Weak AIS Signal?

[theway]

I plugged antenna directly into the XB8000 no improvement, still only boats around 3nm... doesn’t make sense if Radio works clear at 15nm

I’m thinking I might need to do a firmware update or perhaps talk with the Vesper folks.

Any other thoughts?

[hoolie]

Certainly sounds like a masthead antenna/coax problem to me. I think the suggestion to buy and try a separate antenna that you can mount on the stern rail is excellent.

[transmitterdan]

Originally Posted by theway

I plugged antenna directly into the XB8000 no improvement, still only boats around 3nm... doesn’t make sense if Radio works clear at 15nm

I’m thinking I might need to do a firmware update or perhaps talk with the Vesper folks.

Any other thoughts?

Old antennas are almost never optimized for the AIS frequencies. Check the VSWR using the maintenance software that comes with the Vesper. It will tell you something useful I think.

If the VSWR is >1.5:1 then it would be good to check out the antenna connection at the top. If the connector is clean and dry then maybe the antenna isn’t compatible with the AIS frequencies.

If the VSWR is <1.1:1 then the coax may be badly corroded inside due to water ingress. Really low VSWR may indicate there is significant losses in the coax.

VHF voice communication isn’t a reliable indicator as to whether the antenna system is working right. VSWR usually tells the story.

[clownfishsydney]

We have noticed many times that some yachts have very poor AIS transmissions. That is, they are relatively close to us but drop in and out all the time. This is at the same time that other boats stay constant, even though much further away. We have found that we get a good 20 to 30 nm range on AIS (Class B) for most yachts in open sea. No idea why this happens, but assume they have a device that is somehow faulty or not as good as others.

[Dsanduril]

The XB-8000 transmits at 2W, as do most Class B AIS. So, it you're looking at Class B signals around you you're looking at 2W 'conversations.'

When you say the VHF does much better than the AIS on the same antenna what power are you using? If you're calling on 16 VHFs usually default to high power (25W) and so you could be comparing a 25W 'conversation' to a 2W conversation. Try switching to low power on the VHF and see if you still get greater range than the AIS.

[ka4wja]

theway,
If you really want an answer, you've already gotten it. (and it isn't a "firmware update")

As others have pointed out, it is most probably a coax, coax-connecter, masthead antenna issues!! (and/or a connector / splice issue, if you have a connection at the mast base??)

Originally Posted by theway

The antenna is at least 8yrs I’ve had the boat and probably many more before that 10-30yrs

Originally Posted by theway

I plugged antenna directly into the XB8000 no improvement, still only boats around 3nm... doesn’t make sense if Radio works clear at 15nm

I’m thinking I might need to do a firmware update or perhaps talk with the Vesper folks.

Any other thoughts?

But, goodness, do you still use 30 year old docklines? or anchor rode/chain?? Or rigging?? Or sails?? Or darn near anything except the hull, keel, rudder, diesel, etc....
Everything needs to be checked / replaced as needed....
Coaxial cable is no exception!! (and especially if the connections were not done correctly to start with, and/or not weather-proofed properly!)

Remember that VHF-FM at 25 watts, is comparable to AIS at about 12.5 watts...but your Class B AIS is 2 watts, which would be ~~ "comparable" to a VHF-FM Voice signal of only 3 to 4 watts (yes, this is approx., but you do see what we're getting at, yes??)

As for your specific comment on communications "range", and why it is better to a shore station, etc....please have a look here:

http://www.cruisersforum.com/forums/...ge-149499.html

You'll learn more than you ever thought you wanted to know!
Have fun!

But, please just replace your entire run of coax (including the short coax jumper cables) with new cable, with properly installed connections (either pre-made, or professionally installed, don't do it yourself!)...
Use good quality, name brand cable (Belden, Times, Commscope, Davis, etc..) use only RG-213 or RG-8x ("mini-8")....
Do NOT be mislead into believing that you need some special "low-loss cable" like LMR-400, as this will be a mistake for you.
Do all of this, and you'll be good-to-go!

Hope this helps.

Fair winds.

John

FYI, I had to Google "Coffs Harbour" to find out you're not in San Fran! Maybe be a bit more specific when answer a question, and you'll get more specific answers.

[theway]

Originally Posted by transmitterdan

Old antennas are almost never optimized for the AIS frequencies. Check the VSWR using the maintenance software that comes with the Vesper. It will tell you something useful I think.

If the VSWR is >1.5:1 then it would be good to check out the antenna connection at the top. If the connector is clean and dry then maybe the antenna isn’t compatible with the AIS frequencies.

If the VSWR is <1.1:1 then the coax may be badly corroded inside due to water ingress. Really low VSWR may indicate there is significant losses in the coax.

VHF voice communication isn’t a reliable indicator as to whether the antenna system is working right. VSWR usually tells the story.

This is very useful. I will check into this as soon as I get up there to learn about the antenna, but since the antenna is probably a lot older than modern AIS I’m guessing there are better ones available.

[theway]

Originally Posted by ka4wja

theway,
If you really want an answer, you've already gotten it. (and it isn't a "firmware update")

As others have pointed out, it is most probably a coax, coax-connecter, masthead antenna issues!! (and/or a connector / splice issue, if you have a connection at the mast base??)

But, goodness, do you still use 30 year old docklines? or anchor rode/chain?? Or rigging?? Or sails?? Or darn near anything except the hull, keel, rudder, diesel, etc....
Everything needs to be checked / replaced as needed....
Coaxial cable is no exception!! (and especially if the connections were not done correctly to start with, and/or not weather-proofed properly!)

