Trends in Amateur Radio

It’s always been accepted that one of the attractions of amateur radio was that it involved the building of kits; if you needed (or wanted) a better or more specific transmitter, receiver or transceiver but couldn’t afford to purchase one from your local retailer, you bought one in kit form and built it yourself.
Kits were ordered over the phone and posted to you. Some were better than others but all had potential risks involved, such as the odd missing component.

The Elecraft KX1 kit came professionally packed with a great instruction manual.

This kit from Virgil Stamps at http://www.hfprojects.com is a good example of a well-produced kit that involves soldering all the components into place in the PCB.

And it wasn’t only on the electronics front that you could heat up your soldering iron and get busy; making a suitable antenna was also a huge part of the hobby.

My homebrew 6m dipole strung up and ready for action.

Baluns are also popular construction projects with homebrewers.

I wound the entire length of coax on a piece of PVC piping I had in my workshop.

Of course, you didn’t have to stick with kits if you needed to construct a radio; you could always build one from scratch with components you happened to have in your proverbial junk box.

I built this regenerative receiver using what I happened to have on hand at the time.

Test equipment is also easy to build from kits.

QRPometer on the left, Hendricks dummy load/power meter on the right.

I have noticed a trend beginning to appear in the world of amateur radio, and that’s a swing away from ‘melting solder’. I first noticed this with the advent of the Elecraft KX3 a few years ago. For the first time this world leader in kit production began marketing a rig that only required mechanical construction; all the electronics came pre-manufactured and only needed slotting into place in the enclosure, which needed first to be put together by the ham. This was due to the high number of surface mount components present.

And now Virgil Stamps, proprietor of the beautifully designed and manufactured HF linear amplifier that is aimed at the SOTA and WWFF fraternity (http://hfprojects.com/) has gone this route with the launching of his latest offering, the HFPacker Amp MiniHFPA2. By all accounts it looks like this new trend in amateur radio is here to stay, but as long as it helps get more people on air, that’s sure to be a good thing.

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Softrock RXTX v6.3: PTT circuitry

The PTT circuit is all about connecting the PTT and Keyer inputs up to the SDR software via a serial interface. However, the DB9 connector will be installed in a later part of the build. I will be using instead, a USB I2C interface as both my Surface Pro 4 and my Compaq laptop, which runs Arch Linux, don’t have serial ports.

This stage involved installing four caps, 12 resisters, a diode, an RF choke and four transistors.

All appeared to go well until it was time to carry out some tests. Current tests proved spot on, and so did the initial voltage tests. Until it came time to prove that the transistors were turning on when voltage was applied to the PTT_IN connection.

What is supposed to happen is this: when 12V is supplied to PTT_IN, Q1 turns on, pulling R21 and PTT_IN to a low level. Q2 then turns on and I should be able to measure about 12V at S12V. This means the rig is transmitting.

I did not see this on my DMM. My reading was of the order of 0.02V.

So it was out with the schematic once more (I had become quite familiar with this piece of paper). I started by tracing the power supply to the transistors to see what was wrong and why Q2 wasn’t turning on. After much thought, I noticed that two vital resisters were missing on my PCB.

These resisters were missing on my PCB

These resisters were missing on my PCB

It was then that I decided to check if any other components were also missing. What I discovered was that I had omitted to solder in all the capacitors and all the resisters for this stage! No wonder Q2 wasn’t turning on.

Once this slight oversight had been corrected I ran through the test once more, with perfect results.

Next will be the RX Switching stage.

 

Softrock RXTX v6.3: TX Mixer

The next stage in the project was to construct the TX Mixer stage. The job of this stage is to provide the modulation of the Dividers’ output signals by the four I and Q signals from the Op Amps. The result is a double sideband RF waveform that will be coupled into the PA stage.

This stage centres around U3: FST3253 which is a SOIC-16 Dual 4:1 Mux/Demux Bus Switch. There were also four resisters, a capacitor and two connector sockets that completed the build.

When that was done it was time to test if all was as it should be.

This was when I hit a snag.

First, I had to jumper the hairpin bend of R26 (which hadn’t yet been installed) to ground and then jumper pins two, three and four of socket J1.

R26 needed to be jumpered to ground.

R26 needed to be jumpered to ground.

Current readings were fine, and so were the initial voltage readings. But when it came to measuring the voltage on pins 7 and 9 of U3, instead of getting around 2v I was reading 0.01v.

I tried again but this time noticed that when I turned on my power supply (12V DC) the current surged to around 2A before settling down to more normal levels. I cut the power and began scratching my head.

All the solder joints looked fine as did the components, which were all in the right places. That’s when I decided to take a break and sleep on it.

After the dust had settled, I decided to consult the schematic. I started by tracing the 5V power route, through U4 and into U3. I could see its path to ground was through pins 1 and 15, then on to the as yet uninstalled R26 to ground via C43. So that’s why I needed to insert a jumper.

I then connected up my DMM and swung the switch to the continuity setting. Probing the jumper connection I had inserted into R26 produced nothing. So I probed R26’s other hole and bingo. I had jumpered the wrong whole!

My mistake was immediately apparent.

I had presumed the jumper needed to be in the whole marked with a white circle around it (to indicate that’s where the body of the resister fits). The instructions called for jumpering the hairpin of R26, which I suddenly realised was not the hole indicated by the circle, but the other one.

Resoldering the jumper took only a few seconds, but the satisfaction I received from a full set of good readings lasted quite a lot longer.

This little exercise highlighted to me the importance of being able to read a schematic diagram.

 

Building a Software Defined Radio

I have decided to melt solder once more and build another QRP radio. This time it’s a Softrock RXTX v 6.3 that Wal, VK4CBW gave me. He said his eyesight doesn’t allow him to tackle such projects anymore.

