inneedofadvice

AIS receiver info anyone?

Recommended Posts

Is a stand alone AIS receiver like the http://www.raymarine.com/view/index.cfm?id=559 any better performing than a combo VHF/AIS receiver like the http://www.standardhorizon.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=83&encProdID=27C38D916BB23B1B8A53F18ED6C711B7&DivisionID=3&isArchived=0

I have a VHF that is adequate but both units are about the same price. My plotter is an A50 raymarine with nmea 2000 and seatalk so can be easily connected to display AIS info. Any advantage of one over the other?

Share this post


Link to post
Share on other sites

At current pricing, is there a compelling reason to install an AIS receiver vs. a class B transceiver?

Share this post


Link to post
Share on other sites

My current electronics setup includes a defunct chartplotter, defunct entertainment stereo, and flaky VHF transceiver at the chart table, plus a functional sonar/GPS plotter at the wheel and a handheld VHF which is way more convenient for talking to bridge tenders than the one that's past the wheel down the stairs inside.

I'm thinking about completely reworking the chart table electronics bank, replacing the entertainment stereo with something from this millennium, and possibly getting an integrated VHF/AIS that could act as backup incase the GPS plotter at the wheel (and my cellphone) goes out.  Are there any integrated VHF/AIS that provide more than minimal nav support from their GPS info?

As for relative performance, I think that's all about the antenna placement.  If the integrated VHF/AIS has an internal GPS antenna, that's going to be a little less sensitive than one that can "see the sky," might not matter except on a marginally rainy day the external antenna could "see through the rain" a little better than one that is also dealing with interference from the hull and other things around it.  Not as dramatic as the difference between a mast-top mounted VHF antenna and a handheld, but it's something.

For me, I like the simplicity of an integrated unit - when it dies, it's dead, much fewer external connections to configure and check, and hopefully it's a bit more reliable with fewer external opportunities for problems.

Share this post


Link to post
Share on other sites
2 hours ago, inneedofadvice said:

Is a stand alone AIS receiver like the http://www.raymarine.com/view/index.cfm?id=559 any better performing than a combo VHF/AIS receiver like the http://www.standardhorizon.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=83&encProdID=27C38D916BB23B1B8A53F18ED6C711B7&DivisionID=3&isArchived=0

I have a VHF that is adequate but both units are about the same price. My plotter is an A50 raymarine with nmea 2000 and seatalk so can be easily connected to display AIS info. Any advantage of one over the other?

At the same price, getting the combo gives you a redundant radio. Not necessarily a bad thing. However, you could put a transceiver on a splitter and use the same masthead antenna and get superior range. 

A dedicated receiver seems a bit anachronistic. 

 

Share this post


Link to post
Share on other sites

With modern phones and software defined radios, how about a phone that you can also use for vhf and AIS. Yes, 162 MHz is a bit more difficult than 700 antenna-wise, so?

Share this post


Link to post
Share on other sites
42 minutes ago, Varan said:

With modern phones and software defined radios, how about a phone that you can also use for vhf and AIS. Yes, 162 MHz is a bit more difficult than 700 antenna-wise, so?

Great idea, Motorola made a cell phone paired with a VHF trunking service that was quite popular in Central Florida for awhile - every contractor and his wife had one.

Share this post


Link to post
Share on other sites
7 hours ago, DDW said:

At current pricing, is there a compelling reason to install an AIS receiver vs. a class B transceiver?

I don't think so. Just a few years ago there was a big price differential and I bought an AIS capable VHF radio, but if I were doing it today I would get a transceiver and a less expensive VHF with DSC but no AIS.

Share this post


Link to post
Share on other sites
7 hours ago, George Dewey said:

I don't think so. Just a few years ago there was a big price differential and I bought an AIS capable VHF radio, but if I were doing it today I would get a transceiver and a less expensive VHF with DSC but no AIS.

