T2FD Calculator

I love a good T2FD antenna and have built a good few. There’s a few variations but they all work well and are easy to construct. I’ve been asked a few time about the length and spacing so I made a small Excel sheet to work it all out and provide data for the 3 most popular variations.

Free free to download and use. The sheet is protected to prevent the formulas from getting messed up but if you would like to experiment with alternative formulas then please just contact me for the password. All I require is for my original credit to remain on any derivative works.

M0LMK T2FD Calculator

9 Replies to “T2FD Calculator”

  1. When I click on Frequency, I get a message,
    “Protected Cells cannot be modified”
    What do I do to make that work.
    I’m using OpenOffice.

  2. Hi Mike. I don’t know if it will work in Open Office. I use Excel. If you send me an email via my contact form then I’ll send you an unprotected sheet over to see if that works.

  3. I tried to ask from your comments page but somehow it didn’t send. Could you kindly send me a password for the file?

  4. The contact form should be fixed. Please try sending me a message again or email me direct matt@.co.uk and I’ll send a copy over to you.

  5. Hi Mike, thanks for your work, I’ve often wished for a T2FD calculator.
    Maybe I’m missing something but there’s nothing appearing (other than a row of Xs )under the ‘Feeding’ section; no info about the resistor or the impedance transformer.

  6. This is what it should say:

    Modern: Feed in the centre on the bottom with 50 Ohm coax to a 16:1 BalUn (you can also try a 16:1 UnUn with a 1:1 BalUn after if you can’t find or build a good 16: BalUn).Use a 820 Ohm non inductive resistor rated to at least 1/3 of your total power (I prefer to use a rating of at least 1/2 on the shorter 1/2 wave model) in the centre at the top.

    Traditional: Feed in the centre with 300 Ohm twin feed (any length). Terminate the twin feed in a 4:1 BalUn and run 50 Ohm coax to the radio. Use a 300 Ohm non inductive resistor rated to at least 1/3 of your total power (I prefer to use a rating of at least 1/2 on the shorter 1/2 wave model) in the centre at the top.

    I hope that helps.

    Matt
    M0LMK

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