Saturday, July 22, 2017

Amazon Lightsail doesn't have virtual memory

My cloud hosting needs are modest. A couple of Wordpress blogs, an OpenVPN server, and a Tiny tiny RSS server. I use Amazon’s AWS services for S3 storage for miscellaneous files and backups using ARQ. When Amazon launched Lightsail with a VPS starting at just $5 a month (for 512MB RAM and 20GB SSD), I moved over from Linode where I was paying double that.

All seemed good at first, Amazon’s infrastructure gave me better ping times than others, but I noticed that mysql was going away from time to time. Tailing the system log I could see kernel out of memory messages and that it was killing mysqld. You see entries saying "OOM". The kernel kills the process that's using the most memory which tends to be mysqld.

My first thought was to increase the RAM but there’s no simple way to do this on Lightsail, you must take a snapshot (backup), make a new instance with the new memory and build it from the snapshot. When all is up the external static address is simply re-pointed to the new instance and the old instance can be stopped. This isn’t at all difficult but it seems like something computer software should do.

After upgrading the RAM it dawned on me why Linux was running out of RAM - Lightsail instances have no virtual memory! It turns out there’s no easy way to add a swap partition and they actually warn that if you did it would be too slow.

Paying $10 a month for a Lightsail instance with zero virtual memory becomes uncompetitive with my old favourite Linode who offer 1GB RAM and 30GB SSD including VM for the same price.

So, I’m back on Linode and frankly happy to be there. Amazon is a gorilla in the hosting game but their offering is incredibly complex and, it turns out, has some little gaps.

I realise my home use is at the very low end but, as the song says, “from little things, big things grow”.

Not having any virtual memory is a major problem for any real server.

Friday, July 21, 2017

New weak signal mode FT8

Although it sounds disturbingly like a new rig from Yaesu, FT8 is actually a weak signal QSO mode from K1JT, Joe Taylor, and the folks who gave us WSPR and other modes. The mode is Franke-Taylor design, 8-FSK modulation.

I've just had my first contact with Steve VK6IR who is located right across this wide brown land.


I saw his CQ, received at -4dB, double clicked the line and the rest of the QSO, including signal reports each way, was automated.

Unlike WSPR where each over takes two minutes, the cycle time in FT8 is just 15 seconds so it feels a lot more like you're actually having some sort of conversation.

This new mode is in the latest builds of WSJT-X, version 1.8.0-rc1 in my case.

The release notes describe FT8 as follows:

"New mode called FT8: sensitivity down to -20 dB on the AWGN channel; QSOs 4 times faster than JT65 or JT9; auto-sequencing includes an option to respond automatically to first decoded reply to your CQ."

AWGN is Additive white Gaussian noise, obviously.

I kind of wish this was all a little bit more manual and that I could have a few more characters to personalise the QSO. Maybe we need a Twitter like digital mode?

Tuesday, July 11, 2017

Participating in GovHack

It's GovHack time again! This year it will be held over the weekend from Friday 28th to Sunday 30th July 2017. Back in 2015 I joined a team called "Hackasaurus Rex" with daughter Cat and her boss Ben and we participated at the Canberra location.

Ben brought graphic design skills, Cat did data analysis and transformation (in python) and I did iOS development.

On Friday night we looked at the amazing array of data available and came up with the idea of making an app that lets you check a place to live to see how... "liveable" it is.


The effort involved grabbing data from a variety of sources, normalising that data into scores that indicated the "goodness" of a location. Some data sets used postcodes and others used suburb names so there was some work required to map these.

While it was freezing cold in Canberra, the atmosphere in the room was warm and focussed.


I think having a small team worked well for us and the fact that our skills were all different and yet complementary meant there wasn't much overlap. Our entry suited the iterative development style that a hackathon invites in that we had something working pretty early on Saturday and were then able to add more data until we figured it was time to write up what we'd done and make the video you need to enter:


Making the video does take time and our approach was to make a recording of the mobile device screen first and then record a description which was added as the audio track later. Some teams did things as simple as making a slide show and exporting it as a movie while others made full on documentaries about their entry.

GovHack is a wonderful event, it encourages diverse teams to come together to work with fantastic data from enlightened government departments. The sponsors that get behind it are to be applauded and the organisers do a great job. This year I'm a volunteer and will be hanging out at the Sydney event.

