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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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.

Andrew_Goorooyarro

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.

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We did wonder how these old cars got there.

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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.

 

Building the QRPometer

One thing that all QRPers  seem interested in is just how much (or is it little?) power their rigs put out. I am no exception. You see, QRP is all about making contact with someone using as little power as possible.

Until now, the way I have worked out how much power I am using is by using a great piece of kit produced by Doug Hendricks called the Dummy Load/Power Meter, It requires you to make use of a mathematical formula to compute your output power.

Recently the Four State QRP Group produced a fabulous piece of gear they call the QRPometer. This is an inexpensive, highly accurate VSWR and Power Meter for QRP levels. They say it permits the testing of a QRP transmitter to an accuracy of 2% or better from 100 mW to over 10W. It also has a resistive bridge type circuit which inerts 6 dB of attenuation between the rig and the antenna for tune up purposes. This is great, especially if your rig has no VSWR protection.

The kit came beautifully packed and sorted into component groups. All components were there, something that isn’t all that common these days.

The components as unpacked.

The instructions were easy to follow and it took me about 4 hours to complete. Calibration was super simple, requiring a trim pot to be adjusted until a voltage reading of 5V was obtained on a digital multimeter. Once that was done, an RF signal from a QRP rig was inserted and the calibration pot on the back of the display was adjusted until a reading of 1.00 was obtained. That was all there was to it. Simple.

An interesting aspect to this kit is that the two PCBs fit together to form the enclosure.

The two PCBs ready to be connected together to form the enclosure.

The kit came with the necessary hardware to secure the two boards together.

The completed QRPometer with the two boards screwed together to form a nice looking enclosure.

So how does it perform?

Using my DC40A 1W transmitter, I got a reading of 900mW at 13.8v supply. This computes well compared to the mathematical method in which I got 942mW.

My DC40A rig is putting out 900mW.

Power levels for my two RockMites are as follows:

RM80 = 460mW at 13.8v

RM20 = 330mW at 13.8v

Turning now to my PFR-3 rig, these are the readings I obtained for the three operational bands:

20m = 5.29W

30m = 4.70W

40m = 5.11W

So now I have an accurate indication of just how much my QRP rigs put out.

Stand for my Nissei SWR & Power Meter

I decided it would be nice to have a wooden stand for my Nissei SWR and Power Meter. I wanted to have the meter standing at an angle so that it would be easier to read while operating at the bench in my shack.

So I found some ply wood and some sheets of foam material and got to work. Once the basic design was proved, I screwed it all together and applies two coats of mahogany varnish. Then I cut the foam to fit the stand.

I am happy with the end result. And it works too.

The stand angles the meter so that it is easier to read while operating. Looks good too.