Inexpensive utility rechargeable 9V battery pack for test instruments

There is often a need for a 9V battery for portable test equipment (NNA, Noise Bridge, Low R meter, Power Meter etc). A solution is a 8 cell NiMH pack.

BatteryPack9VAbove, a battery pack made from two Hobbyking 4 low self discharge AA cells. The packs come with JR servo connectors, and the pins are rewired to use the -ve from one pack and +ve from the other pack to one of the JR connectors. The other wires are connected via a 3A Polyswitch for s/c protection. A short JR to 2.1mm DC connector is made from a JR extension cable and 2.1mm connector. Continue reading Inexpensive utility rechargeable 9V battery pack for test instruments

The fraud of energy efficient lighting – e-ballasts

In Australia, conservationists have led a push for replacement of a range of appliances that were in good working condition for more energy efficient appliances. For this reason, some types of appliance can no longer be purchased, or serviced with spares as required.

The humble flourescent light is one of those. Although still one of our most efficient lights, rivalled only by the best of LEDs, the push is on to replace the conventional magnetic ballast flourescent T8 flourescent with T5 lights, and in the interim, T8 lights with electronic ballasts. Continue reading The fraud of energy efficient lighting – e-ballasts

Review of Ceramica ceramic bearing fans

For some years I have used Ceramica muffin fans for low noise and long life. They use a ceramic bearing which is quieter than ball bearings, but longer life than sintered bronze bearings which dry out.

FanImpeller

In the last month, I have replaced three Ceramica fans that have failed, one with less than a year’s service and two with less than one month’s service. Continue reading Review of Ceramica ceramic bearing fans

Fan frustrations

For some years I have used Ceramica muffin fans for low noise and long life. They use ceramic bearing which are quieter than ball bearings, but longer life than sintered bronze bearings which dry out.

That said, I was annoyed to find the fan I have replaced in a one year old computer power supply fail after another three years. The original was a bronze bushed fan which dried up. Continue reading Fan frustrations

Using an attenuator for NoiseLo/NoiseHi in NFM

A common method of making Noise Figure measurements of a receiver is to use a noise generator of known noise power. The output power of the DUT is measured with the generator off (NoiseLo) and on (NoiseHi), a Y factor calculated, and from that Noise Figure is calculated.

Continue reading Using an attenuator for NoiseLo/NoiseHi in NFM