25 September 2012

Back on the 10m waves

This antenna was easy to tune, since I have enough support to hold a 10m quarter of wave radiator (4m long fiberglass telescopic fishing pole).

I had a couple of hours to tidy up the shack-lab while putting out some CQ's.
First I tried on 10m WSPR at 0.5W, receiving report from DU and VK lands. Then, not satisfied with the gratification coming from an automated system since I was in the shack, I remembered of PSK31. I tuned down a little and managed 8 QSO's, including a new one OD Lebanon that came back to my call.

The antenna is fed with RG58 coax coiled up to form an RF choke. The choke is held in place with a clip-on ferrite bar. I have no idea if RF is flowing back to the shack. At the indoor coax connector the SWR is 1.5:1 on 10m and 2.5:1 on 12m, so the antenna is somehow a dualbander.

The fishing pole is long enough for a 15m quarter of wave radiator without needing loading coils, so I might give it a try.

22 September 2012

How it all began

After my initial interest in electronics (will be in another post), sometime in 1980's my brother and I were given a pair of 27 MHz walkie talkies. I could have been 8 or 10 years old.

Those walkies worked on 27.145 MHz, an "alpha" CB channel used also for remote controls. The microphone was the loudspeaker itself. The receiver was broad, very broad but sensitive: I could hear truck drivers on channel 5 (27.015 MHz) from kilometres away.

With no understanding of frequencies or channels, my mother and grandparents took me along the truckers' road trying to talk with them. No success, of course.

I don't remember if it was the very same Summer or the next, I got a 3 channel portable CB, then followed by a CTE Alan 48 which gave me my first sporadic-E DX on channel 34 FM with an Austrian station.

Yesterday my mother asked me what to do with those walkies, "Gig Bravo 2000": no way they're going to the recycle bin!

I am tempted at replacing the XTAL and try some extreme HF AM portable operation...

13 September 2012

HVPP fusebit doctor for AVR's

Great job did these Polish guys that created the High Voltage Parallel Programmer (HVPP) for Atmel AVR microcontrollers. HVP programming is the only way to regain control of an AVR uC that has received wrong "fuse" settings, like I did with RSTDISBL=on.

An OM asked me to program a couple of ATmega32, he sent them over but they were not reacting to my serial programmer. A quick check with the Engbedded AVR Fuse calculator swapping high and low fuse bytes suggested that the previous owner had mixed them up, locking the chip to HVPP.

So I built the Polish circuit using an ATmega168 as the fusebit doctor on the protoboard. Pictures show the mess of wires, but it worked nevertheless. While I was at it I also recovered my locked 2xATmega168.
Green LED = chip rescued!

05 September 2012

Adding contact information to digital storage media

Following my own year-old post about backing up digital contents (pictures/videos) while on the go, I want to share a simple idea against the physical loss of digital storage media.

Unlike a mobile phone, when a digital (video)camera is forgotten somewhere, there is usually little or no means of getting it back to the owner. While the electronic device itself can be easily replaced, it is not the case for the digital content that has been stored on it. So, how about adding your own contact information to your digital storage media? If it falls in friendly hands then there are good chances it will be returned.

I came up with these ways of making our digital belongings:
  • handwrite an email address on the storage card (SD/SDHC, CF, TF, xD, ...) with a permanent marker, if there's room for it [your mobile phone may have been lost/stolen together with the camera, so just a phone number is not a safe idea]
  • create a README.txt or OWNER-INFO.txt file in the root folder of the storage card containing contact information, return info, reward, ...
  • create a digital picture containing contact information (the same of the README.txt file) and place it amongst your other pictures
The latter suggestion comes in handy if who rescues your lost device decides to browse through the content instead of plugging it to a computer. Imagine this: you find a digital camera on a bench, you check the content and find a picture showing owner's phone number, you call/text that number and return the device right away.
Oh, by the way, you don't have to edit the picture on the computer: write everyting on a large piece of paper and take a picture of it ;-)

Writing your details on the digital camera may make it less attractive for a future sale, but it can work as well as long as the card is not removed (i.e. for a sale). Remember that your main concern is to recover your memories, not the device itself.

03 September 2012

RasPi from RS delayed

Not that I am longing for another Raspberry Pi, but I got an email from RS that my order with them will be shipped about 4 weeks later than expected. Weird, since Farnell was weeks early! Maybe there is an unbalance of orders they receive?

This is a good chance to cancel my order with RS, unless someone in a hurry wants to buy it from me (how much I paid it + S&H to your doorstep).