Directional Couplers with RF output and DC output for 28MHz to 435MHz
pa0nhc.  Ver. 2003 10 03. / .20110306 /  20130509 / 20150217 / 20170929 / 20171231 update 20180201
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Coupler with DC-output in TEKO 371 box.

Tests (in 1999) on finished prototypes like above showed nearly NO reflected power at 25W transmitter output, when terminated with a good dummy load
. It clearly showed differences in return loss between different types of low power 50/51 ohms terminating resistors, and higher power dummy loads. Good terminators showed up to 30 dB return loss.

        Possible uses :
The RF-output directional couplers + a portophone or signal generator + a step attenuator + a common receiver with the S-meter as indicator, can be used to measure with very low RF power the return loss of  :
- small receiver filters
- large cavity filers
- large helix filters    
    - low pass
    - high pass
    - band pass.
- antenna systems

They also can be used to safely inject RF signals into a live operating
repeater, and measure
- its real practical sensitivity
- the correct action of the CTCSS system
- the squelch action
- large signal handling (blocking). 
- the
duplex filter using a portophone at low power and step attenuators 
    - frequency characteristic
    - up to -120dBc suppression at the notch frequencies
See PI3RTD and pa0nhc cavity filter .

The DC output couplers + the RF power from a transmitter can be used to measure :
- RF transmitter output (1W - 800 W)
- returned power from loads such as antenna's (1W - 800 W)
- to high VSWR to shutdown a power amplifier or driver stage