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

 

Advertisements

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.

First portable operation with the Packer 6m amplifier

I decided to take the bull by the horns and activate a SOTA summit on 6m only, using my newly-built Packer 6m 30W linear amplifier. The summit I chose was Tamborine Mountain, VK4/SE-059.

My rig this time was the Yaesu FT-817 and the antenna was a homebrew 6m dipole, strung up as a sloper.

The rig connected to the amp and the LDG antenna tuner. The battery is a 7a/h gel cell. The power cords are routed through a SotaBeams 4-Way distribution box.

As soon as I put out my first call, the game was on. In the space of a short 30 minutes I had made 15 contacts. Wonderful.

The action came thick and fast and the view was excellent.

One aim of the activation was to test the amp, especially how long the battery would last as it draws around 6A.

At the start of the activation my battery had 12.58V, and at the end, 12.49V. That’s pretty incredible, especially seeing I was operating almost continuously. Input power from the radio was 1W and output 30W.

Another test I carried out (with Peter VK4JD) was to get an idea of the difference the amp made to an actual QSO. On bypass, with 1W, my signal was down some 20dB. So the amp was doing a fine job.

VHF Packer 6m Amp alignment

Andrew VK1DA pointed out to me that I had inadvertently set the bias on the amp to 0.5A instead of my intended 0.7A. This meant I had set it up for use on FM instead of SSB.

This was easily corrected; all that was needed was to adjust the variable resister while monitoring the DMM.

Now the bias is set correctly, it’s time to see if it makes any difference to live, on-air operations.

All set for SSB now.

 

Building a VHF Packer 6m Amp

I was given this kit by Wal, VK4CBW, as he had purchased it some years ago and knew he would not get around to building it.

The kit was produced and sold by http://www.hfprojects.com in America and came well packaged in a series of sealed plastic packets. Everything including the enclosure and heavy duty heat sink were included.

This little amp requires 1W drive for 30W output and features a Mitsubishi RF mosfet module mounted on the heatsink. There is also a filtered Anderson Power Pole DC input that takes 12V at around 6.2A. And measuring only 5.25 x 3 x 3 inches and weighing less than 1 lb, I figured it would be perfect for SOTA or VKFF operations.

I started my working on the well-made PCB.

Populating the PCB

Then I began making the power cable assembly, the RF cable assembly and the switch cable wiring.

The cables were installed inside the top enclosure case.

I had to fabricate a make-shift mounting plate for the Anderson Power Poles as this was missing from the kit. It has been ordered but hasn’t arrived yet. Eager to avoid delays so I could catch the 6m band opening, I made a replacement out of PCB material.

This isn’t perfect but it would do until the genuine item arrives in the post.

After a little fiddling it went in well and did the job.

The mounting plate in place.

Next, the circuit board and amp module were installed and the initial check carried out.

Ready for alignment and the first smoke test.

The bias current had to be set to 0.7A if the amp is to be used for SSB work, or 0.5A for FM. I chose the former.

The bias current set correctly.

I skipped the next step, which was to align the low pass filter as I don’t have the correct instrumentation. But as I had constructed coils L1 and L2 according to the instructions, this wouldn’t be too critical.

The power output test was more important. I connected the amp up to my Yaesu FT-817 (with power wound back to 1W) and attached my homebrew dummy load and an SWP/Power meter. RF output was shown to be a mere 16W. So I flicked the bypass switch and measured the output as 1W with an SWR of 1.0:1. All good there.

Tweaking the coils of L1 and L2 soon produced the required 30W, so it was time to disconnect the dummy load and attach my 6m monoband dipole antenna.

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

Keying down produced the power output reading I was after.

RF out was now 30W with the SWR indicated as around 1.7:1. Not bad at all.

Next, I attached my LDG auto tuner to the chain and was ready for an on-air test.

All set up and ready for action.

The result was most pleasing. I worked a bunch of VK7 stations (SSB and CW) and well as VK2s and 3s. I am in business and ready to take advantage of the summer openings.

Oh, and all reports received were most favourable. Nice clear signals, good reports and clear audio were what most operators reported back: they were all impressed that I was only using 30W – most stations were in the 200-400W range.

Building SOTABeams’ PowerPole PP-4 Way power distribution board

One of the challenges I was having while operating portable was making sure that my power polarity was correct. Fiddling around on a mountain peak with red and black connectors on a 7a/h gel cell is fraught with danger. And when I have two or more components to connect, well …

The answer I found on the SotaBeams web site (http://www.sotabeams.co.uk/).

I placed an order for their PowerPole PP-4 Way power distribution board.

A week or so later, a padded envelope arrived in my mail box.

The contents of the envelope.

Construction was easy as the kit is very simple. All that was needed was a soldering iron and some solder.

 

The power poles ready for soldering.

I ordered the kit only (without the enclosure), so I headed to the local supermarket and bought a cheap plastic sealable container that would do just fine. All I had to do was to cut out a piece wide enough from the lid for the connectors to stick through.

The PCB sits under the lid with the connectors sticking through. I secured it into place with four nuts and bolts.

The power supply connects to one set of power poles and the radio, atu and other items connect to the others. Simple.

Works like a charm. Will make a difference in a park or on a summit.

Softrock RXTX v 6.3: RX Switching and RX Muting

This stage handles the muting of the RX section when I PTT goes high. After soldering in all the component, the testing went according to plan, until taking resistance readings of the power rail.

The initial current readings were as expected, but when I switched the DMM over to read resistance levels, nothing registered. I was expecting to see around 7 Meg ohms at the 12V test point, 950 Ohms at the 5V test point and 10 K Ohms at the 3.3V test point. Resistance readings of the band pass filter’s secondary windings were fine.

That’s where I left things for the night. My philosophy is to sleep on it when things get tough.

It was at around 4am the next morning that I woke suddenly with the answer as to why the resistance readings for the power rail were non-existent: I was taking the readings with the power to the PCB turned on! So I took readings again, this time with the board dead and all was just as it should be.

Still flushed with success, I decided to push on and continue with the rest of the testing. All readings on my DMM were as they should be, so it was time for the best part, to solder in a temporary antenna, connect up a lead to the input of the computer’s sound card, start up the software (Rocky in my case) and see if the rig could detect a test signal on 7.046 MHz (the centre frequency of the 40m band that the rig is tuned to).

This is the spectrum before sending a test signal from my FT-817.

This is the spectrum before sending a test signal from my FT-817.

Now came the moment of truth.

The test signal is clearly visible now. The spike at 7046.7 is the signal. It has a mirror image at roughly the same distance to the left of the centre frequency. This is due to ground loops on the PCB.

The test signal is clearly visible now. The spike at 7046.7 is the signal. It has a mirror image at roughly the same distance to the left of the centre frequency. This is due to ground loops on the PCB.

Once the rig has been completed and installed into an enclosure I will try to filter out any signal images that mayexist.

This completes the build of the main board. Next is the difficult part: the PA filters.