Foxhole Radio Modifications

I played around with the foxhole radio we made earlier to try to increase the signal.  In a traditional foxhole radio a single diode is used, which cuts off half of the AC from the signal and converts it to a useable audio wave.  This is a half wave rectifier, which does not make use of all the power potentially available in the signal.

I used four LEDs hooked together in a diode bridge to make a full wave rectifier where current flowing in both directions in the signal are converted to an audio wave. 

Here is the actual setup.

And a closeup of the LED diode bridge.

Before with the single diode I was able to tune in stations from 10 to 15 miles away.  I was able to find the same stations again, so it is not worse, and I also found three more stations, the tower of one of these is just over 20 miles away!  Below is a map of the station locations I tuned in using this setup (click for a larger image).

So there seems to be some improvement.  I searched for mention of this online and in forums I read that using a full wave rectifier in an unamplified radio wouldn't help because of the voltage loss from the signal going through two diodes instead of just one (these types of radios work with very low power so any loss is bad).  However, my results suggest is does help.  For much beyond 20 miles I am going to run out of island.  I need to bring in signals from over 50 miles away to reach the next island, Moloka'i.  Perhaps next I will try to increase the size of the antenna.

Christmas

We had our first Christmas in Hawai'i; it was also F's first Christmas anywhere!

The night before M made some snickerdoodle cookies, and each of the older kids read a short Christmas book to the family (M read Merry Christmas, Merry Crow and T read Who's That Knocking on Christmas Eve?), which has become something of a family tradition. 

Sprinkling cinnamon on top of the cookies before baking.

The kids had a lot of fun opening all of their presents.  Thanks to everyone for the presents!

Christmas Loot

F didn't understand what was going on at first, but she quickly learned.  She got a lot of blocks, stuffed animals and soft toys.  She was playing with the older kids, they would stack up the blocks then she would excitedly knock them down.  She also got a large new toybox to store them in.  She is starting to figure out how to drop the blocks in the box. 

T got lots of legos and construction sets, and books (he is an avid reader).  He quickly set up his new magnetic dart board and was enticing us to contest with him. 

M got some craft sets and a kindle!  We registered the kindle and set it to charge up.  Then she broke out a ceramic painting set and started to paint her own bowls. 

I surprised V with tickets in her stocking for her and the older kids to go to a live radio show that will be broadcasting from Honolulu on Christmas eve.  (I will stay home with F; children under six are not allowed to the show.)

M made a gift for me within the minecraft game we have been playing.  It is a house filled with gold and diamond blocks, which are valuable in the game. She was very thoughtful and left a special pick inside the house to use to mine them.  She made the outside of the house in a present pattern using blue and yellow dyed wool.  She also put a sign next to the door saying it was to me and from her. 

A gift house in Minecraft

It was a warm day, a high of 83 F, and the weather was perfect so we decided to have a picnic.  We ran to the store to pick up bread and meat for sandwiches.  I let F hold on to the steering wheel for a minute just before we left and pretend to drive.  She let out two sharp high pitched squeaks as a laugh in her excitement.

We drove up to the north shore and had the beach to ourselves.  We played on the beach, ate sandwiches, and played on the beach some more before heading back.  Then we all relaxed around the house and later V fixed one of my favorites, chicken and dumplings for supper. 

Looking for sea creatures in the rock pools.

The beach to ourselves.  The people in the distance are T and M.

F in her pink wetsuit playing in the sand. 

Drive to Waianae

It is still Christmas Eve here.  We took a drive this afternoon up the west side of Oahu to Waianae.  We haven't been up that way yet so we did some exploring for a bit.  We stopped at a place that had lava formations at the beach.  It is riddeled with holes that the surf moves through. 

There are crabs that hang onto the rocks as the waves beat down over them; they remain in exactly the same place between waves. 

Here is the view back towards Honolulu from Makakilo.  In the foreground is a lot of construction for new houses.  In the distance Perl City is to the left and the towers of Honolulu are in the distance to the right.  Diamond head is the peak on the horizon that sticks out in the ocean on the right.

In a completely unrelated point.  We planted some hibiscus plants in the back yard.  The one M picked out had two nice blooms on it today. 

Waiting for Christmas

Hawai'i is close to the international date line and on the "wrong" side of it.  It is now Christmas over most of the world but we will be one of the last places for it to arrive.  Along with our neighbors to the north the Aleutian Islands and French Polynesia to the south we are at UTC-10:00.  Our closer neighbors to the south, Kiribati, moved to the other side of the date line in 1995 and have been celebrating Christmas all day now.  The only ones behind us are one hour later in UTC-11:00, they are American Samoa and Niue. 

