T-Kit 1380 Kit Build: Part 1

I won a T-Kit 1380 80m 3 watt CW transceiver kit at the WCRA Hamfest back in 2014, and it’s been sitting on my bench unopened since then.  I didn’t have my license at the time, but I got my General license about a week later. I decided that this summer was a good time to start building it. Here’s a link to one you can pick up if you’re interested : http://www.rkrdesignsllc.com/-13/

I have quite a lot of kit-building experience, but most of it is digital electronics, so this is probably the most complex kit I’ve ever built, both in number of components and circuit complexity.

If you’re not familiar with amateur radio, this kit will let you transmit and receive on the 80m band (between 3.5 and 3.75 MHz) using CW (morse code).

1380 Manual

The schematics in the manual are a bit low-res, but the instructions for assembly are very good.  My biggest complaint with the manual so far is that errata are supplied as a stack of papers inside the manual.  Some of them referenced parts this kit doesn’t use, so it was a bit of a chore to go through and update the instructions and update the steps by hand.

The assembly process is documented in phases, with testing procedures at the end of each phase.

Phase 1 is construction of the DC input circuitry as well as the keying circuit.  The keying circuit is connected to the code key, and disables the receive circuitry while transmitting.  Here’s the diagram for phase 1.

Phase 1 schematic

Phase 1 schematic

Here’s the board as assembled:

Phase 1 assembled

Phase 1 assembled

This is a pretty densely packed board, and the silkscreen suffers for it.  The manual gives pretty decent drawings of the section of the board each phase is concerned with, and this helps quite a lot.  You can usually locate a component by finding a nearby component you’ve already installed, or one whose silkscreen isn’t broken up by a pad.

Once this phase was assembled, there was a short test procedure to verify that it is operating correctly.  Essentially, I had to apply 12v to the 12v input, and then verify that R13 (the resistor in the center of the board, just between the two beige ceramic capacitors) read 0v while the key wires were disconnected (the white and black wires just under ‘J1’), and 12v while they were touched together.

I misread the directions and it took me a while to figure out what I was doing wrong (I was measuring voltage drop across the resistor, not between the resistor terminal and ground), but in the end, everything checked out.

The full board

The full board

As you can see, there’s quite a lot of work still to do, so come back next time, when I move on to assembly and testing of the VFO section!

New (well, old) Workshop Phone

I picked up an OBi100 adapter for the space a few weeks ago, and have been hunting around for a phone that we can use with it.

I stopped by the local Goodwill on my way in to the workshop one morning, and picked up two phones for $1.99 each.  One was a Lucent speakerphone that was missing a power adapter (I managed to dig a compatible one out of our giant box of wall warts in the electronics room).  The other was a fantastic old GE Model 500 rotary dial phone.  One of our members with a bit of experience in the area pegged the year of manufacture as 1965, with the last service in 1984.  I cleaned it up with some rubbing alcohol, and we swapped the old phone number placard for a W88 circuit board mask:

It took about 10 minutes of googling to find the pinout on the 4-prong adapter so we could hook it up, and it was hooked up to our Google Voice phone number and ringing.

Model 500 Plugbox Render (top)

The alligator clips aren’t a great solution, so I started designing a box to plug it into.  I used OpenSCAD to do the design.  The source files are available in my GitHub repo, but here’s a couple quick screenshots of the render:

I measured for the holes on the top using a pair of digital calipers, and then did some quick trig to figure out the offsets from the center point of the box.

Model 500 Plugbox Render (bottom)

The pins on the plug are arranged in a trapezoidal fashion so you can’t insert the plug backwards.  The bottom of the box is set up so that I can drop in a Radio Shack perfboard with a standard phone line connected to a couple of spring contacts on the wider pair of the two holes.  The standoff holes in the perfboard line up with the blocks in the corner of the box, and I have a second 3D model for the bottom of the box that sits below the perfboard.

The most difficult part of designing the box was getting the Workshop 88 logo to come out right.  I found this great tutorial on how to use InkScape to build 3D shapes in OpenSCAD and I used the source image for the same circuit board mask that we stuck on the phone.  Once I had that in place, it wasn’t too difficult to use it in OpenSCAD.  Check out the GitHub repo for details.

Model 500 Adapter with perfboard

I did a couple of test prints on the MakerBot to make sure everything fit together, and it looks like it is working pretty well.  I haven’t done another print with the logo, but judging from the generated STL, it is going to be much more involved than the basic prints.

When I added the logos, the STL went from about 300K to over 2MB.  I’m hoping that the print itself will be stable enough that the logo won’t lose resolution and look bad.  We’ve got a new stepper motor extruder ordered for our MakerBot, so that may help a little bit with the resolution.

Model 500 Adapter 3D print (bottom)

The next project is to get this puppy to dial out.  We’ve had a few suggestions, from converting the pulse dial to DTMF using an Arduino Teensy to hooking up a Blue Box with an acoustic coupler.  Right now the easiest way to use it is to dial out on a different phone, and then pick up the handset.  That really isn’t all that much fun.  I’m leaning towards the acoustic coupler method, but early experiments with DTMF generators on our cell phones didn’t go too well, so we may have a bit more work cut out for us.  The Wikipedia article says that blue boxes no longer work due to changes in the switching infrastucture, which… ahem… anecdotal evidence would tend to confirm.