Kits and things – AB4UG Radioblog

A frequency counter kit

One of the items from the KB1SH collection of parts I bought at Hamcation was an unassembled frequency counter kit. A packing slip still in the box showed it was purchased from a company called S&S Engineering out of Maryland in 1993. A quick search on Google didn’t yield anything that looked like it might have been related, so the S&S Engineering that produced this kit probably isn’t around anymore.

I love assembling and soldering a good kit, and this looked like a pretty good one. Documentation included the assembly instructions as well as a circuit schematic and a brief theory of operation section. This particular kit included an option for an additional 4 digit LCD display. All the necessary parts turned out to be there, except for a TO-92 voltage regulator that could very well be buried in my carpet somewhere. I neglected to get any photos of the boxed kit, but I did remember to take photos while I was soldering parts on.

The circuit board for the counter is relatively large, 13.1×13.5 cm and the part density wasn’t high so there’s plenty of room to work on the board while soldering things on. The printed circuit board itself is etched and tinned, but without a solder mask that you’d normally see. The only problem I ran into while soldering were two parts that went into a very large ground plane/heat sink. This would have been a good point to break out the flux and switch to a larger tip on the soldering iron had I thought about it.

Partially assembled frequency counter kit from S&S Engineering, part of the KB1SH collection purchased at Hamcation 2022 — Partially assembled frequency counter kit from S&S Engineering

There are a total of 10 ICs in the kit, which I decided to use sockets for. 8 of the sockets and all the resistors are installed in the photo above. The other two were for the 40 pin ICs used to support the LCD displays at the top of the board.

Above is the fully populated board, except for the two LCD driver ICs and the LCDs themselves.

LCD driver ICs installed on the PCB with header pins for the LCD displays

The kit came with two 40 pin sockets, which the instructions say to cut apart and use for the LCD displays. I opted to use the sockets for the ICs, and some tall header sockets for the LCDs.

Assembled frequency counter kit from S&S Engineering, part of the KB1SH collection purchased at Hamcation 2022 — Assembled frequency counter kit from S&S Engineering

The fully assembled board looks pretty nice. Unfortunately, the frequency counter isn’t working yet. I’ve confirmed that the 10 MHz test point puts out something close to a 10 MHz signal, according to one of my DMMs. Not sure if I’ve put in something wrong, bad soldering, or if there’s just a problem with the LCD displays.

Random LCD segments showing up with power applied

A few seemingly random LCD segments show up and then eventually fade after a few minutes. This makes me think it might be an issue with the LCD displays themselves. They are almost 30 years old (at least) after all. I’ll see if I can stick them into a breadboard or something and test them out. Wonder if it would be possible to wire in some other kind of display.

Figuring out how to get this frequency counter working will be as much fun as putting it together I think.

Update: Getting closer to figuring out the problem. Turned out I had the LCD driver ICs installed upside down. I wasn’t paying close enough attention to the installation instructions. With the ICs installed properly (glad I had them in sockets), now I can get the digits to display properly if I wiggle the LCDs in the header sockets to get them into a certain position. I might need to replace the header sockets with something else.

A trio of QRPGuys kits

A while ago (back in October) I ordered a few kits from QRPGuys: a dummy load, mini-paddle, mini keyer and two digital frequency counters (PTH and SMD versions).

Awesome, #qrpguys kits arrived! Now I need to get the workbench up and running pic.twitter.com/oDT9zITArg

— imabug (@imabug) October 1, 2016

I finally got around to assembling the dummy load, paddle and keyer over the past week.

QRPGuys kits — Iambic paddle, mini-keyer and dummy load from QRPGuys

The dummy load was the easiest to assemble, and parts placement was pretty obvious (I’m only a little bit bothered because the resistors don’t line up…). 5 minutes of soldering and you’ve got yourself a nice compact little 12 watt dummy load that also lets you measure power output via a voltage measurement.

The mini-paddle was only a little more difficult because of the size and length of the screws being used to attach the paddles. Still a relatively easy build, although you have to be careful with the alignment of the little PCB pieces that are soldered onto the base. The hardest part was getting the little nuts that hold the paddles secured. There’s not a whole lot of space to work in, you have to hold the screw, spacers, washers and metal paddle part while trying to get the nut on, and there’s not a whole lot of screw remaining to get the nut started on. Moderately difficult to assemble.

In terms of parts count, the single lever keyer/paddle was the largest kit, but easier to assemble than the iambic mini-paddle. On the electronics side, the only thing I had to consult the assembly manual for was to find out the correct orientation for the 1N4148 diodes. Placement of all the other parts is pretty obvious from the silkscreen outlines. On the keyer side, assembly was similar to the mini-paddle, but with only one lever to worry about, getting it put together was significantly easier. I did end up leaving off two nuts for the two screws that serve as contacts for the paddle. With the nuts, the screws were just too far away from the paddle. I don’t know if the screws I got were just too short to begin with, or if the kitting changed but the instructions didn’t get updated.

True to their mission, these are fun, inexpensive little kits to put together. Looking forward to working on the frequency counters next.

Ensemble RXTX build – Driver/PA

The driver/PA section is the final section of the build.

Three capacitors are the final SMD components left to solder onto the back of the board.

Two binocular core transformers are part of this section. You might be tempted to do these last, but I suggest making them the first components to install. The top of the board is starting to get pretty crowded at this point and you’ll want a bit of room to thread the wires for the transformers through the holes. Same for the RF choke (RFC1, which I noticed I inadvertently left out).

The transformers themselves can be tough to wind. Make sure you pull each wire tightly through the hole or you’ll have a hard time fitting all the windings in.

The three BS170 FETs get covered up by a heatsink and pad. The 2N2222 transistor also gets a heatsink treatment. There are a few components that get partially covered up by the heatsinks, so make the FETs and 2N2222 the last parts you work on.

Everything else is pretty simple and should go together without any issues.

The top and bottom of the (practically) completed board.

Ensemble RXTX build – TX mixer

The TX mixer section doesn’t have quite as many components as the previous section, but there are a few band specific components including a toroid and transformer so you’ll want to make sure you have the right band selected if you’re following the WB5RVZ build instructions.

Like the RF mixer stage, the only SMD components are the FST3253 IC and three accompanying capacitors.

The through hole components consist of a 3904 transistor and a few capacitors and resistors. Watch out for accidental solder bridges between the closely spaced holes of the transistor.

Both the L1 inductor and T2 transformer have a lot of turns to wind onto a relatively small T30 core. If you have some 28 or 30 gauge magnet wire that’s a different colour than what comes in the kit, use it for either the primary or secondary winding on T2. That will help make it easier to separate out the T2 wires before soldering onto the board.

Here’s the top and bottom of the board so far.

One more section left in the build: the driver/PA section.

Ensemble RXTX build – TX op amps

Lots of parts to solder on in the TX op amp section, but most of them are through hole. No band specific compnents to worry about.

You might be tempted to place them all at once and then start soldering, but with all the dangling leads you end up with, it can make getting around with the solder and soldering iron a bit difficult. I found it easier to place a few components, solder, trim the leads and then repeat with a few more components.

I cross-wired JP1 here instead of jumpering them straight across, based on the notes in the build instructions. May end up having to change this, but we’ll see.

Two SMD op amps and accompanying capacitors go on the bottom of the board. By now, soldering the SMD components should be pretty easy, even if you’re new at working with them.

Getting near the end of the build now. Only two more sections left: the TX mixer and PA. TX mixer section is up next.