My VHF won't broadcast more than 300 yards. I can receive just fine. The mike is permanetly attached to the unit. What else do i need to look at???? Thanks PaulH S/V Lind Belle 95 H26
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Need More Info
What is the set up? What kind of unit? FWIW, mine has three different power settings for transmission - 300 yards is about right at the low end.
What is the set up? What kind of unit? FWIW, mine has three different power settings for transmission - 300 yards is about right at the low end.
VHF Transmission Distance
Paul, There is usually at least High (H) and Low (L) level setting for transmission (maybe more as Drew says). Look for a H/L indicator on your VHF set. Franklin, it is not the 'size' of the VHF Antenna (they are usually 30 In. long/high), but it is the height of the Antenna above the surface of the water that determines the maximum transmission distance. VHF frequencies are mostly straight line transmissions - their 'line of sight' to the horizon is based on height. (The square root of the height in feet times about 1.15 is the distance in nautical miles to the horizon.) If your antenna on the mast is 49 FT high then the distance is 7 x 1.15 or 8.05 nm. Another vessel on the far side of the horizon has (for the same antenna height) the same distance. So you could communicate with them for up to about 16 nm. Coast Guard antennas are much higher and they can transmitt much longer distances. But, dont count on reaching the Coast Guard much over 30 nm away. For longer distances you need to get into SSB (Single Side Band) radios.
Paul, There is usually at least High (H) and Low (L) level setting for transmission (maybe more as Drew says). Look for a H/L indicator on your VHF set. Franklin, it is not the 'size' of the VHF Antenna (they are usually 30 In. long/high), but it is the height of the Antenna above the surface of the water that determines the maximum transmission distance. VHF frequencies are mostly straight line transmissions - their 'line of sight' to the horizon is based on height. (The square root of the height in feet times about 1.15 is the distance in nautical miles to the horizon.) If your antenna on the mast is 49 FT high then the distance is 7 x 1.15 or 8.05 nm. Another vessel on the far side of the horizon has (for the same antenna height) the same distance. So you could communicate with them for up to about 16 nm. Coast Guard antennas are much higher and they can transmitt much longer distances. But, dont count on reaching the Coast Guard much over 30 nm away. For longer distances you need to get into SSB (Single Side Band) radios.
Check your connections
I agree with checking the High/Low setting. You can also lose a lot of transmitting power in poor connections. Biggest culprit is the one through the deck. The insulation in the coaxial cable in the mast may also be in bad shape. None of these will affect the ability of your VHF to receive, as it is designed to receive very low strength signals. Good luck. Peter H23 "Raven"
I agree with checking the High/Low setting. You can also lose a lot of transmitting power in poor connections. Biggest culprit is the one through the deck. The insulation in the coaxial cable in the mast may also be in bad shape. None of these will affect the ability of your VHF to receive, as it is designed to receive very low strength signals. Good luck. Peter H23 "Raven"
Re Connections
Cavitating says there should be NO Connection between inner and outer of an aerial cable. Some (the best) VHF antennas do not have a plug and socket whereby they can be disconnected at the masthead and many VHF antennas are designed with a loading or matching coil which IS a direct short across the inner and outer as measured by a meter. This is NOT a short at VHF though but 50 ohms. So you cannot tell whether the cable is broken, connected or shorted using a digital meter. You need to do a VSWR check using a Standing Wave meter. These are fairly cheap to buy or are best borrowed.
Cavitating says there should be NO Connection between inner and outer of an aerial cable. Some (the best) VHF antennas do not have a plug and socket whereby they can be disconnected at the masthead and many VHF antennas are designed with a loading or matching coil which IS a direct short across the inner and outer as measured by a meter. This is NOT a short at VHF though but 50 ohms. So you cannot tell whether the cable is broken, connected or shorted using a digital meter. You need to do a VSWR check using a Standing Wave meter. These are fairly cheap to buy or are best borrowed.
Power connections
There is a lot of talk about the coax but you need to also check the power supply connection from the battery. A VHF radio draws 5 amps when transmitting. If your wire is too small and/or too long then the amperage draw may be too much. Also, the connections may be corroded. Don Casey says to determine the size, you need to determine the "round trip" length. For a 5 amp draw a round trip length of 10' requires 16 ga. for a 20' round trip length use 14 guage.
There is a lot of talk about the coax but you need to also check the power supply connection from the battery. A VHF radio draws 5 amps when transmitting. If your wire is too small and/or too long then the amperage draw may be too much. Also, the connections may be corroded. Don Casey says to determine the size, you need to determine the "round trip" length. For a 5 amp draw a round trip length of 10' requires 16 ga. for a 20' round trip length use 14 guage.
Thnaks for the Info
You guys have given me a lot to work through. Thanks for all the suggestions Paul H S/V Linda Belle 95 H26
You guys have given me a lot to work through. Thanks for all the suggestions Paul H S/V Linda Belle 95 H26
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