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Author Topic: I got a home brew Dipole but not sure what it is.  (Read 4948 times)
KB1OJR
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Posts: 2




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« on: September 21, 2011, 05:37:37 PM »

I have 2 home brew dipoles I just picked up from a ham that has decided to drop everything he had and give it to me.

The first Dipole is 2 wires connected to a center with a rg-8, each wire coming from the center is about 25' totaling about 50' in length

The second Dipole has a center piece with 8 wires coming off of it, they are all varying lengths the 2 longest are 50' from the center and then there are 6 more that all get shorter and shorter from there, I have never seen one like this nor do I have any idea what band it is for, but it was in use at the time I took it. I am unable to ask the operator as he is no longer able to be communicated with.
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WD5GWY
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Posts: 397




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« Reply #1 on: September 21, 2011, 06:00:16 PM »

First dipole (single one with two wires) sounds like a 17 meter dipole.
The other is a fan dipole and the multiple sets of wires are for several
bands all fed from a single coax. Measure them and see what lengths
you get to get an idea of what bands they cover. Then hang them up
and use them!! You might have to add or subtract some length to the
dipoles depending on the height you mount it and whether or not you
mount them between two supports or a single one (inverted V).
The 8 wire fan dipole is probably for 4 bands. Without the measurements
it is hard to know but, given that the longest is about the same as the
single dipole you have (25' per leg), it could cover, 17, 15, 12, 10 meters.
Good luck!
james
WD5GWY
 
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KB1OJR
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« Reply #2 on: September 21, 2011, 07:47:36 PM »

WOW! Hopefully I will get some time and a little bit of extra daylight soon to attempt to hang it up. I got the perfect spot for it, thank you so much for the info Smiley

73's

Eric
KB1OJR
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VU2NAN
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Posts: 248




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« Reply #3 on: September 21, 2011, 09:10:51 PM »

I have 2 home brew dipoles I just picked up from a ham that has decided to drop everything he had and give it to me.

The first Dipole is 2 wires connected to a center with a rg-8, each wire coming from the center is about 25' totaling about 50' in length

The second Dipole has a center piece with 8 wires coming off of it, they are all varying lengths the 2 longest are 50' from the center and then there are 6 more that all get shorter and shorter from there, I have never seen one like this nor do I have any idea what band it is for, but it was in use at the time I took it. I am unable to ask the operator as he is no longer able to be communicated with.

Hi OM Eric,

For a leg length 'L' in feet the frequency 'f' in MHz is given by f = 234/L.

So the first dipole is for 10MHz (30m).

The 50' wires on the second are for 5MHz (60m).

The other frequencies covered by the second dipole may be calculated likewise.

73

Nandu.
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KA4POL
Member

Posts: 1996




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« Reply #4 on: September 21, 2011, 11:32:53 PM »

If we assume a 1/2 WL dipole the frequency calculates to about 9.6 MHz. I guess feet and meters got mixed up in GWY's reply. How nice if we had all metric  Tongue NASA lost a Mars explorer by mixing up metric and inch. On the dipole I'd consider using a common mode current filter. If you can get your hands on a network analyzer you'll have exact information about your antennas.
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WY3X
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Posts: 768




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« Reply #5 on: September 22, 2011, 07:41:24 AM »

How nice if we had all metric

How nice if the rest of the world would move AWAY from metric!!!

One easy way to think of metric antennas is to remember that a meter is approximately 39 inches. 39 inches is pretty close to 36 inches, which is (of course) a yard. A yard is 3 feet. So if you think of one meter being approximately 3 feet, it makes it easy to "guesstimate" the required length of an antenna (very roughly, of course). You could always subtract 3 inches for every meter for nearly exact measurements. Once you have the "overall length" (i.e. a full wavelength) you can then divide by 2 for a half wavelength or by 4 for a quarter wavelength. This "guesstimation" works to figure out the correct answers on licensing tests every time. You just have to remember that a dipole is actually two 1/4 wavelength wires so you don't get confused. ("Di" meaning "two".) The ENTIRE length of a dipole will be 1/2 wavelength, but ONE SIDE of a dipole is a 1/4 wavelength.

