EFHW Tuner / LED SWR Bridge

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Buick Mackane
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EFHW Tuner / LED SWR Bridge

Post by Buick Mackane »

One of my other hobbies besides hanging about here is camping, But iv'e never done any portable radio work, I have an original 817 (Non ND) Model with all the accessories, So i decided to homebrew a EFHW Tuner / SWR LED Bridge to use for portable work whilst camping, Idea is you chuck out a halfwave length of wire from a tree or whatever and tune till the LED goes out (Lowest SWR point), This tuner is available in kit form from various online sellers (Around £30)

So i looked up the instructions for the kit online and copied the schematic, Already had most of the parts in the junk box, Had to shell out £6 quid for the parts i needed,

The tuner is working nicely, Tunes from 15m - 40m Still waiting on some resistors for the SWR bridge, Will update when i have the SWR Bridge built

Box is a wrist watch box, Connecting posts from an auld CB power pack, Tuning cap and pointer from a chinese AM kit radio (Have a few of them)

Tuner is good up to 10w but could be beefed up for higher power,


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Re: EFHW Tuner / LED SWR Bridge

Post by Auldgeek »

Good use of old parts Jason. I'll be interested to hear how you get on. Nice one 👍
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I've changed radios so many times, I've forgotten what I have :think:
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Re: EFHW Tuner / LED SWR Bridge

Post by Buick Mackane »

SWR bridge built minus the resistors i'm still waiting on, They better come tomorrow :x

Kit instructions & Schematic for anybody that's interested

https://sites.create-cdn.net/sitefiles/ ... A-ATU2.pdf
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Re: EFHW Tuner / LED SWR Bridge

Post by Buick Mackane »

Well after being busy with other stuff and waiting forever for the resistors to arrive it's finally finished, Takes one watt for the LED to fully illuminate, Although it would probably fully illuminate with half a watt if i lowered the value of the LED ballast resistor, I moved the ground post from the left side to the right, It now gets its ground from the SWR bridge board, Cuts down on wire length.

Whilst tuning up the radio only see's a SWR of around 1.5 according to my analyser.



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Re: EFHW Tuner / LED SWR Bridge

Post by Buick Mackane »

Additional.

If you build this circuit and you can't get it to tune up on 40m trying adjusting the trimmers on the rear of the variable capacitor. And the same applies if it won't tune up on the higher bands, You'll need to balance it out so it covers 40m - 15m,

And if possible use a decent quality variable capacitor, I had to swap mine as the first one i tried turned out to be utter junk, :x
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Re: EFHW Tuner / LED SWR Bridge

Post by DX-Digger »

A Very good simple project.
I have a similar tuner called the ZM-2 it will tune endfed longwires, coax fed antennas and balanced twin feeder fed antennas.
You can buy them ready built or as a kit.
https://steadynet.com/emtech/
Or you could build your own.
https://www.dropbox.com/s/gzsja9dxe9kog ... l.pdf?dl=1

Its a bit more complex but does more ham bands
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Re: EFHW Tuner / LED SWR Bridge

Post by Buick Mackane »

Well i used the tuner on a two day camping trip and it worked like a dream, Very easy to tune, Rather than carry the radio and battery over to the tuner and TX & tune till the LED goes out i just used the 817's built in SWR Meter. Tuned for maximum noise then checked the SWR on the 817 and more often than not it was spot on.

Great little gadget for portable work
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Re: EFHW Tuner / LED SWR Bridge

Post by theEarwigger »

Hi,

Having the transformer as an auto-transformer gets an extra 0.5dB signal. Also use a bigger toroid to avoid saturation.

I moved on from these types of antenna years ago as they only cover 1 band.

73s.
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Re: EFHW Tuner / LED SWR Bridge

Post by Buick Mackane »

theEarwigger wrote: 08 May 2022, 14:27 Hi,

Having the transformer as an auto-transformer gets an extra 0.5dB signal. Also use a bigger toroid to avoid saturation.

I moved on from these types of antenna years ago as they only cover 1 band.

73s.
They cover more than one band via harmonics, If you have a wire length of 66ft then you can work 40m / 20m / 15m / 10m
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