[ARC5] ARC-5 antenna match

[Brian Clarke]

Hello Neil,

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.

Voila! No need for an external antenna coupler, reversed or straight.

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.

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.

73 de Brian, VK2GCE.

On Sunday, July 28, 2013 5:49 PM, Neil said:


> An antenna tuner can match a 50 ohm transmitter to a wide range
> of antenna impedances.
> I got to wondering whether one could be connected backwards to
> match the unknown output impedance of an ARC-5 transmitter to
> a 50 ohm antenna.
>
> My theory is that the configuration of the tuner is not symmetrical
> and is designed to favour the orientation where the unknown Z is
> connected to the Antenna terminal.
>
> Would it have a wide enough range to do that? On the built-in SWR
> meter, forward power would indicate as reflected power, and vice
> versa but I can’t think of any adverse effect.
>
> 73 de Neil ZL1ANM