Common VHF/UHF FM Simplex
and Frequencies for U.S. ham bands above 50Mhz.
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
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
Common VHF/UHF FM Simplex
* National simplex
Every 25 kHz to
Note that the
"National Simplex Frequencies in RED are also
know as the Calling 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.
frequency is often used when mobile on long trips in unknown repeater
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!
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
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.
example of using various "line of site to the horizon" calculators will
enable you to see how additional antenna height should add to your
We used the KD4SAI line of sight
calculator for the
You can see
more line of sight calculators and an explanation of line of sight to the
horizon as used in VHF/UHF radio operation here.
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.)
height is above ground (flat terrain)." Using station "A" and station
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
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
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
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
5. Now for a
repeater and an HT at 6 feet example, (hand held radio) with a repeater at
1000 feet on the other
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!
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!
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??
types, power levels and other info for working
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
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
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
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
4. Be patient!
Using simplex for
making random uscheduled contacts is a lot like
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.
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
Have fun and encourage others to use
simplex whenever possible. 73, Don