Saturday, March 31, 2018

Leadstar D12 TV with Raspberry Pi

The Leadstar 12V TV I bought for the van has HDMI input and it's an obvious possible display for a Raspberry Pi.

The screen's native resolution is 1280x800 but by default the Raspberry Pi doesn't offer this resolution in the GUI configuration software.

By default the Pi outputs 1080 lines which is readable on this screen but a little fuzzy.

To get the Pi to output the native resolution I edited /boot/config.txt as follows:

hdmi_group=2
hdmi_mode=27

This now boots up in 1280x800 at 60Hz and works nicely. As mentioned in a previous post this TV cost $130 on eBay and seems decent. It runs on 12V and has an internal re-chargeable battery. The built-in software doesn't know about the Australian band plan. The seller sent me a RAR archive with new software but for some reason it doesn't like it and won't update.

Anyhow, this is a good screen for a small Raspberry Pi setup.


Friday, March 30, 2018

Increasingly irritating trying to read text on the web

Presumably desperate measures to fund journalism are leading to increasingly intrusive ads but I'm finding reading text on line is getting difficult. Here's what it's like opening a story on Vice.com:


Ads load above content, scrolling down what I'm reading. Ads slide up from the bottom obscuring the text and animation down the right draw my eye. To top it off, Safari now warns that significant energy is being used - maybe they're mining crypto-currency too?


Safari now won't auto-play videos with sound and soon Google Chrome will do the same thing plus block other annoying styles of ads. This is a war for our attention and I doubt it will stop there.

The answer on macOS and iOS is to use "reader view" which works well on most sites but strips away all the design. I've set reader view as on by default on some sites and maybe that's the answer.


Sorry for the rant but reading the news shouldn't be irritating. Note that I pay for Fairfax and Guardian but like to read more widely.

Tuesday, March 27, 2018

Vanlife: Improved electric system

The van came with a big box of batteries and wires in the middle of the space behind the driver's seat.

This box was a bit of a mess and contained two different sorts of batteries in parallel. There was a Redarc SBI12 relay that lets the auxiliary battery charge from the alternator but it avoids flattening the starter battery by only connecting when the motor is running and the alternator voltage is good.

Mysteriously though the 60A fuse was blown...

I ripped all the old stuff out and have been gradually re-using bits and getting things going again.

This week I figured out the correct wiring for the Redarc SBI12 and confirmed that it's working correctly. This will be particularly important if I'm out and not getting enough sun to run the fridge.

The 12V cable from the starter battery emerged from a hole in the floor and this morning I paid a few hundred dollars at an auto-electrician to run a new cable and remove the old one. Also I've mounted the old switch box in a plastic case screwed to the wall. All looks much neater now.


There is still room for improvement but it feels more spacious and I'm happy that I now understand how everything is wired.

The auto-electrician put the van up on a hoist which let me take a good look underneath for the first time. There's a few mystery wires hanging down and I can see the replaced differential but otherwise it looks pretty good for a van that's done 378,000Km.




In other news, I've purchased a 12 inch TV that runs on 12V for the van. $130 on eBay. It seems to be a Leadstar D12 and has the ability to play from USB or SD card and can record off air. Having HDMI in means that it might be useful as a portable screen for a Raspberry Pi project.


The TV is re-chargeable but I read reviews saying that it only runs about 2 hours. It came without the Australian band plan but I scanned in Czech and it seemed to find channels. The seller has sent me new firmware which I'll flash shortly.

Update

I took the TV but never used it and will keep it for Raspberry Pi use.

Saturday, March 24, 2018

Home brew group meeting: switching HT supply and Raspberry Pi SDR

Today the ARNSW Home Brew Group met at Dural for our regular bi-monthly meeting.

John, VK2ASU, demonstrated GQRX SDR software on a Raspberry Pi using an RTL-SDR dongle to receive 2m stations. Performance was amazingly good for such a small computer.

I had tried something similar recently, on Raspian, but my GQRX crashed on start up. John seems to have figured out that the settings file must be edited before launching to avoid this problem.

My favourite thing is John's cooling arrangement as he finds the Pi gets rather hot when working as an SDR (Software Defined Radio).


John also brought a low cost Android tablet which can be used as a pretty good SDR.


The main talk by Mike, VK2BMR, was the story of his project to build a 2.5KV regulated power supply.


It was a fantastic presentation where Mike described his journey to build a power supply that could easily kill you if something went wrong. In the end he has achieved excellent performance and efficiency. The best bit of these presentations is to hear what went wrong and how it was debugged.

At the trash and treasure I picked up a home brew radio with a lovely reduction drive.


Something I haven't seen for a few years was an OLPC laptop that seems to run Linux quite well. Not sure what happened to these devices, I know they failed to hit the $100 price point at the time but perhaps Raspberry Pi's have taken over from these but I still wish we had a durable laptop version.


A lovely day at Dural again.

Vanlife: A new driver's seat

When I got the van it had three seat covers layered one on the next. Taking them off revealed the reason - the driver's seat foam had fallen apart on the side, presumably due to the driver sliding out again and again.

Enquiries at a panel beater pointed me to an upholsterer who did a great job as you see here. Interestingly they make the seat from scratch, sculpting foam and sewing the cover. It cost $385 but given how important it is to have a comfortable seat for long drives I think it's worth it.

Thursday, March 22, 2018

Belrose Optus satellite earth station

I was fortunate to have a tour of the Belrose satellite earth station run by Optus today. It's a fantastic facility that serves various satellites used for TV, NBN and other services.

Uplinks are on 12GHz and downlinks on 14GHz. Satellites have gone through several generations and staff have interesting skills ranging from orbital mechanics through to microwave power RF.

One of the dishes is quite mobile and is used for tracking and commanding newly launched satellites.


At 12GHz the waveguide really looks like plumbing.


Smaller dishes are fixed and used for telemetry reception.


This next shot shows how RF gets up to the big mobile dish from below. 


Belrose is near Terry Hills which has the highest rainfall in Sydney. I've often seen these dishes as I drive on Forest Way, it was great to see them up close. Click to enlarge any of the photos.

For more, there's a rather cheesy promo video here and a bit more about the steerable dish here.

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.