Tuesday, March 20, 2018

First stage of the Great North Walk

The Great North Walk is a well known track starting in Sydney and going, you guessed it, North. Peter, VK2EMU, mentioned that he was planning to start it and I was keen to join him.

The whole walk is over 250km in sections that end up in Newcastle.

We did the first section, beginning at "The obelisk" in Sydney city, near circular quay and ending near Chatswood.

While there is some walking through leafy Sydney streets the best bits in this section were the surprising wetlands around the harbour.

We walked for about five hours and while it's not a hard walk I was pretty tired at the end of it.

Thanks to Peter for taking me along and I look forward to doing more parts of it in the future.

The marker where it kicks off:

Most of the walk is well sign posted like this (although we took a few wrong turns along the way).

I love how they show how far to Newcastle on signs.

There's some lovely bush to enjoy.

US Military vastly outspends opponents on radio gear

At the Wyong field day this year I bought a book on the history of military radio. An entertaining read although the author covers the history of wars and radio along the way.

Ars Technica has an interesting piece about US army radio which has chosen a hard technical path requiring the use of CORBA software interfaces in radio software.

This seems particularly amusing in the light of all those images we've seen of non-american combatants using Icom and more recently Baufeng radios which cost tens of dollars each instead of hundreds of thousands of dollars each.

How does the US pay for all of their extravagent military expense?

Saturday, March 17, 2018

Enjoyed the John Moyle field day

Today, and tonight, is the annual John Moyle field day which encourages portable operation from portable power. Peter, VK2EMU, kindly invited me to join the team from the St George Amateur Radio Society who had arranged a wonderful location at Oakdale, west of Sydney.

The gang had a veritable antenna farm with everything from 160m up to UHF. I was planning to just use the 20m vertical on the van but Con, VK2FCDL had a new off centre fed dipole that he was keen to try out of China. It's called a BG7PNV HF20A Dipole and it tuned up beautifully on both 20m and 40m. It claims to work with low SWR from 500KHz up to 30MHz and while I can't vouch for that, we had contacts on 20 and 40m. There is a big resistor in line very near the end of the long leg, perhaps that keeps the SWR low?

It was a warm day but with a very pleasant breeze.

Tuesday, March 06, 2018

Vanlife: a quick trip to low noise land

Last week I had a quick trip north and camped near the Wallamba river near Failford before heading off to Black Head to visit Patrick, VK2PN and Heidi.

I purchased a whip for 20m from Stephen, VK2BLQ, and took the opportunity to compare reception with the end fed wire I've been using.

To my surprise, signals were much stronger, perhaps 2 S points, on the vertical. Presumably the van makes an excellent ground plane. You can see the whip on a small magnetic base in the photo here. The base is too weak for driving while attached.

Here's some video of a tune around on 20m. Nice low noise and strong signals.

Sleeping by the river meant dealing with a few mosquitos. Happily I have a net which I hung over the bed with magnets - a system which worked well. There is a benefit to having a van made of steel rather than an aluminium caravan.

Common fault with boxed RTL-SDR devices

I have one of these boxed up RTL-SDR devices that has a low pass filter and the modification for direct sampling for HF. They work pretty well. Mine stopped working recently. When plugged in to USB the power light comes on but the USB device was no longer seen on the computer.

Mentioning this to John, VK2ASU, it turned out that he had exactly the same problem but he noticed that when he dropped the box it started working again - this suggested a bad solder joint.

There are some connections between the main board and the embedded TV stick and adding extra solder to the two points marked with red arrows has fixed mine.

Thanks to John VK2ASU for diagnosing this, I would have tossed it out except that I thought I'd used the nice box for something else.

Sunday, February 25, 2018

Woodpecker CNC 1610 progress - slow

Progress with the $200 CNC is slow but starting to get there.

It seems that I have a Woodpecker CNC board that has an embedded Arduino Nano with Atmega 328 chip on it. I think the hardware is called a CNC 1610. Useful info here.

First thing I noticed is that it came with the Arduino CNC software called grbl 0.9j and common client driver software such as Candle likes to work with grbl 1.0 or later.

I got started with an old version of Candle and was able to jog the CNC through x,y & z as well as having it draw circles in the air.

To flash the firmware to grbl 1.1f I used XLoader under Windows (which is a simple front end to avrdude command line).

To do this you download the .hex file and connect to the board and Upload.

After the upload, I confirmed that the board had been updated by connecting to the serial port and seeing that it announces grbl 1.1f.

Re-connecting Candle it seemed that the tool no longer moved but a slight clicking noise was heard from each of the stepper motors. It turned out that it was moving but extremely small amounts. The reason is that the "feed" rate needs to be set. Changing this from feed of 1 to feed of 1000 gets it to jog in a similar way to before.

There's a lot of software out there if you search for "grbl software". My current favourite is bCNC running on Fedora linux. I simply cloned the git repo. When I ran it it asked for pyserial which is installed with sudo dnf install pyserial

I'm still a long way from etching copper boards but progress is being made.

