Among forum experts, there are ready recommendations for the ideal ferrite material (or mix) for a balun, often without knowing any detail of the application.
The ‘magic’ mixes include K. Perhaps they are devotees of Sevick.
Over some years I have searched for manufacturer’s data on K mix, and found only two references:
- Amidon who give a very brief table summarising characteristics, inadequate for RF inductor design; and
- Ferronics who give characteristic curves, albeit in less common format.
Problem is that Ferronics µi is 125 against Amidon’s 290… so their K materials are different.
One has hoped that an interested competent person might have made measurements of some samples from Amidon to give full characteristic curves, it isn’t that hard. Continue reading Ferrite K mix
I tested a couple of LM386 audio power amplifier modules.
The larger one was a kit using the DIP package, the smaller came assembled and used a SO package. Both cost less than $2 each posted on eBay.
They both deliver close to 3Vpk into an 8Ω load at 1kHz when powered from 12.0V. That is close to 0.5W out, but the SO chip cannot withstand the associated dissipation of 0.5W continuous output.
Both handle broadcast program quite happily at 0.5W peak, the chip temperature rise is 15° and 25° respectively.
I wrote in the fraud of energy efficient lighting – e-ballasts of frustration with green measures forced on us, measures that have replaced tried and true reliable lighting solutions with high tech low reliability solutions in a false promise of net energy saving.
Typically, the cost of repair and replacement of this unreliable technology is much greater than their direct energy saving, indeed much greater than their energy consumption of the life of the equipment.
Above is a ballast removed from a light this morning after 4 years during which it was hardly ever used… perhaps 10 hours at most… so the original capital cost of $80 for luminaire and fitting for 10 hours service gives an average cost of $8/hr for capital and about $0.01/hr for energy. Continue reading Another Osram e-ballast bites the dust
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.
Above, 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
I mentioned in Solder cream has a use-by date that a current project is another QRP2000 synthesiser.
Above, the topside of the synthesiser board. The optional output transformer can be seen at lower left. Continue reading QRP2000 synthesiser build
A current project is another QRP2000 synthesiser.
It has about 15 surface mount parts on the board underside, and it was tempting to use solder paste / cream and hot air to solder the parts on… less risk of flicking them on the floor and the self align due to surface tension in the molten solder. Continue reading Solder cream has a use-by date
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
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.
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
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
Much is written about the virtues of some types of coax connectors over others.
Continue reading Coax connectors and accurate / repeatable measurements