<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>hansihe</author><text>As far as I understand it near-field effects stop being relevant at a couple of wavelengths away from the transmitter. For 2.4ghz that would give you what, a meter of distance?&lt;p&gt;Can you link me to reading material explaining how an antenna can have no sidelobes?</text><parent_chain><item><author>Emrod</author><text>The antenna size is governed by the wavelength and the distance between Tx and Rx (or relays).&lt;p&gt;There are no sidelobes. We are using near-field and catching close to 100% of the radiated energy.&lt;p&gt;Range is only limited by line of site and an antenna size which is practical. Mind you, we can reduce antenna size and increase range by using passive relays.&lt;p&gt;Using a phased array, operating in the near-field. strictly point-to-point between Tx&amp;#x2F;Rx.&lt;p&gt;At the moment we are working with about 60% end to end efficiency so sending 1kw means you will get 600w at the far end… not 1w :)</text></item><item><author>superkuh</author><text>What frequency are you using and over what bandwidth? How many dB down are your sidelobes from your main beam? Are you using parabolic reflectors for your primary antennas, how big are they relative to your wavelength (what&amp;#x27;s the beamwidth)? What role do meta-materials play, are they the collimating relay? What about the sidelobes on the relay?&lt;p&gt;Why do you think 100 mW&amp;#x2F;cm^2 is &amp;#x27;safe&amp;#x27;? You must know from experience this is enough for tissue heating, even from sidelobes many dB down.&lt;p&gt;Over what ranges do you think this is feasible? With, say 20 km of free space path loss in the 2.4 GHz ISM and 40 dB antenna gain at each end you&amp;#x27;re going to be at least 50 dB down. Doesn&amp;#x27;t this mean for things like transmitting power to islands this tech is not useful?&lt;p&gt;Even if you start at 1 KW in (60 dBm), over 20 km the receiving antenna is going to get about 0-10 dBm, or milliwatts.&lt;p&gt;With the same generous setup at 1 km and 1 kW you get 10 watts at the far end.&lt;p&gt;This just doesn&amp;#x27;t work out.</text></item><item><author>Emrod</author><text>Guys, This is Greg Kushnir, founder of Emrod.&lt;p&gt;I am excited and humbled by your support.&lt;p&gt;At Emrod we have safety and environmental considerations at the core.
I’m happy to explain why our tech is not only safe but also has a far smaller environmental footprint than any powerlines, communications antennas, etc.&lt;p&gt;As with any new transformative technology, there will always be sceptics. All we can do is rely on solid science and engineering, listen to the public and address their concerns.&lt;p&gt;I invite you to engage us in an open honest conversation. We would love to hear your concerns, thoughts about possible applications, or even just drop us a line to say what you think about wireless power.</text></item></parent_chain></comment><story><title>New Zealand is about to test long-range wireless power transmission</title><url>https://singularityhub.com/2020/08/30/new-zealand-is-about-to-test-long-range-wireless-power-transmission/</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>superkuh</author><text>60% end to end efficiency at what distance? It&amp;#x27;s a function of distance. I&amp;#x27;m guessing about 30 meters?</text><parent_chain><item><author>Emrod</author><text>The antenna size is governed by the wavelength and the distance between Tx and Rx (or relays).&lt;p&gt;There are no sidelobes. We are using near-field and catching close to 100% of the radiated energy.&lt;p&gt;Range is only limited by line of site and an antenna size which is practical. Mind you, we can reduce antenna size and increase range by using passive relays.&lt;p&gt;Using a phased array, operating in the near-field. strictly point-to-point between Tx&amp;#x2F;Rx.&lt;p&gt;At the moment we are working with about 60% end to end efficiency so sending 1kw means you will get 600w at the far end… not 1w :)</text></item><item><author>superkuh</author><text>What frequency are you using and over what bandwidth? How many dB down are your sidelobes from your main beam? Are you using parabolic reflectors for your primary antennas, how big are they relative to your wavelength (what&amp;#x27;s the beamwidth)? What role do meta-materials play, are they the collimating relay? What about the sidelobes on the relay?&lt;p&gt;Why do you think 100 mW&amp;#x2F;cm^2 is &amp;#x27;safe&amp;#x27;? You must know from experience this is enough for tissue heating, even from sidelobes many dB down.&lt;p&gt;Over what ranges do you think this is feasible? With, say 20 km of free space path loss in the 2.4 GHz ISM and 40 dB antenna gain at each end you&amp;#x27;re going to be at least 50 dB down. Doesn&amp;#x27;t this mean for things like transmitting power to islands this tech is not useful?&lt;p&gt;Even if you start at 1 KW in (60 dBm), over 20 km the receiving antenna is going to get about 0-10 dBm, or milliwatts.&lt;p&gt;With the same generous setup at 1 km and 1 kW you get 10 watts at the far end.&lt;p&gt;This just doesn&amp;#x27;t work out.</text></item><item><author>Emrod</author><text>Guys, This is Greg Kushnir, founder of Emrod.&lt;p&gt;I am excited and humbled by your support.&lt;p&gt;At Emrod we have safety and environmental considerations at the core.
I’m happy to explain why our tech is not only safe but also has a far smaller environmental footprint than any powerlines, communications antennas, etc.&lt;p&gt;As with any new transformative technology, there will always be sceptics. All we can do is rely on solid science and engineering, listen to the public and address their concerns.&lt;p&gt;I invite you to engage us in an open honest conversation. We would love to hear your concerns, thoughts about possible applications, or even just drop us a line to say what you think about wireless power.</text></item></parent_chain></comment><story><title>New Zealand is about to test long-range wireless power transmission</title><url>https://singularityhub.com/2020/08/30/new-zealand-is-about-to-test-long-range-wireless-power-transmission/</url></story>