Bird Model 43 RF Directional Thruline Wattmeter Review by ZS1JHG

Page | 1 Bird Model 43 RF Directional Thruline Wattmeter Review by ZS1JHG I have given the full title of the Bird 43 as it correctly describes the test instrument. So if you only need a wattmeter / swr indicator read no further. Here the Diawa CN-801hp cross needle models are my choice. The Bird is a very well built test instrument with its very accurate Thruline© directional coupler. For HF only one element is needed if you only use up to 500 Watts (100H). A very simple mod described in QST adds a switch and two variable resistors to give you 200W and 500W or 100W in the centre off position. For a 500H element this will give 1000W or 2500W for the big guns. The case of the Bird 43 is made of aluminium and has provision for two spare elements or better a shorting slug and one element so if you dislike making holes in you Bird 43 you can mount the switch for variable power mod in one of these spaces. The readings on the Bird 43 are taken in the forward power and then by rotating the slug in the reflected power position. SWR

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A Bird model 43 wattmeter reviewed by ZS1JHG

Transcript of Bird Model 43 RF Directional Thruline Wattmeter Review by ZS1JHG

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Bird Model 43 RF Directional Thruline Wattmeter Review by ZS1JHG

I have given the full title of the Bird 43 as it correctly describes the test instrument.

So if you only need a wattmeter / swr indicator read no further. Here the Diawa CN-801hp cross needle models are my choice.

The Bird is a very well built test instrument with its very accurate Thruline© directional coupler.For HF only one element is needed if you only use up to 500 Watts (100H). A very simple mod described in QST adds a switch and two variable resistors to give you 200W and 500W or 100W in the centre off position. For a 500H element this will give 1000W or 2500W for the big guns.The case of the Bird 43 is made of aluminium and has provision for two spare elements or better a shorting slug and one element so if you dislike making holes in you Bird 43 you can mount the switch for variable power mod in one of these spaces.The readings on the Bird 43 are taken in the forward power and then by rotating the slug in the reflected power position. SWR cannot be read directly due to the coupling circuits construction.A set of VSWR conversion charts are supplied in the manual.I tested the Bird 43 with its 100H element up to 100W against a Rohde & Schwarz Wattmeter and the readings agreed at low mid and high scale agreed within 1W.For the VHF readings a 50C element was used and this was found to be within specified accuracy range or better. In comparison two commercial Wattmeter/SWR indicators were more than 10% out at full scale.So if you are looking for a test instrument that can measure accurately up

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to UHF then the Bird 43 is a necessary investment.The elements and Bird 43 can be purchased second hand from specialist dealers in the USA.In my case I mostly use three of my five elementsFor HF the 100H for VHF the 50C and 5c .I also have a 50D (200 to 500 MHz) and a 400 -2 2.5W at 400 to 850 MHz.Another quality wattmeter that can be looked at is the Coaxial Dynamics 83000 -A and the elements are compatible.

Photo of my homebrew version to show power switch range mod.