Pacific Aerial P6121 VHF Antenna
$155.70+ GST
P6121 VHF Pacific Aerial Longreach Pro Series antenna
- 1.8m antenna
- Suitable for high deck or side mount installation points
- Unique Pro Series design allows the antenna to be removed and remounted at the owner's convenience
- The stainless steel ferrule enhances the appearance and strength of the antenna
- The half-wave design produces a radiation pattern which is especially suitable for small boats
- UltraGlass stands up to high UV and harsh marine environments for years
Marine VHF aerials for sale. VHF marine aerials for sale.
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What is "Gain"?
Gain measures how much of the energy sent from the radio to the antenna is concentrated in a specific direction, and in which direction the antenna has the greatest "reach" when receiving a signal. Gain is measured in decibels (dB), related to a known standard reference, usually an ''isotropic'' antenna. Gain figures which show the comparison with an isotropic antenna are written dBi. For example, a 2.5m VHF colinear antenna with two radiating elements has a gain rating of 6dBi.
So, 2.5 metre marine antennas are high gain, right?
Only if they have two or more radiating elements. A 2.5 metre halfwave antenna has one radiating element and a gain of 3dBi.
Is more gain better?
Not always. High gain antennas need a larger, stable vessel, because the extra gain has been achieved by flattening out the "lobe'' of the antenna. Smaller boats which roll around more, or yachts that are heeled over, may find that stations they are calling fade in and out of the antenna's lobe as the antenna moves away from vertical.
What is "Marine Gain"?
”Marine Gain” is used by some marine antenna manufacturers because allows the marketing department to invent numbers so the specifications appear more impressive. "Marine Gain" is not used by marine electronics technicians. But so that you can compare apples with apples, Pacific's antennas have both dBi and "Marine Gain" figures listed.
ANTENNA PERFORMANCE ISSUES
If antennas can only transmit and receive on a "line of sight" basis, how is it I can talk to boats which are miles away?
You are probably using a "repeater" to do this. The repeater radio sits high on a hill, and re-broadcasts your transmission. Because of the height of the repeater radio, both your antenna and the antenna on the boat you are talking to have an effective line of sight through the repeater radio.
My antenna is receiving but not transmitting. What's wrong?
Probably nothing with the antenna. Check that the battery is fully charged and the connections to the radio are sound. Receiving only takes a little power; transmitting takes a lot and a low battery or bad connections will fail on transmit. Check that your radio is set to the correct channel plan.
My antenna’s performance was fine when it was first installed, but is now marginal. What’s happened?
Most likely, a problem with the coaxial cable. Check that there are no splits in the jacket for water to get in, and that the cable hasn’t been crushed or tightly kinked during the installation. Check that all connectors are fitted properly.
INSTALLATION ISSUES
Can I shorten or lengthen the coaxial cable on the antenna?
Sure, but think before you cut. You will have to fit a new connector, and that's not always easy. It might be better to leave the surplus length in a loose coil out of sight. If you want to lengthen the cable, Pacific has ready made cable packs with fitted connectors. If in doubt, talk to us.
How close together can antennas be installed?
The rule of thumb is to install all antennas an antenna's length away from other antennas. If you can't get that separation, just as far apart as possible. If transmitting on your VHF causes interference on other electronic equipment, consider installing ferrite clamps around the equipment's battery and connecting cables.
Is it OK to rake my antennas back on an angle?
You can, but every degree that your antenna is off vertical decreases the performance of the antenna by 1%. Communications antennas should be vertical.
MARINE ANTENNAS
What is the difference between fibreglass and stainless steel antennas?
There is no difference in electrical performance between the fibreglass and stainless steel antennas. Both are halfwave antennas. The stainless steel whip antennas are light, low windage antennas for installation on a mast, which is usually the highest point on the boat. The fibreglass antennas have the radiating element at the top of the radome, which gets the antenna as high as possible for deck, side or rail installations. The larger, white fibreglass antennas make a boat look "better dressed". Fibreglass antennas may be either halfwave or colinear antennas. Colinear antennas have higher gain and are suitable for larger more stable vessels which may want communications at maximum range.
Why are there generally both 1.8 metre and 2.5 metre antennas?
In an ideal world smaller boats would fit longer antennas, because longer antennas can "see" further than shorter antennas. Bigger boats, where the antenna mount may be several metres above the waterline, can achieve the same horizon range with shorter antennas. In the real world many small boat owners find the 2.5 metre antenna just a bit too long; the 1.8 metre antenna seems to be the right size for most trailer boats. Colinear antennas are recommended for larger more stable vessels which may want communications at maximum range. VHF, AM/FM and Cellular antennas are all available in 1.8 metre and 2.5 metre sizes, so VHF antennas can be "twinned" with either an AM/FM or a Cellular antenna.
