Simplex Channel Confusion on 2 Meters
I often get asked questions about the band plan for 2 meters (144 to 148 MHz). Usually, this is about choosing a suitable simplex frequency, because the repeater frequencies are already coordinated and visible.
I’ve written about 2m band plans before. This article attempts to cover the topic in a way that applies to all of the US. This is actually a challenge because VHF/UHF band plans are regional in nature.
I also wrote this article which is specific to the state of Colorado.
It is always best to check your local VHF band plan, usually supplied by the frequency coordinating body for your area. Typically, their main focus is coordinating repeaters but simplex frequencies are also listed. Most frequency coordinating bodies kind of follow the ARRL 2m band plan, while adapting it for local use.
Channel Spacing: 15 kHz or 20 kHz
A big issue for the 2-meter band is that some areas have adopted a 15-kHz channel spacing while others use a 20-kHz channel spacing. A typical FM signal is about 16 kHz wide, so the 15 kHz channel spacing is a bit tight but does allow for more channels (resulting in more adjacent channel interference issues). The 20-kHz spacing is “cleaner” but with fewer channels.
This map from the ARRL web site shows the channel spacing in use across the various states.
The channel spacing is driven by factors associated with repeater coordination, and simplex usage tends to adopt the same spacing. (There is no technical reason that simplex has to use the same channel spacing as the repeaters but that’s what usually happens.)
Some repeater coordinating organizations have done a good job of prescribing FM simplex frequencies. The Colorado 2m band plan (called the Frequency Use Plan) lists each simplex frequency individually. The Illinois Repeater Association uses a similar approach: Illinois 2m Band Plan. The Southeastern Repeater Association (SERA) 2m band plan is also very specific. Note that the SERA band plan indicates that some of the usual 2m simplex frequencies may be used as repeater pairs — an example of a local decision on frequency use.
The Arizona 2m band plan shows a range of frequencies to be used for FM simplex, such as 146.400 – 146.600 MHz along with a note that says the Even 20 kHz Frequencies should be used. So that means the preferred simplex frequencies in this range are 146.40, 146.42, 146.44, 146.46, 146.48, 146.50, 146.52, 146.54, 146.56, 146.58 and 146.60 MHz. Some repeater coordinating bodies just give the frequency segment allocated to FM simplex and don’t mention the channel spacing. And some organizations don’t say anything about FM simplex so you have to figure them out on your own.
So what do we make of all of this? When it comes to 2m FM simplex frequencies, try to find your local band plan. If it recommends 2m FM simplex frequencies, then follow that guidance.
If that doesn’t work, look at the map above to determine if your state uses 15 kHz or 20 kHz spacing. Then follow the guidance in the HamRadioSchool.com article: What Frequency Do I Use on 2 Meters?
|2M FM Simplex Frequencies (typical usage, check your local band plan)|
|15 kHz Channels||146.400, 146.415, 146.430, 146.445, 146.460, 146.475, 146.490, 146.505,146.520, 146.535, 146.550, 146.565, 146.580, 146.595 147.405, 147.420, 147.435, 147.450, 147.465, 147.480, 147.495,147.510, 147.525, 147.540, 147.555, 147.570, 147.585|
|20 kHz Channels||146.400, 146.420, 146.440, 146.460, 146.480, 146.500, 146.520, 146.540, 146.560, 146.580, 146.600 147.400, 147.420, 147.440, 147.460, 147.480, 147.500, 147.520, 147.540, 147.560, 147.580|
In all cases, remember that these are shared frequencies so you need to cooperate with other radio hams. If you bump into existing activity, go ahead and try another frequency. There are usually plenty of quiet simplex channels around.
The one simplex frequency that everyone does seem to agree on is the National Simplex Calling Frequency: 146.52 MHz. For some thoughts on how to use that frequency see: The Use of 146.52 MHz.
I do think that frequency coordination bodies would be wise to provide guidance on simplex channels. This is not frequency coordination but it helps the amateur radio community be more effective in using the spectrum.
73 Bob K0NR
The post Simplex Channel Confusion on 2 Meters appeared first on The KØNR Radio Site.
Thanks, I have never seen this map before. Nice to have while traveling.
It is nice to know I was not the only one confused. In this case, I found the prescribed channel spacing for Montana 2m (20kHz) difficult to find. Your map and article helped me. Thank you.
Thanks – very useful!
On the map what does the “INV” mean in southern California, and northern Baja?
Southern Cal uses a rather unique repeater offset approach that intermingles + and – offset repeaters together (“inverted”).
Since the use of 146.52 varies so much, just listening will tell you something. One practice will help everybody. If you are on the frequency for any length of time, pause for a minute, saying you are going to do so: “We’re going to step aside for a minute, so anyone who needs the frequency can get a chance to use it.”
If there are others, then it is dead easy on modern units to switch to another simplex frequency which you have already programmed into your HT.