Saturday, February 24, 2018

Wyong Field Day

The Wyong Field day today turned out to be very pleasant despite predicted rain. This year I again helped out on David's digital voice stand and kept a bit of an eye on the Home-brew group table next door.

The configuration at Wyong was improved this year with vendors in a big air-conditioned tent. I bought a van worthy LED light strip and a book on the history of military radio.

Ross, VK1UN, came up from Melbourne and attended the Wyong show for the first time. It was great to catch up with many friends and it was amazing how many people asked about the van which presumably they'd read about here.

Seen in the photo above are Matt Magee, John Hale, Stephen Stebbing and David Rowe. Thanks to the Central Coast Amateur Radio Club for their excellent organisation and professional running of the event.

A bit of nostalgia at the field day, I spotted a Mini-SCAMP board and front panel. I built one of these back in 1980 from memory.

Thursday, February 22, 2018

Upgrading AirspyHF+ firmware

I really like the Airspy HF+ SDR. Mine came with firmware 1.0 and I found it a bit of a puzzle to upgrade to the latest version 1.5 dated 2018-02-22.

First, you get the firmware (with flash bat file) not from the Download page but oddly right down the bottom of the Products page here. (I learned this from the excellent discussion group).

Second, you must be running Microsoft Windows to flash the firmware. This seems like a poor choice given that Airspy have made good choices in other areas such as open sourcing the drivers on GitHub here and providing a build of spyserver for the Raspberry Pi and similar ARM boards.

You can see what version of the firmware you have in the Source tab in SDR#.

Mine is now showing R1.5 but originally it was showing 1.0.

Because of a bug in 1.0 the simpler flash procedure outlined in the README doesn't work and you must open the box and short two contacts labelled Erase. You can see them here in this picture with the back off just below the shielded area (click image to enlarge):

I won't reproduce the README here as it might change but the process works and you see firmware update progress bars and as I said when you run SDR# it shows the new version.

Wednesday, February 21, 2018

Low cost carry bag for Elecraft KX3

The KX3's front face controls makes it vulnerable to damage when being carried with other items. In the past I've put it in a solid case but it's rather large. This week I found a camera bag for $20 that fits it very well. It's a Manfrotto shoulder bag, Amica 25W.

Pockets on the side can carry mic and a small end fed antenna.

It's a snug fit and won't allow operation while inside the bag.

I've been using 3S LiPo batteries from a quadcopter and one of these might almost fit in a side pocket.

These bags are $20 at Fletchers Fotographics in Chatswood. The price seems better than online so perhaps they're running down the stock.

Tuesday, February 20, 2018

First electricity bill after installing solar PV

Just over five months ago we installed 3.3kW of solar electric panels on the house. I've just received the first bill for a three month period with panels.

Our usage compared to the same period in the year before was down 46% plus we got a feed in credit of $82.

Last quarter our bill was $318, this time it's $226. Note that the included supply charge is $76.

We spent $6,000 on the system so at this rate it will take 15 years to pay for itself if electricity stays at the same price and you don't count interest on that amount.

Our usage has changed over summer in that we've used air-conditioning more on hot sunny afternoons where it's now virtually free and that's an improvement in comfort. I expect that the quarter we're in now will have a more dramatic saving as it includes the hottest part of the year here.

This graph shows usage and generation on a typical sunny day:

This graph shows a series of days of generation and direct usage:

A battery would dramatically increase the amount we use directly but at current prices I can't see it paying for itself for decades by which time the battery's life would be over.

Despite the long payback time of our system, I'm happy to have it and feel that it will add to the sale price of the house when the time comes.

Friday, February 16, 2018

A AU$200 CNC milling machine

When Peter, VK2EMU, showed an amazing CNC milling machine at the recent ARNSW Home Brew group show 'n tell meeting and then mentioned the price was just $200 I couldn't resist ordering one.

These are on eBay for AU$203.99 including postage.

You get a box of parts and a tiny CD-ROM which a bunch of files in Chinese and English including a word document that passes as instructions on how to put it together.

The instructions are terse.

Like other home constructors, I went down several false paths including using the wrong lengths of aluminium. It's all there but somehow not sequenced as clearly as it could be. The other frustration is the captive nuts that look like they should be able to be inserted sideways and then turn to lock in place. Perhaps it's poor manufacturing tolerance but I had to undo parts of the machine to slide in more at various times.

It took me about two hours to complete the job. Here's the components as they came.

The controller is a custom Arduino board with stepper motor drivers. The software on this board is GRBL 0.9 and to send commands to it (over the serial port) you need version 1.x of Candle available here.

So far I have confirmed that servos work and can send it instructions to draw a 1 inch circle. There is lots to learn.

For the money, it's a bargain. A beautiful machine. Some corners have been cut, there are 3D printed parts in there that probably reduce accuracy. Certainly this is a good way to have a tinker.

What I'd like to be able to do is have it etch the copper to make a prototype circuit board.

