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



Building an all-band HF Air Choke

Having recently installed an end-fed 10m long wire antenna, the problem I was facing was feedline radiation, or RF into the shack. I knew this was happening because a touch-operated desk lamp would come on and off and I transmitted, which was most annoying.

I needed to build a 1:1 choke balun. So I did a quick search on the internet an arrived at the page of K8DNS (

After collecting the various pieces of gear I would need (thanks Wal VK4CBW for 21 feet of RG58), I proceeded to build this simple choke.

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

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

I held the coils in place with zip ties, then soldered on the PL259 connectors.

All ready for connecting up to my end-fed antenna at the feedpoint.

All ready for connecting up to my end-fed antenna at the feedpoint.

I connected it up to the end fed 80-6m portable HF antenna matchbox system, the UJM-150 that I purchased from Nelson Antennas and put it to the test.

All in place and ready to operate.

All in place and ready to operate.

Initial tests were disappointing: my touch lamp still turned itself on when I transmitted a test signal. Undeterred, I then added two ferrite chokes to the antenna feedline inside the shack and this solved the problem.

One of the ferrite choked taped to the antenna feeder.

One of the ferrite choked taped to the antenna feeder.

The other thing this new setup solved is my ability to tune up on 80m!

DX on 1.5W from a SOTA summit

Who said life is too short for QRP? Not true. Let me explain …

Andrew (VK1AD who used to be VK1NAM) and I activated Mt Goorooyarro (yes, say that with your teeth out!) which lies on Canberra’s border with New South Wales the other evening and it was up there that I made my first real DX contact with my Elecraft KX1.

But let me start at the beginning and save the juicy bits for later.

Mt Goorooyarro (VK1/AC-036) has an altitude of 872m and comes with only one SOTA activator’s point as a result. But don’t let this minimal number fool you; it lies on private property behind a locked gate with a sign warning visitors to keep out as there are unexploded ordinances there. This area, you see, used to be a military firing range and even today it borders on a range that is still in use by the military.

We had permission as long as we kept to the track to the top. So we parked the car on the dirt road near the gate, hoisted our backpacks on and made for the gate.

It was an easy matter to climb over, but not so easy to keep our eyes from that warning sign.


That sign! Scaling the gate backwards was the way to go.

The walk up to the summit took about 45 minutes with the going ranging from easy to pantingly tough. But we did pass some interesting sights.


We did wonder how these old cars got there.


Andrew with one of the many ant hills we encountered.

Once on the summit, we set up our stations and set to work.

Now for that juicy bit I alluded to earlier.

I heard Bernard, F9IE calling on 14.028 CW and as no one responded, I did. And he answered! We had a lovely, longish QSO, which was my first SOTA DX contact. My station consisted of the Elecraft KX1 putting out 1.5W and a Buddistick vertical antenna. Then I worked a JA station (JL1MUT) but conditions were noisy at his end.

That got me thinking about the magic of QRP. Think of it this way: if 100W gets you a S9 reading on someone’s S-meter, what will that same meter read you if you were, like me, putting out a meagre 1.5W?

Here’s the thing: it takes four time the power to move the S-meter one S unit. So going the other way, it takes a signal four times as weak to move the S-meter one S unit down.

So if 100W registers an S9, 25W will register S8, 6W will register S7 and 1.5W will register S6. Remember, we are reducing power by a magnitude of four each time.

So is life really too short for QRP?


John Moyle Field Day 2014

One of the aims of the John Moyle Field Day is to test your ability or readiness for portable operations. This is an even I like to take part in as it not only allows me to prepare for remote operations, it also guarantees contacts.

This year as always, I prepared my kit, made a check list and ensured I had thought of everything. My mode of operation would once again by CW only on the HF bands. My rig of choice was my Elecraft KX1 and my antenna my new Buddistick. My location would be up on Mt Coot-tha, which is not very far from my QTH.

This year I took the added precaution on including a few backup options, and boy was I glad I did. These included a long wire antenna, extra batteries and a multi-tool.

When I reached to top of Mt Coot-tha, I found an unattended BBQ area off the side of the road near the Channel 9 TV studios. Perfect. There was a nice table and bench seat provided too.

I unpacked my gear and started by assembling the Buddistick antenna. Bugger, I had left the all-important antenna mast and stand at home in my haste to get going. And worse still, it had the mounting plate still attached so I couldn’t make use of the small tripod that came with the Buddistick.

Thank goodness for the long wire antenna. I proceeded to cast the end of it up over a high branch of a nearby tree but the weight at the end of it twirled around the branch a few times causing the thing to become stuck. I wasn’t able to pull on it and raise the wire antenna up into the tree. There was now nothing for it but to cut the line loose and try again. Second time around was more successful.

The stand I made to keep the counterpoise off the ground.

The stand I made to keep the counterpoise off the ground.

The rest of the station deployed easily enough and I was able to get a 1.3:1 SWR reading using the new inbuilt antenna tuning unit in the KX1 on the 40m band. No such luck on 20m; 7:1 was the lowest I could obtain and there was no time to fiddle with reducing the length of the wire. I needed to make contacts and score points.

My operating conditions.

My operating conditions.

