FW: Re: [TowerTalk] one way coupler

[Tom McDermott]

Sure, it's called a 'circulator' - a 3-port device. If you terminate one of
the ports with a resistive load, it's usually called an 'isolator'. The
reflected power is dumped into the dummy load, so the transmitter sees a 1:1
SWR even if the load impedance is mismatched. They are used a lot at VHF and
up. The broadband ones at VHF and up use magnetic films and a strong magnet.
It should be possible to build one for HF over a narrow frequency range
using phasing lines, but it may prove more difficult to make it broadband at
HF.

Typically, phased antennas will have significant mutual impedance, so power
will couple between the elements. It may be easier to combine the two
amplifier outputs, and then figure out how to match the summed output to the
individual elements.  Forest Gehrke, K2BT wrote the definitive work on
feeding multi-element vetical arrays in Ham Radio Magazine: "Vertical Phased
Arrays: Part 1" through Part-6, May, June, July, Oct, Dec 1983, And May
1984. Purchasing the Ham Radio CDROM set would be worth it for that one
series alone.

   -- Tom, N5EG





> I tried running two smaller (HF1250) amps each feeding one element of
> a phased vertical. One amp receives a lot of reflected power from the 
> other element. I would like to know if there is a circuit to stop 
> reflected power but allow the forward power ?
>
> 73 Steve VE3TU