Saturday, February 28, 2009

Installed Antenna at Local Fire Station

This morning I went down to one of the local fire stations in Davis and helped some of the other ARES guys finish up the installation of the new 2m/70cm antenna. They had already mounted the antenna on the 70' tower, so we only needed to run the coax through the building to the radio room. More pictures here and here. Thanks to Greg KG6SJT for taking and posting pictures.

Friday, February 27, 2009

Free Power Battery Charger

I was bored last week and pulled out the toroid I had wound last year for the ever popular Joule Thief. There is many dead AA batteries in our apartments future thanks to the joyful presence of a Wii and the entertainment that follows it.
One thing that I am doing with it that is somewhat interesting is that I'm charging a set of Lithium ion batteries I salvaged out of one of the laptops Michael gave me over Winter break. Li-ion batteries are weird; each cell has a charging voltage of 4.2V. Even with only 0.5V from the AA, hooked to a capacitor, the circuit develops about 15V, and at 4V charges the cells at about 8mA, which isn't much, but is also quite safe for the cells. My plans for the Li-ions is to make them into 3 cell bundles as a 12V pack. Not really ideal, but until I get my (cheap) hands on a lead acid battery, they'll be the best I can do in that department.

I'm really only using the LED as a diode, with the added advantage that it gives a relative current indicator (and when the battery has fallen out of my hacked together holder for it). For better performance, one could use a lower bias vanilla diode instead.
The toroid was a random one I salvaged from some piece of junk that crossed my desk. Standard magnet wire at 30 turns for both sides. Rumor has it that having mismatched coils will give it better performance.
The transistor is a 2N2222, just like it should. Buying 100 of those was an outstanding idea.

Sunday, February 1, 2009

Amateur Radio Updates

A few things have been going on as of late.
  • I've renewed my energies in studying for my Extra license. I would have to say that this test is where my previous common knowledge has hit a well. Huge sections of the Extra exam are completely new to me, which frankly, is what I really expected from the General test. Now is when I get to prove something to myself, right?
  • I've been refining what I want out of this hobby, since last quarter was something of a crisis for me when, after the initial appeal of having my shiny new license wore off, I didn't know what I wanted to do. I am truly interested in the QRP homebrew scene (build my own low power radios). I have built my own Pixie 2, and am planning on going back to it to try and get it working once I get it from Sunnyvale on my next trip.
  • I have joined the NAQCC (North American QRP CW Club). It's free, and I am member #3160. If you have any interest in Morse code, I encourage you to join, and make sure to say that you were refered by W6KWF. If you do, I stand a chance of winning a prize, which would be much appreciated.
  • I have finally ordered my own copy of the ARRL Handbook. I've read through a lot of it, and I'm having mixed feelings about it. It certainly isn't the ultimate amateur radio book everyone seems to make it out to be. It is expansive, and very useful, but it doesn't leave nothing left to be desired. I have nothing to compare it too, but I don't doubt the grumbles about it being less focused on homebrew than it used to be. I'd like to see more than two transceivers in it, but that is likely only my personal preference. What I can't believe is the people who go out every year and buy the latest edition. I read through the section they have on WiFi, and I can't believe how aged it already is. It makes no mention of 802.11n, which has been in the works since 2004 and already has consumer products on the shelf, but what was totally unexcusable was where it said WEP was the cryptography system in use. WEP has been broken for 8 years, and its replacement, WPA, has been around since 2004.
All in all, I do not regret buying the ARRL Handbook. It was on sale, and I had an Amazon gift card, so it only ended up costing me $20 cash. The paperback binding of it is very lightweight, so if you think you'd be using it extensively, I would think the hard cover binding wouldn't be unjustified. Nitpicks aside, there is a lot of useful information in here that I will use.

Out of curiosity, if anyone happens to have an edition from 40s-70s, I'd be interested to look through it to see how the focus has changed from tube projects to IC based projects.