NEC-2 and NEC-4 support a GM card to translate and rotate a structure in three dimensions.
At Exploitation of NEC’s GM card I gave a small example of using the GM card.
Antennas often have some degree of symmetry and it is the key to simplification through use of the GM card.
This article gives a simple but practical example of exploitation of this often overlooked facility to a Lazy H antenna.
Continue reading Exploitation of NEC’s GM card #2
At Baluns – show me the numbers I raised the value of quantitative measurement of the complex common mode impedance of current baluns as a figure of merit for certain antenna applications.
At Measuring balun common mode impedance – #1 I showed a technique that can be used with a common antenna analyser that properly measures impedance (including the sign of reactance).
This article demonstrates a simple method of measuring the complex common mode impedance of a Guanella 1:1 current balun using a one port VNA, though of course the technique is equally applicable to a two port VNA.
This article shows a simple method of measuring the complex common mode impedance of a Guanella 1:1 current balun using a modern Antenna Analyser.
The instrument used for this demonstration is a AIMuhf with AIM 865A PC client. This is back level software as I have demonstrated AIM 882 produces internally inconsistent results. Continue reading Measuring balun common mode impedance – #2
APRS traffic study – VK2OMD-3 11/10/2014 reported a study of APRS traffic.
This article is an update after configuration changes at VK2RHR-1 to make it a ‘fill-in digi’, it repeats packets addressed to WIDE1 only.
The study of APRS traffic was conducted by analysing the log of VK2OMD-3, a VHF APRS ‘fill-in’ digi and iGate.
The capture period was during from 0700-1700 local time on Sunday 08/02/2015. Continue reading APRS traffic study – VK2OMD-3 08/02/2015
A forum expert recently opined:
Unless there’s a compelling reason NOT to, always use CURRENT sources instead of voltage sources.
Like most online advice, the writer did not give reasons for is advice, and given the strength of it, an explanation is warranted.
Of course, many people giving compelling advice online don’t actually understand the matter and cannot give a rational explanation.
Continue reading NEC – current or voltage source