[Amps] how to make an HF dual directional coupler?

[Dan Sawyer]

All,

I have purchased a vector volt meter and apparently need a "dual 
directional coupler" to use the instrument. Where is there a good write 
up on these? I would like one to use on an HF antenna.

To be honest the whole concept of 'reflected power' has always been a 
bit of a mystery. I am very familular with transmission lines and the 
effects of non uniform or discontinuous terminations. However these 
effects are vi sable in the transmit signal. If this effect were 
observed by use of a dual directional coupler and a vector voltmeter 
could these effects be measured?

Anyway, is there a reference on how to make a dual directional coupler 
for HF?

Thanks,
Dan