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[TG11] Ais 700 "saw "targets only 0.3 nm range
07-02-19, 06:40 AM (This post was last modified: 07-19-19 07:53 AM by Chuck - Raymarine - Moderator.)
Post: #1
[TG11] Ais 700 "saw "targets only 0.3 nm range
Hallo, my ais 700 interfaced with my old raymarine c80 was always fine, targets visibility at 10/12 nautical miles. Last week the system shows me only a range of 0.3 nautical miles ais target. I was thinking was the antenna whf on the top of my mast, I changend the antenna with a brand new Banten one. Nothing is change. My whf is a foruno and it work fine. I have also done the diagnostics with the pro ais, all is marked "green" and also the light on the ais 700 is green.
What can be ?
Thank you
Antonio
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07-10-19, 01:30 AM (This post was last modified: 07-19-19 07:53 AM by Chuck - Raymarine - Moderator.)
Post: #2
RE: [TG11] Ais 700 "saw "targets only 0.3 nm range
Hello Antonio,

What does ProAIS report is the antenna's VSWR value? That sounds like a high VSWR. VSWR is a measurement of how well-matched the antenna's impedance is with the AIS, and a poor (high) VSWR means poor power transfer between the antenna and the AIS.

It is worth being aware that VSWR depends on frequency, and VHF radio does not operate on quite the same frequency as AIS. Most VHF antennas are tuned to give their best performance at around the Channel 16 frequency (approx. 156MHz), whereas AIS operates at 162MHz. Many VHF antennas have a good VSWR at 156MHz but a poor VSWR at 162MHz. For good AIS performance it's important to either use a broadly-tuned antenna that has a good VSWR from 156 all the way to 162MHz, or (only if you are using this antenna just for the AIS) use an AIS-tuned antenna. Don't use an AIS-tuned antenna for VHF using the AIS700's internal splitter because the VHF RF power can be reflected back into the AIS causing damage.

If the antenna VSWR reported by ProAIS is good (e.g. under 2) then it's possible you have a source of RF interference which is drowning out the VHF reception. This sort of thing is increasingly common, and LED lighting drivers are a common culprit.

Regards,
Tom

Raymarine since 1999.
Interests: Diagnosis of problems in sonar/fishfinders, NMEA2000, ethernet comms, autopilots, thermal cameras
Location: Sydney, Australia
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07-19-19, 05:39 AM (This post was last modified: 07-19-19 07:53 AM by Chuck - Raymarine - Moderator.)
Post: #3
RE: [TG11] Ais 700 "saw "targets only 0.3 nm range
Dear Tom,
the VSWR is 1.6

My sailboat have all led light, I have to change ?!??

Thank you
Ciao
Antonio

What does ProAIS report is the antenna's VSWR value? That sounds like a high VSWR. VSWR is a measurement of how well-matched the antenna's impedance is with the AIS, and a poor (high) VSWR means poor power transfer between the antenna and the AIS.

It is worth being aware that VSWR depends on frequency, and VHF radio does not operate on quite the same frequency as AIS. Most VHF antennas are tuned to give their best performance at around the Channel 16 frequency (approx. 156MHz), whereas AIS operates at 162MHz. Many VHF antennas have a good VSWR at 156MHz but a poor VSWR at 162MHz. For good AIS performance it's important to either use a broadly-tuned antenna that has a good VSWR from 156 all the way to 162MHz, or (only if you are using this antenna just for the AIS) use an AIS-tuned antenna. Don't use an AIS-tuned antenna for VHF using the AIS700's internal splitter because the VHF RF power can be reflected back into the AIS causing damage.

If the antenna VSWR reported by ProAIS is good (e.g. under 2) then it's possible you have a source of RF interference which is drowning out the VHF reception. This sort of thing is increasingly common, and LED lighting drivers are a common culprit.

