AIM 865A produces inconsistent / incorrect results

 

AIMuhfAt Measuring balun common mode impedance – #2 I mentioned a glitch on the AIMuhf scan that appears to be a defect of the instrument / client software and that it undermines confidence in the system.

The article documents a test of a known load to attempt to prove the measurement system good. Continue reading AIM 865A produces inconsistent / incorrect results

Exploitation of NEC’s GM card #2

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

Measuring balun common mode impedance – #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

NEC – current or voltage source

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

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.

Clip 094

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

Measuring balun common mode impedance – #1

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.

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 Rigexpert AA-600, and its PC client Antscope. Continue reading Measuring balun common mode impedance – #1

Diamond X50N measurements – AIMuhf and AA-600

At Diamond X-50N #2 at VK2OMD I reported some details of a new antenna at VK2OMD, including some baseline measurements using a Rigexpert AA-600.

This article expands that information with some measurements made using AIMuhf, and gives some contrasts between the two tools.

The AA-600 measurements were made 26/11/2014, and AIMuhf a couple of months later on 29/01/2015. The system measured should have been identical, the feed line is 9.83m of LDF4-50A with N-type connectors at both ends. Continue reading Diamond X50N measurements – AIMuhf and AA-600

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