms for a little more power. The keyer is the Pico Keyer from http://www.hamgadgets.com.

I am very exited about building the K1. More on that later…

I decided to build an Elecraft K1. What the hell is that You might ask.. Though you probably guessed it is a radio. I’m on a roll. I know, I know, I just finished building a small one (DC20B) and am waiting for another tiny transceiver called a Rock-Mite. You need to learn to walk before you can run.. Why not buy something already made? It isn’t more expensive.. Well, the Elecraft K1 has an excellent reputation, and it isn’t sold assembled. If you want a new one, you must build it. I am good at that stuff, and do enjoy the process. Still, I could find a working Ham radio on Ebay for the same price; but that would be a used item. Not to mention that the K1 is the cutest little radio (did I just say that?).

There is one peculiar thing about this radio, aside from all it’s qualities, that is, you can’t talk in it.. Morse code only! Also known as “CW” (continuous wave). So I am learning Morse code, and it is far from easy. Why bother? First, a Morse-only transceiver is much simpler and smaller than an SSB (voice) one. It draws less current, which becomes very important when operating on batteries. The K1 will happily work for days on eight AA batteries! For example, a Yaesu FT-817ND draws 450mA on receive. The K1 draws 55mA! More importantly, when propagation conditions are bad, a CW signal will punch through the ether when another mode won’t. In an emergency, being heard might be a life-or-death condition. Even with no cell phone coverage and no satellites overhead, there is a good chance the K1 will be heard somewhere, even thousands of miles away. Yes, thousands of miles directly, on eight AA batteries! What else can do that? It doesn’t mean I won’t take my cell phone or a Spot when hiking far from civilization. However, cell phone coverage is spotty in the North West, and with the Spot, you can’t specify the type of emergency, and can only use it for dire situations. If I need anti-venom after a snake bite, it won’t do me any good to get picked-up by a helicopter if they don’t have the serum with them.. A radio allows you to call for a specific kind of help. Like any other gear, if it is too heavy or too big, you will most likely not take it with you. Light and small is better when you need to carry it on your back.

My plans are to first complete the 20/40m model with no add-ons. Then, I will build the built-in antenna tuner. This option allows you to use a random wire as an antenna without risking frying the transmitter. If you lost your antenna and all you can find is a length of barb wire, the tuner can save your bacon. Just hang it up a tree, press the tuner button, and seconds later, if you’re lucky, you will be having a conversation. I might add a noise blanker later.. One item I decided against is the built-in battery pack. You can’t charge the batteries while they are inside the case, so what’s the point? I heard it is a flimsy add-on anyway. I don’t think I’ll need more than two bands, but time will tell. The antenna I chose is the Par EF-10/20/40 MkII end-fed dipole. Also on my wish list is a solar panel (PowerFilm AA Battery Solar Panel Charger) to charge those AA rechargeable batteries. For EMP protection, I decided to get some TechProtect Faraday bags.

I will document the build and post it. Average build time is about thirty hours, but I am pretty fast with a soldering iron. I will start next week-end (June 9th), stay tuned for the article, and maybe a video. Hopefully by then I will have learned a few more letters of Morse!

How big of a radio, and for how much money can you communicate across thousands of miles? What about something that fits inside a box of Altoids mints for $29? The best part is, nobody can ever cut you off!

Rock-Mite

Rock-Mite PCB


This is the “Rock-Mite” from Small Wonder Labs.
(Google “rock mite” for Altoids-mounted boards!)

Sure, you’ll have to learn morse code… I can’t think of anything that small however that truly can be used as a pocket emergency radio. Add a long wire antenna, a mini tuner, AA batteries, and you are in business. With the “Mity Box,” and connectors, your total cost comes to $70, still a bargain. My RockMite is on it’s way (20m version)!

Another kit I just completed is the DC20B.

DXxxB

DXxxB PCB

You can see that it is a bit more complex than the RockMite. You need to wind transformers by wrapping a certain number of turns across small toroids with very thin wire. The kit also requires tuning. The Rockmite is pre-tuned. Performance is supposed to be better, we will see…

Assembly took a whole afternoon and evening. I had never soldered on a double-sided circuit board, but it turned out to be fairly easy. I just made sure I had a good solder joint on both sides. I started with the smallest components, resistors and diodes, then integrated circuit sockets, capacitors, and transistors, leaving out the final transistor until everything was squared away. To my delight, I heard morse code when I turned it on and attached a long wire! The volume was very faint, hopefully that will change with a tuned dipole up in the air.

There is one little problem remaining. I have also built the frequency counter kit from N3ZI. The oscillator frequency of the DC20B is supposed to be 14,060khz. I get 14,063.2 minimum.