Regards,
Tom
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07-22-19, 07:48 PM
Post: #4
RE: [TG11] Ais 700 "saw "targets only 0.3 nm range
(07-10-19 01:30 AM)Tom - Raymarine - Moderator Wrote:  Hello Antonio,

What does ProAIS report is the antenna's VSWR value? That sounds like a high VSWR. VSWR is a measurement of how well-matched the antenna's impedance is with the AIS, and a poor (high) VSWR means poor power transfer between the antenna and the AIS.

It is worth being aware that VSWR depends on frequency, and VHF radio does not operate on quite the same frequency as AIS. Most VHF antennas are tuned to give their best performance at around the Channel 16 frequency (approx. 156MHz), whereas AIS operates at 162MHz. Many VHF antennas have a good VSWR at 156MHz but a poor VSWR at 162MHz. For good AIS performance it's important to either use a broadly-tuned antenna that has a good VSWR from 156 all the way to 162MHz, or (only if you are using this antenna just for the AIS) use an AIS-tuned antenna. Don't use an AIS-tuned antenna for VHF using the AIS700's internal splitter because the VHF RF power can be reflected back into the AIS causing damage.

If the antenna VSWR reported by ProAIS is good (e.g. under 2) then it's possible you have a source of RF interference which is drowning out the VHF reception. This sort of thing is increasingly common, and LED lighting drivers are a common culprit.

Regards,
Tom

How do I see the VSWR value in ProAIS?
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07-22-19, 07:59 PM
Post: #5
RE: [TG11] Ais 700 "saw "targets only 0.3 nm range
(07-10-19 01:30 AM)Tom - Raymarine - Moderator Wrote:  Hello Antonio,

What does ProAIS report is the antenna's VSWR value? That sounds like a high VSWR. VSWR is a measurement of how well-matched the antenna's impedance is with the AIS, and a poor (high) VSWR means poor power transfer between the antenna and the AIS.

It is worth being aware that VSWR depends on frequency, and VHF radio does not operate on quite the same frequency as AIS. Most VHF antennas are tuned to give their best performance at around the Channel 16 frequency (approx. 156MHz), whereas AIS operates at 162MHz. Many VHF antennas have a good VSWR at 156MHz but a poor VSWR at 162MHz. For good AIS performance it's important to either use a broadly-tuned antenna that has a good VSWR from 156 all the way to 162MHz, or (only if you are using this antenna just for the AIS) use an AIS-tuned antenna. Don't use an AIS-tuned antenna for VHF using the AIS700's internal splitter because the VHF RF power can be reflected back into the AIS causing damage.

If the antenna VSWR reported by ProAIS is good (e.g. under 2) then it's possible you have a source of RF interference which is drowning out the VHF reception. This sort of thing is increasingly common, and LED lighting drivers are a common culprit.

Regards,
Tom

My VSWR ratio is 1.5:1 in ProAIS. Is that a good value?
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07-22-19, 11:37 PM
Post: #6
RE: [TG11] Ais 700 "saw "targets only 0.3 nm range
Hello Antonia and marlahe,

VSWR readings of 1.6 and 1.5, measured at the AIS, are good values. They don't tell you for sure that the antenna is actually radiating the power effectively as radio, but they do tell you that the AIS's output power will effectively be transferred into the antenna.

How are your AIS's transmit ranges? If you check with other boats, how far away can they see you? If your transmit range is good but your receive range is poor then interference is a likely cause.
Before you think about removing anything from the boat though, try powering the AIS off a separate battery (e.g. a smaller 12V motorcycle battery) with the boat's main battery isolators off: if the AIS works well then and gets good receive range, interference is the cause. If the performance hasn't improved then interference is either caused by something powered straight off the battery or the problem isn't interference.

As another alternative, you could have a technical Service Dealer check with an RF analysis tool (here in Australia we recommend our dealers use a type of low-cost portable spectrum analyser called RTL-SDR for this sort of testing) to identify noise levels and sources.

Regards,
Tom

Raymarine since 1999.
Interests: Diagnosis of problems in sonar/fishfinders, NMEA2000, ethernet comms, autopilots, thermal cameras
Location: Sydney, Australia
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