[ARC5] ARC-5 antenna match

[Neil]

>From Brian, VK2GCE
> There is a much simpler and totally reversible mod. Temporarily remove the 
> top cover. Lift the grounded end of the Antenna Coupler (the rotatable 
> coil in the centre of the PA tank). Wind a few turns of insulated wire 
> around the bottom of the PA tank coil. Connect this new coil between the 
> lifted end of the Antenna Coupler and the chassis. Try 3 or 4 turns to 
> start with. It should come out very close to 50 Ohm. The present output 
> impedance is somewhere around 12 to 15 Ohm. The Antenna Coupler coil has 4 
> turns, as I recall. Double the turns will give you 4 times the impedance.

Well yes, that may provide a very good match, although I think you're
overstating its simplicity. It doesn't seem as simple as connecting an
antenna coupler back to front, and I'm sorry to say it didn't answer the
question I posed.

> While theoretically it may appear that an antenna coupling device is 
> totally passive and possibly reversible, there is a problem with reversing 
> it. The input capacitor is designed for a low Voltage while the output is 
> designed for both high Voltage and high current. If you reverse the 
> device, you may exceed the flashover Voltage on what was the input 
> (transmitter) loading capacitor.

The design voltages are based on the impedances seen at each connector.
If a 50 ohm antenna is connected to the (50 ohm) transmitter socket, and
a high reactance ARC-5 transmitter is connected to the antenna socket,
we still have the same order of impedances at each socket, so why won't
the voltage ratings be appropriate?
There may be high voltages across components while the operator is
adjusting for a match, but that's exactly what happens in a normal 
situation.


> I prefer not to use the words 'antenna tuner' or similar. The only way to 
> tune an antenna is with a pair of sidecutters. The device you are 
> discussing is either an antenna matching or an antenna coupling device.

I have to concede that point.

73 de Neil ZL1ANM