Quiet solar radio flux interpolations calculator

My Quiet solar radio flux interpolations calculator has been broken recently, a result of changes at NOAA where they withdrew the observation data on which the calculator was based.

The data remains available on an FTP server, but my web server cannot access it for security reasons, and it would be unacceptably slow anyway. Continue reading Quiet solar radio flux interpolations calculator

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

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”, if 10m of this line is used in a G5RV, 0.075dB/m at 3.6MHz gives 0.75dB loss… that is just 16%, so what.

That ‘back of the envelope’ calculation is incorrect, that feed line section operates with standing waves and the loss under standing waves must be evaluated. If we took the feed point impedance of the popular G5RV to be around 10-j340Ω at 3.6MHz, the expected loss in 10m of Wireman 553 with that load based on the above MLL is 3.3dB or 53%. By way of contrast, my own G5RV uses 10m of home made open wire line using 2mm copper wires spaced 50mm and the loss is 0.9dB, 2.4dB less. Continue reading Loss of Wireman 553 windowed ladder line at MF/HF – does it matter

Loss of Wireman 553 windowed ladder line at MF/HF

Over a long time I have voiced concern at the likely performance at MF / low HF of the very popular windowed ladder lines that use CCS conductors.

A very popular form of commercial ladder line is that using #18 wire, comprised of 19 strands of #31 30% IACS conductivity copper clad steel. The copper cladding on such a conductor is about 14µm in thickness.

This article reports and analyses measurements of a length of Wireman 553 windowed ladder line. Continue reading Loss of Wireman 553 windowed ladder line at MF/HF

AIM 882 produces internally inconsistent results

I have had cause to validate the output produced by an AIMuhf measurement using AIM882 (current version, released about three months ago).

The test scenario is a pair of nominal 50+j0Ω loads on a Tee piece, connected to the AIMuhf by about 1m of RG58 coax and swept from 10 to 50MHz.

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It is mental arithmetic that the VSWR should be very close to 2:1, and since the loss of the cable is quite low, VSWR should be almost uniform with frequency. Continue reading AIM 882 produces internally inconsistent results