DC20B Frequency off

DC20B Frequency off

Hopefully I will be able to fix the problem. It might be a calibration issue with the frequency counter. Since I do not have an HF Ham radio, I can’t check it. Once I build the RockMite I will have a way to verify the frequency.

 
[warning]DCxxB builders: C36 has a missing trace to ground. Make sure you solder a short piece of wire from the pad closest to the board edge to the ground..[/warning]

Both the DCxxB and Rock-Mite have keyer chips included. That means it can generate Morse code from an Iambic paddle you plug-in. These radios serve the same purpose. For some, there is the challenge of contacting distant stations on very little power (500mw to 1w). Others take them camping, hiking, and on all kinds of adventures. I am of the second type. The RockMite will have it’s place in my bug-out bag as well. Heck, I might build a second one as a backup.

My choice between the two? Rock-Mite; because it requires no tuning and has no toroids to wind. You can easily find help online, along with a list of possible modifications. Both kits have a Yahoo group. The Rock-Mite group though did not at first accept me! Why? Because I don’t yet have a license and call-sign! The DCxxB group had no problem with me joining. It turns out that the groups are owned by the same person.. And I was accepted at last, after complaining. These kits are a great way to get started, and while groups need to be monitored, access shouldn’t be restricted…

Learning Morse Code turns out to be pretty hard for me. Some people have no trouble and wrap it up in a couple weeks. I’ll be lucky to take only three months! My brain isn’t wired that way I guess.. I use an iPod app: AA9PW Ham Morse. It uses the Koch Method, which is supposed to be better. I had to slow down the learning speed from 15wpm to 12wpm, just to be able to write fast enough. I might just try to build the sentences in my head… I don’t think anyone can write that fast; not me anyway.

As to my HAM license(s), I am in no hurry. I read the Technician class book once and never miss more than one questions on the QRZ.com practice exams. So, I took three General class practice exams, just out of curiosity, passed two! Barely, but still… I am reviewing for that class now. I might as well pass both tests at the same time. Maybe I should get the Extra class as well, why not? If not just to see the face of the examiners, asked which license I am testing for, I’ll say “All of them!” and get close to 100%. Listening to HAM conversations, I have to say that what I have heard isn’t that interesting. It is a somewhat weird crowd. Mostly old fat guys (no offense intended). As to public service, in times of relative safety, radios are useless. You don’t need a ham radio to help with a local fund-raising marathon.. Just use cell phones! I laughed when I heard a “Net,” the controller asking “Is there any emergency traffic?” Are you kidding? We call 911 for emergencies! There is also the “contesters,” who won’t give you the time of day and just want a call-sign and “grid number” to add to their collection. How useless is that? Anyway, there are also great things in Ham radio. Groups do take their transceivers atop mountains and in all kinds of remote areas. I like the idea of it being a safety net, some kind of support apparatus. Besides, you don’t stay in shape by sitting in front of a radio all day…

I will post an article on building the RockMite, with a video, when I get the kit (I was told ten days before it ships).

Here is what comes to my mind when talking about any item: “If it can’t carry you, and you can’t carry it, don’t bother.” These two small transceivers certainly get my thumbs up!

Update (May 27th): I think I am going to ditch the DC20B. I have a box for it, and should complete the build, but after that, it’s going away. I can’t get it on frequency, and I am not the only one… The Rock-Mite kit should arrive this week. I can’t wait to build it. Look for the article!

Update (May 30th): Well, I gave it one last try.. Changed C36 to a 100pF, and C29 to 47pF. It worked! Now I get 14,059.72 on transmit. Receive goes from 14,060.16 to 14,060.32, a perfect 600Hz offset. The problem is the receiver, which has no selectivity. I receive Chinese, French and Spanish commercial radio stations, but little, faint CW signals. Maybe the problem comes from the wire I use as an antenna, which isn’t tuned. I will try a tuned dipole during the day and see if I can get clear CW (morse code). I boxed up the DC20B in a nice Hammond cast aluminum box. I made a hole in the cover to tune CT1 and glued a piece of coax outer insulation so that I can’t touch anything with my screwdriver upon insertion.. The box is a little big, but it looks good and as though it would survive being run over by a semi-truck.. I might make another hole for access to CT2 and add an RCA plug for a frequency counter (for tuning).

Update (August 1st): The tuned antenna did the trick. Good selectivity now, and the radio is on frequency. The DC20B gets the thumbs up!

DC20B Boxed

DC20B Boxed

Note the piece of insulation glued on top of CT1.
I wish that damn iPod could focus up-close.
Still waiting for the Rock-Mite.
I am starting to think about an Elecraft K1.

