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A Top Band 1/4 wave vertical?
This current interest (and privacy furore) about drones set me thinking,
what an interesting way to elevate a TopBand vertical, but being a temporary structure, not breaching any planning permission (Brit) or zonal (Yank) restrictions. One problem would be the flight time / battery life, so one approach could be to power the drone through the antenna cable (much as with mast-head preamps), in which case, being tethered, it would no longer be a drone! The power considerations, however, would call for too heavy a cable to be lifted aloft, so, taking the cure from the electricity grids, perhaps the solution would be to power with 1kV AC (say, 10kHz, to reduce the sizes of aloft transformers) going up a twin feeder, with the top band excitation driving both of the AC feeder wires in parallel? (Not too dissimilar in principle from the electicity grid using Pilot Tone protection) Gareth G4SDW PS. By varying the frequency and / or phase of the 1kV AC, the positioning of the ex-drone woulc be controlled thatway. |
A Top Band 1/4 wave vertical?
gareth wrote:
This current interest (and privacy furore) about drones set me thinking, what an interesting way to elevate a TopBand vertical, but being a temporary structure, not breaching any planning permission (Brit) or zonal (Yank) restrictions. One problem would be the flight time / battery life, so one approach could be to power the drone through the antenna cable (much as with mast-head preamps), in which case, being tethered, it would no longer be a drone! The power considerations, however, would call for too heavy a cable to be lifted aloft, so, taking the cure from the electricity grids, perhaps the solution would be to power with 1kV AC (say, 10kHz, to reduce the sizes of aloft transformers) going up a twin feeder, with the top band excitation driving both of the AC feeder wires in parallel? (Not too dissimilar in principle from the electicity grid using Pilot Tone protection) Gareth G4SDW PS. By varying the frequency and / or phase of the 1kV AC, the positioning of the ex-drone woulc be controlled thatway. Ever heard of a helikite? -- Jim Pennino |
A Top Band 1/4 wave vertical?
gareth wrote:
This current interest (and privacy furore) about drones set me thinking, what an interesting way to elevate a TopBand vertical, but being a temporary structure, not breaching any planning permission (Brit) or zonal (Yank) restrictions. However the height of a 1/4 vertical would be such that it may fall under the regulations of the CAA (UK) and the FAA (US) depending on the location. -- Jim Pennino |
A Top Band 1/4 wave vertical?
Jeff wrote:
On 18/04/2015 17:58, wrote: gareth wrote: This current interest (and privacy furore) about drones set me thinking, what an interesting way to elevate a TopBand vertical, but being a temporary structure, not breaching any planning permission (Brit) or zonal (Yank) restrictions. However the height of a 1/4 vertical would be such that it may fall under the regulations of the CAA (UK) and the FAA (US) depending on the location. Under 60m (~200') does not require any permission in the UK. Jeff But do you want a radio controlled gadget with 4 electric motors at the top end of your vertical? Ok you could put a length of isolating rope between it, but still... Anyway, all drone flying is now strictly regulated here (Netherlands). I'm not sure what exactly is allowed and what isn't, but for camera flying for example you need a permit for the specific case that requires at least 6 weeks to process. (to the dismay of firefighters who wanted to use camera drones to examine burning objects and were unable to get a "generic" permit for such usage) |
A Top Band 1/4 wave vertical?
Jeff wrote:
On 18/04/2015 17:58, wrote: gareth wrote: This current interest (and privacy furore) about drones set me thinking, what an interesting way to elevate a TopBand vertical, but being a temporary structure, not breaching any planning permission (Brit) or zonal (Yank) restrictions. However the height of a 1/4 vertical would be such that it may fall under the regulations of the CAA (UK) and the FAA (US) depending on the location. Under 60m (~200') does not require any permission in the UK. Jeff I didn't say anything about "permission", I said regulations, and you may want to check the fine print, e.g. the FAA has language about 200 feet AGL within 3 nautical miles of an airport, which is why I said "depending on the location". And if one is thinking about a balloon or kite antenna, the FAA also has language about within 5 miles of an airport and visibily of less than 3 miles. I am sure the CAA has similar fine print. -- Jim Pennino |
A Top Band 1/4 wave vertical?
Rob wrote:
Jeff wrote: On 18/04/2015 17:58, wrote: gareth wrote: This current interest (and privacy furore) about drones set me thinking, what an interesting way to elevate a TopBand vertical, but being a temporary structure, not breaching any planning permission (Brit) or zonal (Yank) restrictions. However the height of a 1/4 vertical would be such that it may fall under the regulations of the CAA (UK) and the FAA (US) depending on the location. Under 60m (~200') does not require any permission in the UK. Jeff But do you want a radio controlled gadget with 4 electric motors at the top end of your vertical? Ok you could put a length of isolating rope between it, but still... Some sort of aerostat makes a lot more sense than a thing that requires continuous power. -- Jim Pennino |
A Top Band 1/4 wave vertical?
