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Miscellaneous Information for Bird Technologies RF Test Equipment Compiled by Mike Morris WA6ILQ

If anyone has photos of Bird coaxial resistors, coaxial attenuators, or other non 43-series equipment we'd appreciate it, and we'd be happy to give photo credit.

A brief rundown of Bird model numbers that I've run across (note this is not intended to be a comprehensive product list, just a list of what I've used and seen):

43   General Purpose wattmeter
81B   80 watt dummy load, female N connector, no metering.
694   1 Kw 2-30 MHz oil-filled continuous duty Termaline - uses standard QC connectors - with a flip-up steel protective cover over a meter calibrated to 1000 Watts.
4041   Relative Field Strength Meter.
4275-020   adjustable (-60 dB) signal sampler for 20 MHz to 1 GHz, 1 kw, BNC output. Uses standard QC Connectors for the main RF line.
4304A   Fixed 25-1000 MHz, 5-500 Watts, Portable, see note below.
4305A   Portable, High-Power.
4308   Cellular Specialist, Portable.
4300-400   Conversion Kit for Model 43 Wattmeter to accurately read peak power in AM and SSB.
4314B   PEP, Single element, Portable.
4360 / 4362 "Ham-mate" thruline for HF (1.8-30 MHz, model 4360) and VHF (140-180 MHz, model 4362).
4410A   Multiple ranges with the same (special) slug, ±5% Reading Accuracy, Portable.
4431   A variation on the 43 that adds a variable RF Tap, see the note below.
4520   The 45 Series are rack panel mounted wattmeters.
6734-030   2-35 MHz oil-filled 500 watt continuous duty Termaline with a removable meter calibrated in 3 ranges (25 Watt, 100 Watt, 500 Watt) plus "Off".
8135   A later version of the 81B, 150 Watts, uses the quick-change connectors, DC to 1 GHz at 1.1 max SWR, 1 to 2.5 GHz at 1.2 max, 2.5 to 4 GHz at 1.3 max.

The most popular Bird product is the model 43 "Thruline". The name comes because it is designed such that the RF power has to go through the meter. The model 43 was originally designed for the military, and gained wide acceptance in the LMR industry. It uses a plug in element to select the frequency and power level. Some folks call the plug-in element the "coupler", or "plug", but the word "slug" is the term I've heard used the most. The frequency range is 450 kHz-2700 MHz depending on the slug used. The power handling range is 100 mW-10 KW, again depending on the slug. On one of my repeater site trips I was invited into a UHF Channel 30 TV transmitting building for a tour. They had a Bird Thruline metering section mounted next to the transmitter and connected to a remotely mounted line section in the 6-and-3/8 inch(!) Heliax™ feedline. The line section 75 feet away was reading the reverse power... with a 1.5 KW slug.

If you are having an issue with a mis-reading Model 43 please remember that it is basically a 30 µa meter connected to a metering slug encased in a coaxial line section. The meter can be tested easily with a 1.5 volt battery and a 100 K resistor in series to the meter. It should read half scale (15 µa).

The "Termaline" models are dummy loads with a wattmeter built into the housing.

The 4314 has an internal peak-reading option. It is made up of a small circuit board that mounts on the back of the microammeter itself, an on-off switch, two 9v batteries (in series for 18vDC) and a switch that is labeled "CW" or "Peak". There is an external power jack on the left side (18vDC). If you want to modify your own meter you can buy an add-on kit from NM3E. Note that most laptop power bricks are about 18 volts...

The Bird 4430 and 4431 series are 43 variants that adds a built-in variable signal sampler unit connected to a BNC connector (on the right side of the meter) for monitoring the transmitter output on a spectrum analyzer, frequency counter, oscilloscope, etc. It uses standard Bird 43 family elements. The coupling of the sampler port can be varied (with the power on) from approximately -15 dB to -70 dB. The adjustment is just above the slug socket and is uncalibrated, the obvious assumption is that you start with minimal coupling and dial it up until you have enough to satisfy the external equipment. The sampler is limited to 5kw on frequencies from 2 to 30 MHz, and to 1 kw on signals from 30 MHz to 1 GHz.

A Bird 43/45 Series Slug Reference Table

STANDARD ELEMENT PART NUMBERS VERSUS FREQUENCY BANDS (MHz)
Power Range	2 - 30	25 - 60	50 - 125	100 - 250	200 - 500	400 - 1000
5 Watts	-	5A	5B	5C	5D	5E
10 Watts	-	10A	10B	10C	10D	10E
25 Watts	-	25A	25B	25C	25D	25E
50 Watts	50H	50A	50B	50C	50D	50E
100 Watts	100H	100A	100B	100C	100D	100E
250 Watts	250H	250A	250B	250C	250D	250E
500 Watts	500H	500A	500B	500C	500D	500E
1000 Watts	1000H	1000A	1000B	1000C	1000D	1000E
2500 Watts	2500H	-	-	-	-	-
5000 Watts	5000H	-	-	-	-	-

Special ordered slugs I've seen:

250mw at 50-150 MHz
"2.5M" range 2.5 watts at 2200-2300 MHz.
1 watt at 2300-2400 MHz.
1 watt at 2400-2500 MHz.

Others have seen:

"E" range slugs have been seen at 1.5 KW, 5 KW and 10 KW.
"J" range slugs have been seen at 950-1260 MHz.
"K" range slugs have been seen at 1.1 to 1.8 GHz
"L" range slugs have been seen at 1.7 to 2.2 GHz.
"L1" range slugs have been seen for 1.7 to 2.0 GHz.
"L2" range slugs have been seen for 2.0 to 2.2 GHz.

Some strange part numbbers:
430-2   100 mw 72-76 MHz.
430-5   100 mw 108-112 MHz.
430-6   100 mw 105-120MHz.
430-263   100 mw 800-1000 MHz.
430-265   500 mw 800-1000 MHz.
800-2   2.5 watt 800-950 MHz.
801-2   2.5 watt 800-1000 MHz.
800-1   1 watt 800-950 MHz.
801-1   1 watt 800-1000 MHz.

The author can be contacted at: his-callsign // at // repeater-builder // dot // com.

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This page initially created 04-Jul-2018.

This web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.