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Thursday, March 30, 2023

An Antenna for the High-School Direct Conversion Receiver (and Next Steps in the Project)

We have reached the point where we have to decide on an antenna for the high-school direct conversion receiver.  It needs to be simple and easy.  It needs to be something that students can easily install from a bedroom window in an apartment or a town house.  

We thought about an End Fed Half Wave, but 66 feet of wire seemed to be too much, and the EFHW would require both coax and the construction of a transformer.  That seemed like too much. 

So here is what happens with just 33 feet of wire (1/4 wave on 40 meters), with another 33 feet as a counterpoise.  I found that the counterpoise worked just as well spread out on the bedroom floor as it did hanging out the window along the outside of the building.  As you can see in the video, the counterpoise is really necessary with this kind of antenna.  It makes a big difference. 

We know that the students could have dispensed with the counterpoise by connecting the copper clad boards to a cold water pipe, but that might be difficult for them.  So we went with the counterpoise. 

After the antenna demonstration I ramble on a bit about the high-school construction project, and where the students could go from here. 

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