On 19 Apr 2015 10:45:10 GMT, Rob wrote:
But do you want a radio controlled gadget with 4 electric motors at the top end of your vertical? A drone would work, but does not have enough battery capacity to be able to keep the antenna in place for more than about 10-20 mins. Longer would require seperate power wires, which would interfere with the radiation pattern. 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. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
A Top Band 1/4 wave vertical?
In message , Jeff Liebermann
writes On 19 Apr 2015 10:45:10 GMT, Rob wrote: But do you want a radio controlled gadget with 4 electric motors at the top end of your vertical? A drone would work, but does not have enough battery capacity to be able to keep the antenna in place for more than about 10-20 mins. Longer would require seperate power wires, which would interfere with the radiation pattern. 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. 16AWG wire does indeed seem a bit overkill (at least for the sort of powers that UK amateurs are allowed to run). Something much thinner and lighter would do (eg PVC covered multistrand flex). With a little ingenuity, there's no reason why you couldn't feed DC 'line power' up the antenna wires (or, more accurately RF up the power wires). If there's any danger of the pull of the copter snapping the wires, it could be restrained with (say) thin woven nylon cord. However, how would the intricate control circuitry in the copter cope with the very high level of RF signal? -- Ian |
A Top Band 1/4 wave vertical?
On Sun, 19 Apr 2015 20:00:49 +0100, Ian Jackson
wrote: In message , Jeff Liebermann writes On 19 Apr 2015 10:45:10 GMT, Rob wrote: But do you want a radio controlled gadget with 4 electric motors at the top end of your vertical? A drone would work, but does not have enough battery capacity to be able to keep the antenna in place for more than about 10-20 mins. Longer would require seperate power wires, which would interfere with the radiation pattern. 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. 16AWG wire does indeed seem a bit overkill (at least for the sort of powers that UK amateurs are allowed to run). Something much thinner and lighter would do (eg PVC covered multistrand flex). Yep 16AWG is a bit heavy. I have one of these: http://rotorconcept.com/Discovery.asp which will allegedly lift 1 lb (0.45 kg) for 10-15 mins. My guess is more like 300 grams for about 10 minutes including landing time. Trying to land with a dead battery is a really bad idea. http://www.engineersedge.com/copper_wire.htm Eyeballing the above chart, if I limit the lifting weight to about 300 grams, the largest wire gauge for 40 meters of wire would be roughly 18AWG leaving a little slack for an insulating line. With a little ingenuity, there's no reason why you couldn't feed DC 'line power' up the antenna wires (or, more accurately RF up the power wires). I'm sure it can be done. I'm not so sure the added weight of the insulation and isolating chokes at the top will be tolerable. A 1.7 MHz RF choke is not a small or light weight device and this thing will need two chokes at the top. Also, there's another reason for the 10-15 minute limit. The motors do get rather hot after a flight. Running them continuously from a tether wire might cause a meltdown. If there's any danger of the pull of the copter snapping the wires, it could be restrained with (say) thin woven nylon cord. Hardly. If something goes wrong, I want the quadcopter to break the connection and fly freely away, not get dragged into the ground by some bird attacking the wire antenna. I would probably add some thin fishing line as both an insulator, and as a safety feature, at the point of attachment. However, how would the intricate control circuitry in the copter cope with the very high level of RF signal? Dunno. I've never tried it near a BCB transmitting station. My guess(tm) is that it will be ok. I haven't had it long enough to see how it will deal with strong RF areas. I plan to use it for tower inspections, which will certainly require substantial RF compatibility. We'll see. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
A Top Band 1/4 wave vertical?
In message , Jeff Liebermann
writes On Sun, 19 Apr 2015 20:00:49 +0100, Ian Jackson wrote: With a little ingenuity, there's no reason why you couldn't feed DC 'line power' up the antenna wires (or, more accurately RF up the power wires). I'm sure it can be done. I'm not so sure the added weight of the insulation and isolating chokes at the top will be tolerable. A 1.7 MHz RF choke is not a small or light weight device and this thing will need two chokes at the top. Also, there's another reason for the 10-15 minute limit. The motors do get rather hot after a flight. Running them continuously from a tether wire might cause a meltdown. Would you need a power extractor at the top end? The whole copter could simply ride on the RF voltage, ie a bit like a bird perched on a high-voltage power line (assuming that the copter electronics were happy). Even if you had zero-weight power extraction chokes etc, I doubt if it would make much difference -- Ian |
A Top Band 1/4 wave vertical?
