October 2016 – Page 3 – owenduffy.net

iinet – pre-connect experience

The NBN is coming….

Our NBN street cabinet, or Node in FTTN. The pic is not crooked, the cabinet is out of level.

We received advice that NBN access is now available in our street… about 10 months after the street cabinet was installed.

This is the best hope we have had of escaping Telstra’s appalling service that we have endured for 6 years.

Above is a plot of the median download speed of the Telstra 8Mb/s ADSL service.

Above, the distribution for last week show that although HTTP speeds would appear to be capped at 2Mb/s on an 8Mb/s access pipe, the inevitable slide to poorer performance is shown where around 10% of the measurements are below 0.25Mb/s. Continue reading iinet – pre-connect experience

Last update: 3rd October, 2016, 11:51 AM

OCF short vertical dipole for HF

The OCF short vertical dipole for HF has become popular, particularly disguised as a flag pole for low impact installations and encouraged by claims of outstanding performance. The antenna was described in QST and a commercial version was available at time of writing.

The rationale for the design is that it is a short dipole, not requiring radials, and feed point offset downwards by 30% as an optimal value for performance (driven by often unsound assessments of coax loss).

Claims include:

Off-Center Fed Vertical Dipole design means no radials, 90% efficient or better across 80m – 10m

Above is the promising gain plot for one of the commercial implementations, it is only one S point (6dB) behind a quarter wave vertical with 4 buried radials. Continue reading OCF short vertical dipole for HF

Last update: 25th November, 2018, 7:03 AM

Cadweld Plus Control Unit

The CADWELDPLUSCU is the igniter for the Cadweld Plus line of electrically initiated thermite weld capsules. The plug seen on the end of the cable slides over the flat connection strip to the capsule.

The environment around the weld crucible is subject to a sudden ejection of hot gases and smoke, much of which is emitted out of the slot in a Oneshot crucible intended for the connection strip, and this is only a 45g capsule. There is probably less gas emitted towards the connector on reusable moulds as the gap for the connection strip is very narrow.

Despite dressing the plug away from the stream of hot gasses emitted, it can be seen above that the plug has suffered heat damage. Of particular concern is deformation of the parts at the cable clamp rendering it less effective. The plugs come on a new lead set that is relatively expensive.

Since one wants to be able to yank the cord away from the crucible as soon as possible to minimise heat damage, the cord grip needs to be effective.

This article describes two measures taken to protect the plug and ensure the cord grip works. Continue reading Cadweld Plus Control Unit

Last update: 3rd October, 2016, 5:52 PM