In total I operated for three hours and chalked up eight QSOs, mostly with VK2 stations. So considering I was only putting out a tad over two watts, I was more than satisfied. Oh, the new paddle worked fine too, even though I found it to flex a little too much for my liking on the enclosure, resulting in some errors in sending. But all in all, I was satisfied.

Listening for signals.

Listening for signals.

Now to wait for the results. At least I have learnt the lesson about being prepared and taking contingencies into account.


Thinking about C4FM

I have noticed that activity on the HF bands has been very poor over the last few months. So much so that I hear absolutely nothing on 80m and minimal DX on the other bands.

At first I suspected my antenna, which is a long wire. But I do get good reports from DX stations that I am able to work. Then I started noticing reports about low solar activity. I came across an article entitled entitled Cooling Kills: Governments Must Shift to Cold Preparation by TOM HARRIS and DR. MADHAV KHANDEKAR:

Of particular concern are the warnings from solar scientists that over the next three decades, we are headed toward significant global cooling as the sun weakens into a grand minimum. The last time the sun was as weak as solar experts predict will occur starting after 2030, the Earth was in a particularly cold phase of the Little Ice Age that lasted from about 1350-1850, a period when there was great misery around the world.
Tom Harris is Executive Director of the International Climate Science Coalition. Dr. Madhav Khandekar is a former Research Scientist with Environment Canada.

This got me thinking. If their predictions are correct, we can expect reduced HF activity. However, I have also noticed that VHF/UHF FM activity seems to perform okay. This, together with the notion that technology is fast evolving, I think I will look deeper into C4FM technology. This is basically a digital FM mode that allows for the transmission of voice as well as date communications, using commercially available equipment. In the amateur radio domain, Yeasu have just launched a range of transceivers that I plan to purchase, once I have sold off my HF gear to make space on my workbench.

Watch this space.

Sorting out RFI on my Rockmite 80m QRP rig

When I heard that Dave Banson had announced his decision to close Small Wonder Labs, I decided to press my Rockmite 80m rig back into service. So I connected it up to my long wire antenna and turned it on.

What I heard was a local commercial station booming in real loud. And no amount of tuning would get rid of it. I even connected up my NesCaf filter to see if that would do the trick, but it didn’t.

I consulted the rig’s instruction sheet once more and sure enough, Dave had foreseen this problem and suggested a fix. All that was needed was to install a 1K resister into the two unused pads immediately below D1/D2 on the PCB.

That called for the PCB to be removed from it’s nice enclosure, an Altoids tin.

The PCB safely removed from the Altoids tin enclosure.

The PCB safely removed from the Altoids tin enclosure.


The two unused pads can be seen below the two diodes on the right (middle) edge of the board.

The two unused pads can be seen below the two diodes on the right (middle) edge of the board.

Once the resister had been soldered into place, it was just a matter of putting everything back together again.

Everything back snugly in the Altoids tin and ready for use.

Everything back snugly in the Altoids tin and ready for use.

So how did the rig now perform? Nicely, although the offending station is still slightly audible. But not enough to bother me. I must add that some nights I can’t hear it at all.
All I now need is a QSO. I call CW every evening in the hope of a contact but so far this has proved elusive. The 397mW output makes this a challenge, but this is what the fun of QRP is all about. It will come.

Installing a Long Wire antenna

Today I decided to pull down my 20m dipole and replace it with a long wire antenna. The reason for this was so I could work the 80m band in addition to the normal HF bands I was currently working.

Some time ago I printed out a table by AA8AF which he called the End Fed Antenna Length Study as I was sure it would come in handy one day. Well that day has come. It was based on the work by G3CCB that was published in “The Antenna File”. The aim was to determine the length of an end fed antenna suitable for the 40, 30, 20 and 15m bands, steering clear of the high impedance half wave points.

The table I saved pointed out a few good lengths, and I chose the one that covered all the bands from 80 to 10m. The ideal length, the table said, was 15m or 10m.
I settled for 15m.

Now everything I had read about end fed antennae suggested that a balun is needed at the transceiver end of the wire. Better still, mount the balun outside the shack to keep RF out, most experts said.

Now I happen to have an LDG RBA-4:1 Balun, which is a voltage balun. I also have the spec sheet which says a long wire is basically an elevated wire at least a half-wavelenght long at the lowest frequency to be used. As a general rule, the higher the better and the longer the better, it pointed out.

Performance will also depend in large part on the quality of the ground connection. It should be connected to a counterpoise or ground for best results.

My balun is mounted outside the shack above the front door and just below the antenna mast on the roof. This would be ideal for the long wire, so up it went.

The LDG balun is fed with coax on the input side and the long wire and ground connect to binding posts on the other side.

The LDG balun is fed with coax on the input side and the long wire and ground connect to binding posts on the other side.

I connected the far end of the long wire to a ceramic insulator and a palm tree, then connected a length of wire to a copper ground stake and headed into the shack to see if it would tune up on all bands.

It did and I was delighted.

My first qso was with Sergei DL1DGS in Germany on 20m CW. Then I worked John VK4WID in Toowoomba on 40m.

At least I know the thing works. It is a bit noisier than I am used to but the day was one of the hottest on record for this time of year at 37C. Maybe the bands were just plain noisy. I’ll try another day to be sure.