While we are waiting, below is a short video clip T pointed out to me.  (Don't worry, everyone is OK.) 

Our 2011 Christmas Tree

Here is a picture of our Christmas tree with presents.  If you look closely you can see our ornaments.  We have a Christmas pickle, a surfing Santa, a red shiny ball and a snowman M made yesterday out of plastic and cardboard.  Below the tree is our Christmas light setup.  I added a potentiometer (variable resistor) to adjust the rate the lights blink by turning the dial, also there are now 10 LEDs.  It is powered by a 9 volt battery hidden behind the tree. 

Winter weather and random catching up

I can't believe it is almost Christmas; we noted the solstice passing two days ago.  The weather here has cooled slightly and is a bit more windy and rainy compared to a few months ago.  We are living on the dry, leeward, side of Oahu.  There are actually nopales (Opuntia cactus) growing here and there wild.  The grass in our yard was dry and brown but with the increase in rain lately it has started turning green and growing.  I took today off of work and T and I did some yard work to cut the grass and weeds.  Then I put both T and M to work to collect bits of trash out of the yard.  (We live in a densely populated area and small pieces of plastic can blow around and accumulate.)   Each day I have been watering some plants we have planted and I was worried about how dry it has been, but this increase in rain and cloudiness has helped a lot. 

We have adjusted a lot to the temperatures here.  When I say the weather has cooled this means it gets down to about 70 F before sunrise, perhaps in the high 60s.  We were laughing at ourselves when V said she was cold in the morning and I checked to see what the temperature was.  A year ago this would have been unbelievably warm. 

We use a clothesline in the back yard to dry our laundry.  Now that it is raining intermittently this would seem to be a problem, but if we don't get the clothes off in time the rain quickly clears up and they dry right out again.  A couple of times we have had heavy downpours, but so far the rain here has never lasted long. 

We drove around last night to look at the lights and decorations people have put up.  V and the kids went out again tonight to have another look.  There were several barges from the west coast that came in a month ago carrying Christmas trees.  They were selling like hotcakes at some of the stores around here.  We put up a small Charlie Brown tree for fun.  Next year I would like to decorate a small palm tree with lights.

I programmed our microcontroller to blink a series of different colored LEDs in various patterns as a Christmas decoration.  I tried to teach the kids how to count in binary numbers while doing it, but they seemed more interested in the "Knight Rider" pattern as the light sweeps back and fourth.  Here is a picture of the lights with the system hanging up from a hook on the wall and running off a 9 volt battery.

Here is part of the source code that flashes the lights in a binary integer series. 

There is a potential bug, the interior for loop should start with "count=(LEDnumber-1);" to make it more general.

In other news, V earned her first paycheck in years!  (She could not work legally in Germany because she was not an EU citizen.)  It was just a one time thing, but every bit helps.  She got paid to ... sleep!  She was a guinea pig in the control group for a medical sleep study.  I took care of the kids over night (we had a party!) and she got to go, get a good nights sleep while hooked up to monitors, and get paid for it!  I need to find a job like that.  It is too bad she can't do that more often, but V is job hunting for more permanent work. 

And here is a random picture:

If you look closely you can see one of our neighbors dogs relaxing on a back porch.

And here is a picture of F from this morning.  We are out on our back porch.  It is tricky to hold her and take a picture at the same time. 

Above is a picture of M in another project.  We are trying to make our own batteries.  We picked up some used film canisters from a local pharmacy for the containers and made the battery out of aluminum foil, pennies, felt, wire and diluted vinegar.  After hooking eight of them together in series we only managed three volts.  This one is still a work in progress. 

This is a giant centipede (Scolopendra subspinipes) that is native to Hawai'i and can give a nasty bite.  It was on the sidewalk in front of our house one morning.

As a final thing to mention on this update, the kids have had a lot of fun playing a computer game called minecraft lately.  You can play it as a single player, but I set up a server so they could play together in the same game world (my setting up the server seemed to impress them much more than showing them how to make a motor, radio or speaker out of household parts).  One one hand the game is simple, but on the other it can be very creative.  You mine blocks that have different properties and you can combine them to make new tools, etc.  You can also arrange things to build complex machines.  I was playing with them and we made an automatic harvester and a powered rail line you could ride on in the game.