Thursday, February 15, 2018

Vanlife: A ten day trip

Following on from the test night out at Cattai National Park, I've just returned from a ten day trip in northern NSW.

I stayed at Patonga, "The Ruin" Booti Booti, Wauchope's "Timbertown", Dorrigo, Coffs Harbour and Gosford.

Along the way I enjoyed some lovely country and met some friendly people. In the last few days however it became uncomfortably hot and humid and I ended up in a motel.

The van went well although I'm still optimising where to store frequently used items. It's important to park in the right orientation so that the van shields me from the late afternoon sun which gets low enough to get under the awning.

There was a little ham radio activity although I got told off for hanging a "clothes line" up in one location.

I struggled to put up the awning on my own. Only after serval nights did I realise that the extra poles were for the sides, even so it was hard. One night my neighbour had a similar awning he'd put up on his own. He was missing a leg from bone cancer. We had a beer and an entertaining chat.

There are amazing vans around, this "teardrop" trailer caught my eye. It was built by a boat builder. Early models suffered from water ingress while in motion. This was fixed by adding a scoop that causes positive pressure while moving.

In the distance here you see the crowded powered sites while my area, the unpowered sites, is nice and clear.

People are friendly in caravan parks, particularly in the unpowered sites. I waved at a nearby couple who were setting up a small tent, plus various bits of gear including small stoves and lights. As the sun was setting they came over to say hello. They had cups of tea, I was slightly embarrassed to be sipping whiskey. "We're not a couple" she said almost immediately, "that must be challenging in that tent" I commented.

I slept very well, going to bed as the sun set around 8:30pm and rising early to watch the sunrise.


Coffs Harbour:

Lovely Repton for a quick visit on the way back:

On the last day the van was difficult to start. The starter battery had trouble turning the engine over. The van has always started easily but my volt meter showed that the voltage was low. I headed for a battery shop who tested the battery and found it at about 20% capacity. It was manufactured five years ago so I replaced it for $160. Hopefully that's the last mechanical repair for a while.

Saturday, February 03, 2018

QRP by the harbour - a lovely day

Today's QRP by the harbour event in McIlwaine Park at Rhodes was a lovely day and a fine collection of visitors.

I strung out an end fed from the top of the shelter to a 6m squid pole held up by a new 1m garden stake. At the transmitter end there's a home brew 9:1 Unun and it tuned up on 40m perfectly.

We had a CW station and 2m operations with a magnetic mount on the roof of the shelter.

Conditions on 40m were not good and my best contact was with Henry during the VK2WI callback.

No hail this year and the predicted rain held off. After a few pleasant hours of contacts, local chat and some sandwiches we packed up and headed to the Kokoda cafe about 150m away.

Friday, February 02, 2018

Vanlife: Radiator coolant warning light mystery solved

Since the day I bought the van the coolant warning light has shown from time to time. Usually it would come on when I started driving and eventually go out. The previous owner had mentioned it and said not to worry about it. Being a little concerned I topped up the coolant expansion tank but it quickly overflowed the first time I parked.

I asked the service folks to check it out, they reported no leaks in the radiator and suggested that the coolant level sensor might be faulty. This week, I parked after a reasonable drive and noticed a stream  of green coolant running down the road. The expansion tank was definitely empty. Back to Jason at the service centre.

It turned out that the radiator cap, which has some sort of pressure release mechanism, was faulty and this explains the behaviour. Kindly they only charged me $12 for a replacement cap. No more warning light - I won't miss it.

Thursday, February 01, 2018

Car jump starter for portable ham radio power? Unfortunately no.

There are some interesting car jump starter battery packs available that claim to have amazing capacity and flexible charging and power supply options.

While designed to supply huge current briefly to jump start a car, this one claims to have almost 90AHrs of capacity and also offers USB power, laptop power (at switchable 15 or 19V) and even a strange torch.

I thought this might be a great power source for portable operation at this weekend's QRP by the harbour. It arrived partly charged and I measured 15V at the output. The giant clip leads were removed and an Anderson Powerpole connector added but when I charged it and connected the KX3 it quickly complained that the voltage exceeded 16V and turned itself off. Nice feature there Elecraft!

These gadgets are basically a LiPo battery wrapped in some charging and voltage regulating electronics. I'm sure the 16V output is the result of 4*3.7V cells in series directly connected. One thought is to use an adjustable buck converter to efficiently bring this down to 13V but switching noise might be an issue.

The torch is rather fun but looks rather too much like police lights I think.

Update - built the voltage reducer

I have set up a buck converter to reduce the voltage to 13.8V. Here's the raw board.

Boxed up with sockets for input and output the KX3 radio seems happy and there is no obvious noise audible. These buck converters run at 180kHz and don't seem to produce much noise.

This buck converter isn't rated for much current. I can see a clean AM carrier transmitted but the voltage drops from 13.8 to 13.6 under that load. I'll try this on Sunday (but take alternate power).