On Mon, 20 Apr 2015 08:14:29 +0100, Ian Jackson
wrote: In message , Jeff Liebermann writes On Sun, 19 Apr 2015 20:00:49 +0100, Ian Jackson wrote: With a little ingenuity, there's no reason why you couldn't feed DC 'line power' up the antenna wires (or, more accurately RF up the power wires). I'm sure it can be done. I'm not so sure the added weight of the insulation and isolating chokes at the top will be tolerable. A 1.7 MHz RF choke is not a small or light weight device and this thing will need two chokes at the top. Also, there's another reason for the 10-15 minute limit. The motors do get rather hot after a flight. Running them continuously from a tether wire might cause a meltdown. Would you need a power extractor at the top end? The whole copter could simply ride on the RF voltage, ie a bit like a bird perched on a high-voltage power line (assuming that the copter electronics were happy). Even if you had zero-weight power extraction chokes etc, I doubt if it would make much difference Good point. That should work, but I would feel better if the quadcopter were not at RF potential. I don't want to find out that it doesn't work when I key the transmitter when the quadcopter is 40 meters in the air. There's also a small chance that some of the wiring in the quadcopter will pickup RF from the antenna independent of the power/antenna wiring, which might cause some havoc. Different problem, where more RF chokes might be needed. I guess I could just fly it around an AM BCB transmitting antenna and see what breaks. The only problem is that the local AM transmitting antennas are surrounded by water. Incidentally, the biggest quadcopter helistat of them all: http://en.wikipedia.org/wiki/Piasecki_PA-97 A helium filled ZPG-2W dirigible and 4 old H-34J helicopters underneath. It was designed to lift 26 tons of logs out of the forest. https://www.youtube.com/watch?v=_7jENWKgMPY Oops. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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. |
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 |
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 |
A Top Band 1/4 wave vertical?
In message , Jeff Liebermann
writes On Mon, 20 Apr 2015 08:14:29 +0100, Ian Jackson wrote: Would you need a power extractor at the top end? The whole copter could simply ride on the RF voltage, ie a bit like a bird perched on a high-voltage power line (assuming that the copter electronics were happy). Even if you had zero-weight power extraction chokes etc, I doubt if it would make much difference Good point. That should work, but I would feel better if the quadcopter were not at RF potential. Because the copter is at the very end of the antenna (a very high impedance point) there is essentially no RF current flow into it. You would need extremely high inductance RF chokes to get any significant RF voltage drop across them. I don't want to find out that it doesn't work when I key the transmitter when the quadcopter is 40 meters in the air. There's also a small chance that some of the wiring in the quadcopter will pickup RF from the antenna independent of the power/antenna wiring, which might cause some havoc. Different problem, where more RF chokes might be needed. I guess I could just fly it around an AM BCB transmitting antenna and see what breaks. The only problem is that the local AM transmitting antennas are surrounded by water. The important thing is that the twin wires comprising the antenna be both at the same RF voltage. They need to well capacitively coupled to each other at the TX end and at the top end. As long as you can ensure that all the parts of the copter and its circuitry are leaping up and down at the same RF voltage, it shouldn't suffer any interference. However.................. -- Ian |
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 |
A Top Band 1/4 wave vertical?
On 2015-04-18 08:38:31 +0000, gareth said:
This current interest (and privacy furore) about drones set me thinking, what an interesting way to elevate a TopBand vertical, but being a temporary structure, not breaching any planning permission (Brit) or zonal (Yank) restrictions. One problem would be the flight time / battery life, so one approach could be to power the drone through the antenna cable (much as with mast-head preamps), in which case, being tethered, it would no longer be a drone! The power considerations, however, would call for too heavy a cable to be lifted aloft, so, taking the cure from the electricity grids, perhaps the solution would be to power with 1kV AC (say, 10kHz, to reduce the sizes of aloft transformers) going up a twin feeder, with the top band excitation driving both of the AC feeder wires in parallel? (Not too dissimilar in principle from the electicity grid using Pilot Tone protection) Gareth G4SDW PS. By varying the frequency and / or phase of the 1kV AC, the positioning of the ex-drone woulc be controlled thatway. How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. You could use some SpiderWire kevlar fishing line to make a few tethers so that the balloon doesn't whip around too fiercely in the wind, and it would require no power at all. |
A Top Band 1/4 wave vertical?
In message , Oregonian Haruspex
writes How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. Many amateurs would give their right arm for a functioning helium balloon. It's the sort of thing that most LF band aficionados can only dream about. It's a lot easier to obtain electricity than helium. -- Ian |
A Top Band 1/4 wave vertical?
