Loss of Wireman 553 windowed ladder line at MF/HF – does it matter #2

Loss of Wireman 553 windowed ladder line at MF/HF discussed the matched line loss of a windowed ladder line with 19 strand CCS conductors.

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Above, the loss curves from the article

You might look at this and ask “does it matter”.

A recent thread on QRZ (Any special consideration for long run of twin-lead?) gives an interesting example.

The poster is considering 300′ of ladder line to a 260′ dipole to use it on 160-40m.

G3TXQ reports he calculated using EZNEC the feed point impedance of the dipole to be around 7670-j760Ω at 3.6MHz. This is a case of a long feed line with high standing waves and warrants evaluation of the losses.

Taking the Matched Line Loss (MLL) of Wireman 553 to be 0.0075dB/m from the graph above, and assuming the loss is entirely conductor loss at this frequency, the loss can be calculated using ATLLC.

Screenshot - 31_01_2015 , 06_50_24

Although the MLL for the 91.44m (300′) is only 0.686dB, the effect of the mismatch is to deliver a loss of 4.1dB, or a transmission line efficiency of just 38%.

Screenshot - 31_01_2015 , 06_55_11

By contrast, the above calculates loss in nominal 600Ω 2mm copper conductors spaced 150mm, just 0.63dB, some 3dB better or more than twice the efficiency.


  • Loss in open wire line is not necessarily insignificant, and proper evaluation is needed to understand its significance.