Except that the price differential between a VHF with DSC but no AIS and one with all three is very small. Even though I already had a transceiver, I got the latter for redundancy. Even if everything on my N2K network shits the bed, I've still got AIS receive as long as I have 12V.

Share this post


Link to post
Share on other sites

There are AIS tranceivers way cheaper than the Raymarine unit. As cheap as $200 on eBay. In a name brand quality unit, I'd go with the Vesper XB6000. For a few bucks more the Vesper XB8000 will also WiFi all your data (including instrument) to whatever you've got. Vesper quality and support are excellent. 

It's too bad these VHF companies don't offer transceiver function, as they could subsume the antenna splitter as well with virtually no cost. Maybe there are some like that?

AIS receive is half the job. SEE and BE SEEN.

Share this post


Link to post
Share on other sites
49 minutes ago, DDW said:

There are AIS tranceivers way cheaper than the Raymarine unit. As cheap as $200 on eBay. In a name brand quality unit, I'd go with the Vesper XB6000. For a few bucks more the Vesper XB8000 will also WiFi all your data (including instrument) to whatever you've got. Vesper quality and support are excellent. 

It's too bad these VHF companies don't offer transceiver function, as they could subsume the antenna splitter as well with virtually no cost. Maybe there are some like that?

AIS receive is half the job. SEE and BE SEEN.

The Standard Horizon GX6500 was supposed to be the first but it was stillborn and didn't integrate a splitter, you still need a separate AIS antenna and an external GPS antenna (supplied). I hear it has all sorts of problems too. Here's a thread from Panbo.

https://www.panbo.com/standard-horizon-gx6500-a-loaded-vhf-radio-also-integrated-with-class-b-ais/

All SH really needs to do is make a GX2200 with AIS transceive, an integrated splitter, and N2K. Is that so hard?

Share this post


Link to post
Share on other sites
1 hour ago, IStream said:

The Standard Horizon GX6500 was supposed to be the first but it was stillborn and didn't integrate a splitter, you still need a separate AIS antenna and an external GPS antenna (supplied). I hear it has all sorts of problems too. Here's a thread from Panbo.

https://www.panbo.com/standard-horizon-gx6500-a-loaded-vhf-radio-also-integrated-with-class-b-ais/

All SH really needs to do is make a GX2200 with AIS transceive, an integrated splitter, and N2K. Is that so hard?

I think they addressed the splitter?

image.png.03eb5a31c23916ef1769ef61372022aa.png 

Share this post


Link to post
Share on other sites

But it is NMEA 0183 

Share this post


Link to post
Share on other sites
5 hours ago, DDW said:

There are AIS tranceivers way cheaper than the Raymarine unit. As cheap as $200 on eBay. In a name brand quality unit, I'd go with the Vesper XB6000. For a few bucks more the Vesper XB8000 will also WiFi all your data (including instrument) to whatever you've got. Vesper quality and support are excellent.

Do tell re: these $200 Ebay deals!

+1 on the XB6000, but don't forget the splitter.  Puts you back in the $800 range.

+1 on Vesper support.  They are outstanding.

Share this post


Link to post
Share on other sites
3 hours ago, Raz'r said:

I think they addressed the splitter?

image.png.03eb5a31c23916ef1769ef61372022aa.png 

Almost but not quite. The 2200 has a VHF transmitter, a VHF receiver, and an AIS receiver. It can have both receivers connected to the antenna at the same time but needs to disconnect the AIS from the antenna during VHF transmit.

When you add AIS transmit to the mix, you need to do the above as well as disconnect the VHF from the antenna during AIS transmit with logic to prioritize VHF transmit over AIS transmit should there be a conflict. 

It's still not hard but the GX2200 antenna sharing/splitting scheme would need to be adapted for two transmitters.

Share this post


Link to post
Share on other sites
26 minutes ago, IStream said:

Almost but not quite. The 2200 has a VHF transmitter, a VHF receiver, and an AIS receiver. It can have both receivers connected to the antenna at the same time but needs to disconnect the AIS from the antenna during VHF transmit.