Remember that VHF-FM at 25 watts, is comparable to AIS at about 12.5 watts...but your Class B AIS is 2 watts, which would be ~~ "comparable" to a VHF-FM Voice signal of only 3 to 4 watts (yes, this is approx., but you do see what we're getting at, yes??)

As for your specific comment on communications "range", and why it is better to a shore station, etc....please have a look here:

http://www.cruisersforum.com/forums/...ge-149499.html

You'll learn more than you ever thought you wanted to know!
Have fun!

But, please just replace your entire run of coax (including the short coax jumper cables) with new cable, with properly installed connections (either pre-made, or professionally installed, don't do it yourself!)...
Use good quality, name brand cable (Belden, Times, Commscope, Davis, etc..) use only RG-213 or RG-8x ("mini-8")....
Do NOT be mislead into believing that you need some special "low-loss cable" like LMR-400, as this will be a mistake for you.
Do all of this, and you'll be good-to-go!

Hope this helps.

Fair winds.

John

FYI, I had to Google "Coffs Harbour" to find out you're not in San Fran! Maybe be a bit more specific when answer a question, and you'll get more specific answers.

Thanks for the thorough reply... I usually go by the saying, if it ain’t broke don’t fix it, so yes their are many things that are old and could use replacing, but they continue to server there purpose and so I let them be. Then it’s a matter of having spares or being in a place that’s convenient when it does break.

The thing about Coffs wasn’t meant to be specific, I suppose point a to point b would have done the same.

And yes, I hope you’re right about the replacement of things, but have you ever replaced something and still had a problem persist? I’m just trying to understand the system and possibilities before replacing things for the sake of it.

[ka4wja]

Not sure what happened to the last part of my bold type....but here it is:
And, replace the VHF antenna as well!

Originally Posted by ka4wja

theway,
As for your specific comment on communications "range", and why it is better to a shore station, etc....please have a look here:

http://www.cruisersforum.com/forums/...ge-149499.html

You'll learn more than you ever thought you wanted to know!
Have fun!

But, please just replace your entire run of coax (including the short coax jumper cables) with new cable, with properly installed connections (either pre-made, or professionally installed, don't do it yourself!)...
Use good quality, name brand cable (Belden, Times, Commscope, Davis, etc..) use only RG-213 or RG-8x ("mini-8")....
Do NOT be mislead into believing that you need some special "low-loss cable" like LMR-400, as this will be a mistake for you.
And, replace the VHF antenna as well!
Do all of this, and you'll be good-to-go!


Hope this helps.

Fair winds.

John

FYI, I had to Google "Coffs Harbour" to find out you're not in San Fran! Maybe be a bit more specific when answer a question, and you'll get more specific answers.

Sorry, if I sound so emphatic....but, I've been in radio comms for ~ 45 years. on boats and on shore....and unless you know a significant amount about radiowave propagation, etc., it might not make a lot of sense to you...

That's why I gave you the link...to learn for yourself...

But, also provided you with the solutions to your problems...

The choice is yours:
a) learn everything you need to know to troubleshoot the problem.
or
b) take the advice of those that know.


Fair winds.

John

[theway]

Originally Posted by ka4wja

Not sure what happened to the last part of my bold type....but here it is:
And, replace the VHF antenna as well!



Sorry, if I sound so emphatic....but, I've been in radio comms for ~ 45 years. on boats and on shore....and unless you know a significant amount about radiowave propagation, etc., it might not make a lot of sense to you...

That's why I gave you the link...to learn for yourself...

But, also provided you with the solutions to your problems...

The choice is yours:
a) learn everything you need to know to troubleshoot the problem.
or
b) take the advice of those that know.


Fair winds.

John

Thanks John,
The VHF antenna will definitely be replaced.

(Maybe the first thing... then I can check the system again to see if it’s fixed or the problem remains, then continue through the system in such approach)

And I don’t mind the emphasis... I often make things harder if it means I’ll learn something along the way. It’s almost too easy to just replace everything and move on. Maybe it’s a deep rooted human tendency towards understanding.

[a64pilot]

Originally Posted by theway

This is very useful. I will check into this as soon as I get up there to learn about the antenna, but since the antenna is probably a lot older than modern AIS I’m guessing there are better ones available.

I had high SWR on my installation with 30yr old coax and antenna, but it still worked very well.
When my mast was down I had the coax replaced and a new antenna installed.
Vesper makes an antenna that is supposedly tuned for both VHF and AIS, it seems to work well, lowered the SWR anyway.
https://www2.vespermarine.com/antenn...ed-ais-antenna

Also just in case you haven’t heard, your Vesper splitter actually works better for AIS than a stand alone antenna without a splitter, the splitter isn’t a weak link

[transmitterdan]

Originally Posted by theway

This is very useful. I will check into this as soon as I get up there to learn about the antenna, but since the antenna is probably a lot older than modern AIS I’m guessing there are better ones available.

You don't need to climb up there to check VSWR. The Vesper has that feature so you can do it without climbing.

[theway]

Originally Posted by transmitterdan

You don't need to climb up there to check VSWR. The Vesper has that feature so you can do it without climbing.

Says OK....

[transmitterdan]

I thought those units gave an actual number for VSWR. I must have been thinking of a different brand. Just saying "OK" is less helpful in this situation.

[DavefromNZ]

I had exactly the same problem. I knew the signal from my yacht was very poor as I tried to satellite track her plus it was average around the coast. The problem was simply that I was using a splitter through my VHF aerial. If you want to fix it then get a proper AIS tuned aerial and fit it on your top spreader. It must not be at the level of your VHF aerial as that can cause interference. It does not have interference even though close to a stay.

I am now tracked 100% by SAT AIS and I see big ships 80nm away. Aerial set at about 60ft. The signal is very strong.

I know it is a hassle to fit a new aerial but a splitter is poor.