Common VHF/UHF FM Simplex Frequencies
Simplex Operation and Frequencies for U.S. ham bands above 50Mhz.
This article will give you the suggested and recommended simplex frequencies that are set aside for simplex operation and should help you understand how to operate simplex on the upper ham bands.
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.
Choose a simplex frequency for the band you want to use from the chart and have fun! 2-Meter Band 146.52* 146.535 146.55 146.565 146.58 146.595 147.42 147.435 147.45 147.465 147.48 147.495 147.51 147.525 147.54 147.555 147.57 147.585 1.25-Meter Band 223.42 223.44 223.46 223.48 223.50* 223.52 446.0* 906.5* 1294.000 1294.025 1294.500* Every 25 kHz to 1295 Note that the "National Simplex Frequencies in RED are also know as the Calling Frequency.
Common VHF/UHF FM Simplex Frequencies
* National simplex frequency
See Notes **
* National simplex frequency
Monitor it often and make your calls there but move to another simplex frequency if possible to keep it open for use by others wishing to make simplex contacts.
This frequency is often used when mobile on long trips in unknown repeater coverage areas.
Notes**! See the ARRL BAND PLAN for more detailed info when using bands above 1.25 meters! They can be very congested and may be used by other services!
Continued from above.....
Every 25 kHz to 1295
Note that the "National Simplex Frequencies in RED are also know as the Calling Frequency.
When using simplex, both station's antenna height, power output, type of antenna, other factors and terrain between both stations will have a great deal to to with how strong the signals are on your radio and how he would hear you if at all.
Radio transmissions at these frequencies are usually limited to "line of sight" between station antennas. Line of sight simply means that there is a "radio horizon" from your antenna stretching out to the earth's horizon or other structures which normally blocks or attenuates the radio signals. An analogy would be if you imagine your radio signal as a light beam reaching out to the other station's antenna, so anything in the way of your "light beam" would tend to block or shield it from the other station' antenna and vice versa. Some factors involved in the blocking, or attenuating the signals are tall buildings with lots of metal in them, high hills, mountains, local "ground clutter" near you with a combination of everything mentioned above.
Antenna Height above average terrain means everything!!!
Overcoming many of the obstructions mentioned above, that reduce your signal strength to the receiving station, can be a simple or major problem. One of the most important things you can do to help increase your "range" and extend the "radio horizon" is to increase your antenna height above average terrain within your station limits. Much depends on whether or not you want to go to the extra expense of increasing that height by mounting your transmitter's antenna up as high as feasible.
An example of using various "line of site to the horizon" calculators will enable you to see how additional antenna height should add to your station's range.
We used the KD4SAI line of sight calculator for the examples below.
Note: These examples below assume ONLY height change and take into account no other factors involved to change the amount of power getting to the transmitting antenna nor have there been any changes to the receive antenna unless specified. (Note that increasing height will mean the adding of additional losses involved with adding longer coax so the numbers below will not be exact in real life.)
"Antenna height is above ground (flat terrain)." Using station "A" and station "B"
1. Antenna height for each station: 6 feet. Line of sight to horizon for each station's line of sight = 3 miles
Both stations A and B line of sight between each other = 6 miles. So within 6 miles of each other, communications should be possible.
2. Antenna height increased to 12 feet by each station A and B = 5 miles for each station
Total line of sight =10 miles between the two stations. So within 10 miles of each other, communications should be possible.
3. Both stations increase their height to 50 feet = 10 mile line of sight for each station
Total line of sight between stations = 20 miles. If the stations are within 20 miles of each other, communications should be possible.
Now using the same calculation with no changes in either station other then height of one station:
4. Station A remains at 6 feet.
Station B uses 50 feet....total range between stations = 13 miles. So if each station is within 13 miles from the other...you guessed it, they should be able to communicate.
5. Now for a repeater and an HT at 6 feet example, (hand held radio) with a repeater at 1000 feet on the other end:
HT line of sight to the horizon = 3 miles
Repeater line of sight to horizon = 48 miles!
So you can see by this last example above that you stand a much better chance of getting into a repeater that has a very tall antenna or is on a tall building or mountain, hill, etc!
In the example, the repeater can "see" much farther than you can and "sees" not only your station but well beyond you! Now substitute the repeater height for an HT on top of a 1000 foot mountain....same line of sight!
One more EXTREME example that is out of this world.
Assume an HT in the International Space Station (ISS) next to a window facing the Earth with no obstructions!
It's line of sight at 200 miles (1,056,000 feet) above the Earth would be about 1,456 MILES!
Now how's that for a line of sight distance using simplex??
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