HFU HF Underground
Technical Topics => Equipment => Topic started by: jordan on April 28, 2016, 1302 UTC
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For a shortwave pirate on 6930 kHz, would a G5RV antenna work well? Does it matter what direction the antenna is in? If so, how should I position my antenna if my target audience is south of my location (average bearing of 170 degrees)?
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G5RV will work with an antenna tuner but a resonant 1/2 wave dipole antenna for that freq is only 67.82 ft long where as the G5RV would be 102 ft or so.
468/freq in Mhz is the half wave dipole formula. So 468/6.9 then divide by 2 to get the length of each side of the dipole antenna. This assumes 50 ohm feed.
If you can only get it up 30/35 ft it will be rather omni directional. If you get it up closer to 60 ft or more the pattern is broadside/perpendicular to the wire.
Depending on power output should be good for few hundred miles in daytime, and a lot further at night.
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I mainly used an inverted "v". You only need one high point instead of two or three for the flat-top dipole. The " v"works very well for hit and run pirating, quickly up and quickly down. The height range would be roughly the same as what Fred said for the regular dipole but you get vertical and horizontal propagation with "v".
Get either to at least a minimum height of 25 or 30 ft. and you'll do fine. Of course, higher is better, if possible.
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http://newsuperantenna.com/
The loading coil makes it very top heavy, so it will fall over in any kind of wind if you use the supplied tripod. This is guaranteed to break the whip. Better to clamp it to something substantial, such as a heavy barstool or a picnic table or fence. It also can't be used in the rain.
Otherwise, it sets up in just a couple of minutes, and gets out well.
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http://newsuperantenna.com/
The loading coil makes it very top heavy, so it will fall over in any kind of wind if you use the supplied tripod. This is guaranteed to break the whip. Better to clamp it to something substantial, such as a heavy barstool or a picnic table or fence. It also can't be used in the rain.
Otherwise, it sets up in just a couple of minutes, and gets out well.
Have you tried clamping it to your tongue? The steel plate in your forehead would make a dandy reflector.
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The HFU seeks to document and log all radio transmissions, and does not encourage any radio operation involving surgical attachment of transmitting antennae to one's head.
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The HFU seeks to document and log all radio transmissions, and does not encourage any radio operation involving surgical attachment of transmitting antennae to one's head.
Nothing surgical about it. It's the same as when he wears his clip on pearl earrings to the Winterfest banquet and auction.
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I have a nice letter from the Voice of Layrngitis's Genghis Huxley from the 1980's where he says he used a large bedspring for his broadcast 'cause the wife had the weeks laundry hanging on the antenna...signal was well received here for that program, so I put forward this as a viable means of getting your signal out :). Has anybody else tried this, and if so, does the bedspring function in a manner ??? similar to a curtain array?
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I did load up my wood stove with metal chimney one time. The RF burns from the rig were memorable. Nothing like an RF burn.
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A dipole cut for the frequency of operation will be about as efficient as you can get with a simple wire antenna, but the off-center-fed dipoles, wich is what g5rv and the like are, radiate well. I doubt if much directionality will be noticed by changing the antenna orientation at typical dipole heights (15 to 35ft), but if you can get it up a quarter wave or higher it will become more directional. That being said, what region do you want to cover?
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Would http://www.mfjenterprises.com/Product.php?productid=MFJ-1778 (http://www.mfjenterprises.com/Product.php?productid=MFJ-1778) work?
Or would it have to be cut, for 6920?
Trying to figure out the best for stretchyman's LuLu.
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Good god. Inverter v dipole. Center up at least 20 ft. Each leg about 33 ft. 10 watts quiet night half the US. Works with anything 6900 plus or minus whatever. Now if you want to run power you have to test that shit out.
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I did load up my wood stove with metal chimney one time. The RF burns from the rig were memorable. Nothing like an RF burn.
I found that out when using 100 feet lengths of speaker wire. I would split it down to 33 feet a leg and use the rest, taped up securely at the top to prevent further splitting as a feedline. Run it into a tuner and you had yourself good functioning antenna from the dollar store for a buck.
One night while using my first version I noticed mid-tx the feedline had really twisted. I thought, "I'll straighten it out and never leave the air, fourteen watts ain't gonna hurt." Wrong. The burn I got from that barely insulated cheap wire was somewhere between the sting I got from a sand hornet as a kid and accidentally touching the section of copper pipe I was sweating installing my great-Aunt's new hot water heater. And it lasted. That little spot was twingie for over two weeks.
To add insult to injury it was the same spot where the copper pipe had got me two decades before.
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The HFU seeks to document and log all radio transmissions, and does not encourage any radio operation involving surgical attachment of transmitting antennae to one's head.
It doesn't ??
I may have been mis-informed...
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The HFU seeks to document and log all radio transmissions, and does not encourage any radio operation involving surgical attachment of transmitting antennae to one's head.
Nothing surgical about it. It's the same as when he wears his clip on pearl earrings to the Winterfest banquet and auction.
I was thinking a magnet would do, quick to place and remove, and Al's head would be left shiny and new!
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A folded dipole works better. Use ladder line 33 ft each side, and terminate the ends together. Use a 3:1 Balon.
That way you have a full wave antenna rather than half wave, plus there is no surgery needed. :D