The kit is fairly complex as one would imagine and although this particular model is now no longer in production, there is still detailed build information on the internet.

The first stage of the build involves constructing the power supply section. This contains many surface mount components, which are tricky to install due to their small size. First to do was to install the board mounting hardware that consisted of nuts, bolts and spacers. Then it was a matter of those pesky little capacitors: eight 0.01 uF caps and eighteen 0.01 uF caps.

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The SMT caps all soldered into place.

Next came U5, the tiny 3.3v regulator. At first I couldn’t find this item it was so small. But after about 20 minutes of searching, I noticed it tucked away in a fold of the anti-static bag the ICs came in. Phew.

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That’s U5 nestled in among the SMT caps. Notice the liberal amount of flux I used just to help the parts ‘stick’ in place prior to soldering.

I am taking this project nice and slowly so will post regular updates as I go along.

Building and adding the KXAT1 automatic antenna tuner to the KX1

The final part of the upgrade to my Elecraft KX1 involved building and installing the internal antenna tuning unit.

The kit is remarkably small; it comes in one plastic zip up envelope together with a concise and well put together 12 page Assembly and Operating Instructions booklet. It also contains a note telling you who put the kit together, which is nice and reassuring. If anyone is willing to put there name to something, there must be good reason! Confidence that no parts are missing is my guess, and I think I’d be right because none were. This, of course, isn’t generally the case with electronic kits, as most builders would know.

The kit was very easy to build and align. The instructions are excellent and leave nothing to chance. I found winding the three coils and one transformer easy to do too.

Populating the PCB.

Populating the PCB.

As the KX1 is a small, compact piece of gear, the ATU needs to fit in without touching other components because if it does, the back of the enclosure won’t fit properly. This is one reason both sides of the PCB are used.

The yellow relays are on one side of the board while other components nestle underneath.

The yellow relays are on one side of the board while other components nestle underneath.

The only ‘snag’ I ran into (I always tend to make things more difficult for myself) was when it came to installing the mating male connectors. I misread the instruction to ensure they were fully seated before soldering. I read that to mean the black plastic bodies needed to be fully seated on their female counterparts. So I slid them down further until they did with a pair of long nose pliers. This presented problems when it came to ensuring the ATU’s PCB seated properly, so I returned them to their original positions, soldered them in and all went together well.

Fitting the ATU into the KX1.

Fitting the ATU into the KX1.

Alignment was easy to accomplish. All that was needed was a DDM and an insulated screwdriver.

Time to put it all back together again.

Time to put it all back together again.

The ATU worked perfectly first time. This is a wonderful addition to the KX1 that adds to its functionality.

Building Elecraft’s KXPD1 plug-in keyer paddle

Part of my Elecraft KX1 upgrade program involved adding the KXPD1 plug-in keyer paddle to the rig. I decided to do this as I like the idea of having one less component to worry about, especially when operating portable. And with the annual John Moyle Field Day only a week away, now is the time to get organised.

I placed my order for the kit over the phone and it arrived in Australia in less than a week.

The kit came well packed and with good instructions. Typical Elecraft.

This was a rather simple kit to put together, being more mechanical in nature than electronic. I only had to use the soldering iron once to solder the wires to the 3.5mm stereo plug. This was also the most tricky part as you need to ensure that there are no short circuits. The space in the aluminium bracket where the soldering takes place is small and cramped.

When all was together, it was time to run some tests. I plugged the keyer into the rig and turned it on. I immediately heard a series of dits and dahs in the headphones, indicating that something was wrong.

I read through the instruction manual and found this case covered: there was a short between one of the plug wires and the bracket. But I knew this not to be the case as I had checked with my DMM beforehand and all was okay. So I read on and found the next test was to remove a rubber grip and see if that stops the noise. It did. So now I knew I had a build up of solder or something between the lever and contact wire.
I pulled the lever apart and inspected it closely. There was a small bit of flux on the lever. That responded well to my finger nail and fell off. So I put it all back together again, slipped on the rubber grip and plugged it into the rig. I held my breath as I turned on the power and heard … nothing. Phew, all good.

Now all I need to do is try out the keyer paddle next time I fire up the rig for the QRP net.

My new KXPD1 keyer paddle all ready to go.

My new KXPD1 keyer paddle all ready to go.

QRP with an Elecraft KX1 and a Long Wire Antenna

Having gone 100% QRP, I have decided to operate in the true spirit of doing more with less. That means all my radio work takes place on my deck, using battery power and as basic set up as possible.

And boy, am I having fun.

Since making the switch to QRP I have been operating on Tuesday nights with the CW Operator’s Club net on 7.028 MHz. My equipment so far has been the KX1 feeding 3W into a long wire antenna that I string up along the railings of my deck at my QTH.

The long wire antenna is attached to the deck railing and works surprisingly well.

The long wire antenna is attached to the deck railing and works surprisingly well.

The deck is up on the second floor of my house facing SE. I use a BLT Tuner to take care of tuning the antenna, a Whiterook paddle and a 2 Ah rechargeable battery.

My operating position on my deck. From left: battery, KX1 with Whiterook paddle connected, BLT tuner.

My operating position on my deck. From left: battery, KX1 with Whiterook paddle connected, BLT tuner.

I have no trouble making good contact with operators in Sydney and Canberra and have worked into Melbourne too with this setup. But I need to maximise efficiency so have embarked on an upgrade. I have ordered an internal antenna tuning unit and the plug-in paddle as well as a Buddistick vertical antenna from Elecraft. That should arrive this week. I expect better performance once I’ve had a chance to build and install these pieces of gear.