W3RSW
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Rick & "Roosevelt"
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« on: March 19, 2013, 11:47:31 AM » |
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Skywave hunter, pretty neat. Azmimuth and elevation (approximately.) Ought to be able to lash one up for 40 too. http://www.youtube.com/watch?v=ZgJJiyXEbkgAll you need additionally is a nice compass rose. |
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RICK *W3RSW*
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W1FVB
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« Reply #1 on: March 19, 2013, 04:45:28 PM » |
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Pretty Cool,
Looks like a magnetic loop design. I've build one a few years ago out of a hula hoop.
Worked pretty good
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Jeff W9GY
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« Reply #2 on: March 19, 2013, 06:26:49 PM » |
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Sounds like it can achieve a pretty deep null.
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Jeff W9GY Calumet, Michigan
(Copper Country)
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flintstone mop
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« Reply #3 on: March 21, 2013, 06:25:21 AM » |
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Pretty wild idea to move in any direction to null out an HF signal
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Fred KC4MOP
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W3GMS
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« Reply #4 on: March 21, 2013, 10:50:18 AM » |
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Pretty wild idea to move in any direction to null out an HF signal
Fred, Are you still happy with yours? I am thinking about ordering one. Joe, W3GMS |
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Simplicity is the Elegance of Design---W3GMS
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ke7trp
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« Reply #5 on: March 21, 2013, 12:12:51 PM » |
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Very neat. Need to get started on some more loop experiments. Question.. What is the inside small loop for?
C
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W1FVB
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« Reply #6 on: March 21, 2013, 07:24:57 PM » |
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Very neat. Need to get started on some more loop experiments. Question.. What is the inside small loop for?
C
The inside loop is the active loop attached to the receiver.. the outside is a passive loop tuned with a capacitor. The bandwidth is extremely narrow , so not great for overall shortwave listening unless you like to re-tune every Khz or so, but very useful for DF'ing. Do a search for magnetic loop antenna, and you'll find a ton of stuff Frits |
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ke7trp
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« Reply #7 on: March 21, 2013, 07:29:11 PM » |
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Thanks. I have played around with some simple shielded loops but not this type. Looks neat.
C
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W2VW
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« Reply #8 on: March 21, 2013, 07:34:32 PM » |
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A few servos, some software, marry that to a Flex and you can null out people by callsign.
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Steve - K4HX
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« Reply #9 on: March 21, 2013, 08:58:20 PM » |
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Systems that use the direction of the field (e.g. loops) for DF are limited on skywave signals.
No matter what, without ionosounder info, DFing at HF is nearly impossible.
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W3RSW
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Rick & "Roosevelt"
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« Reply #10 on: March 22, 2013, 09:11:28 AM » |
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Yeah, even with a sense ant, you mike get it from the backside.  I've Gotta look up the ionosounder info. Is it kind of like HAARP research? |
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RICK *W3RSW*
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Steve - K4HX
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« Reply #11 on: March 22, 2013, 01:55:09 PM » |
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Nothing like HAARP.
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W3RSW
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Rick & "Roosevelt"
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« Reply #13 on: March 22, 2013, 07:07:30 PM » |
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Thanks. Neat.
I like the Gakona site presentation and options best of the three.
Buttons work.
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RICK *W3RSW*
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Steve - K4HX
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« Reply #14 on: March 22, 2013, 07:42:10 PM » |
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Of course HAARP has ionosound info. Think about what HAARP is doing.
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K1JJ
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"Let's go kayaking, Tommy!" - Yaz
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« Reply #15 on: March 22, 2013, 07:51:39 PM » |
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About 15 years ago I built an Adcock antenna for 75M DFing. It was about 20' off the ground and rotated with a prop pitch. I found it to be very good for low angle arrival, but poor for higher angle local stuff. It was fixed at vertical polarization.
The loop antenna shown in the video seemed very sensitive to rotating it from vertical to horizontal polarization. What practical information would this tell us about DFing a signal? Does it help for higher angle 75M DFing that seems so difficult?
T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed. Easily done in DSP.
Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."
There's nothing like an old dog.
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Steve - K4HX
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« Reply #16 on: March 22, 2013, 10:49:20 PM » |
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With a second Adcock array, you could use the Watson-Watt method to get the bearing without rotating either antenna. Still doesn't help with the very high angle signals. A correlative interferometer system with ionosound data is what is needed to really get in the game. This isn't something most hams (if any) are going to have.
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kb3ouk
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« Reply #17 on: March 22, 2013, 10:53:02 PM » |
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That antenna might not be the greatest thing for high angle DFing, but I do see another good use for it, eliminating local interference. If you nulled out the locals causing interference, then the low angle stuff should still come in loud.
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Clarke's Second Law: The only way of discovering the limits of the possible is by venturing a little past them into the impossible
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Steve - K4HX
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« Reply #18 on: March 22, 2013, 11:01:04 PM » |
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Bingo! Even more so on 160 meters. That antenna might not be the greatest thing for high angle DFing, but I do see another good use for it, eliminating local interference. If you nulled out the locals causing interference, then the low angle stuff should still come in loud.
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