MF & HF-SSB Simplex Frequencies

Simplex frequencies whether MF, HF, or VHF are primarily used for distress, safety, hailing, ship to ship, and also for ship to shore communications. So why is it that duplex channels can’t be used for ship to ship communications? Well, technically they can. The problem is that it would require completely different equipment than today's common HF Transceiver found aboard most vessels.

Let's take a look at what happens when (2) vessels try to communicate on a common duplex channel. You can choose any ITU channel that you wish, but for this example we will pick channel 601.

So you are cruising along in Penobscot Bay and you call a friend on 6215.0 kHz who is, let’s say a couple of hundred miles south of Bermuda. After making contact, you both agree to switch to 601 to talk. So you both dial up channel 601 on your HF radios and here is what your frequency selection would look like:

ITU Channel 601
Your Boat   The Other Boat
You Xmit You Recv   They Xmit They Recv
6200.0 kHz 6501.0 kHz   6200.0 kHz 6501.0 kHz
         

You are both transmitting on 6200.0 kHz, but you are both listening on 6501.0 kHz neither one of you are listening on 6200.0 kHz. So no one hears what the other is saying. Public Coast Stations on the other hand are set up differently and that is why duplex channels work for them. When they dial up 601 the frequencies are reversed. They are transmitting on 6501.0 kHz and listening on 6200.0 kHz

This brings us back again to the use of simplex frequencies for ship to ship communications.

Primary MF/HF-SSB Simplex Frequencies

Medium and High Frequency Simplex is provided for worldwide common use by ships of all categories and of all nations. By international agreement, it is used for communications with other ships or shore stations. Intership communications being the primary use for simplex frequencies.

2 MHz 4 MHz 6 MHz 8 MHz 12 MHz 16 MHz 18/19 MHz 22 MHz 25/26 MHz
2065.0 4146.0 6224.0 8294.0 12353.0 16528.0 18825.0 22159.0 25100.0
2079.0 4149.0 6227.0 8297.0 12356.0 16531.0 18828.0 22162.0 25103.0
2093.0 4417.0 6230.0   12359.0 16534.0 18831.0 22165.0 25106.0
2096.5   *6516.0   12362.0 16537.0 18834.0 22168.0 25109.0
2214.0       12365.0 16540.0 18837.0 22171.0 25112.0
          16543.0 18840.0 22174.0 25115.0
          16546.0 18843.0 22177.0 25118.0
* Authorized for Daytime Use Only
All frequencies in "kHz."

Shared HF-SSB Simplex Frequencies

In addition to the primary simplex frequencies above, there are a large number of frequencies in the 4 MHz and 8 MHz bands that may be used on a shared basis with fixed services ashore.

4 MHz Band 8 MHz Band
4000.0 kHz 8101.0 kHz
4003.0 kHz 8104.0 kHz
4006.0 kHz 8107.0 kHz
4009.0 kHz 8110.0 kHz
4012.0 kHz 8113.0 kHz
4015.0 kHz 8116.0 kHz
4018.0 kHz 8119.0 kHz
4021.0 kHz 8122.0 kHz
4024.0 kHz 8125.0 kHz
4027.0 kHz 8128.0 kHz
4030.0 kHz 8131.0 kHz
4033.0 kHz 8134.0 kHz
4036.0 kHz 8137.0 kHz
4039.0 kHz 8140.0 kHz
4042.0 kHz 8143.0 kHz
4045.0 kHz 8146.0 kHz
4048.0 kHz 8149.0 kHz
4051.0 kHz 8152.0 kHz
4054.0 kHz 8155.0 kHz
4057.0 kHz 8158.0 kHz
4060.0 kHz 8161.0 kHz
---- 8164.0 kHz
---- 8167.0 kHz
---- 8170.0 kHz
---- 8173.0 kHz
---- 8176.0 kHz
---- 8179.0 kHz
---- 8182.0 kHz
---- 8185.0 kHz
---- 8188.0 kHz
---- 8191.0 kHz
   

Special Use Simplex Frequencies

In addition to the international frequencies listed above, individual nation states will often have other frequencies available for use for particular purposes or for use in particular geographic areas. An example would be in the United States there are additional 2 MHz simplex frequencies shown below:

Intership Safety and Operational Communications
Frequency Geographic Area
2003.0 kHz Great Lakes Only.
2782.0 kHz Mississippi River Working Frequency.
2082.5 kHz All Areas. Also Intership Non-Commercial Fishing.
2086.0 kHz Mississippi River Working Frequency
2093.0 kHz All Areas.
2142.0 kHz Pacific Coast, Daily, South of 42°N.
2203.0 kHz Gulf of Mexico. Also, Intership Non-Commercial Fishing.
2214.0 kHz All Areas.
2635.0 kHz ITU Regions 2-3 (ITU RR 4193). Not in FCC rules.
2638.0 kHz All Areas.
2670.0 kHz All Areas.
2738.0 kHz All Areas, Except Great Lakes. Shared with Aircraft.
2830.0 kHz Gulf of Mexico Only. Shared with Aircraft.
   
   
Business and Operational Frequencies
Frequency Geographic Area
2065.0 kHz All Areas.
2079.0 kHz All Areas.
2096.5 kHz All Areas.
3023.0 kHz Government shore, ship and aircraft stations for search and rescue coordination.
   
These 2 MHz SSB simplex radiotelephone frequencies are available for ships in or near U.S. waters.

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