Overview

DX Engineering Dual Impedance Antenna Transformers

DX Engineering Dual Impedance Antenna Transformers are dual ratio UNUN (unbalanced to unbalanced line) transformers. They're great for coupling your 50 ohm coax to an antenna with a feed point impedance of either 25 or 12.5 ohms, typically found at HF mobile antennas.

DX Engineering Dual Impedance Antenna Transformers are ideal for antennas that have been enhanced with a Hot Rodz capacity hat. These transformers are housed in an aluminum enclosure and use silver plated PTFE SO-239 connectors.

Many mobile HF antennas are naturally between 10 ohms and 36 ohms at resonance. With 10 ohms at a 50 ohm feed point the resulting SWR is 5:1! Likewise, 36 ohms yields a 1.4:1 SWR. Matching at 1.4:1 isn't too bad, but 5:1 is definitely an issue.

DX Engineering MM-1 Dual Impedance Antenna Transformers are ideal for adjusting the impedance mismatch in your HF mobile! When the natural resonant impedance of the antenna is at 30 ohms or below, the MM-1 mobile unun can provide the needed match. With a 50 ohm input, it provides a 25 ohm port and a 12.5 ohm port to facilitate mobile HF matching.

Let's say that your antenna analyzer indicates a resonant antenna impedance of 22 ohms. Your SWR without an MM-1 would be 50/22 or 2.27:1. That's enough to cause considerable power rollback in most modern HF rigs. Using the MM-1 25 ohm port, your SWR would be 25/22, or 1.14:1. That's a very significant improvement!

Many hams are using antenna analyzers to adjust mobile HF antennas. When a mismatch is indicated at resonance, a DX Engineering MM-1 Unun can solve the problem!

Power handling capability depends on the match:

* Using the 25 ohm to 50 ohm port, with SWR below 2:1 on the 50 ohm side, -- 750 watts PEP
* Using the 12.5 ohm to 50 ohm port, with SWR below 2:1 on the 50 ohm side, -- 500 watts PEP

Note: Whenever the DX Engineering "Documentation" tab is available, please look at the associated files for additional product information.

Antenna analyzers are becoming more common. Buy or borrow one to check the impedance of your mobile antennas. Then get DX Engineering Dual Impedance Antenna Transformers to get the best match and highest efficiency you can!

Documentation

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