Tuesday, September 01, 2015

Radio data link for $1

John, VK2ASU, showed a little data link he'd built at a recent home brew group meeting at Dural and I've started experimenting.

Here's the transmitter.


They only say it’s on 433MHz but mine seems to be on about 433.9112. I can pick it up on a little hand held scanner and given that there’s no antenna connected the range seems excellent. There is a plated hole to add an antenna. I make it 17cm for a quarter wave.

I’m using RadioHead’s ASK mode here.

With an arduino sketch example.

These are the modules I bought for $1 (including postage) on ebay.

Applications of such a link are things like sending back temperature or battery voltage readings from remote sensors.

My plan is to slow down the transmission rate, test on uhf and then get it to work on 40m with the Frog sounds transceiver.

Friday, August 21, 2015

Helping a soon to be new ham in Bowral

Recently I had a very pleasant train trip to Bowral to assist and old friend, and soon to be amateur radio operator, William.

I was able to make the full return journey using my Opal card at no cost, which was an unexpected bonus.

William lives on a nice sized block near the centre of Bowral. Here he is in a very nice shed.


By the time I turned up, William had the rig up and running with a run of coax to a simple dipole in the back yard. I was very impressed with how far he's got. Electrical noise seems to be a significant problem though.

I brought along an antenna analyser and it turned out that the dipole was rather short for 40m and was nicely resonant at 9MHz. We replaced the simple centre connection direct to co-ax with a proper balun and made a longer dipole.


Unfortunately the two trees are a little close together but we managed to get everything going (after the picture above was taken) by having down hanging ends. (Also I did put the co-ax through the strain relief on the balun.

Here's William's operating position:


I responded to a call and had a good contact with a chap in Victoria who gave us 57.

The electrical noise could be from high voltage power lines running just a house away or it could be from an appliance in the house - more investigation is required.

Thanks William for the hospitality and I look forward to our first on air contact.

Sunday, July 26, 2015

ARNSW Home Brew Group meeting

Another interesting meeting today with lots of "show and tell" and a talk on filters. Here's some photos.

Bob had a high quality component analyser with probes that work with surface mount components.


The room was enthralled as always.


A prototype weather station with links from the remote sensor working over Bluetooth.


Convenor Peter VK2EMU at the helm.


John VK2ASU demonstrated a wireless link running over 432MHz using a $1 transmitter (but he recommends a more expensive receiver).


Stephen, VK2BLQ has constructed an amazing SSB phasing transmitter for 80m.


Eric showed the new Powerpole distribution box from the Waverley Amateur Radio Society.


The full kit is $35 - much cheaper than commercial equivalents.


Cameron, VK2CKP, showed his arduino controlled rotator.


Eric talked about filters and why you shouldn't open email enclosures while running Windows.



Saturday, July 18, 2015

Low price 40m CW transceiver "frog sounds"

There's a very low cost CW transceiver for 40m available out of China on ebay dubbed "frog sounds".

For just $19 including free postage you get a decent kit with circuit diagram. I put mine together in about two hours and it worked first go.



The circuit is available via this link. Basically it's a conventional NE612 LM368 direct conversion receiver. The transmitter ads a side tone generator using some NAND gates.

As I've observed before you can't purchase the individual components for the price of the whole kit and the board and documentation is decent.

Update not all smooth construction for some.

John, VK2ASU, sent this:

"Built the Frog Sounds transceiver today. Many problems and many hours spent trying to fix. Have it going to a degree. Getting 1 watt out on 12 volts compared to 3 watts on the previous one.

One major problem I found is that the holes are not all plated through perfect and this stopped the receiver until I found it. The rx works now but "deaf". More time and effort to go.

Decided to do a search on the net if others had problems. Yep!

Here is a link to look at and this.

When you solder a component in make sure you let enough solder to flow into the hole to work right through. There is a hole about in the middle of the board (when it's all built you will find). It is at the end of a track which then goes through the board to the underneath. I had to scrape insulation off both sides and add a wire through it.

For all that the circuit looks really good it's a shame that the board is so bad.

On the plus side the keying is crisp and the sidetone quite good."

Sunday, June 07, 2015

Liking Google Photos

Google has done such a great job with Google photos that it puts Apple's equivalent to shame. Apple has had face identification for some time but the genius here is that it doesn't wait for you to name people, it just groups by face.


Now, for some reason this feature is disabled for Australian users by default. To enable it I followed the instructions here and used an Android device as they suggest. I used TunnelBear for the VPN and all went as described.

I'm currently in the process of copying 22,000 photos from my iPhoto and Aperture libraries up using Google Photos Uploader app for MacOS. Unfortunately, although I have 100Mbps download speed my upload speed is just 2Mbps and so the upload will take several days.

It would have taken much longer as the Mac goes to sleep when idle. To stop it sleeping during the mega-upload I'm running Caffeine which is free from the app store.

I hope Apple responds to this competition, they need to do the following:

  • Offer an unlimited (image size capped is fine) photo archive
  • Cut the price of their cloud storage (for 1TB: Google is $10/month, Apple is $25/month)
WWDC is next week but I doubt this is on the agenda. Interesting times.

Sunday, May 17, 2015

Download this show wins IT journalism "best audio program" award

Marc Fennell does everything on this show, producer, presenter, interviewer, editor, music mixer and talent wrangler. All credit to the new generation of tech-savvy media stars. It's a privilege to be a very small small part of the show.


Congratulations mate!

Friday, May 15, 2015

Very low cost i2c LCD interface board

Listening to the marvellous Soldersmoke podcast I learned of these serial interface boards for driving an LCD display using just two pins of an Arduino. These boards are just $1 out of China on eBay. Amazing.

With some help from Brainwagon I was soon up and running.


The little board solders nicely on to the back of standard Hitachi LCD boards.


I'm stunned that China can manufacture stuff like this for such great prices. Everything I make will have a display.

SM1000 FreeDV in a box arrived

Very excited this week when the SmartMic 1000 arrived. This is a FreeDV digital voice codec in a very nice box. It's designed so you can hold it in your hand rather like a big microphone and just talk in to it to transmit and receive digital voice.


The case has 3.5mm sockets for everything and also an RJ45 socket for a single cable connection. It's like the Signalink boxes and has a similar internal jumper system for wiring it. I followed the instructions and quickly had it working with my FT817.




The button marked "select" on the front switches between analog passthrough (so you can hear what the radio hears) and digital mode.

To test transmission, I listen off air and decode with the FreeDV app. My scatter plot looks reasonable I think:

I can hear my voice decoded so the next step is some contacts on 14.236 where I'm listening and calling.

Notes: 
  • Mic Gain control operates in reverse.
  • Select button switches between analog and digital. On power on it defaults to analog.
  • Back button isn't used.
Stephen, VK2BLQ, also has one of these and I was able to receive him on 40m, here's a snippet.