Although it is possible to envelope detect amateur stations if strong enough, identifying amateur SSB stations can be quite hard. The first amateur stations copied were on 160m AM way back in the 1960s. Since then I have copied amateur SSB stations on 80m at some distance. Signals need to be S9++.
In a crystal set all the power is from the TX end, with nothing at the RX end. No batteries, nothing.
I have seen broadcast signals from all over the world and these were genuine in original country broadcasts, not via relays. These days there are fewer English language broadcasters as more and more people move to the Internet.
The circuit shown here is capable of hearing this DX even though it is ultra-simple. For the detector I used a germanium diode, but a hot carrier diode might be suitable. The secret is choosing a diode with a very low turn-on voltage. Silicon diodes are not suitable.
I am sure there will be better circuits around.
See https://sites.google.com/site/g3xbmqrp3/hf/crystalset .
See also http://www.arrl.org/files/file/Technology/tis/info/pdf/culter.pdf
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