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ABCinventor
Posted on Friday, November 19, 2004 - 6:32 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

i couldn't find the phone plug EXACTLY the same as yours but i managed to find the same model but it has 3 pins, the other 2 pins is the same.I was told that it was for 2 earphones. I build the transmitter as told in the site, and i pluged the phone plug to the CD player the same order as the blue and green wire. i then tune my radio to 100 X10k Hz. there is a very soft pop song even if i adjusted my CD player and radio volume to the max. then i touched the third wire from the phone plug and the volume got louder. but i have a wierd feeling in my hand when holding the wire as if i am having a electrical shock. Please help me with the problem. This site is cool!!! but it should get a little more detailed...
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Simon Quellen Field (Sfield)
Posted on Friday, November 19, 2004 - 10:51 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

You are using a stereo phone plug instead of a monaural phone plug.

Check the output impedance of your CD player. Not all of them are
designed to use 8 ohm earphones. Some use 16 or 32 ohm earphones,
and will not modulate the transmitter well. Try different audio
sources.

You will also get better results with a longer antenna and a good
ground connection (connect the negative side of the battery to a
cold water pipe).
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ABCinventor
Posted on Saturday, November 20, 2004 - 4:38 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Well... after checking and testing, it seems that it it using me as the "earth" wire(the "ground"). after modifications, the problem is solved but still, the sound coming out of the radio is not very loud... so now i have a problem. i am using a transformer that reads 0V,115V,230V on one side and 9V,0V,9V on the other side.on the top, it says 0.3A . Am i using the right transformer or should i change one?? i have been to the radio shacks in my country but they all tell me that transformers are measured by voltage, not ohms...i doubt that there is something to do with the transformer that affects the volume. please give me some explanations.Thanks Simon!!!
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Simon Quellen Field (Sfield)
Posted on Saturday, November 20, 2004 - 7:23 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

You are confusing a power transformer with an audio transformer.
If you are having trouble finding an audio transformer, try here.
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ABCinventor
Posted on Saturday, November 20, 2004 - 10:44 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Oh so mine are power transformer, not radio... but it still works quite ok except that the volume is about normal speech volume. i would like to buy from your catalog, but i dont have a credit card and buying from a radio shack is cheaper. well there are plenty of radio shacks in Singapore so i will try to look for them there first... even so finding a radio transformer may be difficult also as in my country, radio transformers are not common. i even have trouble searching for 1MHz oscillators . the more common ones are the 1.8432 MHz ones. but in the end i finally found the 1MHz oscillator. if i couldn't find them i will definitely get it from you!!!
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ABCinventor
Posted on Saturday, November 20, 2004 - 10:46 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Oh one more question. Why do we have to connect the negetive to the Earth to get a good connection??
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Simon Quellen Field (Sfield)
Posted on Monday, November 22, 2004 - 12:51 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Why grounding the transmitter increases the range is a complicated
thing to explain and understand. However, a very simplified explanation
is to think of the earth as a mirror for the antenna, making the antenna
seem to be twice as large (because the receiver gets the signal from the
antenna and the reflection).

Also, when looking for the transformer, remember to ask for an audio
transformer, not a radio transformer. Audio, radio, and power are all
three different types of transformer.
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ABCinventor
Posted on Monday, November 22, 2004 - 3:16 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I've just been to the radio shacks and almost all of them only sells
power transformer. when asked about transformer, many of them replied that
transformers are measured in voltage. asked about ohms and they said that there
are either no such things or they don't sell it. only one radio shack that i
have been to sells transformers measured in ohms but were far beyond the needs
of the transmitter. they were 0,4,8 (ohm)on one side and 0,5k,10k(ohm) on the
other side and 0,4,8(ohm) on the side of ther other transformer and 0,3.5k,7k
ohm) on the other side.So i bought a small one measruring 1 cm by 1cm by 1cm
with 3 pins on one side and 2 pins on the other side. i am not sure if it's a
power or audio transformer but i think the number of coils in the pri inducer
and sec inducer is of little diference. Even if i bought the wrong kind, it
doesn't matter because it cost Sin$0.80 or US$0.47.
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ABCinventor
Posted on Monday, November 22, 2004 - 4:52 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

After checking and testing the new-bought transformer, i concluded that the 9V
power transformer produces a louder sound than the 1X1X1 cm transformer...

