Motorola® T-1500 Duplexer / Cavity Filter panel

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Duplexer / Cavity Filter panel
Page by Mike Morris WA6ILQ

Photo 1: Rear view -
Note that the left pair of cavities have the cables connected at the rear of the cavities, and the right pair are at the front (which is defined as the end with the mounting panel, and the tuning shaft or knob).

Photo 2: Front view -
This photo is unusual in that the knobs are present, as opposed to 90% of the ones I've seen in the field where they are missing. The absence of the knobs keeps the children from messing up the careful tuning. Also note that the cavities are labeled "transmit" and "receive". Well, ignore that labeling. You want to think in terms of "high frequency side" and "low frequency side" as in some geographical areas the amateur transmitter is on the higher of the two frequencies and other areas the receiver is on the high side... Regardless of which of the frequency pair is receive or transmit, the lower of the two frequencies should connect to a loop cavity, which has the two connectors close to the front of the cavity, and the higher of the two frequencies should connect to a probe cavity, which has the two connectors close to the butt (rear) of the cavity. Also be careful to use only silver plated connectors (especially NOT nickel plated).

Photo 3: One cavity's adjustment shaft -
If anybody has some locknuts, please let me (WA6ILQ) know, as I need five of them.
My email address is (callsign)@arrl.net, also available via QRZ.com

Photo 4: top view (click for full size image)

Photo 5: The high frequency side

Photo 6: The low frequency side

Photo 7: Another top view
The side panels visible in this photo are rare. They allow the duplexer to be offset in a cabinet rack for easier mounting and adjustment. Note how the center coax T-fitting is cabled in this photo versus the other photos. This photo shows it miscabled - while more physically symmetrical, the coax lengths are precisely measured to the 1/8 of an inch, and cabled as shown in this picture is incorrect.
AND NEVER, EVER LIFT OR CARRY A DUPLEXER BY THE HARNESS The harness cables can be easily stretched, which changes the dimensions and velocity factor, which changes the duplexer tuning and the system performance.

Documentation:
The Motorola T-1500 manual is part number 68-81102E96, titled "Filters and Duplexers, T-1500A series, 406-512mhz"

T-1500 manual version "G" dated 01/25/1983 1.3mb PDF file

Below are scans of another version of the T-1500 manual (version "F" dated 9-30-1977)
Page 01 1.1mb
Page 02 261kb
Page 03 305kb
Page 04 338kb
Pull-out Parts List Page 05 Left 207kb Page 05 Middle (physical drawing) 153kb Page 05 Right 196kb
Pull-out Inter-cavity cabling drawing Page 06 Left 162kb Page 06 Middle 197kb Page 06 Right 252kb
Page 07 216kb
Page 08 280kb
Page 09 248kb
Page 10 224kb
Page 11 206kb
Page 12 289kb
Page 13 261kb
Page 14 299kb
Page 15 324kb
Page 16 206kb
Pull-out Performance graphs (first page of graphs) Page 17 Left 239kb Page 17 Right 245kb
Pull-out Performance graphs (second page of graphs) Page 18 Left 199kb Page 18 Right 195kb

A single 8mb PDF file of a version "E" writeup dated 4/7/1976.

The Cactus Radio group has published a tech note on refurbishing the T-1500 cavities.
From their web site at http://www.cactus-intertie.org:

This Technical Application Note describes the process for disassembling, cleaning and reassembling the Motorola T-1500 Series Cavities. http://www.cactus-intertie.org/LA/tec_not6.pdf dated June 26, 1999

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Scans of the over-20-year-old, version "F", no-longer-available-data sheet made by A. Nony Mous, date unknown
Photos 1-6 by Bob Meister WA1MIK
Motorola® is a registered trademark of Motorola Inc.

This web page created by Mike Morris WA6ILQ Aug 2004

This web page, 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.