Below is a simple circuit to interface your Bird inline section to the WN-1. Peak and average
power will be displayed on the Wavenode software. There are two schematics, they are identical
except the supply voltage being +5V or +13 Volt. The +5V is easier, since your WN-1 can supply
it through the cable. However, it will display power only to 1000 watts or less. The +13 Volt will
display power up to 8 Kilowatt, and can come from your station supply. The circuit allows for the
WN-1 AND your Bird meter to be operational at the same time. Build the circuit that best satisfies
your power requirement.
Instructions:
- build the circuit and connect to an unused WN-1 input. The opamp should be just a few millivolts output when no RF
is present.
- If using a slug for < 300 watts, set the configuration page sensor for HF-1. If using a slug > 300 watts, use the 8KW
sensor selection on the configuration page.
- Key your transmitter at a KNOWN power (use your Wavenode sensor), and adjust R5 until the software meter shows
the same power. You should use a power close to mid-scale for that slug (i.e. if using a 250 watt slug, set your
transmitter to roughly 100 watts).
Plug the Bird meter cable into your Bird meter and set R8 until it indicates the same power.
- Need help or have questions? Send us an email, we’ll get you started.
HOW IT WORKS:
The Opamp U1 is a rail-to-rail input/ouput opamp connected as a non-inverting amplifier. The output current from the
Bird coupler goes through R1 to generate a voltage on pin 3 of the opamp. The output of the opamp provides the proper
voltage to the WN-1 input that is proportional to RF voltage on the coax. The calibration gain for the WN-1 is R5, and R3
sets the proper current for the Bird meter movement (typically 30 microamp full scale). C95, 96 and 97 keep RF out of the
amplifer, but still provide enough bandwidth to capture peak RF power on the WN-1 display.