If you're reading this before 28th July, get over to govhack.org to find out more and register. I look forward to seeing you there!

Monday, June 19, 2017

Lo-Key features QRP by the harbour

Thanks Lo-Key for featuring QRP by the harbour on the cover and in a feature article. It's a great newsletter of general interest beyond just CW operators. More info at http://www.vkqrpclub.org

Thanks to editor Terry, VK2KTJ, for promoting the event and giving us this coverage in such an auspicious journal. I encourage readers to subscribe via this page.

Future of Radio Australia Shortwave broadcasting - Senate Committee Hearings begin

Last Friday the Senate Committee hearings into a bill by Senator Xenophon to compel the ABC to resume short wave broadcasting began.

The SWLing Post reports that former RA transmission manager Nigel Holmes appeared. He jovially described being "grilled like a breakfast kipper" but I'm confident his encyclopaedic knowledge would have served the committee well.

I think it's important that there is a discussion about the value of short wave broadcasting at this time,  there have been many interesting submissions, in my submission I argue that it's not the archaic technology as it has been presented and in times of conflict or natural disaster it's the only thing that gets through.

Geoff Heriot has written that abandoning shortwave is just one more step in the winding down of Australia's engagement in the Pacific. Graeme Dobell describes the end of our shortwave service as "technical bastardly".

The inquiry has been granted an extension of time and will report on 9th August 2017.

Sunday, June 18, 2017

Switched to the NBN - seems good

We've been receiving letters for months from ISPs offering to be the ones to connect us to the NBN which has just arrived in our area.

As we were already on Telstra cable we decided to switch with them. I chose to self install the modem and a router arrived a week ago. It was puzzling because it didn't have a cable connection on the back.

Today the missing piece, the black box shown at right, appeared and it connects to the cable and to the router.

The router is a white box titled "F@st 5355TLS" made by Sagemcom Broadband SAS, not a company I was previously aware of. It seems like a competent device with 2.4GHz and 5GHz radios, two ethernet ports (not counting the WAN port), USB file sharing, and a telephone line port which we don't plan to use.


In the past I had put the Netgear modem into bridge mode and used a TP-Link wireless router which served us well and I may well switch to that again if the Sagemcom box proves unreliable. So far all seems good and the measured speed is more than I was expecting (I'm paying for 50Mbps down and 20Mbps up).


Ping time is better than reported there, normally around 10-12ms. I'm not clear if the Sagemcom box is actually needed given that I have other routers here I'm happy with.

I had a few problems getting ethernet connected devices going, in the end connecting them one by one did the trick, there was some sort of network storm going on possibly triggered by the change in IP address range.

It's weird that when switching to the NBN you are compelled to get a landline phone - something we have not had for some years. Here's the bit of the signup form that forces you to get a phone:


I tried putting my mobile phone in there but it wouldn't let me. (Probably a bad idea anyhow). A few more tests tonight:



Update - first problems

Tonight I started to see high ping losses. This is from the router:

 Pinging 8.8.8.8 with 64 bytes of data:

 Reply from 8.8.8.8:  bytes=64  time=7  TTL=59  seq=1
 Reply from 8.8.8.8:  bytes=64  time=9  TTL=59  seq=2
 Reply from 8.8.8.8:  bytes=64  time=8  TTL=59  seq=3
 Reply from 8.8.8.8:  bytes=64  time=7  TTL=59  seq=4
 Request timed out.
 Reply from 8.8.8.8:  bytes=64  time=7  TTL=59  seq=6
 Reply from 8.8.8.8:  bytes=64  time=8  TTL=59  seq=7
 Reply from 8.8.8.8:  bytes=64  time=9  TTL=59  seq=8
 Request timed out.
 Reply from 8.8.8.8:  bytes=64  time=8  TTL=59  seq=10

 Ping statistics for 8.8.8.8
  Packets: Sent = 10, Received = 8, Lost = 2 (20% loss),
 Approximate round trip times in milliseconds:
  Minimum = 7, Maximum = 9, Average = 7

Telstra's service status shows no known issues, but I'm not sure if that is relevant any more.  Rebooted the router, no change. Rebooted the NBN cable interface box fixed it.

Now ping from my computer on the network looks pretty good:


Friday, June 02, 2017

Good value laptop for linux - not what you might expect


There are very low cost laptops around but they're often unsatisfying in the end. The family is down one Mac laptop at the moment due to a fault in the keyboard and I had a look at what's available second hand.

