Wednesday, November 22, 2023

Adapting Ozito battery for ham radio power

We have quite a few low cost Ozito (Bunnings) battery powered tools around here even though I've been transitioning to Makita. The battery packs put out about 20V when fully charged which is too much for nominal 12V radios. I purchased a variable buck converter that can regulate this voltage down. 

To get power from an Ozito battery I butchered a spare single battery charger with pins like this:

Internally, there's quite a bit of circuitry - a bit surprising considering the low cost. The metal pins are soldered right through the board so rather than trying to remove the board I just clipped the power input and soldered on to the back of the battery + and - pads:

A few cables later and we were up and running receiving FT8:

Regrettably, the buck converter produces noticeable noise peaks on the waterfall:

Threading the output DC cable through a toroid improved things quite a bit:

The spectrum looks much better although there is room for improvement:

Credit to VK3KR, David, for the inspiration for this project.

Talking tech on ABC Radio

After contributing technology commentary for many years on ABC radio, I've had a break this year but now I'm back. This week I did a spot with Philip Clark on ABC local radio's Night Life program.

You can stream it here.

ABC Radio Sydney is turning 100 about now although NightLife is a national program.

It looks like I'll be a regular contributor to the program presented by Philip Clark.

Sunday, November 12, 2023

Rosebud Radiofest excellent again this year

Like 12 months ago, I joined Richard, VK3LRJ in the journey down to the Rosebud Radiofest.

It seemed bigger than last year. Certainly there was lots of great gear on sale.

Even Ralph, VK3ZZC, was tempted with some exotic equipment.

I came away with just one item. A rather mysterious Ten-Tec "Energy Amplifier":

It turned out to be what I had hoped - a nice little amplifier with decent speaker in a box. Very handy for monitoring projects on the workbench. It was missing a screw but on disassembly it was found stuck to the speaker magnet.

There were wonderful antique radios on display again this year.

Like last year it was a very well organised event with lots to see. I was tempted by quite a few items but managed to hold back. Great to catch up with a few friends.

Friday, November 10, 2023

FreeDV 700e contact with VK3RV

It's been a while since I've fired up FreeDV. For some reason there isn't a pre-made build for Linux so I grabbed the source code and simply followed the instructions to build it (really just a few dependencies and the build script does the rest).

The user interface looks nicer and there's a better initial setup dialog that makes it easier than when I last tried it. Peter, VK3RV, (who incidentally I first met on FreeDV), was kind enough to have a contact with me.

We first talked on 700e, then tried 1200 and finally 2200. Each sounded better although Peter couldn't copy me on 2200 but it looks like he had some local interference which was pretty severe:

Amazing he could hear me at all with that going on! His screen shot reminded me that you can have several of the visualisations showing at once. It's not obvious how to do this but the trick is to drag the additional tabs up and a bit to the left, until you see an area highlighting, then drop.

A terrific innovation is the new FreeDV reporter window which shows who's on and what frequency and mode they're set to:

FreeDV is looking better than ever and I know David, VK5DR, has received some funding to support additional work on the project.