When you add AIS transmit to the mix, you need to do the above as well as disconnect the VHF from the antenna during AIS transmit with logic to prioritize VHF transmit over AIS transmit should there be a conflict. 

It's still not hard but the GX2200 antenna sharing/splitting scheme would need to be adapted for two transmitters.

ahh, if I understand correctly, not an issue if I'm not broadcasting AIS....

 

I know I dont get full value of the tech if not broadcasting.

 

Share this post


Link to post
Share on other sites
11 hours ago, IStream said:

Except that the price differential between a VHF with DSC but no AIS and one with all three is very small. Even though I already had a transceiver, I got the latter for redundancy. Even if everything on my N2K network shits the bed, I've still got AIS receive as long as I have 12V.

That's a very fair point.

Share this post


Link to post
Share on other sites

It's also worth noting that while class B AIS transceivers are available with very aggressive pricing, those are generally not the class B SOTDMA standard, which is a fantastic improvement over the earlier class B CS standard. It's more power, 5 watts vs 2 watts, and a more robust protocol. There are now services that can receive class B SOTDMA signals via satellite, making this standard  useful when you're well offshore, at least as far as someone tracking you from afar. It's extra money but I think it's worth it. I plan to get the Garmin AIS 800 before Spring. This unit integrates the splitter.

Share this post


Link to post
Share on other sites

Three different antenna configurations for sailboats to consider:

- two antennas on the mast, AIS antenna optimized for AIS frequency, separate cables - Antenna nirvana, nobody does this on sailboats under 45 feet because of all the extra weight on the extra cable impacts sailing performance, and antennas likely interfere with each other when VHF is transmitting so next option is inviting, which is...

- a shared antenna on the mast with a splitter, very popular. Tradeoff's, there is a degradation in VHF range and clarity, AIS signals (transmit and receive) inhibited while talking, splitter uses a bit of power. While the antenna isn't optimized for AIS frequency, being on top of a mast provides a range already longer than you would ever need.

- a dedicated AIS antenna put on the aft rail of the sailboat. None of the trade-offs of using a splitter, AIS range is reduced with the lower antenna mount but acceptable in that big tall ships can be seen from 6-12 nm based on how big and tall a ship is, short little boats can only be seen a few miles out. Which is fine, you need to SEE AND BE SEEN based on the size of the other boat, so this seems perfect for me. 

Transmitters

- Writers above covered everything, nothing for me to add except emphsis on have one, don't choose a receive-only solution. SEE AND BE SEEN

Radar Reflectors,

- There is a terrific little known option for radar reflectors perfect for a sailboat to be seen by larger ships (lightweight, no sharp edges, a large reflection surface, etc.). Set-up a spot in your rigging and just clip it on before any journey into iffy weather or night sailing.    https://www.panbo.com/the-passive-radar-reflector-solution-for-sailboats 

 

 

Share this post


Link to post
Share on other sites

3x the cost of the Davis on that radar reflector is a bit of a big pill to swallow.  Does doubling up the reflectors like that make a big difference?

I'm surprised that the panbo article talks about no one having reflectors installed.  It's a requirement for most racing, so I'm used to seeing a Davis reflector in the catch-rain position on almost every sailboat around here.  Ours is a little bent up from checkstays catching on it, so having a second one to hoist on a flag halyard in bad weather wouldn't be the worst thing.

Share this post


Link to post
Share on other sites
34 minutes ago, b393capt said:

Three different antenna configurations for sailboats to consider:

- two antennas on the mast, AIS antenna optimized for AIS frequency, separate cables - Antenna nirvana, nobody does this on sailboats under 45 feet because of all the extra weight on the extra cable impacts sailing performance, and antennas likely interfere with each other when VHF is transmitting so next option is inviting, which is...

- a shared antenna on the mast with a splitter, very popular. Tradeoff's, there is a degradation in VHF range and clarity, AIS signals (transmit and receive) inhibited while talking, splitter uses a bit of power. While the antenna isn't optimized for AIS frequency, being on top of a mast provides a range already longer than you would ever need.

