Category: Amateur Radio

A response to VK3HZ’s comment on amateur licence trends

In a recent posting on VKLOGGER, I posted the graph below of licence trends to Jun 2013.

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VK3HZ commented at Re: Amateur population trends – 2013:

I wonder who it really was who first said “Lies, damned lies and statistics”?

I’m surprised any conclusions can be reached based on the data presented:
– the last point on the graph totally influences the outcome. Take that point away and there’s quite a different (rising) trend line.
– Is this final point influenced by some other effects (e.g. changes or delays in license processing …)?
– why should a second-order polonomial be used to model number of licenses vs. time? Why does it have to have a turning point?
– the vertical axis is greatly expanded, over-emphasising visually any noise on the data
– if the same analysis had been done after the 2007 data had been released, the trend would be even more disastrous. However, reality was much different.

So, I don’t (yet) believe the sky is falling.

I will respond here as I now refrain from posting on VKLOGGER. Continue reading A response to VK3HZ’s comment on amateur licence trends

Last update: 1st November, 2014, 7:15 PM

Australian amateur population trends 1998 – 2014

This is a 2014 update of an article written originally in October 2005, earlier editions published on VK1OD.net which is now offline.

Over recent years to 2002, the number of issued amateur licences was declining, the trend was about 2.8% pa decline over the five years to 2002.

This has concerned some people, who took the view that the decline was a harbinger of the impending demise of Amateur Radio. Continue reading Australian amateur population trends 1998 – 2014

Last update: 6th October, 2015, 10:58 AM

Exploring VK2XSO’s transmission line example

VK2XSO posted a sweep of “Return Loss (SWR) (the lower plot) from 500 to 2500MHz of a 50Ω load through ~5m of RG59” apparently to demonstrate his knowledge of transmission line basics. As he says “here are also many other things we can deduce from looking at these two lines.”

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For students of transmission lines, some deductions… Continue reading Exploring VK2XSO’s transmission line example

Last update: 31st October, 2014, 6:53 AM

Feed line length affect on VSWR

This article explores the way in which VSWR varies along a feed line.

Actual VSWR

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The graph above shows R and X, and VSWR along a feed line with a 100+j0Ω load at 3.6MHz. The feed line is Belden 8262 50Ω coax, manufacturing tolerances are taken to be zero, and the displacement is relative to the feed point, ie -ve distance is distance before the feed point, the feed point then is at the right hand side of the graph.
Continue reading Feed line length affect on VSWR

Last update: 25th December, 2014, 6:44 AM

Why the preference for Guanella 1:1 current baluns for HF wire antennas

I am often asked why I recommend a Guanella 1:1 balun with high choking impedance for most HF wire antennas over voltage baluns and 4:1 current baluns. This article explores the topic using SPICE models for a voltage balun, 1:1 current balun, and 4:1 current balun. Continue reading Why the preference for Guanella 1:1 current baluns for HF wire antennas

Last update: 6th February, 2016, 7:15 AM

Adjusting KISS TNC AFSK tx level using an isochronous test packet

This post explains a technique to drive a KISS TNC with a specially constructed packet that contains an ISOCHRONOUS test packet, a packet that will produce equal high and low tone alternation in the transmitted AFSK signal.

F0000TEK

Above is the waveform recovered from a receiver without de-emphasis (a Motorola R2009D communications analyser in this case).
Continue reading Adjusting KISS TNC AFSK tx level using an isochronous test packet

Last update: 9th August, 2019, 6:33 AM