Planet Linux Australia
While watching another disappointing day in Australian political life unfold, I wondered: How long has it been since Tony Abbott declared, “good government starts today“?
It’s such a great example of Abbott’s hopelessness: He survived as Prime Minister after a failed party room spill motion only to deliver another classic clanger. Good job, Tony.
Then I checked the date and realised it had only been 38 days since the attempted spill. It seems much longer because barely a day goes by without a spectacular cock-up or gaffe by Abbott or one of his ministers.
Laura Tingle wrote yesterday that “we are being governed by idiots and fools“, excoriating the Abbott government for recklessness and incompetence, hinting at a deeper problem in our political system. Jonathan Green picked up where Tingle left off, suggesting Australia’s next great reforms “will be of this stagnant polity itself”. We can only hope.
I don’t want to juggle the date arithmetic next time I ponder how long we’ve been blessed with “good government”. The obvious* solution is a Twitter account to remind everyone*, right?
Thus, an automated, single-serving Twitter account that tweets the number of days since the spill, with a topical news item and photo, neither of which tend to reflect well on the Prime Minister.
— Good job, Tony (@goodjobtony) March 19, 2015Violence Against Women
Late yesterday evening, a wise voice caught me off guard: There’s a lot of men making a lot of noise about data retention today. Where’s that noise when a woman is killed every week by a partner or ex-partner?
If central Sydney can undergo substantial social and commercial upheaval after the deaths of two young men in “king hit” attacks, surely 8 intimate partner homicides (and 22 total suspicious deaths) of women so far this year would elicit some response? History suggests otherwise.
So we must make more noise.
My meagre contribution today is, yes, a single-serving Twitter account. I know it’s silly and practically meaningless, but hopefully people will see it, share it, and support women like Rosie Batty who are doing the really important work.
It will tweet updated figures from two sources:
First, Guardian Australia has a page for women who have died “where police have later laid charges against their partners or ex-partners”. (It’s a mouthful of legalese because they have to be careful about affecting trials.)
Second, Destroy the Joint’s Counting Dead Women Australia team maintains a Facebook post that documents every woman who has died violently, and follows what happens after. It’s based on a UK project of the same name.
38 days since “good government” began. 22 women violently killed in Australia this year. Two very different numbers.
— Counting Dead Women (@WomenKilledAus) March 19, 2015
Shortly after I published the first post on a simple VHF SDR, Brady KC9TPA started making suggestions about optimising the code. So I encouraged him to have a look into the transmit side. How can we take a baseband modem signal (like GMSK) and convert it up to a HF IF frequency like 10.7 MHz using the STM32F4 DAC?
After a busy month (and not much sleep) Brady has done it! The following figures explain how it works:
Normally we would use a baseband DAC, mixer, LO, and crystal filter to generate a signal at HF (top). However Brady has shown it is possible to use a much simpler architecture (bottom).
So with the STM32F4, some clever software, and a buffer amplifier, he has generated a 10.7MHz HF signal. The DAC runs at 2MHz, which creates images (aliases) spaced every 1 MHz. The Band Pass Filter (BPF) selects just the image you want, e.g. 10.7 MHz in our case. The BPF doesn’t have to be very demanding like an Xtal filter, as the other images are 1MHz away. It is possible to tune the exact frequency a few hundred kHz in software.
Compared to a baseband IQ design this architecture doesn’t need two DACs, and doesn’t have have any IQ balance issues.
He used a GMSK modem signal as the baseband signal, however it could have easily been SSB, analog FM, or FreeDV. This is basically a baseband to HF SSB exciter. With a suitable BPF it could easily be tuned to anywhere on the lower HF bands. Software could then be used to tune the tx frequency within that band.
Brady received and sampled the 10.7MHz signal using an off the shelf SDR and it demodulated perfectly. Here are few photos showing his experimental set up, just a STM32F4 Discovery board and a buffer amplifier connected to the DAC. Note the sharp edges on the scope plot – this indicates lots of juicy HF content that we can tune to. He hasn’t added a BPF yet. The last plot is the GMSK signal as received by our demodulator running in Octave.
Our next step will be to mix this signal to VHF and add a PA to produce a 1 Watt 2M signal, to support our VHF FreeDV work. Please contact us if you can help us with a VHF PA design!
This design and the previous post that demonstrated the HF rx side suggests that the SM1000 could be modified to be a HF SDR transceiver. It already has a microphone and speaker amplifier, and even runs FreeDV out of the box! We would need to add a BPF, PA, and some gain on the rx side.
There is still a question over the STM32F4 internal ADC, e.g. it’s inter-modulation performance when used in over-sampled mode (thanks Glen English for pointing this out). Some more work required there. However this architecture is not limited to the STM32F4 – any uC connected to a few M-sample/s DAC and ADC (internal or external) will do. That’s the great thing about radios based on gcc C code and nearly no hardware!