Ian Jackson wrote:
In message , Oregonian Haruspex writes How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. Many amateurs would give their right arm for a functioning helium balloon. It's the sort of thing that most LF band aficionados can only dream about. It's a lot easier to obtain electricity than helium. Then I guess the solution would be an electric balloon! :-) de Irv VE6BP |
A Top Band 1/4 wave vertical?
On 4/23/2015 3:37 PM, Ian Jackson wrote:
In message , Oregonian Haruspex writes How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. Many amateurs would give their right arm for a functioning helium balloon. It's the sort of thing that most LF band aficionados can only dream about. It's a lot easier to obtain electricity than helium. Weather balloons can be found for sale all over the web, and in all sizes and skin thicknesses. They work quite well for hoisting a wire. I tried it one time with two NWS balloons (about 3 feet in diameter, IIRC); the only problem was they bounced against each other constantly. Next time I would arrange them so that one is above the other. A tank of helium isn't overly expensive, either. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
A Top Band 1/4 wave vertical?
On Thu, 23 Apr 2015 11:56:18 -0700, Oregonian Haruspex
wrote: How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. I've been on a few field days that had helium balloon antennas. Like all ham projects, we successfully duplicated every mistake possible: - The wind blew the balloon and antenna horizontally. The downdraft on the lee side of the hilltop finished the job by pushing the balloon down further, and into the trees. I suspect a kite and a balloon might have prevented this problem, but we never tried it. - We didn't install a static bleeder on the antenna terminal. After throwing a few lightning bolts, a bleeder to ground was hastily fabricated to prevent vaporizing the receiver front end. - A large part of the antenna tuning is the capacitance between the antenna and ground. That can be tuned out easily with an antenna tuner, but not so easily if the antenna is flopping around in the wind with the capacitance changing rapidly. An automagic antenna tuner helps, but is not capable of tuning continuously or at operating power levels. - The wind resistance of a 3 ft dia balloon is fairly substantial. The air flow is turbulent. The result is considerable pull on the antenna wire. I would have expected the wire to break. Instead, it dragged the radio off the operating table and later caused the knot holding the balloon to the wire to come apart. - Helium is expensive. 1 liter of helium can lift about 1 gram. If the 1/4 wave 160 meter antenna uses #16 AWG wire, which weighs; 40 meters * 11.6 grams/meter = 464 grams antenna weight Add to that a 200 gram 3ft dia weather balloon for a total of 664 grams load which requires: 664 grams * 1 liter/gram = 664 liters of helium required for neutral buoyancy. To get it off the ground, I would add about 10%: 1.1 * 664 = 730 liters of helium. Helium previously costs about $8/liter but is now running about $20/liter thanks to the helium shortage. That's $14,600 for 730 liters. Are you sure you want to do this? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
A Top Band 1/4 wave vertical?
On Thu, 23 Apr 2015 11:56:18 -0700, Oregonian Haruspex wrote:
How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. Then (for a full sized Top Band vertical) you'd better be prepared for some VERY SERIOUS static electricity issues. (And, it won't be vertical. It'll be a "slooper", I believe.) One Field Day we threw up a cross-valley long wire (running horizontal, of course) and, after the violent static display made itself known inside the Field Day trailer, several fellas got knocked on their asses trying to get it disconnected and away from all the other gear and antennas around the site. That sucker was approx. 2200 feet long. (Could've gotten 100 pts for "Natural Power", I s'pose...) The Colorado Rockies: Low humidity - steady breeze -- sure was exciting for awhile! Jonesy -- Marvin L Jones | W3DHJ | W3DHJ | http://W3DHJ.net/ Pueblo, Colorado | @ | Jonesy | __ 38.238N 104.547W | jonz.net | DM78rf | 73 SK |
A Top Band 1/4 wave vertical?
On Thu, 23 Apr 2015 18:32:56 -0700, Jeff Liebermann
wrote: Helium previously costs about $8/liter but is now running about $20/liter thanks to the helium shortage. That's $14,600 for 730 liters. Are you sure you want to do this? Hmmm... that can't be right. The problem is that I'm getting prices for helium that are all over the map. For example: http://www.reuters.com/article/2013/09/19/us-helium-shortage-analysis-idUSBRE98I0AN20130919 "... spot price of liquid helium has jumped to $25-$30 per liter from $8 last year." http://www.crainsnewyork.com/article/20140126/FINANCE/301269974/helium-shortage-deflates-party-city "prices have doubled since 2006, to $6.13 per-cubic meter, according to the latest figures from the U.S. Geological Survey." 1 cubic-meter = 1000 liters, so that is $0.00613/liter which seems rather low. http://minerals.usgs.gov/minerals/pubs/commodity/helium/mcs-2014-heliu.pdf "The estimated price range for private industry’s Grade-A gaseous helium was about $7.21 per cubic meter ($200 per thousand cubic feet), with some producers posting surcharges to this price. 1 cubic-meter = 1000 liters, so that is $0.00721/liter, which agrees with the previous article, mostly because the price came from the same source. Ok, let's try party helium: http://www.sfparty.com/products.php?product=Helium%3A-Balloon-Time-Disposable-Helium-Tank-Purchase $55 for 14.9 cubic-ft. 14.9 ft^3 = 422 liters $55 / 422 liters = $0.13/liter Does anyone have the real price of helium? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
A Top Band 1/4 wave vertical?
