Reverse Polarity Protection

As the Yaesu FT-817 doesn’t have any reverse polarity protection or an in-line fuse, I decided to build myself one seeing I do a lot of portable work on summits or in parks.
Diodes work fine but they do incur quite high losses in eventual output power, so with only 5W max available, this isn’t desirable.
The answer lies with the P channel MOSFET (FQP27PO6)
A quick search on line turned up this schematic.

Only one component!

This is quite a simple affair: when the battery is connected up correctly, the MOSFET is turned on allowing current to flow. When connected up incorrectly, it turns off.

It works thus: when the gate to source voltage is around -4V or less, it turns on. So if the battery is a 12V gel cell (as in my case), the voltage through the MOSFET  = 12V Р1V loss (due to the parasitic body diode) which equals 11V with respect to ground.The voltage at the gate is 0V as it is connected to ground. This means that Vgs = 0V Р11V = -11V. This is less than -4V so it turns on.

If the battery is connected up incorrectly, then we have Vgs = 0V –11V = 11V. so the devise turns off.

I mounted the MOSFET on a piece of vero board and used an ice cream stick as strain relief. I also included an in-line quick blow 5A fuse in the positive line.

All the components before final assembly.

Once the heat shrink had been slipped over the component, I heated it up with a hairdryer to achieve a nice, tight finish.

While I was at it I built another one for my Elecraft KX1.

Now it was time to test it.

 

All working as expected with the battery connected up correctly.

Now to switch polarity.

No voltage with reversed polarity.

Samford Conservation Park VKFF-1639

Easter Saturday was the day I decided to activate Samford Conservation Park, VKFF-1639, which is situated around 40km from my QTH. This time I had insect repellent in my go-bag and I’m glad I did.

I set up my equipment on a park bench that was at the far end of Iron Bark Gully, a picnic area in the park. As usual, I had my FT-817, LDG Z100 Pro ATU and endfed antenna held up at the far end by a 7m squid pole.

All set up and ready for calls.

I could hear lots of SOTA action but even though I had self-spotted, I was getting nothing. So I decided to pounce on a SOTA QSO. The first one I came across was VK2HRX operating fromVK2/NW-019, which also happened to be a National Park, VKFF-0111, so when he completed working a chaser, I pounced. He replied and I was up and running. And with a park-to-park QSO at that. Then I heard my old mate John, VK4TJ working him so I tail-gated that QSO and worked him too. Two in the bag, but that’s as far as I got.

I think my position in the gully was not the best, so I decided to pack it in and head off for a restaurant for lunch. Also, using only 5W could have been the problem. Mean time, Scott VK4CZ posted on Facebook that he would like to visit my operating position as he lived nearby. But I had already hit the road. Along the way I stopped to admire the view from McAvee’s Lookout in Mount Nebo, which is situated in the D’Aguilar National Park VKFF-0129. As luck would have it, he called me on 146.500 FM (simplex calling frequency) so I was able to add that to my log, and from a different park.

So I was happy with the way the day turned out. But there is unfinished business. I will return.

Denmark Hill Conservation Reserve VKFF-1529

Saturday 8 April was the day chosen to head out to Ipswich and activate Denmark Hill Conservation Reserve VKFF-1529. I chose this park as it happens to be around 30km from my QTH as well as the fact that it hadn’t been activated before. This would be sure to arouse the interest of hunters.

On arrival, I was amazed to discover that the club house of the Ipswich and District Radio Club borders the Reserve. They were holding a meeting when I walked past in headed into the think bush.

It wasn’t long before I came across a picnic bench which would make an ideal operating position. So I assembled my gear and prepared to put out my first CQ. That’s when the giant mozzies began their attack. I knew then that I should have packed in some insect repellent. I added it to my check list for next time.

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The rig I was using was my trusty FT-817 with an LDG auto tuner and end fed long wire antenna that was supported by a squid pole. I mounted the pole to the support for a dust bin that was conveniently situated nearby.

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I usually operate CW but decided to stick to 40m and 20m SSB this time: what a difference it made. In the short space of half an hour I had made 11 good contacts. With CW I’d be pleased to have made 4 in that time.

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Delighted with my results, and reeling under the concerted efforts of the mosquitoes, I packed up and headed for the car. Along the way I came across the site of some dinosaur footprints. There was a well presented display that explained the history of the site and its rich fossil field.

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This was a most enjoyable activation, especially as the weather was good; we have had plenty of flooding and chaos thanks to Cyclone Debbie.

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Activating Mt Warning, VK2/NR-001

January 11, 2017 had hardly got going when my son Garrett, his partner Vicky and I set out to activate Mt Warning, an ancient volcano that is said to be over 20 million years old. For this expedition, we hired accommodation in Byron Bay as this would cut down travelling time to the mountain. You see, we wanted to watch the sun rise from the summit.

Mt Warning as seen from Byron Bay.

Mt Warning as seen from Byron Bay.

We packed the car and headed for the base of the mountain at 2.45 am, arriving there at 4.11 am. I was a little surprised to see that we weren’t the only ones with that idea; there were around ten cars parked in the car park already!

An information board advised us that the hike would take between 4 and 6 hours to cover the 9 km track.

