Author Topic: End Fed Half Wave antenna coupler  (Read 7317 times)

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DragoSapien

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End Fed Half Wave antenna coupler
« on: June 13, 2015, 12:24:57 PM »
Has anybody seen this yet. What do you think. Look interesting.

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=31077

spacecase0

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Re: End Fed Half Wave antenna coupler
« Reply #1 on: June 13, 2015, 01:29:37 PM »
quite innovative and small

I just use a 1/4 wave twin lead feed line with the 1/2 wave antenna connected to one side of the feedline
my solution is easy to make, needs no tuning within the band, just takes up lots of space

AD

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Re: End Fed Half Wave antenna coupler
« Reply #2 on: June 13, 2015, 06:49:19 PM »
Thanks for posting that Drago
The only dumb question is the one that did not get asked!!

Tevin

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Re: End Fed Half Wave antenna coupler
« Reply #3 on: June 14, 2015, 08:30:31 AM »
Wow, that guy has some seriously good engineering skills. He even made an on line calculator to compute the component values. (bow down)

The system will have a lot of inherent loss, but if one must use an end fed antenna, this gizmo will make the best of it.

Very nicely done. Excellent work.

BTPost

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Re: End Fed Half Wave antenna coupler
« Reply #4 on: June 14, 2015, 01:53:43 PM »
Also understand, that an End-feed 1/2 wave will approach Infinite Impedance at it's Resonant Frequency.... and that makes designing an AUTO-Tune Antenna Tuner for that specific situation, as real BEAR.....
Bruce in alaska AL7AQ

Lamewolf

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Re: End Fed Half Wave antenna coupler
« Reply #5 on: October 13, 2015, 09:15:21 AM »
Wow, that guy has some seriously good engineering skills. He even made an on line calculator to compute the component values. (bow down)

The system will have a lot of inherent loss, but if one must use an end fed antenna, this gizmo will make the best of it.

Very nicely done. Excellent work.

WHy does everyone keep saying that an endfed halfwave has a lot of loss ?  Tests have shown that with the proper type of matching equipment, efficiency will be on the order of 97% which is pretty good in my book.  Efficiency of a center fed halfwave is only about 75 - 80 % at best.

spacecase0

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Re: End Fed Half Wave antenna coupler
« Reply #6 on: October 13, 2015, 12:59:10 PM »
if you feed an end feed a half wave with 1/4 wave of ladder line it is quite efficient,

if you feed an end feed a half wave with transformers, you are going to loose lots more because the voltage is the highest at the ends,
and trying to convert your 50 ohm out from your radio to infinity ohms is just not the best job for a transformer to do,
also it leaves you with trying to come up with some sort of a ground as well

Lamewolf

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Re: End Fed Half Wave antenna coupler
« Reply #7 on: October 13, 2015, 01:25:38 PM »
if you feed an end feed a half wave with 1/4 wave of ladder line it is quite efficient,

if you feed an end feed a half wave with transformers, you are going to loose lots more because the voltage is the highest at the ends,
and trying to convert your 50 ohm out from your radio to infinity ohms is just not the best job for a transformer to do,
also it leaves you with trying to come up with some sort of a ground as well

Don't use a transformer which is basically what a quarter wave transmission line is, use a tuned circuit to match it with which can be around 97% efficient.  And thinking about the ground situation with the EFHW antenna, since it is voltage fed with little to no current at the feedpoint, the ground is less important other than a static or lightening ground.  The high current point is out at the middle of the wire !

jnr0104

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Re: End Fed Half Wave antenna coupler
« Reply #8 on: November 01, 2015, 06:21:33 AM »
I didn't make one ,but I use LNR precision end feds, and they work great, have mine all set horizontal and  15-18 ft off the ground. I use 40m SSB the most, this antenna and 200 watts covers Texas well. Also have 80m, 17m,20m,10m . All work very well.

Lamewolf

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Re: End Fed Half Wave antenna coupler
« Reply #9 on: November 02, 2015, 07:13:29 AM »
I didn't make one ,but I use LNR precision end feds, and they work great, have mine all set horizontal and  15-18 ft off the ground. I use 40m SSB the most, this antenna and 200 watts covers Texas well. Also have 80m, 17m,20m,10m . All work very well.

Just remember, an end fed half wave has the same pattern/performance of a center fed dipole that is mounted and the same height and configuration.  Its just more convenient sometimes to feed it from the end and also eliminates losses associated with a long feed line.  I love end fed antennas - they work great !  My 160 meter antenna is basically an end fed sloper, see attached diagram.

kc8aon

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Re: End Fed Half Wave antenna coupler
« Reply #10 on: November 02, 2015, 09:07:12 AM »
LW

How do you use the "Movable Tap" on this antenna?
The only dumb question is the one that did not get asked!!

Lamewolf

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Re: End Fed Half Wave antenna coupler
« Reply #11 on: November 02, 2015, 03:14:52 PM »
LW

How do you use the "Movable Tap" on this antenna?

Ever seen an Outbacker mobile antenna that has a wire lead on it that plugs into various points on coil to change bands/frequencies ?  This one works the same way and the coil came from and old Buddiestick antenna.  It has taps you can move around on the coil to preset the frequency and I have 3 of these on the coil then a wire lead that has a mini banana plug on it that plugs into the taps.  With the full coil and no tap selected it covers the bottom of 160, the first tap gives me the middle of the band and, and the second one gives me the top of the band.  The coil is about 6 feet from my back door and easy to get to and change frequencies.

AD

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Re: End Fed Half Wave antenna coupler
« Reply #12 on: November 02, 2015, 03:29:09 PM »
Perfect.  Thx for the Splain'in
The only dumb question is the one that did not get asked!!

ghrit

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Re: End Fed Half Wave antenna coupler
« Reply #13 on: November 02, 2015, 03:37:20 PM »
Ever seen an Outbacker mobile antenna that has a wire lead on it that plugs into various points on coil to change bands/frequencies ?  This one works the same way and the coil came from and old Buddiestick antenna.  It has taps you can move around on the coil to preset the frequency and I have 3 of these on the coil then a wire lead that has a mini banana plug on it that plugs into the taps.  With the full coil and no tap selected it covers the bottom of 160, the first tap gives me the middle of the band and, and the second one gives me the top of the band.  The coil is about 6 feet from my back door and easy to get to and change frequencies.
I like the scheme.  Is the coil weather proof?
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Lamewolf

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Re: End Fed Half Wave antenna coupler
« Reply #14 on: November 02, 2015, 04:51:09 PM »
I like the scheme.  Is the coil weather proof?

The coil is not waterproof, but it is mounted under my back porch roof to keep it out of the rain.