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Author Topic: Build a crystal radio in Myanmar - components  (Read 47498 times)
HS0ZIB
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Posts: 436




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« on: December 23, 2013, 03:38:32 AM »

After spending a year in Myanmar teaching at a local school and trying in vain to get a ham license, I took a break for a few months at my home in Thailand.

But in a few weeks, I'll return again to work at a school in Yangon, teaching primary age (8 years old) children.

I've given up trying to get an XZ licence (Zorro clearly has more clout than me..).  But I do want to spark interest in  my young students about all things radio.  What better way than building a crystal radio set from household items?

This is the web-site that I'm using for resources:

http://sci-toys.com/scitoys/scitoys/radio/homemade_radio.html


I'd appreciate advice on what components I can source from household items, and what components I'll need to buy.  Remember that there is no Radio Shack in Myanmar!  It looks like I must obtain the piezo earpiece here in Thailand before I travel to Yangon.  But what about the germanium diode? I read on that resource web-site that lead pencils can be used as an alternative to a commercial diode.

Any advice is very much appreciated. The children that I teach are a wonderful group of learners and they would really love the practical aspects of building a crystal set.

Simon
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W1JKA
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« Reply #1 on: December 23, 2013, 04:51:43 AM »

In the site it says you can use LEDs for the diodes, a cheap source would be those strings of 50-75 led XMas tree lights. I'm going to try it. Also those miniature speakers inside musical/talking greeting cards will work as well as a piezoelectric ear piece (in a QUIET room).
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W8QZ
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« Reply #2 on: February 20, 2014, 12:43:06 PM »

Another helpful site:

http://www.midnightscience.com/

I've read that a rusty razor blade can work as a detector, along with several other unusual methods.
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AA4PB
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« Reply #3 on: February 20, 2014, 01:19:26 PM »

We used to use pencil lead and a Gillett "blue blade" razor blade. I haven't seen those blades around in a long time.

I'd suggest you get a bunch of 1N34A diodes to use. You can buy 100 for $10 on ebay.
 
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KH2G
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Posts: 341




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« Reply #4 on: February 21, 2014, 06:08:29 PM »

empty toilet tissue roll makes good coil form and old transformers from wall wart etc gives a source of wire. Hi impedance earphones are great but an old audio amp from a broken transistor radio can be used well. There are probably some broken computers there where you'll find a wealth of parts. You can build a capacitor across your coil and make a slide bar for tuning by shorting out turns.
Have fun.
Dick KH2G
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LA9XNA
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Posts: 110




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« Reply #5 on: February 23, 2014, 05:16:13 AM »

For tuning it might be simpler to have a fixed capacitor and use tappings on the coil to tune the reciever.
Another way is to stretch / compress the coil.
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VU2NAN
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« Reply #6 on: March 02, 2014, 10:01:55 PM »

After spending a year in Myanmar teaching at a local school and trying in vain to get a ham license, I took a break for a few months at my home in Thailand.........................................

.....What better way than building a crystal radio set from household items?

Any advice is very much appreciated. The children that I teach are a wonderful group of learners and they would really love the practical aspects of building a crystal set.

Simon

Hi OM Simon,

I suppose the best source for you would be the flea market.

Old telephone earpieces would do for the phones. Germainum diodes can be got from old radios. Even good junctions of blown Germanium transistors would do.

Do go through this for some ideas.

http://nandustips.blogspot.in/2013/05/foxhole-radio-detector-variant.html

73,

Nandu.
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K4PIH
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« Reply #7 on: April 01, 2014, 06:49:41 PM »

You can also use the common 2n2222 or similar transistor. Look at the diagram and use it as a crystal, just cut the unused leg off. Worked for me.
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VU2NAN
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« Reply #8 on: April 02, 2014, 08:27:52 AM »

You can also use the common 2n2222 or similar transistor. Look at the diagram and use it as a crystal, just cut the unused leg off. Worked for me.

Hi OM Jacquet,

Afraid silicon transistor 2N2222 wouldn't work (forward voltage being 0.7 V for silicon junction compared to 0.3V for germanium).

73,

Nandu.
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K2OWK
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Posts: 1077




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« Reply #9 on: April 02, 2014, 03:31:08 PM »

I built a radio using a safety pin and a razor blade. Just follow the plans of any crystal radio and instead of a catswisker germanium crystal or a germanium diode use the safety pin and razor as a detector.

73s

K2OWK
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VU2NAN
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« Reply #10 on: April 03, 2014, 07:35:48 AM »

I built a radio using a safety pin and a razor blade. Just follow the plans of any crystal radio and instead of a catswisker germanium crystal or a germanium diode use the safety pin and razor as a detector.

73s

K2OWK

Hi OM Barry,

Here's what I've tried.

http://nandustips.blogspot.in/2013/05/foxhole-radio-detector-variant.html

73,

Nandu.

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