On Thu, 23 Apr 2015 19:25:21 -0700, Jeff Liebermann
wrote: On Thu, 23 Apr 2015 18:32:56 -0700, Jeff Liebermann wrote: Helium previously costs about $8/liter but is now running about $20/liter thanks to the helium shortage. That's $14,600 for 730 liters. Are you sure you want to do this? Hmmm... that can't be right. The problem is that I'm getting prices for helium that are all over the map. For example: http://www.reuters.com/article/2013/09/19/us-helium-shortage-analysis-idUSBRE98I0AN20130919 "... spot price of liquid helium has jumped to $25-$30 per liter from $8 last year." http://www.crainsnewyork.com/article/20140126/FINANCE/301269974/helium-shortage-deflates-party-city "prices have doubled since 2006, to $6.13 per-cubic meter, according to the latest figures from the U.S. Geological Survey." 1 cubic-meter = 1000 liters, so that is $0.00613/liter which seems rather low. http://minerals.usgs.gov/minerals/pubs/commodity/helium/mcs-2014-heliu.pdf "The estimated price range for private industry’s Grade-A gaseous helium was about $7.21 per cubic meter ($200 per thousand cubic feet), with some producers posting surcharges to this price. 1 cubic-meter = 1000 liters, so that is $0.00721/liter, which agrees with the previous article, mostly because the price came from the same source. Ok, let's try party helium: http://www.sfparty.com/products.php?product=Helium%3A-Balloon-Time-Disposable-Helium-Tank-Purchase $55 for 14.9 cubic-ft. 14.9 ft^3 = 422 liters $55 / 422 liters = $0.13/liter Does anyone have the real price of helium? Never mind. I see the problem. There's a big difference between medical grade helium used to cool MRI machines, and the helium sold at party stores for filling balloons. http://www.bbc.com/news/uk-19676639 The party store helium is recycled from the MRI gas and is mixed (i.e. diluted) with air. "The helium we use is not pure," he said. "It's recycled from the gas which is used in the medical industry, and mixed with air. We call it balloon gas rather than helium for that reason." Mythbusters found this out the hard way when they tried to lift a 3 year old with a large number of helium balloons. http://www.discovery.com/tv-shows/mythbusters/videos/balloon-girl-minimyth/ They needed over double the number of balloons needed to lift the kid mostly because they used party balloon gas instead of the pure stuff. That also explains the price difference. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
A Top Band 1/4 wave vertical?
On 4/19/2015 2:17 PM, Jeff Liebermann wrote:
On 19 Apr 2015 10:45:10 GMT, Rob wrote: But do you want a radio controlled gadget with 4 electric motors at the top end of your vertical? A drone would work, but does not have enough battery capacity to be able to keep the antenna in place for more than about 10-20 mins. Longer would require seperate power wires, which would interfere with the radiation pattern. 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. Did you read the OP? He discusses all of the above and suggests a way to work around. -- Rick |
A Top Band 1/4 wave vertical?
On 4/23/2015 10:38 PM, Jeff Liebermann wrote:
On Thu, 23 Apr 2015 19:25:21 -0700, Jeff Liebermann wrote: On Thu, 23 Apr 2015 18:32:56 -0700, Jeff Liebermann wrote: Helium previously costs about $8/liter but is now running about $20/liter thanks to the helium shortage. That's $14,600 for 730 liters. Are you sure you want to do this? Hmmm... that can't be right. The problem is that I'm getting prices for helium that are all over the map. For example: http://www.reuters.com/article/2013/09/19/us-helium-shortage-analysis-idUSBRE98I0AN20130919 "... spot price of liquid helium has jumped to $25-$30 per liter from $8 last year." http://www.crainsnewyork.com/article/20140126/FINANCE/301269974/helium-shortage-deflates-party-city "prices have doubled since 2006, to $6.13 per-cubic meter, according to the latest figures from the U.S. Geological Survey." 1 cubic-meter = 1000 liters, so that is $0.00613/liter which seems rather low. http://minerals.usgs.gov/minerals/pubs/commodity/helium/mcs-2014-heliu.pdf "The estimated price range for private industry’s Grade-A gaseous helium was about $7.21 per cubic meter ($200 per thousand cubic feet), with some producers posting surcharges to this price. 1 cubic-meter = 1000 liters, so that is $0.00721/liter, which agrees with the previous article, mostly because the price came from the same source. Ok, let's try party helium: http://www.sfparty.com/products.php?product=Helium%3A-Balloon-Time-Disposable-Helium-Tank-Purchase $55 for 14.9 cubic-ft. 14.9 ft^3 = 422 liters $55 / 422 liters = $0.13/liter Does anyone have the real price of helium? Never mind. I see the problem. There's a big difference between medical grade helium used to cool MRI machines, and the helium sold at party stores for filling balloons. http://www.bbc.com/news/uk-19676639 The party store helium is recycled from the MRI gas and is mixed (i.e. diluted) with air. "The helium we use is not pure," he said. "It's recycled from the gas which is used in the medical industry, and mixed with air. We call it balloon gas rather than helium for that reason." Mythbusters found this out the hard way when they tried to lift a 3 year old with a large number of helium balloons. http://www.discovery.com/tv-shows/mythbusters/videos/balloon-girl-minimyth/ They needed over double the number of balloons needed to lift the kid mostly because they used party balloon gas instead of the pure stuff. That also explains the price difference. You are also confusing gaseous helium and liquid helium. Not much in common. -- Rick |
A Top Band 1/4 wave vertical?
