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.

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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.

First real test of the HF Packer Amp

HF conditions are terrible at the moment, so when could be better to put the latest version of the HF Packer Amp, the miniHFPA2 edition, to the test?

The amp is set to accept an input of 5W for an estimated output of around 30W. It also has the 60/40 and 30/20 Low Pass Filters installed.

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A side view of the amp enclosure with the side panel removed, showing the clip-in LPF board.

I chose to look for a station operating on 40m as this is the best band for local (VK) signals during the day. My luck, the band was dead. Then I heard Gerard, VK2JNG calling CQ from Lake Innes Nature Reserve (VKFF-1955). I returned his call and received a report of 5/9.

I was delighted as I seldom receive such good reports when using my Yaesu FT-817 at 5W into VK2. You see, a quick check on Google Maps told me that we were 445 Km apart. So I asked Gerard if he could give me another report, this time with the amp in bypass mode. He gave me a 5/3. He went on to say that with the amp switched on, my signal was “crisp and the audio nice and clear.”

So there we have it: the amp certainly does what Virgil, the designer, set out to achieve.

I have LPFs for all bands and will use them when the time is right.

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The LPF boards are professional quality.

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Each board is marked with the bands they are designed for. The while guides aid with slotting them into place.

Each LPF is a 2×1 inch plug-in circuit board that is interchangeable in the field with the entire family of same size modules. Each LPF hasĀ a unique ID, and the panel LEDs inform you which LPF is active. Two LPF boards are plugged into the enclosure, one on each side. To select the one you need, all you have to do is flip the LPF toggle switch on the front panel of the amp. FieldĀ replacement consists of removing a side panel, unplugging an LPF and sliding in a different one.

To find out more, visit http://www.hfprojects.com