We also noticed that right from the start the going was uphill. I could feel this was going to be a most challenging activation. What was beginning to concern me was that I might have bitten off more than I could chew. I mean, Garrett is a professional sportsman and Vicky is an ultra-marathon and Iron Man competitor while I am a newly retired ‘senior’. Was I in the right company or what? At least there were four helicopter landing platforms, which gave some sort of comfort.

The first of four helicopter landing platforms.

The first of four helicopter landing platforms.

Sunrise was around 6 am, but we weren’t at the summit to view it. However, we were close enough and boy, was it spectacular!

This made the climb worthwhile.

This made the climb worthwhile.

We arrived at the hardest part of the climb; this involves a very challenging rock climb that was billed as a grade 5 climb – the hardest in the book. A heavy chain provides essential support all the way up; this part took us a good 20 minutes to complete.

This is a grade 5 climb.

This is a grade 5 climb.

After resting for a few minutes and taking in the view, I erected my squidpole and long wire antenna.

This antenna is prefect for my Elecraft KX1.

This antenna is prefect for my Elecraft KX1.

Then I began calling CQ. After my first contact (with ZL1BZY) the ants appeared. They seemed as fascinated with what was going on as the other mountain climbers.

Ants on my 7 a/h gel cell.

Ants on my 7 a/h gel cell.

I also found out that their bites were painful!

It's hard flicking them away while trying to operate the paddle.

My new QSO board in use. There are some more mods I need to make.

After making six contacts, it was time to pack up and head back down. The weather forecast was for heavy rain and we didn’t fancy the prospect of tackling the chains in the wet.

We passed some massive trees on the way down.

We passed some massive trees on the way down.

We arrived back at the base of the mountain at 10.24 am and headed for a wonderful cafe in the heart of the Wollumbin National Park for breakfast.

This was the hardest activation I have done so far. I still wonder how an old fella who passed us on the way up did so bare foot. He said he could feel the rocks better that way!

This activation bought home to me the absolute necessity of minimizing weight as much as possible. My back pack weighed in at a hefty 8 kg, and that was without our water bottles. The biggest culprit here was my gel cell, which is far too heavy. I think next time I will use six internal AA cells and sacrifice 3 Watts of power. Either that or I will invest in a  LiPo battery pack. I also took up items that I never used, like binoculars.

Having done most of my climbing in the ACT so far, I was inappropriately dressed. All other climbers were in shorts and singlets while I wore long pants and a long sleeve shirt; far too hot.

So there are always lessons to be learned, aren’t there?

SOTA Activation of Mt Tamborine, VK4/SE-059

Mt Tamborine is an iconic Aussie tourist destination situated in the Gold Coast hinterland. The summit is right in the middle of a suburb but fortunately there is a good lookout in the Tamborine National Park very nearby.

This activation was a good chance for me to try out my new Pico Paddle with my Elecraft KX1.

I had ordered a Pico plate as well; this is a thin plated piece of metal with self-adhesive tabs on the back. The idea is for this to stick onto whatever surface you want to mount the paddle on. I decided to mount mine on my newly made QSO board.

After erecting my squid pole to secure the end of a 24 foot long wire to, I ran out the two counterpoises and connected up the rig.

Installing the long wire antenna.

Installing the long wire antenna.

Then I began calling on 20m.

This was my first attempt at using my new QSO board, with the Pico Paddle mounted in place.

This was my first attempt at using my new QSO board, with the Pico Paddle mounted in place.

It wasn’t long before I realised the Pico plate was simply not up to the job; the paddle began moving around. The magnets were just not strong enough, even though my sending was gentle. I would need to fix this.

Anyway, the bands were in bad shape and I only managed three contacts all morning. Those were with ZL1BYQ and VK7CW on 20m, and VK4EKA on 40m. I also tried SSB with my Yaesu FT-817 on both bands but to no avail.

Back home I began modifying my QSO board.

The Pico Paddle with the Pico plate in place on the board.

The Pico Paddle with the Pico plate in place on the board.

A quick email to Palm Radio in Germany brought the suggestion that I should try using a metal plate instead of the Pico plate, so I raided my workshop and cut a piece of plate to fit. This was then hot glued into place.

The Pico Paddle now attaches itself really firmly to my board, thanks to the metal plate.

The Pico Paddle now attaches itself really firmly to my board, thanks to the metal plate.

Now to head back to Mt Tamborine some day to give it a go. Perhaps then I will manage four contacts and score the two points that are on offer.

A clipboard for SOTA

One of the challenges I have had to contend with while operating in hostile environments up on a distant summit has been logistical or organisational in nature. You know, trying to deal with various pieces of equipment, pen and notebook, wires, seating arrangements etc, all while trying to decipher morse code, taking notes and ensuring that everything works as intended.

This takes more than one set of hands to do properly.

While sitting on my chair up on The Knobby recently (VK4/SE-097) it occurred to me that the time had come to construct a simple clip board upon which I could mount my Elecraft KX1, my log sheets and anything else I might need. So I headed back down once the activation was completed and rushed straight to my workshop, where I selected some suitable pieces of timber for the job.

This is what I came up with:

sota-clipboard