Common VHF/UHF FM Simplex Frequencies
BY N4UJW

If you are new to the ham bands and especially to the VHF and higher frequencies, you no doubt may love to try your luck with simplex operating. Using simplex is really simple and it is nothing more than two ham stations using mobile or hand held radio transceivers to communicate on the same frequency without a repeater re-transmitting your signals. If you understand the operation of repeaters, then you will understand that using repeaters when you are close enough for simplex operation with good signals would only tie up the repeater for others that may not be able to use simplex.

So how do you know if you can use simplex with a station you are hearing?

One good method of knowing if you could contact a particular station directly using simplex would be to listen to the repeater's input frequency that he is using. If you can hear the station well (when your receiver is tuned to it's input frequency), then you are close enough to use simplex with that particular station at that point in time! The station you are listening to is transmitting directly to your antenna and also to the input frequency that the repeater is tuned to. It may either be a mobile from his vehicle or sitting back in his favorite chair at home or wherever he may be. If he is mobile, then his signal may be getting stronger or weaker as time passes depending on which direction from you he is traveling. An HT (hand held) transceiver will usually be the same signal strength all of the time if the operator is not moving around, and likewise, a mobile signal will tend to vary if the mobile is moving but usually will not vary if it is stationary.

So now is the time to contact the particular station you want to talk to by using the repeater to see if you and he/she can "go simplex" and give it a try! Get on the repeater  while the station is still on and use common repeater procedures and make a schedule (sked) with the other station. Be sure that both you and the other station pick the same exact simplex frequency. See the chart below. Others who hear you make the (sked) may also want to join in with the fun. You may be surprised at how many stations were just waiting for the opportunity to "go simplex" and many may join in with you! Here again, is another chance to make "sked" with them.

Antenna types, power levels and other info for working simplex:
If you are really excited by now to "work" simplex, then here are some good suggestions that may help you get the most out of your station.

1. Use very low loss coaxial feed line....the lowest loss per foot you can afford. This will get the maximum amount of power from your radio to your antenna. At these higher frequencies, coaxial cable attenuates rf more rapidly and drastically than lower HF frequencies. An example using RG-58 type coax on 10Mhz vs 400Mhz increases loss by about 10db per hundred feet!

2. Use a high gain outside antenna if at all possible. The "rubber duck" antenna on your HT as if comes from the factory actually is a poor excuse to tack the word "antenna" on! Use a minimum of a 3 element Yagi or try a Slim Jim style antenna. Most Yagi's and verticals can be homebrewed with lots of savings in money. Using vertical or Yagi type antennas with 6dbd gain or more will certainly improve your results. If you use a Yagi type antenna, you will want to use a rotor with it so you can try different directions.

3. Get those antennas HIGH up in the air.
Rooftop or tower installations are the best if you can get them up there. Even the very tops of trees can be used in a pinch but be careful in the climb. Don't forget that by adding coax to the total length needed may not give you much if any advantage. This all depends on the loss of the coax per foot vs the old installation and the overall length of the distance from the transmitter to the antenna. You are looking for the most ERP, effective radiated power, possible at the antenna. See this link for more on ERP, db loss, gain, etc and how to figure any advantage of going higher.

4. Be patient!
Using simplex for making random uscheduled contacts is a lot like fishing!

5. Understand that Mother Nature may not let you make DX contacts unless she is "in the mood"! The SSB mode can be very helpful with DX'ing but you need to use horizontal polarity as a usual method. Many marginal contacts using regular FM can be enhanced by both stations use of SSB.

6. When using a handheld (HT) at these frequencies, you can sometimes improve your results by moving horizontally a few feet or sometimes just a few inches. This is due to "shadowing" or shielding of objects between you and the other station. Try tilting your handheld radio one way or the other from vertical. It is best if both stations use the same position for their antennas relative to the ground. In other words, if your antenna is at 45 degrees relative to the ground when transmitting, then the station on the other end should be the same. Experiment with the position of the antenna on both ends of the conversation for best results.
Try increasing your range by adding the "missing" part of your HT antenna! One simple method of increasing your HT range and performance is to add a "pigtail" or missing part of the antenna to the "rubber duck". Just attach the wire hanging down from the metal connector base of the HF antenna where it attaches to the radio. See this link for more info. For 2 meter operation, about 19 to 20 inches should do it. It will really improve your signal in most cases!

7. Remember to stay off of the repeater input frequencies when using simplex. You may be keying them up and creating interference to many others and you will never know it when operating simplex unless someone hears your call sign and abruptly lets you know about it!!!

Have fun and encourage others to use simplex whenever possible. 73, Don N4UJW

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