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Old 11-04-2008, 05:43   #46
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Full Wave

1005 is the number you must use to obtain a full wave antenna (no other fraction will work other than full wave). An RF engineer probably came up with 1005's use in the fomula. I didn't come up with that number, I just trust the fomula to be true. For further reading, obtain a copy of the ARRL Antenna book or the ARRL Handbood for RF engineering reference. This is not the appropriate forum to get into detailed arithmetic lessons.
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Old 11-04-2008, 19:13   #47
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This is not the appropriate forum to get into detailed arithmetic lessons.
Um...says who?

Its ok if you don't know the answer to a question, but be careful about belittling a person asking a question simply because you can't explain it.
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Old 11-04-2008, 19:59   #48
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I believe that 1005 is a constant.

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Old 11-04-2008, 22:56   #49
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I believe that 1005 is a constant.
I'm sure you're correct. In the interest of trivia, it would be interesting to understand from where it was derived. You can take the boy out of engineering, but...
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Old 11-05-2008, 07:07   #50
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My aploogies to anyone offended. I don't know where the 1005 came from, but the formula seems to work.
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Old 11-16-2008, 18:06   #51
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The 1005 is an approximate number for a full wavelength loop antenna. It is derived from the speed at which electrons will travel along a conducting wire, so that the 'waves' of energy that are being transmitted from the radio through the wire will reinforce each other, thus forcing the emission of radiation.

To get back on topic:

Could this antenna be produced with some sort of spring-steel wire so it can be balled up in a pocket and then just 'spring' back to shape whenever it is removed? You could leave a small slider attachment at one end of each wire to allow for frequency tweeks. I am a lazy echo, and if I can just whip something out of my pocket and start talking, I am sold.
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Old 11-17-2008, 06:33   #52
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I was looking in the ARRL Antenna Book and they have similar antennae in a triangular pattern with each leg at 1/3 wavelength and in a square/diamond pattern with each leg at 1/4 wavelength. I suppose using that idea, spring loaded elements could work. If you have the resources and the time, perhaps the spring loaded idea could be experemented with. As it is, the loops can be folded and shoved into a small stowage pouch.
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Old 11-17-2008, 14:40   #53
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The 1005 is an approximate number for a full wavelength loop antenna. It is derived from the speed at which electrons will travel along a conducting wire, so that the 'waves' of energy that are being transmitted from the radio through the wire will reinforce each other, thus forcing the emission of radiation.
Interesting stuff...thanks!
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Old 11-21-2008, 15:29   #54
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The 1005 is an approximate number for a full wavelength loop antenna. It is derived from the speed at which electrons will travel along a conducting wire, so that the 'waves' of energy that are being transmitted from the radio through the wire will reinforce each other, thus forcing the emission of radiation.
To "amplify" this: to be efficient, an antenna needs to resonate at the frequency of the radio broadcast - sort of like a tuning fork. An antenna that is a full wavelength long for the frequency being broadcast is one of the resonant lengths an antenna can have.

Frequency and wavelength are related to each other by the constant c, the speed of light propagating in vacuum.

(Because, for an electromagnetic wave to travel at the speed of light, it has to move 300,000 km / 186,000 miles every second - the shorter the length of the individual wave - the wavelength - the more times the wave has to repeat - the frequency - to make it that far every second. That's why Echoes use to love 20MHz and higher, and dread the 5MHz shots. The antenna got shorter at higher frequencies and thus easier to get up in a tree)

Since light moves at 300,000 km / sec, which equals 300 Mm /sec, dividing the frequency in MHz by the speed of light in Mega-meters (300 Mm) gives you the wavelength in meters. Convert the 300 for feet gives you 984, so the formula for a full wavelength is frequency in Mhz / 984 = wavelength in feet.

So, an infinitely thin wire in a vacuum would be resonant using 984. The 1005 comes from the difference in physical length and electrical length of a physical antenna. The sum of capacitive and inductive effects in a real world antenna make it seem longer to the radio transmitter (its electrical length) than it actually is (its physical length.) So, the 1005 is an empirical number that gives good results in real world antennae.
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Old 03-02-2009, 14:40   #55
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Antenna accepted well

I'm back "over there" and have been sharing the knowledge. The antenna is accepted well; within the first month, I made and distributed 15 antennas and taught about 20 people how to build them. An 18B who made one plugged it in to his PSC-5 and got a squelch reading (on the PSC-5 display) of -33 on his first try. Good to have if the X-wing or egg beater breaks or to replace the AV 2055-3 strapped to the hood.

Oh by the way, I've turned a few dudes on to this web site as well...
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Old 03-19-2009, 09:56   #56
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Blast from the past.

This design is one I used in Afghanistan in 2005. I was the commo SGT for an MP company out of Vicenza, IT at the time and our unit was conducting missions outside of LOS range IVO Bagram. We needed "X-wings" but at the time they were few and far between. I heard a rumor that there was a "reserve" commo guy there on BAF who had developed a homemade satcom antenna and was willing to show us how it was built. After some searching, I was able to find him, a crusty old SSG who had probably forgotten more about comms than I will ever learn. He showed me and my troop how to make them, and we created four working models. The copper was run through PVC, and we mounted them onto the back of our gun-trucks using ratchet straps.

I don't remember that SSG's name, only that he was more than willing to share some knowledge with a rookie who needed his help.

I've included a pic that shows it mounted on my CDR's truck.
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Old 03-20-2009, 17:49   #57
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construction details?

Can you provide some details how it was made then?
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Old 03-20-2009, 19:11   #58
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Can you provide some details how it was made then?
I don't know, can you read the rules and stickies on this board and comply before posting further?

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Old 03-27-2009, 09:36   #59
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Antenna Variations

I'm not surprised that there are variations of the antenna out there. It would be conceited to think I was the only one to think of something like this. He probably read the ARRL antenna book too (or helped write it). I met a pretty knowledgeable guy a few years back. He had a 1/2 mile antenna strung over his property, receiving transmissions from all over the world.
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Old 03-30-2009, 07:05   #60
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I'm not surprised that there are variations of the antenna out there. It would be conceited to think I was the only one to think of something like this. He probably read the ARRL antenna book too (or helped write it). I met a pretty knowledgeable guy a few years back. He had a 1/2 mile antenna strung over his property, receiving transmissions from all over the world.

Sounds like my kind of guy. If I'm ever in NC, I'll look you guys up for a beer or two.
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