On 2015-04-23, Oregonian Haruspex wrote:
On 2015-04-18 08:38:31 +0000, gareth said: How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. This sounds like a neat experiment, which one of our members tried on field day. There are several problems in the electrical side of things, but more importantly on the physical side. As you rise in altitude the wind speed will increase, generally speaking, and perhaps change directions. If the day is completely calm especialy above the tree line, say 100-200ft, then the balloon will remain straight up. But launching a balloon in a 10mph wind, which becomes 15-20mph above the tree line, leads to interesting developments with the tether wire/cord definitely sloping and perhaps being pushed into surrounding objects such as trees, power lines (eh gads!) which can cause it to break or other things. So you need plenty of space with few impediments for the balloon to catch on as it ascends. You certainly can't predict a perfectly calm day, so this can be an unpredictable venture. ha 73 ...Edwin, KD5ZLB __________________________________________________ __________ "Once you have flown, you will walk the earth with your eyes turned skyward, for there you have been, there you long to return."-da Vinci http://www.kd5zlb.org |
A Top Band 1/4 wave vertical?
In message , Edwin Johnson
writes On 2015-04-23, Oregonian Haruspex wrote: On 2015-04-18 08:38:31 +0000, gareth said: How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. This sounds like a neat experiment, which one of our members tried on field day. There are several problems in the electrical side of things, but more importantly on the physical side. As you rise in altitude the wind speed will increase, generally speaking, and perhaps change directions. If the day is completely calm especialy above the tree line, say 100-200ft, then the balloon will remain straight up. But launching a balloon in a 10mph wind, which becomes 15-20mph above the tree line, leads to interesting developments with the tether wire/cord definitely sloping and perhaps being pushed into surrounding objects such as trees, power lines (eh gads!) which can cause it to break or other things. So you need plenty of space with few impediments for the balloon to catch on as it ascends. You certainly can't predict a perfectly calm day, so this can be an unpredictable venture. ha See http://www.allsopp.co.uk/ etc. -- Ian |
A Top Band 1/4 wave vertical?
On Fri, 24 Apr 2015 08:11:20 -0400, rickman wrote:
Did you read the OP? He discusses all of the above and suggests a way to work around. Yep. He talked about using 1kV at 10KHz to somehow control the drone. That's rather impractical, so I supplied what I thought might be more practical methods and some numbers as a sanity check. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
A Top Band 1/4 wave vertical?
"Michael Black" wrote in message
ample.org... I vaguely recall reading about rules for antenna height near airports. In Brit, not exceedng 50 feet within 1/2 mile of any runway, ISTR. |
A Top Band 1/4 wave vertical?
Jeff wrote:
On 25/04/2015 05:32, gareth wrote: "Michael Black" wrote in message ample.org... I vaguely recall reading about rules for antenna height near airports. In Brit, not exceedng 50 feet within 1/2 mile of any runway, ISTR. That clause hasn't been in the UK licence for about the last 30 years. Jeff Perhaps not, but is there not local authority/planning regs that restrict mast and/or antenna height within x distance of airports? I'm sure I read that a while back when researching putting my own mast up (didn't do it in the end), I'm only about 2 miles from Rochester airport so it stuck in my mind. -- STC // M0TEY // twitter.com/ukradioamateur |
A Top Band 1/4 wave vertical?
