Summer 2003 Issue

Go Simplex

Often neglected on our handheld’s dial are the simplex frequencies, and author WB6NOA urges us to check them out. Who knows? We might find new friends and new ways of communicating on the 2-meter and 70-cm ham bands.

By Gordon West,* WB6NOA

If your local repeater seems to be lacking some ham radio excitement, try simplex! You might be surprised by how far 2-meter and 446-MHz simplex will travel using a regular FM transceiver. Getting your club off the repeater and on simplex will also hone operating skills, quickly showing who has the best antenna system.

How many times have you tuned into a repeater only to hear one mobile operator telling the other ahead of him on the road that he has a burned-out brake light? If the two operators are mobiling within such close proximity, why are they tying up a repeater unnecessarily? Also, who needs a repeater if you are running around town mobile and want to stay in touch with your wife-ham on the air? Any decent 2-meter, 440-MHz, or dual-band 144/440-MHz antenna on top of your house might reach 10 or 15 miles simplex rather easily.

Also, house to house with a white fiberglass single- or dual-band base antenna might yield 20- or 30-mile distance contacts. When the weather conditions are just right, you might even reach out over 100 miles on 2-meter or 446-MHz simplex FM.

In southern California hundreds of hams meet regularly on simplex frequencies or on evening nets. The net control station is usually a well-equipped home station with an excellent single-band or dual-band collinear array antenna fed by low-loss coax such as Belden 9913 or Times LMR 400.

The net control station needs to be able to more carefully judge incoming simplex signal strengths than the little color light-emitting diodes on the base transceiver indicate, or the relatively small S-meter, which usually pegs on an extremely strong signal, can tell you. There is an answer!

An External Relative Signal Strength Meter
If the mobile or base transceiver has a conventional D’Arsonaval S-meter, you are set for an easy additional signal-strength-meter hookup. Most conventional needle-movement S-meters are driven by the automatic gain control (AGC) stage of the transceiver, and the meter is normally a 0–100 microamp movement. The meter already built into your mobile or base 2-meter or 446-MHz FM transceiver or multi-mode transceiver won’t load down the AGC circuit, yet it will read a reliable signal strength. The little meter, however, is usually so small that it makes is difficult to judge the difference between two simplex stations that are relatively close in signal strength.

The answer is an external 0–50 or 0–100 microvolt meter found at most ham radio swap meets. Even if you can’t read whether it is a microvolt meter, you can always tell simply by rocking the meter back and forth and watching the needle. If the needle slowly floats up and slowly floats back down, this is indeed a microvolt meter that will make a dandy additional S-meter. However, if the needle abruptly goes up and down when you wiggle the movement, this is probably a milliamp meter, which would not be usable. It must be the “floating” needle microamp meter movement.

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