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
I have spent considerable time over the last few weeks trying to salvage something useful and reliable from the wreckage that is AIMuhf and its PC client program AIM. Continue reading AIMuhf – my strategy
AIM 882 produces internally inconsistent results raised some issues with AIM software.
This article documents some further tests. Continue reading AIM 882 produces internally inconsistent results – more tests
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.
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, 0.0075dB/m at 3.6MHz gives 0.075dB loss… that is just 2%, 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
I have written several articles recently on matters relating to Small Transmitting Loops (STL), or “Magnetic Loops” to hams ().
What of the Hertzian alternative, a small dipole. Continue reading Small Transmitting Dipole
At Efficiency and gain of Small Transmitting Loops (STL) I discussed the use of bandwidth measurement of a small transmitting loop (STL) for estimation of efficiency.
Paul Casper (K4HKX) has built a series of STL which he describes on his K4HKX QRZ page. Continue reading Comparison of two small transmitting loops
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
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.
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
Alpha antenna refers to the Radcom review of their microtune magnetic loop.
(Nichols 2014) describes the loop as 12.7×3.2mm aluminium flat section formed into an ellipse with average diameter 0.84m. The pictures show that it is close to circular and I will take it to be a circle of perimeter 2.64m.
The review offers some measurements of VSWR=3 bandwidth at the feed point on various bands, and an estimate of efficiency based on RJELOOP1. Continue reading Radcom review of Alpha Antenna microtune magnetic loop
Hams talk at length about baluns but rarely in quantitative terms.
A quotation from Lord Kelvin is most appropriate: When you can measure what you are speaking about, and express it in numbers, you know something about it. But when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. It may be the beginning of knowledge but you have scarcely in your thoughts advanced to the state of science.
Continue reading Baluns – show me the numbers