Broadcast - 12 Jan 2025
At least one club weekly event has started for the New Year. Last Wednesday night saw Nic VK7WW back at the helm of the TestNet and TechNet session, almost as if the net hadn’t even taken a break over the Christmas New Year period. It was excellent to hear all the local and mainland call signs fronting up to the radio net discussions, with the ensuing images of Morse Keys, impressively big decks and circuit board miss-haps, all happily flowing on the Discord channel. Keep up the good work fellows.
Last year saw some Internet providers divesting themselves of the hassle of having e-mail customers. Subsequently this caused a large number of new e-mail addresses and updates required for club members. With the New Year all club members e-mail addresses now seem to be correct. Also with the New Year there comes an Annual General Meeting, so expect an e-mail soon with information. So please give serious consideration to any nominations, including yourself, that you would like to make for the new 2025 committee.
Now for something completely different and on a light hearted note. I will hand over to Stuart VK7ES, for an item he recently penned, entitled:
“An interesting piece of Chinese Technology”
The story began a few weeks before Christmas, I purchased a carton of LED Tea Lights for the festive season from a local recycling yard for the bargain basement price of $5.00 per carton. Each carton contained 32 units. At a pre-Christmas Tech night at NTARC, I took a unit with me as a discussion point as to how it was made to flicker like a real candle. Stefan, VK7ZSB suggested that they contained a miniature audio chip, similar to the ones found in Greeting cards. He also gave me a few larger units that had been hanging around the NTARC clubrooms for many years so I decided to reverse engineer my unit and the club units to see if there was any truth to it.
Dismantling one of the units I purchased, I expected to find a miniature potted chip as per a greeting card. Alas, there was only a CR2032 lithium button cell and an LED with a simple but effective switch that simply pushed the positive lead of the LED onto the side of the button cell to power it on...no other components found. How does it flicker? Closer inspection with my microscope showed a small black speck about the size of a grain of finely ground pepper within the LED itself with some barely visible wires emanating from it. Could this be the illusive audio chip?
I removed the LED from its holder and devised a way of extracting the audio. The circuit I used consisted of a 10 volt bench power supply, a 10k current limiter/load resistor on the positive supply line, 100uF DC blocking capacitor followed by a voltage divider to reduce the level enough to feed the line input of my computer. Here is a sample of the audio.
I think you would agree that it’s not what you would like to get for a Birthday Greeting, but, at least it is "Audio" I guess! Maybe it’s a code and it’s sending secret messages back home. A close inspection of the audio wave envelope revealed that there is a varying shift in the DC level that causes the flicker. The larger and older units from the club rooms were a much more elaborate design consisting of two AA cells, a small PCB, a slide switch, an LED and a black potted chip about 4 mm in diameter mounted on the PCB. To extract the audio from this unit was much easier. I simply put a couple of clip leads across the LED. The voltage swing from this unit was much lower so there was no need for a voltage divider, I just placed a 100uF in series with a 1k resistor to the negative of the supply to charge the capacitor and fed the junction of the two directly into the computer line input. Here is the audio.
The audio seems to be a very distorted series of train noises repeated every 30 seconds. Again, I guess it's audio but, personally, I wouldn't be adding it to any of my favourite play lists any time soon.
Pictures of the LED and audio samples are on the NTARC website under Blogs.
This exercise was just a bit of fun but, I believe, as trivial as it is, it is the essence of the hobby and/or pro-fession we enjoy… an endless curiosity of how and why things work.
Stuart VK7ES
Thank you Stuart, my sentiments exactly and as you so eloquently put it, “an endless curiosity of how and why things work”. Certainly brings back memories of my first crystal set, how did it work without batteries? and so my journey started…….
Pictures and audio files will be available on the NTARC Web site under “Blogs” for this broadcast. NTARC Blogs
UPCOMING EVENTS
TestNet and TechNet session - Every Wednesday, TestNet/CW course on 3.580MHz from 7 pm, then a TechNet on 3.567MHz from 7.30 pm till 8.30 pm. Your host for the evening is Nic VK7WW.
Coffee Morning – The first for 2025 will be held on Friday the 17th January in the NTARC Club rooms. Time is from 10 am to noon and we look forward to seeing you all there. So why not pop in, check the QSL cards and join us for a cuppa, there is endless tea and coffee along with biscuits available for a donation.
Club Room Technical night session - The first session will be Wednesday the 22nd January, at the usual time of 6.30 pm at the Club Room Archer Street, Rocherlea.
Annual General Meeting & General Meeting - Wednesday the 12th February 2025 at the NTARC Club Rooms, Rocherlea Scout Hall, Archer Street Rocherlea commencing at 19:30 hours (7.30 pm). Information to be e-mailed to club members soon.
Finally – As club room events are still in recess, but the broadcast continues on, so a reminder to all members that if you have any items of news you would like added to our weekly roundup then please e-mail them to the Secretary at the following address news@ntarc.net
That’s all folks,
73, Stefan VK7ZSB, Secretary NTARC Inc.
