VK5JST Antenna Analyser: completing the build and testing.

The time had come to do the first smoke test of the analyser. I powered up my DMM and checked that the voltage regulators were putting out 8 volts and 5 volts respectively. I obtained 7.94 and 4.93 volts. Phew, all good so far.

Next I checked the signal generator section: I was to expect between 1.10 and 1.25 volts at Test Point 1. No problems there.

The centre pin of IC1 showed 1.534 volts which was just about spot on. And as the oscillator and following amplifiers are dc coupled, this reference voltage has to be correct for everything to work correctly. Now I had a problem: the collector voltage of TR3 was only 0.742 volts.

After much head scratching and tracing through the schematic, I decided to send Jim, the designer, a shout for help. Quick as a flash he responded saying that this is typical of an open circuit switch. So I pulled to offending item from the board and checked it with my DMM. All appeared fine. Jim wasn’t convinced and recommended I make my way to Jaycar to pick up a replacement. This I did, only to find the same result when I checked TR3 once more.

I sent Jim some high resolution photos of the PCB for him to run his beady eye over before resorting to packaging up the board and posting it to him for a more detailed analysis. He picked up that one of the solder connections on the variable capacitor looked a bit dodgy. So I sorted out the offending wire and tried again.

Success! I was back in business.

Next, I had to connect a good quality 50 ohm dummy load directly to the N connector of the analyser. Not having one that would connect to an N connector, I borrowed one from Wallace, VK4CBW, and proceeded to adjust the three 20K linear trimpots as described.

All other tests were well within the specified tolerances, so I was happy.

Final bench test with the dummy load connected.

I decided to check the SWR of a 6m dipole that I build last year using theory only for dimensions. And I know the antenna worked reasonably well because I used it in a VHF/UHF Field Day contest and won my category.

Connecting the analyser directly to the antenna produced a pleasing SWR reading.



VK5JST Antenna Analyser build: Populating the PCB

Once the enclosure had been sorted, it was time to start up the soldering station and melt solder. First I soldered the connector printed circuit board to the mainboard. The important thing here was to make sure the boards were 90 degrees to each other. Next I began mounting all the small components, making sure to double check each resister and capacitor; the resisters are small and the coloured bands not easy to read. The N connector was bolted into place and a short piece of wire soldered to its centre pin.

I always use a fume extractor when soldering.

The tuning switch was mounted on the component side of the PCB and then the inductors were inserted and soldered into place, making sure not to use too much heat or soldering them all into place in one go as this would damage the switch.

A wire was soldered from the switch’s common terminal to the PCB.

The next job was to solder all 16 wires from the PCB to the LCD.

This took time and patience.

Everything in place and ready to be fitted into the enclosure.

All that was left to do was to complete wiring up the various switches and battery compartment. Then, once the eight AA cells were in place, it would be time to run some initial tests.

Looking good and ready for testing.

Building the VK5JST Antenna Analyser

I have long needed a good antenna analyser so that I can tune my existing antennas and build better new ones. Trouble is, they can be very expensive.
All that has changed, now that there is a new kit on the market.
The new analyser covers the HF bands as well as 6m – perfect for my SOTA and WWFF needs.
I ordered mine from their website, http://www.vk5jst.com, and it arrived well packed.

The quality of kit is excellent and came well packaged.

The instructions call for the mechanical build to be tackled first; attending to the enclosure by drilling all the necessary holes and cutting out the hole for the LCD. Suggestions are provided, which I found very useful.

The main PCB is used as a template for positioning and drilling the mounting holes into the lid of the enclosure.

Cutting out the hole for the LCD screen is probably the most tricky part; I used a coping saw and although it took time, I was able to achieve a very satisfying result.

Getting the measurements right was important.

Once I had finished with the drilling and sawing, I cleaned up the mess and took a rest. The result was more than acceptable, I think.

The completed front panel.

The final job to be tackled was to cut the opening for the N-connector and tuning capacitor knob. The instructions suggested using the course wheel of a bench grinder. My initial feeling was that this would be rather ‘drastic’, but it turned out to be a piece of cake.

The bench grinder sliced through the plastic like a knife through butter.

All that was left for me to do was to complete the job using a fine file.

Testing the miniHFPA2 with the Elecraft KX1

I received a query from a reader yesterday regarding tuning up an antenna using the internal ATU in his Elecraft KX2 if it were connected up to the miniHFPA2 amplifier. The reason he wanted to know about this was because he was considering ordering one for use with his Elecraft KX2.

He wanted to know if it is it possible to run an antenna such as a doublet, by tuning the antenna using the KX2’s internal tuner with the amp in bypass mode, then switching the toggle switch on the amp to put it inline. He said that it appeared to him that this procedure would not work because the amp, once in line, would probably change the SWR of the antenna.

I decided to conduct a test to find out if this would in fact be the case. This is what I found:

I carried out the test in two parts:
Firstly, with the KX1 (powered by a 12V supply voltage) connected to a PWR/SWR meter and 50 Ohm dummy load.

On keying down, the PWR/SWR meter read the following: output 3.5W with SWR of 1.0:1

A straight through test with the signal going to the dummy load.Secondly, connected up the miniHFPA2 directly to the KX1, and the Pwr/SWR meter and dummy load.
With the Amp in bypass mode, the reading was 3W output and 1.0:1 SWR.

The only difference now is that the amp has been connected up but left in bypass mode.

With the Amp switched on and placed inline, the reading was 18W output with SWR 1.0:1.

With the amp in action, the SWR remained 1.0:1

Note: the lower than expected power output with the amp inline was due to the fact that the amp is set up for an input of 5W. My KX1 can only supply it with 3W, so the final output of the amp will be lower too. With 5W in, as is the case when connected up to my Yaesu FT-817, it outputs 30W.

