Sunday, September 19, 2010

Chapter 5 - Exercise 31 Final

So, it was a very nice afternoon today (a bit hot, though) in Atlanta - sunny sky, no clouds, no rain. I had a 3 year old helper who was very curious about all the wire and odd bits sitting on the deck table. After running some unshielded copper wire almost 80 feet and tying it off with the recommended polyrope to a tree, I wired up the remaining circuit as shown on page 265 in Figure 5-66.

With high hopes, I inserted my earphone and moved the gator clip down the wrapped bottle, trying each tap.

No luck.

So... I began troubleshooting. First, checked and then double-checked all my gator clip connections. They were good - and every time I clicked on a tap, I'd hear a slight electrical snap in the earphone... kinda like the crackle of static on a radio. Checked each tap again... nothing.

Next I replaced the Germanium diode... I purchased a bunch so I swapped it out two more times, checking the taps. No luck, other than the crackle in the earphone again.

At one point... maybe it was wishful thinking... I honestly think I heard something. Very faint... there just for a second and then gone. I played with various taps and checked all my connections again, but just had no luck picking up anything.

Still... I had fun. And I understand the theory and what SHOULD have happened and WHY. I wish I'd had luck, but I honestly don't even know where the nearest AM broadcast is coming from... living in Atlanta, I've just assumed I'd pick up something!

If any readers perform Exercise 31 and have luck, PLEASE let me know! I'd love to be able to share some pictures or video or even a recording of any transmission you hear with your project.

Up next... I'm going to cut up the parts this week for the robot in Exercise 32... today I managed to swing into the local hardware store and picked up the following:

1 piece of 2x4 1/4" Sandiply (sanded really smooth on both sides) $7.98
1 package of 2" utility hinges (3 per package) - $2.21
1 package 3" diameter felt circles (for under the feet of furniture) - $3.78

Yeah, I know... felt circles? Well, they're 3" in diameter with no center hole drilled and they are very stiff and 1/4" thick. Perfect for the wheels (and, hey... they won't scratch my floor! Bonus!)

1 comment:

  1. Jim, I know I'm late to this, but...see There are two AM stations within 50 miles of me. Fortunately, one is about 3mi. After I moved my antenna outside, I was able to tune into it. When I had it inside, I briefly heard what I thought was Spanish, but it may have been the Brazilian station 15mi away. The nearby station is 1170AM, the further one 1240. With the outside antenna, I get 1170 on all the taps on the upper end and don't get the other. This web article ( goes into detail about calculating inductance. I followed Charles' directions closely, except that my vitamin bottle is about 3.25" diameter. Looking also at, I suspect that I have too many turns on my coil. I bought a variable capacitor from SciToys, and I plan to experiment with that and fuss with the coil to see if I can tun into 1240. Thanks for your blogs--you have been very helpful.