Common VHF/UHF FM Simplex
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
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
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
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.
"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
2. Antenna height increased to 12
feet by each station A and B = 5 miles for each
3. Both stations increase their
height to 50 feet = 10 mile line of sight for each
Now using the same calculation with no changes in either station other then height of one station:
4. Station A remains at 6
for a repeater and an HT at 6 feet example, (hand held radio) with a
repeater at 1000 feet on the other
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!
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:
3. Get those
antennas HIGH up in the air.
4. Be patient!
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.
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