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Author Topic: Vertical-Dipole Feed Line(s)?  (Read 5828 times)
WB6BYU
Member

Posts: 13331




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« Reply #30 on: July 20, 2013, 07:15:33 PM »

Quote from: K7RNO

...what wattage do I need to have for the resistor, with a maximum of 10W output ...




Easily solved using Ohm's law.

At 10 watts into a 50 ohm antenna, the voltage across it would be sqrt( 10 * 50 ) = 22.3 Vrms.
With 22.3V across a 10K resistor it would dissipate 22.3 * 22.3 / 10K = 0.05W.  A 1/10W resistor
should be adequate, but a quarter or half watt would give you plenty of margin.  (And that assumes
100% transmit duty cycle - in practice the actual dissipation averaged over a QSO would be perhaps
1/4 of that.)

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K7RNO
Member

Posts: 279




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« Reply #31 on: July 21, 2013, 03:01:46 PM »

Success story part one:

The vertical ground plane got to radiate today. I made it 40' and don't know if a 35' one would have been even better, but this one was sooo quiet on 20 m, I never had that experience before (okay, I only had this TRX for a month or two, with very weak antennae, apparently). Anyway, with just 5W, I had more contacts than ever before in a certain time span. I heard stations as far as CT, OK, TX, and many closer ones too. On 40 m I only had one contact, but it appeared to be less busy overall. Maybe too early in the day.

Now I am getting really excited for when the dipole is made and up.

Thank you all for your encouragement and help!
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73,
aRNO
NAQCC #6870, SKCC #11131
W5WSS
Member

Posts: 1742




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« Reply #32 on: July 24, 2013, 02:46:15 PM »

Arno., Wanted to share some results with you and my 15m coax fed quarter wave vertical with two sloped quarter wave radials.

It was made of 14 gauge copper wire insulated color black really low visibility.

I used an so-239 and soldered the vertical wire directly into the center pin of the connector and on the tip attached a dogbone insulator.

I next soldered the two radials to the shield driven part of the so 239. opposite one another and attached a dogbone insulator to each far end tip and attached rope and non conductive anchors that I already had.

I screwed the coax and integral coil wound 15m RF choke into the so 239 and weather proofed the connection.

I hoisted the antenna up

I set the spread of the two radials to an downward angle of 45 degrees and anchored into position using the stakes

The strain relief was the rope that dropped straight down from the tree limb that served as the hoist rope and as a tying line for the coax that followed down and across the ground to the shack.
No strain was on the coax antenna or the radials.

The antenna tuned 1:3 and served as a very effective long range dx antenna from a quiet country cottage in Tenn.

Three equal length quarter wave wires total cost about $15.

have fun

73
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K7RNO
Member

Posts: 279




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« Reply #33 on: August 04, 2013, 02:53:09 PM »

UPDATE:

Today, my virgin ZS6BKW went on air, as an inverted V, approx. 60' high. With the prescribed 40' of window line, followed by 70' of coax. No balun, straight through to the tuner/transceiver.

I can only offer two milestones (for me):

1. On 20 m, I thought something was wrong with it. At full volume, I heard NOTHING. Only when I tuned up and down did they come in, loud and clear. How wonderfully quiet! My grin touched both ears.

2. On 17m I could hear M5LRO from England and SP9MZH from Poland. No chance with my 5W to get to them, but still.

The ATU of my KX3 was able to get the following SWRs:
40m: 1.0
20m: 1.0
17m: 1.0
10m: 1.1

Happy camper!
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73,
aRNO
NAQCC #6870, SKCC #11131
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