Invaluable Bird 43 Wattmeter
The Bird 43 Wattmeter is a field-proven portable, insertion-type instrument designed to measure both forward and reflected RF power in transmission lines.
Manufactured by the Bird Electronic Corporation, originally designed many years ago, this particular instrument is still highly regarded and in use today.
A couple of reasons for this are that the Bird 43 has a full-scale accuracy of ±5%, and the wide range of plug in elements, often called slugs, covers an extensive range of frequencies and power levels making it suitable for a huge range of applications.
The all metal casing of the meter has been designed so an additional element may be stored on each sides of the casing. The elements are quickly changed by a simple latch mechanism on the front panel. Elements are calibrated at the point of manufacture, as such they are quite expensive to purchase.
I have three elements for use with my Bird 43 wattmeter, a 25Watt 100-250MHz, a 50Watt 2-30MHz and a 500Watt 2-30MHz, the three of which cover pretty much all my needs.
The Bird 43 is able to measure the forward RF power in the feedline, and also by a simple 180° twist of the element whilst in-situ, the reflected power can be measured.
Download an instruction manual here or visit the Downloads page.
To see what makes up a typical Bird element, have a look at this page.
To compliment the Bird 43, and also to allow P.E.P measurements to be more accurately made, I purchased and installed a Watts Electronics PEP Kit.
This kit simply slows the meter deflection down enough that the peaks of an SSB signal can be measured easily.
Installation of the kit is straightforward, simply remove the bird 43 rear cover, remove the connections on the rear of the meter movement and place the kit’s PCB on the rear of the meter using the terminal nuts.
Calibration is just as easy and although the kit’s are set fairly close at production, it’s simply a matter of making fine adjustments using the multi-turn potentiometers located on the PCB.
Another function of the PEP kit is that the unit also includes a x2 and x5 measurement option. As their name implies, this allows either double, or 5 times, the power of the element to be measured.
Bird Electronics FAQ regarding subjecting the elements to more than their rated power states that up to a minimum of 3x the rated power, no damage will occur – above that, it’s your own risk.
The kit runs from a 9v battery with a very low current draw.