What is "Gain"?
Gain measures how much of the energy sent from the radio to the antenna is concentrated in a specific direction, and in which direction the antenna has the greatest "reach" when receiving a signal. Gain is measured in decibels (dB), related to a known standard reference, usually an ''isotropic'' antenna. Gain figures which show the comparison with an isotropic antenna are written dBi. For example, a 2.5m VHF colinear antenna with two radiating elements has a gain rating of 6dBi.
So, 2.5 metre marine antennas are high gain, right?
Only if they have two or more radiating elements. A 2.5 metre halfwave antenna has one radiating element and a gain of 3dBi.
Is more gain better?
Not always. High gain antennas need a larger, stable vessel, because the extra gain has been achieved by flattening out the "lobe'' of the antenna. Smaller boats which roll around more, or yachts that are heeled over, may find that stations they are calling fade in and out of the antenna's lobe as the antenna moves away from vertical.
What is "Marine Gain"?
”Marine Gain” is used by some marine antenna manufacturers because allows the marketing department to invent numbers so the specifications appear more impressive. "Marine Gain" is not used by marine electronics technicians. But so that you can compare apples with apples, Pacific's antennas have both dBi and "Marine Gain" figures listed.
ANTENNA PERFORMANCE ISSUES
If antennas can only transmit and receive on a "line of sight" basis, how is it I can talk to boats which are miles away?
You are probably using a "repeater" to do this. The repeater radio sits high on a hill, and re-broadcasts your transmission. Because of the height of the repeater radio, both your antenna and the antenna on the boat you are talking to have an effective line of sight through the repeater radio.
My antenna is receiving but not transmitting. What's wrong?
Probably nothing with the antenna. Check that the battery is fully charged and the connections to the radio are sound. Receiving only takes a little power; transmitting takes a lot and a low battery or bad connections will fail on transmit. Check that your radio is set to the correct channel plan.
My antenna’s performance was fine when it was first installed, but is now marginal. What’s happened?
Most likely, a problem with the coaxial cable. Check that there are no splits in the jacket for water to get in, and that the cable hasn’t been crushed or tightly kinked during the installation. Check that all connectors are fitted properly.
INSTALLATION ISSUES
Can I shorten or lengthen the coaxial cable on the antenna?
Sure, but think before you cut. You will have to fit a new connector, and that's not always easy. It might be better to leave the surplus length in a loose coil out of sight. If you want to lengthen the cable, Pacific has ready made cable packs with fitted connectors. If in doubt, talk to us.
How close together can antennas be installed?
The rule of thumb is to install all antennas an antenna's length away from other antennas. If you can't get that separation, just as far apart as possible. If transmitting on your VHF causes interference on other electronic equipment, consider installing ferrite clamps around the equipment's battery and connecting cables.
Is it OK to rake my antennas back on an angle?
You can, but every degree that your antenna is off vertical decreases the performance of the antenna by 1%. Communications antennas should be vertical.
MARINE ANTENNAS
What is the difference between fibreglass and stainless steel antennas?
There is no difference in electrical performance between the fibreglass and stainless steel antennas. Both are halfwave antennas. The stainless steel whip antennas are light, low windage antennas for installation on a mast, which is usually the highest point on the boat. The fibreglass antennas have the radiating element at the top of the radome, which gets the antenna as high as possible for deck, side or rail installations. The larger, white fibreglass antennas make a boat look "better dressed". Fibreglass antennas may be either halfwave or colinear antennas. Colinear antennas have higher gain and are suitable for larger more stable vessels which may want communications at maximum range.
Why are there generally both 1.8 metre and 2.5 metre antennas?
In an ideal world smaller boats would fit longer antennas, because longer antennas can "see" further than shorter antennas. Bigger boats, where the antenna mount may be several metres above the waterline, can achieve the same horizon range with shorter antennas. In the real world many small boat owners find the 2.5 metre antenna just a bit too long; the 1.8 metre antenna seems to be the right size for most trailer boats. Colinear antennas are recommended for larger more stable vessels which may want communications at maximum range. VHF, AM/FM and Cellular antennas are all available in 1.8 metre and 2.5 metre sizes, so VHF antennas can be "twinned" with either an AM/FM or a Cellular antenna.
