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-   -   High Frequency (HF) Radios (http://www.sailnet.com/forums/miscellaneous/21945-high-frequency-hf-radios.html)

SailNet 08-23-2000 08:00 PM

High Frequency (HF) Radios
 
<HTML><!-- eWebEditPro 1.8.0.2 --><P>Offshore cruisers should not leave home without a high frequency radio, either HAM or Single Sideband, for long distance communications, emergencies, receiving weather via weather faxes, and voice weather broadcasts. With advances in technology, HF radio has also become a method for e-mail communications, as well as voice and telephone.</P><B><P>BASIC TERMINOLOGY </P><UL><LI>Amateur Bands </B>are the frequencies between 1.8MHz to 29.7 MHz set aside for amateur radio operators (Hams). <LI><STRONG>Amplitude</STRONG> is the height of a radio or sound wave loudness <LI><STRONG>Amplitude Modulation</STRONG>&nbsp;is the addition of information to a RF carrier by increasing and decreasing amplitude. These are low efficiency types of radio transmissions, which are used for AM radio stations with 100 percent carrier inserted. <LI><STRONG>Carrier</STRONG>&nbsp;is an unmodulated RF signal. <LI><STRONG>Duplex&nbsp;</STRONG>frequencies are available in which ship stations transmit on one frequency while shore stations transmit on another. <LI><STRONG>Frequency </STRONG>is the number of polarity alternations per second measured in Hertz, whereas kHz equals a thousand Hertz and MHz equals a million Hertz. <LI><STRONG>Hertz (Hz)&nbsp;</STRONG>is a measure of frequency, which is one cycle per second. <LI><STRONG>HF</STRONG> is High Frequency, which are frequencies in the 3 to 30 MHz ranges. <LI><STRONG>LSB </STRONG>is the Lower Sideband of a carrier frequency. <LI><STRONG>Modulation </STRONG>is the varying of amplitude, frequency, or phase of a carrier signal. <LI><STRONG>Propagation </STRONG>is the different characteristics of radio frequency transmissions, in which the usable distance of a transmission is related to the frequency and time of day. <LI><STRONG>RF </STRONG>is any frequency, referred to as radio frequency, higher than humans are capable of hearing. <LI><STRONG>Simplex </STRONG>frequencies are for stations to transmit and receive on the same frequencies. <LI><STRONG>Transceiver </STRONG>is equipment, which transmits and receives. <LI><STRONG>USB </STRONG>is Upper Sideband of a carrier frequency.</LI></UL><B><P>MARINE SINGLE SIDEBAND (SSB)<BR></B>Single Sideband transmission is defined, simply, as the suppression of the "lower" or "upper" sideband of a carrier frequency. The frequencies above the carrier frequency are called Upper Sideband, and those below are Lower Sideband, which are a result of Amplitude Modulation (AM) transmissions. In AM transmissions both bands are present. </P><P>&nbsp;</P><P align=center><IMG height=132 src="http://www.sailnet.com/images/content/authors/buyingguides/highfreqradios/ssb66.jpg" width=224></P><B><P>Advantages</P><UL></B><LI>Of the two communications systems, HAM and Marine SSB, SSB is the easiest to obtain licensing. The FCC requires only a station license. A form can be obtained from the store where the equipment is purchased, filled out, and sent to the FCC. <LI>There are no tests and the use protocol is the same as for VHF radios. <LI>On certain Marine SSB frequencies business can be conducted, whereas with HAM radio, business over the airwaves is not permitted. <LI>Commercial radiotelephone calls are permitted. <LI>Weather and information nets are numerous and easily available in all parts of the world. <LI>Can transmit and receive anywhere in the world without reciprocal licensing requirements. </LI></UL><B><P>Disadvantages</P><UL></B><LI>Marine SSB is more limited in usable frequencies than HAM. <LI>Phone patches home will cost money. <LI>Ship-to-ship frequencies available for "chat" are limited.</LI></UL><B><P>EQUIPMENT</P><UL></B><LI>Radio - depending on features, will cost in the $1,500 to $3,000 range. <LI>Antenna - run the antenna the length of the backstay with insulators at either end, keeping the lower one at just above hands’ reach. Alternatively, a whip antenna can be used. <LI>Ground plane – usually copper strap laid in the bilge. <LI>Tuner - SSB radios come with or without&nbsp;automatic tuners. The&nbsp;automatic tuner makes the radio easier to operate, especially for novices. </LI></UL><P>If getting a HAM license in the future is a possibility, buy a SSB radio that also has the HAM frequencies available. Even though you can’t transmit now, it will save purchasing another radio in the future.</P><B><P>HAM RADIO<BR></B>Amateur radio operators are generally called HAM radio operators, although in actuality Marine SSB radio operators are also amateur radio operators. The term means those radio transmissions by HAM and SSB radio operators are to be received only by other amateur radio operators and are not for public broadcast. The difference between HAM and SSB operators is in the licensing requirements. Most sailors consider the license requirements a disadvantage, but the HAM radio operators don’t.</P><B><P>Advantages</P><UL></B><LI>Access to more frequencies, depending on the license, which equates into greater transmission distances. <LI>Packet radio provides e-mail communications between HAMs. <LI>Telephone patches are free, no High Seas Operator required. <LI>Slow Scan TV (SSTV) provides the availability to send pictures anywhere with software and a laptop. <LI>Satellite communications for text e-mail.</LI></UL><B><P>Disadvantages</P><UL></B><LI>Transmissions that are business oriented, or are pecuniary in nature, are not permitted. <LI>Reciprocal licenses are required for each country from where transmissions will originate.</LI></UL><B><P>EQUIPMENT</P><UL></B><LI>Radio - with or without a built in tuner, is usually less expensive than the SSB unit, but most are not "marinized" and may have a shorter life. <LI>With new revisions to the FCC regulations, there are radios now being built to transmit on SSB frequencies also. Many HAM operators illegally "modified" their HAM radios prior to the FCC changes in order to transmit on Marine SSB frequencies. <LI>Tuner - with SWR meter, if the tuner is not built into the radio. <LI>Antenna with insulators, usually mounted at the backstay. <LI>Ground plane, usually copper strap laid in the bilge.</LI></UL><B><P>TIPS</P><UL></B><LI>Each system has its own unique qualities and the obvious choice would be to have one radio with both HAM and SSB capabilities. <LI>Without the HAM license you cannot transmit on the HAM frequencies. <LI>The radio’s owner’s manual will tell you which frequencies to use for HAM or SSB transmissions. <LI>There are also guides available from the FCC, the US Coast Guard, and the American Radio Relay League (AARL).</LI></UL><B><P>INSTALLATION</P><UL></B><LI>Ham and SSB installations require an above average electrical aptitude and electrical toolbox. <LI>Professional installation is recommended for effective operation.</LI></UL><P><HR align=center width="75%"><P></P><P clear=all><P><A class=home href="/store/departments.cfm?id=41"><B>View products</B></A> <BR><BR></P></HTML>


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