Seems like the 9V power transformer is better..
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Simon Quellen Field (Sfield)
Posted on Monday, November 22, 2004 - 12:59 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

The reason we carry the audio transformer in our catalog is because
we got email from people all over the world who couldn't find the
part locally, or who thought that clerks at Radio Shack knew something
about electronics.
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ABCinventor
Posted on Monday, November 22, 2004 - 9:41 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Simon, my friend and i would like to post a project that we had made last year
during the holidays. it is a water rocket launcher that lunches soda bottles
into the air to an alttitude of about 15 metres (MAX). the energy comes from a
hand pump. with every strokes, more air is inserted and compressed into the
launcher and eventually, the rocket shoots right up into the sky. but because
it is a prototype, it is not very perfect. during pumping, a person has to hold
the tip so that the bottle doesn't shoot out before it is being pumped to the
optimum pressure. also because the tip of the launcher is a little smaller than
the mouth of the bottle, we have to fix it with a few rounds of masking tape.
there is a sharp aluminium rod that allows it to be inserted into the ground and
operated with a single man but more masking tapes have to be used to make the
bond stronger for the optimum pressure.
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Dave Goodwin (Goody)
New member
Username: Goody

Post Number: 1
Registered: 1-2010
Posted on Monday, January 4, 2010 - 2:22 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Simon,
First of all, thank you for creating/maintaining this site, it's wonderful. I bought a three-penny radio kit, amplifier kit and bread boards, then other kits from you. I was frustrated in not being able to receive any AM signals where I live. I recently visited a friend in a bigger city and was delighted to pull three stations clearly, and a couple o' faint ones too. The signal was strong, and quite clear.
Now that I've conquered that challenge, i am tackling the AM transmitter. I believe I have constructed the circuit correctly soldering it to a PC board and the parts come, as a kit, from your catalog. I have a 10 meter 24 awg stranded wire tacked to the walls near the ceiling for an antenna (didn't puncture the insulation.) I have the transmitter grounded using the cold water pipe, and tested the conductivity. I hear that the static goes quiet, at 1000 kHz when I connect the battery (I believe from reading here that this means the crystal is oscillating correctly) but I don't hear anything recognizable coming from the receiver (different am/radios; a walkman, a wind up, a three-penny radio on a breadboard, and an Elenco kit radio) I have also, used different audio sources for the transmitter (a walkman, a discman, another radio, an Ipod) and have had no success. I believe, after reading here, that I have a problem with modulation? I believe that my problem lies there and was wondering what I could do to get this working. Options that I'm considering are finding a radio that uses 8 ohm impedance earphones, or finding an audio transformer with 1000 primary and 32 ohms secondary (someone here mentioned that ipods are matched to 32 ohm earphones. I have not had success locating the transformer.
I would like to find out what people, that are successful with this circuit, are using for the audio source. I also wonder if modifying my circuit with a different transformer, or if extending my antenna, or something else entirely, would fix my problem. Sorry this was so wordy, and I hope I have been correct in explaining my problem Thank you, -Dave
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Theresa Simmons (Theresa)
Senior Member
Username: Theresa

Post Number: 140
Registered: 1-2008
Posted on Monday, January 4, 2010 - 1:27 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Your signal source is not capable of driving the transmitter.

iPods and other MP3 players can only drive 32 ohm headphones.

You need to reverse the transformer (as it describes in the
instructions). You will lose a little bit of range, but you will
be able to modulate the signal.

Put the 1,000 ohm side in series with the oscillator, and the 8 ohm
side connected to the iPod. Turn the iPod up so it will be loud enough.
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Dave Goodwin (Goody)
New member
Username: Goody

Post Number: 2
Registered: 1-2010
Posted on Wednesday, January 6, 2010 - 7:19 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Theresa, thank you for the quick reply. I did what you suggested and reversed the transformer. Now, when I dial the receiver to 1000 kHz no audible change occurs when I plug in the battery (no quieting of static.)
Would an Aiwa shelf stereo be powerful enough to drive the transmitter (or 8 ohm impedance speakers?) I need to get a 1/8 in. to 1/4 in. phone jack adapter to try it, and will do, but I am wondering what audio source is recommended to use with the transmitter. Thank you.
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Dave Goodwin (Goody)
New member
Username: Goody

Post Number: 3
Registered: 1-2010
Posted on Friday, January 8, 2010 - 1:30 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Ok, my foot is in my mouth. I set up the circuit on a breadboard and realized I plugged the positive lead from the battery in the wrong hole. After I fixed that, I received a clear signal from a few feet away, (and without an attached ground and antenna!) I then attached the ground and antenna and received good reception around the house. I also received the signal from 106.9 mHz on my alarm clock radio. I'm going to look into how that worked. What an awesome toy! Your kits have inspired me to learn more about radios, and maybe soon get my first amateur license. I purchase a 1/8 to 1/4 in adapter to use my shelf stereo as an audio source with the circuit set up like in the original instructions. Thank you again,
-Dave

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