- chicken (purchase diced for quicker preparation time. This recipe also works very well with prawns if you're more keen on seafood.)
- tomato sauce
- soy sauce
- chilli sauce
- tomatoes (fresh or canned and diced, optional)
- egg (optional)
- cornflour (optional)
- garlic (optional)
- ginger (optional)
- spring onion (optional)
- lemon juice (optional)
Coat chicken with bicarbonate soda if desired (meat tenderiser. This step is not required at all if chicken is diced into small enough pieces and cooked well) and then wash off in cold water. Marinade chicken in corn flour, egg, salt, pepper (optional step). Fry off chicken in pan. Create sauce by using tomato sauce, soy sauce, chill sauce add add to pan (add water to mixture if it reduces too far over time). Add onion and capsicum to pan as well to cook through. Add garlic, ginger, lemon juice, etc... to taste... Goes well with rice or crusty bread.
The following is what it looks like.
Interactive map for this route.
Tags for this post: blog pictures 20150318-goodwin photo canberra bushwalk trig_point belconnen
Related posts: Harcourt and Rogers Trigs; Big Monks; Narrabundah trig and 16 geocaches; Cooleman and Arawang Trigs; One Tree and Painter; A walk around Mount Stranger
Linux Users of Victoria (LUV) Announce: LUV Beginners March Meeting: An Introduction to High Performance Computing Using Linux
RMIT Building 91, 110 Victoria Street, Carlton SouthLink: http://luv.asn.au/meetings/map
Of the top five hundred computers in the world today, 97% of them run Linux. This is no accident, as Linux offers the best platform for efficient and scalable code. In this introductory session, LUV members will be introduced to the core concepts and architecture behind supercomputing, high-performance computing, and parallel processing, along with an introductory session on an actual HPC system.
Linux Users of Victoria Inc., is an incorporated association, registration number A0040056C.March 21, 2015 - 12:30
Walter, K5WH has one of the 3 pre-beta SM1000 units. He writes:
Here’s a pic of the operations setup of the SM1000 on the air today from Houston Texas, into my HPSDR radio. With average Power down to 3 watts even. Made successful contacts to Mel-K0PFX and Gerry-N4DV. After working the audio levels a little, had reports of nice transmitted audio, and the received audio was very clean sounding as well. We were even fortunate enough to have a station breaking in with us from Benin West Africa, TY2BP Pat.
So not only working a couple stateside stations, but first DX as well. Great success with the SM1000! Walter has used the SM1000 with his HSPDR and TS-480 radios at power levels between 4 and 75W.
A warning light is pulsing on the control panel in front of you, but it can wait. You’ll get to it in a moment. So many things to do.
A polite, persistent bleeping began at some point. You weren’t paying enough attention to recall when. It’s ever so slightly out of phase with the warning light.
You feel a dull rumbling through the seat, the floor, between your joints. The room shifts on its axis, as if it’s falling away from under you.
Darkness. A klaxon splutters and honks. Rotating beacons cut the room into contorted still images. Orange, blue, orange, blue.
You watch a wall puncture, crack, and tear. The air around you whistles out into silence.
Metal grinds through metal. It would sound like two trains carving through each other, but for the vacuum.
Then the walls peel away.
Floating. Alone. Adrift. Bewildered.
In depression, no one can hear you scream.
Late last year, I had another crash. (Episode is a silly word.) I should’ve seen it coming. Or, I did see it coming, but pretty much anything else short of anchovies is more pleasant than actually dealing with it.
I have no right or reason to be depressed. There are contributing factors, for sure, but no root cause. In every other respect, life is grand. But that’s not how depression works. It’s a parasite, sucking out every feeling until you’re a dead-eyed husk… except guilt. That one it nurtures.
What’s weird is having a graphical representation of the fall. Check it out: Metadata! The quantified self!
This is a collectd chart of the RAM utilisation in my desktop computer. SLIVER has two big monitors, a nice video card, proper headphones, and so on. It’s where the work gets done, and it’s a dead zone from late November to mid February. My GitHub activity chart looks much the same.
Things improved in February, but I’m still taking a break from work. I need to get my shit together, and don’t want to disappoint anyone if I hit another wall. See that gap in March? Another wall!
But I’m out of the dead zone.
On good days, I’ve been seeing friends, doing personal projects, science experiments, and learning new things. On bad days, sleeping, watching television, reloading web pages. I’m still trading the occasional people-heavy event for a couple of bad days to “recover”. Pfft. That’ll get better.
It sucks being away from work. Lots of big changes and exciting things going on. But I’m grateful for the support, understanding, and time away. Back soon.
– — –
The big difference this time around is hope. Psychologically, I know I can beat depression a hundred times worse, because I did. Financially, I can survive a siege of non-functional depression because I’ve had three years to build a war chest to outlast it. Personally and professionally, I’m more confident because I know where I fit, and what I need to learn.
So, it’s been a shitty few months. But it’s going to be okay.