On 2015-04-24, Ian Jackson wrote:
See http://www.allsopp.co.uk/ Those are pretty sophisticated balloons. Bet those are similar to the aerostats the US uses around the Gulf of Mexico for surveillance purposes. Those are tethered and go up thousands of feet and are marked on our aeronautical charts. Prices must be high on those, out of the limits of the average ham here. hi 73 ...Edwin, KD5ZLB __________________________________________________ __________ "Once you have flown, you will walk the earth with your eyes turned skyward, for there you have been, there you long to return."-da Vinci http://www.kd5zlb.org |
A Top Band 1/4 wave vertical?
On 24/04/15 02:43, Allodoxaphobia wrote:
On Thu, 23 Apr 2015 11:56:18 -0700, Oregonian Haruspex wrote: How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. Then (for a full sized Top Band vertical) you'd better be prepared for some VERY SERIOUS static electricity issues. (And, it won't be vertical. It'll be a "slooper", I believe.) One Field Day we threw up a cross-valley long wire (running horizontal, of course) and, after the violent static display made itself known inside the Field Day trailer, several fellas got knocked on their asses trying to get it disconnected and away from all the other gear and antennas around the site. That sucker was approx. 2200 feet long. (Could've gotten 100 pts for "Natural Power", I s'pose...) The Colorado Rockies: Low humidity - steady breeze -- sure was exciting for awhile! Jonesy ================================ To the matching box (tuner if you like) attached to my twin-feeder dipole I have added a 47Kohm carbon resistor from 1 of the feeder connections to chassis (ground) to avoid static build-up ,since the attached inductor inside the box is not grounded. Of course this does NOT protect against a lightning strike . The 47 KOhm or higher resistor does NOT affect the antenna matching. Before adding the resistor I had a flashover (due to static build-up)to the primary inductor connected to the transceiver input. Fortunately there was no transceiver damage ,but the solar panels /wind generator 13.8V set voltage controller was knocked-out. Since adding the resistor ,many years ago, no more problems. The above shows that (for a home brew matching box of the E-Zee type) it is important that the centre of the inductor connected to the twin feeder is grounded , alternatively a carbon resistor in the 47-100 kohm range connected to one of the feeder connections, is grounded. Frank , GM0CSZ / KN6WH in IO87AT |
A Top Band 1/4 wave vertical?
"Ian Jackson" wrote in message ... In message , Edwin Johnson writes On 2015-04-23, Oregonian Haruspex wrote: On 2015-04-18 08:38:31 +0000, gareth said: How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. This sounds like a neat experiment, which one of our members tried on field day. There are several problems in the electrical side of things, but more importantly on the physical side. As you rise in altitude the wind speed will increase, generally speaking, and perhaps change directions. If the day is completely calm especialy above the tree line, say 100-200ft, then the balloon will remain straight up. But launching a balloon in a 10mph wind, which becomes 15-20mph above the tree line, leads to interesting developments with the tether wire/cord definitely sloping and perhaps being pushed into surrounding objects such as trees, power lines (eh gads!) which can cause it to break or other things. So you need plenty of space with few impediments for the balloon to catch on as it ascends. You certainly can't predict a perfectly calm day, so this can be an unpredictable venture. ha See http://www.allsopp.co.uk/ Is there any practical way to put back the Helium in the bottle in case of success or not too complete failure ? This will surely lower the cost of experimentation. |
A Top Band 1/4 wave vertical?
Stephen Thomas Cole wrote:
Jeff wrote: On 25/04/2015 05:32, gareth wrote: "Michael Black" wrote in message ample.org... I vaguely recall reading about rules for antenna height near airports. In Brit, not exceedng 50 feet within 1/2 mile of any runway, ISTR. That clause hasn't been in the UK licence for about the last 30 years. Jeff Perhaps not, but is there not local authority/planning regs that restrict mast and/or antenna height within x distance of airports? I'm sure I read that a while back when researching putting my own mast up (didn't do it in the end), I'm only about 2 miles from Rochester airport so it stuck in my mind. In the UK it is regulated by the CAA. If you ever intend to do something like this, I would highly suggest going through all the regulations first. In the US, the FAA has regulations about structures near an airport with maximum heights that depend on distance and separate regulations about balloons and kites near airports. I am sure the CAA regs, and most other countries as well, are similar to the FAA regs. -- Jim Pennino |
A Top Band 1/4 wave vertical?
Edwin Johnson wrote:
On 2015-04-24, Ian Jackson wrote: See http://www.allsopp.co.uk/ Those are pretty sophisticated balloons. Bet those are similar to the aerostats the US uses around the Gulf of Mexico for surveillance purposes. Those are tethered and go up thousands of feet and are marked on our aeronautical charts. Prices must be high on those, out of the limits of the average ham here. hi 73 ...Edwin, KD5ZLB __________________________________________________ __________ "Once you have flown, you will walk the earth with your eyes turned skyward, for there you have been, there you long to return."-da Vinci http://www.kd5zlb.org What you want is something that is a combination of a kite and a balloon and is more kite than balloon to avoid having to have a lot of helium. As it need not be man rated, you could make it from tissue, light wood, with party balloon fillers. Or if you are feeling adventurous, use hydrogen making sure there are no sparks at the end of your antenna. -- Jim Pennino |
A Top Band 1/4 wave vertical?
