I recently purchased a new HiQ580RT which required a way to measuring the Standing Wave Ratio remotely. There are a lot of ways to measure SWR, but when you're mobile, the options diminish, and using the notoriously inaccurate build in ones isn't an option either. Fortunately, several different companies manufacture remote SWR bridges so you don't have to run coax hither and yon if your radio is remotely mounted. I don't know about your installation, but I had problems finding a place to mount the head of my Icom, much less finding space for a 4 inch square meter. Well, it turns out you don't have to, thanks to LDG Electronic's TW1 talking wattmeter as shown in the left photo.

There is a review of it in the November 2005 issue of QST starting on page 77. It runs on a nominal 13.8 VDC, and draw less than 90 uA on standby so a power switch isn't needed. You should properly fuse it however.

There is something special about the TW1, and if you've read the review you would know that it not only talks, it squeals. Well, actually it's a tone you hear which changes in pitch (steady or pulsing) to indicate SWR. This function makes resetting a remotely tuned mobile antenna a simple chore that doesn't require you to take your eyes off of the road. This single feature makes it worth the $129 it retails for.

Although it isn't designed to be remoted, it turns out it can be. A close look at the SWR push button will show you that it is a DPDT, which would indicate remoting the SWR function would be difficult. However, after talking with the folks at LDG, I (they) came up with a solution.

The diagram (upper right) depicts the SWR switch from the top front side. Connecting a SPST N/O push button to these two pins will cause the TW1 to report the SWR. Closing the switch for 3 seconds will cause the TW1 to go into the tone mode. It will stay there until RF is removed for about 30 seconds, at which time it goes back to its original programmed mode. If you want it to switch immediately, just push the button again. It can speak in German and Spanish, in addition to English, and has both verbose and terse modes. There's even a VHF model of it.

I've been using the remote controlled TW1 for about 6 weeks now, and it has worked perfectly. It's immune to RF, which most automatic controllers are not, especially if you run high power. In any case, you should RF bypass the wiring to your remote push button with .01 caps. Depending on the remote switch or button you use, it may be necessary to install a .22 uF or .47 uF cap across the internal switch to avoid contact bounce issues (not shown in the photo). Be advised, modifications like this may nullify the warranty.

The photo above left shows the TW1 mounted atop my SG500 amplifier's protective aluminum cover. This cover is spaced 5/8 inch above the amplifier allowing airflow while keeping foreign objects from dropping through the ventilation holes. Although mounted in the trunk, the TW1 has adequate volume to be easily heard even at highway speeds. Is there a drawback? Yes... I didn't think of it first!

Alan Applegate, K0BG