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.