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A Top Band 1/4 wave vertical?
"Jeff Liebermann" wrote in message ... Weight might be a problem. I'll guess(tm) #16 AWG wire, which weighs 7.82 lbs/1000ft or 11.6 gm/meter. 1/4 wave at 160 meters is 40 meters so that antenna would weigh: 11.6 gm/meter * 40 = 464 gm Hmmm... Probably too heavy. By comparison, a GoPro camera body weighs 100 gm. Ok, smaller guage wire or bigger quadcopter. 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 Hi I like the idea of using a bifilar antenna with the 2 wires in parallel for RF and the motors supplied in differential mode. Good motors for the job could be those used in lowcost Dremel tools They reach 20000 RPM and work on 220V AC or DC. Collector noise in receive could be a problem too. May be wiring the 4 motors in serial would be a good idea too to minimise voltage drops and weight. |
#2
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A Top Band 1/4 wave vertical?
bilou wrote:
"Jeff Liebermann" wrote in message ... Weight might be a problem. I'll guess(tm) #16 AWG wire, which weighs 7.82 lbs/1000ft or 11.6 gm/meter. 1/4 wave at 160 meters is 40 meters so that antenna would weigh: 11.6 gm/meter * 40 = 464 gm Hmmm... Probably too heavy. By comparison, a GoPro camera body weighs 100 gm. Ok, smaller guage wire or bigger quadcopter. 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 Hi I like the idea of using a bifilar antenna with the 2 wires in parallel for RF and the motors supplied in differential mode. Good motors for the job could be those used in lowcost Dremel tools They reach 20000 RPM and work on 220V AC or DC. Then all you need is a gear box to get the rotational speed down to where propellors will work. Collector noise in receive could be a problem too. May be wiring the 4 motors in serial would be a good idea too to minimise voltage drops and weight. As control on these things is done through individual motor control, that isn't going to work. -- Jim Pennino |
#3
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A Top Band 1/4 wave vertical?
On Mon, 20 Apr 2015 19:16:55 +0200, "bilou" wrote:
I like the idea of using a bifilar antenna with the 2 wires in parallel for RF and the motors supplied in differential mode. Good motors for the job could be those used in lowcost Dremel tools They reach 20000 RPM and work on 220V AC or DC. Ummm, the Dremel tool probably weighs too much. It would also need a gearbox to produce counter rotating propellers, to keep the reaction torque from spinning the motor and winding up the antenna wire. That's incidentally why quadcopters have two rotors going clockwise, and the other two going anti-clockwise. That's also why you don't see many 3 rotor devices. Collector noise in receive could be a problem too. Not to worry. Collector noise (whatever that is) would probably be buried under the overwhelming atmospheric noise (mostly lightning) on 1.6 MHz. May be wiring the 4 motors in serial would be a good idea too to minimise voltage drops and weight. I assure you that 4 motors wired in series, parallel, differential, or a tangled mess, would weigh exactly the same. However, you're correct that voltage drop would be a problem because the device really sucks power out of the LiIon battery. My quadcopter uses a 2200 ma-hr battery for 15 min maximum flying time. Assuming I drain it completely: 2.2 A-hr / 0.25 hr = 8.8 A drain The 16AWG wire might handle that, but with about several ohms of copper loss, most of the energy will go into heating the antenna. Sorry, but I'm late for a free lunch so let someone else calculate the resistance of 40 meters of 16AWG wire. Incidentally, the battery is rated at 25C, which means that it can theoretically drain at: 2.2 A-hr * 25 = 55 amps https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=26472 Yes, you can weld with the battery. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#4
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A Top Band 1/4 wave vertical?
On Mon, 20 Apr 2015 12:31:13 -0700, Jeff Liebermann
wrote: Marginally related drivel: "The Promise of Drones for Tower Inspection" http://online.qmags.com/AGL0415#pg47&mode2 -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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