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Author Topic: Homebrew L-match antenna coupler for end-feds (video)  (Read 4398 times)
VK3YE
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« on: May 16, 2016, 06:45:19 AM »

This topic always comes up and I'm always getting questions, so here's a video on another L-match antenna coupler.

Operational between 7 and 28 MHz it's small and handles up to 5w.

Video includes circuit and on-air demonstration.

https://www.youtube.com/watch?v=JwVuvu-C30c
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Peter VK3YE

One antenna idea each day. Visit http://dailyantenna.blogspot.com
Author of top selling $US 5 amateur radio ebooks on antennas, QRP, getting started and more. See http://home.alphalink.com.au/~parkerp/vk3yebooks.htm
G3RZP
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« Reply #1 on: May 16, 2016, 03:33:22 PM »

That configuration of L match - like all L matches - has a definite limitation on what antenna lengths  and impedances can be used.
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VE3LYX
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« Reply #2 on: May 16, 2016, 08:11:10 PM »

Perhaps, but an L match does work well with my end fed. I don't know how everyone else runs their shack but here results are all that count. I built a simplified unit for coupling my end fed to my No 19 WS set. The original No 19 antenna tuner is designed for a too short whip and doesn't fit the bill. The homebrew L unit seemed to work exceptionally well and so I use it and nothing else. It may look a little crude and may not pass the algebra test but the darn thing works. A No 19 WS is not a high powered rig by any stretch of the imagination but with this tuner and the endfed wire it is now my AM rig of choice.  So that is why I would defend the first posters decision. If it works the rest is just smoke. Results are all that counts.
donVe3LYX
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VK4FFAB
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« Reply #3 on: May 17, 2016, 12:29:39 AM »

That configuration of L match - like all L matches - has a definite limitation on what antenna lengths  and impedances can be used.

this might be true, but is it relevant? I don't think so. What is important is does it tune to desired bands in a very typical configuration that most portable operators use, namely a half wave length of wire on the lowest band of operation. If it does that, then it is fit for purpose. It is irrelevant that it cannot tune a coke can or a drain pipe on the empire state building.
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K8AC
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« Reply #4 on: May 17, 2016, 11:32:12 AM »

A little more than half a century ago, before anyone knew that such things couldn't work, all my teenage friends and I used random length wires fed with L networks.  If we ran into a situation where a match couldn't be obtained, we just added or subtracted a couple of feet from the antenna.  There were no SWR meters to indicate a match - we used a homebrew field strength meter and tuned for maximum meter deflection.  There were a couple of manufacturers making low power L network tuners that featured a switch for coil taps and a variable capacitor.  They used an NE2 bulb loosely coupled to the output as an indicator of output power. 

73, K8AC
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VK3YE
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« Reply #5 on: May 19, 2016, 04:20:15 AM »

They used an NE2 bulb loosely coupled to the output as an indicator of output power. 

Or these days use an LED and a ferrite toroid.

https://www.youtube.com/watch?v=NjHyXi1SrZs
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Peter VK3YE

One antenna idea each day. Visit http://dailyantenna.blogspot.com
Author of top selling $US 5 amateur radio ebooks on antennas, QRP, getting started and more. See http://home.alphalink.com.au/~parkerp/vk3yebooks.htm
JS6TMW
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« Reply #6 on: May 19, 2016, 05:55:45 PM »

They used an NE2 bulb loosely coupled to the output as an indicator of output power. 

Or these days use an LED and a ferrite toroid.

https://www.youtube.com/watch?v=NjHyXi1SrZs

I thought that was a great idea but I found with a 41-foot wire the LED lights on some bands but not others. I tried sliding the toroid up the wire but couldn't reach a point where it lit. More turns?

Steve
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