A Simple Way to Extend a Whip Antenna

A whip antenna is a simple and effective antenna used by many dead-rail receivers, including the ProMini Air. Still, sometimes it’s not feasible to mount the whip antenna directly to the transceiver and get good RF reception. One solution is a U.FL extender cable connected to the U.FL plug on the receiver, and the other end can be “snaked” outside the locomotive or tender shell. The U.FL whip antenna then plugs into the U.FL socket on the distant end of the extender outside the shell for better RF reception.

A U.FL extension cable. The U.FL connector on the left plugs into the receiver’s U.FL socket, and the U.FL antenna plugs into the U.FL socket on the right.

An extender has some downsides: the U.FL socket is easily broken, requires a fair-sized exit hole, and may be subject to increased RF noise. This post will show you a better solution for some applications.

A Simple Solution

While browsing RF components on AliExpress, I came across “IPX IPEX U.FL Jack RF Cable 1.13mm Jumper Solder Single-head Adapter Connector” in various lengths.

IPEX U.FL Jack Cable Single-head Adapter

If you strip off 82mm (North American) or 86 mm (EU) of the outside plastic cover and grounding wrap to expose the inner plastic insulator and the antenna wire, you have over 200mm of grounded connection for “snaking” the antenna connection to a distant location. A small hole using a #56 drill bit (0.0465″) provides sufficient clearance for the grounded lead to exit the shell.

The stripped cable exposes the antenna wire with its insulating cover.

You can bend the grounded lead to the angle you want and cover the exposed antenna section with small-diameter heat shrink tubing to hide the bright antenna wire.

The final antenna mount with heat shrink tubing covering the exposed antenna wire

Below is a video of this antenna solution in action.

The final “proof in the pudding” of the antenna concept used on a dead-rail O scale Sunset 3rd Rail (2-Rail) UP 4-6-6-4 Early Challenger. The ProMini Air receiver and DCC amp were installed in the tender and controlled via smartphone using the Locontrol app WiFi-connected to the stand-alone ProMini Air transmitter integrated with a WiFI-equipped EX-Command Station. The dynamo sound is much too loud!

Conclusion

I hope you find this simple solution valuable in your future dead-rail endeavors!

Author: Darrell Lamm

I earned my Doctorate in Physics from the Georgia Institute of Technology in 1982, and before retiring in 2019 I worked for 37 years at the Georgia Tech Research Institute. My last position was Chief Scientist of the Electro-Optical Systems Laboratory. Like many people, my love for model railroading began at an early age, and I rekindled that interest starting in 2017.

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