Wednesday, 31 August 2011

10m Slim Jim antenna

For dimensions see PDF
I can't take much credit for this. The original 2m Slim Jim was designed by Fred Judd G2BCX, who lived in Norfolk before he became SK some years ago.

This 10m one, made from 450 Ohm slotted ribbon cable from Moonraker and secured on an 8m fishing pole, was inspired by Jim Bacon G3YLA (also a fellow Norfolk ham) who brought one along to our annual “Radio by the Seaside” event.

It worked so well (beating a Rybakov vertical by about 6 S points) that I thought it needed more attention.

The result is attached - it took a lot of fiddling to optimise the length, cut out and feedpoint, but now you don't need to!

7 comments:

  1. This comment has been removed by the author.

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  2. Not sure yet - I would imagine they will be very similar. Hope to do a back-to-back test this week (weather permitting).

    Also need some signals to hear!

    Steve G0KYA

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  3. I want to use this design on 6M any dimension hints or links to something already done..tnx gene wd5fdl

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  4. You could take the dimensions of this one and scale for 51 MHz. That is, if this was designed for 28.5 MHz just multiply everything by 0.559. It will be in the ballpark.

    Steve G0KYA

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  5. I've been thinking of making a 10 m slim jim for some time. Thanks for the construction guide. The dimensions I was planning to use were slightly different to the one here. I'll give it a go ... 5W into a slim Jim. Chris. G4KDX

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  6. Hi. any chance please someone could give me the adjusted correct figures to resize this antenna for 27.5 instead of 28.5mhz? it would be greatly appreciated as I've had the new 450ohm cable hear waiting for some time for me to get on with it. thanks, peter

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  7. Pete Thomas, OH2EUU wrote to me to say; Dear Steve, just to let you know how much I appreciate your 10m Slim JIM instructions. In the end I had to add 17cm in total length and found the best feedpoint to be at (centre) 24cm and (sheath) 25.5cm rather than your 13cm. This achieved a centre resonance of 28.500 MHz with an SWR 1:1.28.

    So his total length was 7.48m. To make one for 27.5MHz, basically multiply all the figures by 28.5/27.5=1.036

    So length 7.75m, cut out at 2.393m and feed point at about 25.9cm. Should be ballpark figures for 27.5MHz.

    Steve G0KYA

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