Generally Apple gear holds its price very well, which is great if you want to sell to upgrade but not so good of you want to get a cheap Mac.

There is a regular trickle of Mid 2012 MacBook Pros appearing on eBay. This model is the last one before they went retina.

With a 2.5GHz i5 CPU, they are built like a tank but are very easy to open and work on. Some people even say "The 2012 Non-Retina MacBook Pro Is Still the Best Laptop Apple Sells" and while that's not really the case if you value a high resolution screen and light weight, they are attractive at the right price.


I was pretty lucky and got one for AU$415. The battery wasn't great, a few key caps had been substituted, it had 4GB of ram and a slow spinning 500GB disk. Otherwise it's fine.

A few standard cross head screws aside and you're in and able to upgrade the machine.


As it came, and as they were at the time, the machine felt pretty slow. I added the following enhancements:

  • 120GB SSD
  • Extra 4GB RAM to take it to the maximum of 8GB
  • New battery
The SSD makes a huge difference and if you are still running a spinning disk I can't recommend this upgrade enough. Four or five bounces to launch Safari is now just one.

These machines will run the latest edition of macOS, Sierra, and support AirDrop and Handoff.

A non-retina screen is a shock after getting used to it on every other device I look at. Apple's switch to the San Francisco font actually makes a non-retina screen look worse. There is a utility to switch the system font back but I found the font metrics are so wrong that you see lots of glitches running like that so I don't recommend it.

Linux

It turns out that dual booting Linux on a Mac does not require Boot Camp or any of those fancy EFI boot tricks.

To install boot into the recovery system by holding Command-R during power on and use Disk Utility to resize the main partition down to leave free space for Linux. Hold option during power up to boot from a Linux USB install drive.

Fedora Linux was installed into the free space on the disk. To choose which OS to boot into you simply hold the Option key down during power on and you get this nice menu.


Wifi doesn't immediately work after a clean linux install due to proprietary drivers but happily this machine has an ethernet port and I simply followed this recipe to get the driver installed and now Wifi works well. 

Everything else just works including volume, screen brightness keys and sleep on close.


It makes a very respectable Linux laptop. One thing to note that after the install you should boot into macOS and set the startup disk in System Settings so that by default it will boot into macOS (if that's what you want).

Saturday, May 20, 2017

YouKits SK-1A QRP 40m transceiver review

YouKits is getting a good reputation for low cost amateur radio gear. Their antenna analyser is well regarded. When I saw a new mono-band 40m SSB / CW transceiver for US$189 including postage I couldn't resist. It's called an SK-1A.

It arrived very quickly and was easy to figure out even without reading the user manual.

While it comes with a Yaesu branded speaker / microphone, it's not wired to use the speaker in it so you must use headphones or an external speaker. Note that this transceiver does not have a built-in speaker which probably isn't a bad thing given the small size of the case.


I've had two contacts so far, one local and another VK2 to VK3. Both reported good audio from me and I found reception at my end pretty good. Disconnecting the antenna shows that the receiver is sensitive enough to hear band noise which is all you need on 40m.

The display is clear and the backlight is bright. The manual includes instructions for adjusting the display but it's not brightness or contrast, it lets you switch the backlight on, off, or auto.

Internally, construction seems good with lots of surface mount components used throughout. There's no circuit diagram in the manual, which is a pity, but you can see that the 6 crystal IF is on 4.9152Mhz and there are a few SA602A balanced mixers in there along with an LM386 audio amplifier.


The VFO board behind the front panel is compact and the software works well although I find the way pushes on the knob change between going up and down in step size a little weird. The soldering on the PIC microprocessor looks a little rough on my unit but all seems to work reliably.


The final is an IRF510 and I get about 4W peak output. I like the way they use shielded coils.


Main board soldering is good but clearly done by hand rather than machine.


Internally there's a socket for the 18650 Lithium battery pack which they supply with a charger but it looks like you'd need to open the case to charge the battery.

This radio is lower sideband only (along with CW), which is perfectly fine for voice contacts but I was rather hoping to use it for digital modes which normally need USB.

While a traditional SA602 based design, this radio works well enough and is more compact than even an FT-817. 40m is a good choice for a mono band QRP radio. There's no deafening thump during receive / transmit switching like I get on some other designs and audio output is more than enough for headphones but a little low for an external speaker.