I needed a better antenna for my Yaesu FT-270R. My requirements were to find a portable, efficient and easy to build design. The short rubber antenna works fine for me now, especially that I am not transmitting before getting my license. I do want more range however for emergency situations, in case local repeaters are down. My first thought was to make a Yagi-Uda directional antenna. They have a high gain but transmit in only one direction. While this can be an advantage, and I plan on getting one, my go-to antenna needs to be omnidirectional. I found the Slim Jim design to be my best option. It is easily made from soldered copper tubing. All you need is a couple of 5ft lengths of 1/2″ tubing, 90deg corners, end caps and PVC Ts. I added an electrical junction box for the feed-point connector, but it might make it more difficult to attach the coax and tune the antenna.


2m Slim Jim


Total length very-top to very-bottom is 58″. Width center-to-center is 2″. Gap is about 1-3/4″. See the Ham-Universe articles (1 & 2) for exact measurements.

It is easy to calculate dimensions for other frequencies:

  • 3/4w : 8415/F-mhz.
  • 1/2w : 5610/F-mhz.
  • 1/4w : 2805/F-mhz.
  • Feed point : 10-20% of 1/4w.


Slim Jim Gap

Slim Jim Gap


The PVC Ts need to be reamed with a 5/8″ drill bit so that the copper tubing can go through. I used a bit of WD40 to slide them down. Between the two Ts, I epoxied a 1″ piece of 1/2″ plastic tubing. There is one “H” PVC support assembly on the top portion and one on the lower portion, right next to the end cap.


Slim Jim Feed Point

Slim Jim Feed Point


I am not sure that using a plastic electrical junction box was a good idea for the feed point. Since I have not received my SO-239 socket yet, I must hold off on the electrical connection. My concern is that soldering will be difficult without burning the plastic box. I might have to use sheet-metal screws. Tunig might not be easy either, since the best SWR is obtained by moving the feed point up and down, between 3 and 4″ from the very-bottom. Maybe I should have used PVC Ts, like for the two support “H” assemblies. They can be split in half, then the coax soldered after finding the best feed point. Once epoxied, it would look fine. I do like the look of my electrical box though, and if it works fine, I will be happy with the results.

Total building time was about an hour. Everything came from Home Depot, except the SO-239 connector. Soldering turned out to be pretty easy. I sanded the parts and used flux paste before heating up the assembled parts with a torch. Once the parts are hot enough, you put the solder on, which flows in the joint, following the flux. Cost could have been as low as $30, but I spent about twice that much, not counting tools (hacksaw, drill bit, epoxy, solder), which you might have already. If you are starting “empty handed,” plan on $100. While it can cost more than a factory-made antenna, you get the satisfaction of building something yourself, which might be actually sturdier than a store-bought model.

Stay tuned for the finishing touches (painting), electrical connection and reception testing. The transmission test will come after I get my Technician HAM license.

Thanks to Richard KE5FXU SK at hamuniverse.com for the article!

Update, April 11th:

Finally, I got my SO-239 plug. Drilling the PVC box was easy. I didn’t even use my drill press. It only took me a few minutes by hand! Holes are one 5/8″ in the middle, and four 1/8″ around. I drilled in the middle of the lid, hoping I would have enough leeway to adjust the SWR by moving the contact in the box along the tube. First, as I suspected, I could not get the tube hot enough to solder the center of the coax to the copper tube using my 30w soldering iron. I solved the problem by heating up the tube with a Zippo under it while I soldered on top! It worked really well. I did the same to put soldering points in the box, every quarter inch or so. The zippo was placed an inch from the box. I was worried about melting it, but these electrical boxes are pretty heat-resistant. Sorry about picture quality:


Solder Points

Solder Points



It’s a bit ugly, but inside the box anyway..

Feed Box

Feed Box



Reception works great. I was able to listen to a conversation tonight on a distant repeater that I simply could not hear with the HT rubber antenna. I get three extra signal bars with the Slim Jim.
I got a cheap VHF/UHF digital SWR meter from Hong-Kong, which seems to work fine, but for the connectors which are of “N” type.
Digital SWR meter

Digital SWR meter

Update, May 1st:

I painted the antenna sort of a flat olive-drab color for stealth. I can easily hoist it up a tree and it blends in very well. SWR varies from 2.4:1 on the lower part of the band, to 1.8:1 around 146Mhz, and remains around 1.4:1-1.5:1 from 146.5 up. I used a ferrite RF choke kit from Palomar Engineers (photo below), which got the SWR down to 1.36:1 around 147.5Mhz. I much prefer the ferrite choke to the coax balun type, which looks ugly and wastes cable.


Slim Jim Connection Box With Palomar Ferrite Choke

Slim Jim Connection Box With Palomar Ferrite Choke



 
What I like the most about the Slim Jim is it’s sturdiness and that given it’s shape, you can hang it from anywhere, as long as you use an isolator to do so. When hanging it, I plug in an “L” shaped adaptor (photo above) to avoid bending the coax.