First C4FM SOTA contacts in Queensland

Going through the Activator Roll of Honour results for QLD recently, I noticed that there were no results for Digital Voice. Checking the state of play for the other states, I saw that the Australian Capital Territory and Victoria had one each.

It was time to put that right, so on Saturday 23rd June, I headed out for Mt Cotton (VK4/SE-115) with nothing more than my Yaesu FT-70DR hand held radio.

I had activated this summit more than a year previously, so if I logged at least four qso’s, it would count as another activation and my tally would increase by one point.

The climb up to the summit was uneventful and I headed to a clearing that featured a rather tatty picnic table and a good view.

I set the radio’s frequency to 147.400, the calling frequency for digital modes, and the mode to DN (Normal Digital Mode).

I had pre-arranged with Wal, VK4CBW, to listen out for me on simplex. His was the first contact I made. The distance between us was 26.33 Km (16.456 miles) and his Yaesu FT-2DR connected to a beam antenna sounded excellent. I ran a few quick tests too, to see what difference it would make to the signal if I placed my radio flat on the ground while he spoke. It made absolutely none!

Trying to get more height when calling CQ.

I am well used to using FM simplex on summits and noticed immediately that with C4FM there was no background hiss at all. The audio was as perfect as can be, very similar to that of a mobile phone.

I then had a long qso with George, VK4HGT, followed by Phil, VK4MOT and Bob VK4YA. All contacts were remarkable in that the audio was perfect. I think C4FM is far superior to FM analogue and it’s a mode I’ll be using more often in future.



The John Moyle Field Day 2018: Another successful field day.

Another Field Day success. This time my main goal was to rake up a few contacts during the John Moyle Field Day, operating from Mt Coot-tha in Brisbane with my FT-817 and Buddistick antenna. But this time, instead of squeezing the most out of 5W, I hooked up my new HF Packer miniHFPA2 Edition linear amp that puts out a massive 30W. And the beauty of this is that I would only need my 7 A/H gel cell to power it.

My set up for the day, from left: Yaesu FT-817, HF Packer miniHFPA2 amp, LDG-Z100Plus tuner. Behind: Yaesu FT-70D, Sotabeams powwerpole distribution box on top of 7 A/H gel cell.

I mounted my Buddistick antenna to a BBQ grill behind the operating bench that looked as though it had seen better days. Fortunately the G-clamp just fitted.

The Buddistick did a good job and was easy to erect. I chose it over a dipole as there was no ready method to secure my squid pole close to the operating bench.

Well, at the start of my 40 minute activation, my battery showed 12.69 V and at the end, 12.60 V. And that was after continuous SSB work on 40m. So 9 QSOs later, I was content to pack things up and head for home.

Beating the downturn with the miniHFPA2

Everyone’s been complaining lately about poor propagation when it comes to amateur radio. But I think I have found the answer to my situation, especially considering I run an essentially low power operation.
I ordered a miniHFPA2, a linear amplifier that is made for portable operation out in the field.
This little beauty is the 5th generation HF Packer amplifier that comes pre-assembled, tested and calibrated. All I had to do was to hook it up to my Yaesu FT-817, then feed the output through an SWR/Power meter and Antenna Tuning Unit to my long wire antenna.

All set up and ready to test on air.

I happened to notice, on checking SOTA Spotter, that VK2IO Gerard and VK2/G4OBK Phil would be activating three summits, VK2/IL-001, 002 and 005 on Thursday 8 February 2018.. This would present me with an excellent opportunity to try out the new amplifier.

I tuned up on 40m and responded to their calls. Gerard mentioned that he was receiving me well and gave me a signal report of 569. This was excellent news, given the marginal conditions. I worked all three summits as they were activated and couldn’t have been more pleased. You see, normally my 5W output wouldn’t have been up to it in current conditions.

So what is this little gem of an amp all about?

According to Virgil Stamps, who makes the amps, the aim of his project is to give your signal a boost so you can start making memorable contacts under marginal conditions. It certainly has lived up to that! The amp gives a clean, more powerful output signal from a QRP transceiver with a good balance between output power, physical size and weight. And what’s sure to excite any SOTA or WWFF operator, it can be powered by any battery such as a 7.2 AH gel cell or 4.2 AH LiFePo4 battery. The amplifier provides a full output of around 30-35W with as little as 9V DC, making it very tolerant for outdoor battery operation.

What makes this amp a little different is the heat sink that is secured to the top of the enclosure. It isn’t the more common type that features rows of serious fins; it is a flat metal plate of around 1mm in thickness. And it does the job it is intended to do very well indeed. It lends itself to outdoor use as it can easily be accommodated in any backpack, but care does need to be taken so as not to damage the toggle switches on the front panel.

I particularly like the slim heat sink that is secured to the top of the enclosure.

The amp comes complete with two low pass filter modules (60/40m and 30/20m) but mine came complete with additional ones for 160m, 80/75m, 17/15m, and 12/10m as well. These modules are inserted into place by unscrewing the left and/or right hand side panels of the enclosure. They slip in effortlessly, thanks to cleverly designed guide posts on the LPF boards. I think when I proceed on my next SOTA activation, I will decide beforehand what bands I will be operating on as I think unscrewing side panels in a hostile environment such as on a summit could be a little tricky. Virgil did send along a sealed package containing spare enclosure screws, heat sink compound, two spare MOSFETS and some other items. Great service and attention to detail.

At the time of ordering you need to specify what level of input power you will be using. This could range from 1 to 5W; I chose 5W. Output power is an easy 30W. Spurious products are -40dB or better at 35W, with harmonic content at -45dB or better at 35W.

If you’d like to read up on the specifications, visit the web site http://hfprojects.com