Vacuum capacitors – construction implications for Q

Vacuum capacitors are used for high end applications that require high voltage withstand and low loss.

Though they are called capacitors, and simple analyses treat them as a capacitance with some small equivalent series resistance (ESR), there is more to it.

Above is a view (courtesy of N4MQ) looking into one side of a vacuum capacitor. It consists of an outer cup, and a series of 5 inner cups progressively smaller in diameter. The other side of the capacitor has a similar structure but the cups site in the middle of the spaces between cups in the first side.
Continue reading Vacuum capacitors – construction implications for Q

Baofeng charger DC-DC converter

One of the insane things about some Baofeng hand held radios is that the charger cradle requires 10V DC, and malfunctions on car battery voltage.

The cigarette light adapter that came with a Baofeng GT-3TP was simply a pass through device and the charger did not work properly using the adapter plugged into a car.

The charger cradle electronics should include electronics to charge properly from a car, preferably from 10-16V. The implementation is a half-baked idea.

To solve the problem I have made an adapter cable using a small buck DC-DC converter off eBay (~$2), the converter is adjusted to 10V out.

I have used an Anderson Power Pole connector to suit my power distribution, you could use a cigarette lighter plug or some other plug to suit your needs. The output connector is a 2.5mm DC plug. Continue reading Baofeng charger DC-DC converter

A comparo of two bare light dimmer modules

Two bare dimmer modules sold on eBay with identical specification and similar price are compared.

Both claim to have zero hysteresis. Zero hints a lie!

Hysteresis is caused in simple phase control dimmer circuits at low settings because in each half cycle the trigger capacitor starts at a different voltage depending on whether the diac fired on the previous half cycle.

A serious issue with this snap-on effect is that if power is turned off at low power setting and re-applied, the controller may not switch on.

Above is type 1, a very triac basic phase control circuit. The red capacitor and resistor to its left are snubber components, the yellow capacitor, 4.7kΩ resistor to its left and the 500k pot are the phase delay circuit, the diac is just visible above the red capacitor. Continue reading A comparo of two bare light dimmer modules

Do we sound like a bunch of chooks or what?

Though ham radio enthusiasts often rail against CBers, with the eflux of time, it is more difficult to distinguish between the two.

From Innovantennas website, a caption to a pic of one of their antennas explains:

The 10-54MHz LDPA directional antenna at K4ANP. Sadly, Len caught one of the elements and vent it during installation but SWR 1:1.4 thorughout.

The emphasis of the SWR value is mine. They, as antenna ‘professionals’, do not seem to understand the concept of SWR, and that by definition it is a ratio of greater than unity, ie the big number goes first. In fact if they just rationalised the ratio and expressed it as SWR=1.4 it would be briefer, clearer and more importantly, actually correct.

Little wonder hams not really understand what they are buying acquire bad learning from those who might provide accurate information.

End Fed Half Wave matching transformer – 80-20m

A prototype broadband transformer for a End Fed Half Wave operated at fundamental and first, second, and third harmonic is presented.

The transformer comprises a 32t of 0.65mm enameled copper winding on a FT240-43 ferrite core, tapped at 4t to be used as an autotransformer to step down a load impedance of around 3300Ω to around 50Ω. The winding layout is unconventional, most articles describing a similar transformer seem to have their root in a single design.
Continue reading End Fed Half Wave matching transformer – 80-20m