I hope I haven't confused anyone.

73, -Web (WY3X)
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W8JI
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Posts: 9296


WWW

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« Reply #6 on: September 22, 2011, 08:11:00 AM »

Let's see, he says:

Quote
The first Dipole is 2 wires connected to a center with a rg-8, each wire coming from the center is about 25' totaling about 50' in length

"About" 50 feet end-to-end is likely 30 meters.

The second antenna is:

Quote
The second Dipole has a center piece with 8 wires coming off of it, they are all varying lengths the 2 longest are 50' from the center and then there


So that is 100 feet long, if he is accurate, and that is a 4.7 MHz antenna.

My guess is he is guessing at lengths a little, and he has an 80 meter and high fan dipole and a 30 meter dipole, but he really needs to word this better and tell us the lengths better.
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AA4HA
Member

Posts: 1451




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« Reply #7 on: September 22, 2011, 09:09:39 AM »

How nice if we had all metric
How nice if the rest of the world would move AWAY from metric!!!

I grew up as a "the world is going metric" child and engineering school reenforced that. Now, 25 years later after earning my degree I still work everything in metric. It is a pain-in-the-butt to convert things to the old imperial system. (how many drachmas to the dollar? ounces to gallons? newtons to dynes? curies to berquels?, ounces to troy ounces? kilometers to feet?)

Now if we can get rid of the old Sumerian time and degrees systems and move to "star-dates" and radians. <p> (60 was considered a mystical number)

Tisha Hayes, AA4HA
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
KA4POL
Member

Posts: 1996




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« Reply #8 on: September 22, 2011, 12:15:15 PM »

I love the discussion that started from a 50' dipole for 30 meters  Grin

... or was it 98.4252'  Shocked

By the way at the Oktoberfest they serve a 'Mass Beer' which should equal 1 liter but only contains .8 liter. But this actually is equal in business terms  Tongue
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K0CBA
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Posts: 299




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« Reply #9 on: September 23, 2011, 09:01:36 PM »

""It is a pain-in-the-butt to convert things to the old imperial system. (how many drachmas to the dollar? ounces to gallons? newtons to dynes? curies to berquels?, ounces to troy ounces? kilometers to feet?)""

And then there is furlongs per fortnight.
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K4RVN
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Posts: 775




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« Reply #10 on: September 24, 2011, 09:05:50 AM »

My advice is to use the half wave formula 468 divided by the frequency in mhz of the band you want to operate and either make the 50 ft  total length longer or shorter to comply with the results. The total length you mentioned would not be suitable for any band without a tuner, and why do that? Do the same on the multiband dipole. You will have poor results unless you check the total lengths by formula to determine exactly what you have. Sounds like those antennas were for listening to shortwave not amateur use.

Frank
« Last Edit: September 24, 2011, 09:12:32 AM by K4RVN » Logged
K8AXW
Member

Posts: 3860




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« Reply #11 on: September 24, 2011, 09:15:04 AM »

How nice if we had all metric

How nice if the rest of the world would move AWAY from metric!!!


I hope I haven't confused anyone.

73, -Web (WY3X)

I agree!

I hope I haven't confused anyone!
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KA4POL
Member

Posts: 1996




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« Reply #12 on: September 24, 2011, 11:37:31 AM »

According to the American Central Intelligence Agency's Factbook, the International System of Units is the official system of measurement for all nations in the world except for Burma, Liberia and the United States. Quote from Wkipedia http://en.wikipedia.org/wiki/Metric_system

Standing strong... Grin
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KE0NW
Member

Posts: 7




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« Reply #13 on: September 30, 2011, 07:26:16 PM »

Off subject but I had a high school physics teacher who would ask questions like:
Joe's car could travel 161280 furlongs per fortnight. How fast did his car go in miles per hour?
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N3OX
Member

Posts: 8847


WWW

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« Reply #14 on: September 30, 2011, 08:11:02 PM »

Google calculator kind of ruined that sort of question.

http://goo.gl/9idI6


Of course it can be used to further the cause...

http://goo.gl/4BqXu

Grin
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
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