On Sat, 25 Apr 2015 16:42:02 +0200, bilou wrote:
"Ian Jackson" wrote in message ... In message , Edwin Johnson writes On 2015-04-23, Oregonian Haruspex wrote: On 2015-04-18 08:38:31 +0000, gareth said: How about a tethered helium balloon instead? This way you don't have to worry about powering the thing. Bell wire will handle 100 watts all day without turning into smoke. This sounds like a neat experiment, which one of our members tried on field day. There are several problems in the electrical side of things, but more importantly on the physical side. As you rise in altitude the wind speed will increase, generally speaking, and perhaps change directions. If the day is completely calm especialy above the tree line, say 100-200ft, then the balloon will remain straight up. But launching a balloon in a 10mph wind, which becomes 15-20mph above the tree line, leads to interesting developments with the tether wire/cord definitely sloping and perhaps being pushed into surrounding objects such as trees, power lines (eh gads!) which can cause it to break or other things. So you need plenty of space with few impediments for the balloon to catch on as it ascends. You certainly can't predict a perfectly calm day, so this can be an unpredictable venture. ha See http://www.allsopp.co.uk/ Is there any practical way to put back the Helium in the bottle in case of success or not too complete failure ? This will surely lower the cost of experimentation. The cost of Helium will continue to rise. Once used, it is effectively gone for ever as it will leave planet Earth to mix with the rest of the Helium in space. What we have now is from reserves that come from nuclear reactions within our planet, and that is all we have got! Perhaps it's time for us to be less flippant over using this irreplaceable wonder element! |
A Top Band 1/4 wave vertical?
On Sat, 25 Apr 2015 14:17:46 +0000 (UTC), Edwin Johnson
wrote: On 2015-04-24, Ian Jackson wrote: See http://www.allsopp.co.uk/ Those are pretty sophisticated balloons. Bet those are similar to the aerostats the US uses around the Gulf of Mexico for surveillance purposes. Those are tethered and go up thousands of feet and are marked on our aeronautical charts. Prices must be high on those, out of the limits of the average ham here. hi 73 ...Edwin, KD5ZLB Yeah, but not too horrible. See price list at: http://www.allsopp.co.uk/index.php?mod=page&id_pag=35 My guess(tm) on the weight of a 1/4 wave 160 meter monopole was 464 grams without the weight of the balloon, insulators, and whatever else might be needed. Looking at the chart, I could get a "Skyhook" model, that would lift 800 grams with no wind, for $760 excluding VAT, duty, and shipping. You decide if having the loudest signal on 160 meters is worth the expense. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
A Top Band 1/4 wave vertical?
On Mon, 20 Apr 2015 20:36:48 +0100, Ian Jackson
wrote: (...) Today, we had Chen Dubin, owner of Santa Cruz Drones, gave a presentation and a demonstration of his drones at the FLUG (Felton Linux Users Group) meeting: http://www.santacruzdrones.net/#content_area Of course, I mentioned the idea of using a tethered drone aerostat to support a wire antenna and asked how long the motors would last before overheating. His drones have rather large motors, which he says would last for days. He also mentioned that the military is already using such tethered drones to hoist antennas. For example: http://www.skysapience.com http://www.droneaviationcorp.com/tethered-drone.html https://www.google.com/search?q=tethered+drone&oe=utf-8 https://www.google.com/search?q=tethered+drones&tbm=isch I also asked if he has tried any of his drones near the local AM transmitter antennas (KSCO). It seems he lives nearby, hangs around the station, and has not seen any problems. So, it should work at 160 meters. (The control links are usually 2.4GHz. Video is either 900 MHz or 5 GHz). Since the main limitation of a tethered drone is weight lifting ability, doubling the wire length and hoisting a 1/2 wave antenna is easy. A half wave antenna does not need a ground plane, and might work better than a 1/4 wave. End fed 1/2 wave antennas: http://www.aa5tb.com/efha.html http://www.vk2zay.net/article/115 http://pages.suddenlink.net/wa5bdu/efhw.htm http://www.w8ji.com/2end-fed_1_2_wave_matching_system_end%20feed.htm Drivel: Kite and balloon lifting antennas for 160 meters: http://www.qsl.net/g4vgo/ http://www.qsl.net/g4vgo/Kites.htm -- 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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