DB Products DB4030 6m Duplexer



This is a factory tuned DB4030 6m duplexer, serial number D35341 that is in perfect working condition as removed from operation at my repeater station before moving from NJ to NC.

The external cabinet shows some signs of wear and tear to include some dings, minor rust where scratched and tape residue, however the interior is almost like new and all factory labels inside and outside are in place and perfectly legible, all of which can be seen in the photos below.

These duplexers are factory tuned to the frequency pair 53.430/52.430 as originally ordered and have never been retuned.

$1500USD cash picked in Hendersonville, Nc.

Interested parties can reach me via e-mail at n2ckh.com@gmail.com or via phone at 1-828-393-7385.


The DB Products 4030 series of duplexer are the most reduced size 6 meter duplexer ever designed.

The duplexer cavities and cables are contained in a heavy duty metal cabinet enclosure which is floor or wall mountable and provides real protection the cavities and cabling inside, making them perfect for a remote commercial sitting or a home based repeater station.

This self contained cabinet stands 30 inches tall, 19.25 inches wide and 7.38 inches deep and weighs 67lbs.

These duplexers use compact, quarterwave, high performance helical resonators that are interconnected in a band-reject configuration with double shielded cable. They isolate the receiver from the transmitter and reduce Tx noise in most tube or solid state systems.

These cavities provides a tremendous amount of rejection of other signals that may be on-site and from nearby high power 6m weak signal CW/SSB stations, low band commercial FM stations and TV channel 2 stations.

The four cavity Db Products duplexer consists of two band pass and two band reject cavities and tuning stubs. The transmitter is connected to one side of a "T" adapter via a 53.430MHz band pass and a 52.430MHz band reject cavity. The receiver is connected to the other side of the "T" via a 52.430MHz band pass and a 53.430MHz band reject cavity. The center of the "T" is connected to the coax which goes to the antenna.

The duplexers are temperature compensated and provide power handling rated to 150 watts, even in extreme temperatures of -30 to +60 C. The insertion loss (transmitter to antenna) is better than -2 dB and the insertion loss (receiver to antenna) better than -2 dB. The Transmitter noise suppression at receiver frequency -80 dB and the Receiver isolation at transmit frequency -80 dB. The Maximum VSWR (referenced to 50 ohms) is 1.5:1 or better.


Here are two factory documents on the DB4030 duplexer:

Factory DB4030 data sheet

Factory DB4030 tuning instructions


All of the photographs contained within these pages are of the unit that I have for sale.

NOTE: The photos on the additional pages are large closeup images that will take some time to load and are displayed at first in a reduced format after loading, clicking on them will allow for resizing to full resolution and scrolling will then be required.

DB4030 Connectors and Label

DB4030 Starting to Slide Door Open

DB4030 Door Removed

DB4030 Inside

DB4030 Lower Left Wall Bracket

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