Science Buddies: "Ask an Expert"

I am building a low power AM transmitter and it showed a 6 pin transformer but the only one I can find is a 5 wire transformer, Help! I cant make my radio work, is this because of the transformer or something else, also there is no p on it to determine what side goes where.

eicpiemann - I need a little more information on the design and the transformer. Usually in a simple AM transmitter design, the transformer is an audio output transformer that is used to modulate the power output of the transmitter carrier wave. Typically it is a two winding design, so only 4 connections are available. You may have an audio transformer with a center-tapped primary and a single winding secondary, or a total of 5 connections. If that is the case, you can ignore the center-tap connection and just have a 4 connection, two winding transformer. Any other information on the transformer may be helpful. If you still have difficulties, perhaps you can attach a copy of the schematic and bill-of-materials.

Rick Marz

Hi eicpiemann - are you following the instructions in this Science Buddies project?

https://www.sciencebuddies.org/science- ... #materials

If so, is there a reason you weren't able to purchase the suggested transformer from Jameco?

http://www.jameco.com/webapp/wcs/stores ... llDownView

Rick, if he is doing that project, the schematic is on this page: https://www.sciencebuddies.org/science- ... #procedure

eicpiemann - When I looked at the experiment details, they did not provide a schematic diagram. I think that's important and I'm suggesting to Ben that the experiment details be updated to include it. Attached is a typical schematic showing the connections to an audio transformer that has 1000Ω to 8Ω windings. It also shows the 5th connection that you referred to, which I mentioned is the unused 'center tap' for this project. Assuming your transformer is close to these specifications, you should see the transmitter work in the AM band.

Rick Marz

Rick - there's a schematic on the background tab of the project, see Fig 2:

https://www.sciencebuddies.org/science- ... background

[edited this post to avoid future confusion - Rick and I discussed and confirmed that the schematic in Fig 2 of the background is correct]