- a dedicated AIS antenna put on the aft rail of the sailboat. None of the trade-offs of using a splitter, AIS range is reduced with the lower antenna mount but acceptable in that big tall ships can be seen from 6-12 nm based on how big and tall a ship is, short little boats can only be seen a few miles out. Which is fine, you need to SEE AND BE SEEN based on the size of the other boat, so this seems perfect for me. 

I'll add one thing to the above, which is that Vesper sells an antenna that's optimized (or compromised, depending on how you look at it) for both VHF and AIS. Putting that at the masthead, combined with an upgrade of the in-mast cabling which is often poorly implemented and/or barely adequate, works really well. 

 

Share this post


Link to post
Share on other sites

Every test on passive radar reflectors (there have been at least 5 scholarly ones) conclude the same thing: they do little or nothing to make your boat more visible to radar. None except the very largest and most expensive actually meet the SOLAS requirements, which are really a bare minimum (equivalent to a 4' diameter steel ball). Hoist one if you must but don't expect it to make you visible. AIS is FAR more reliable. 

One of the reflector tests proved that 2 reflectors can be even worse than one under some circumstances. If the two end up 1/4 wavelength different in distance to the transmitter, destructive interference causes them to disappear entirely. Best to hang them over and under if you are going to do it. 

  • Like 1

Share this post


Link to post
Share on other sites
On 1/22/2019 at 10:53 PM, WoobaGooba said:

Do tell re: these $200 Ebay deals!

+1 on the XB6000, but don't forget the splitter.  Puts you back in the $800 range.

+1 on Vesper support.  They are outstanding.

can be cheaper

http://www.cactusnav.com/vesper-marine-xb8000-transponder-with-built-wifi-p-12724.html

 

Share this post


Link to post
Share on other sites
3 minutes ago, inneedofadvice said:

I'm liking this setup, Toronto boat show price is $680 CDN ($510 USD)

emtrak AIS Class B Sailor Package with B100 AIS & S100 Splitter

Can't argue with the price but I'd see if you can get the equivalent Vesper setup for a similar price. Vesper updates their systems with new capabilities regularly and has great support in every other way. em-trak's CEO is an asshole and I wouldn't expect any updates. 

 

Share this post


Link to post
Share on other sites
7 minutes ago, inneedofadvice said:

Made me laugh. I'll check it out, thanks.

Here's some related info. FYI, SRT OEMs their AIS guts to lots of manufacturers but em-trak is SRT's house brand and Simon Tucker is the CEO.

https://www.panbo.com/srt-acquires-class-b-ais-patent-consequences-uncertain/

https://www.panbo.com/ais-issues-garmin-navico-mcmurdo-amec-and-srt/

Check out the comments on the second link too.

 

Share this post


Link to post
Share on other sites
13 minutes ago, inneedofadvice said:

That is what I installed on my boat last year.  It works for me, Milltech Marine near Seattle had a good bundle price (under $500).  It looks like now they only have the B300/S300 bundle, which is the same thing with waterproofing added.

To answer IStream's concern, the Vesper packages are about $200 more.  The Vesper XB-8000 is cool with the WiFi support, but the incremental cost is more than just buying a standalone NMEA 2000 to WiFi gateway: http://www.yachtd.com/products/wifi_gateway.html

Share this post


Link to post
Share on other sites
Just now, Alex W said:

That is what I installed on my boat last year.  It works for me, Milltech Marine near Seattle had a good bundle price (under $500).  It looks like now they only have the B300/S300 bundle, which is the same thing with waterproofing added.

To answer IStream's concern, the Vesper packages are about $200 more.  The Vesper XB-8000 is cool with the WiFi support, but the incremental cost is more than just buying a standalone NMEA 2000 to WiFi gateway: http://www.yachtd.com/products/wifi_gateway.html

The XB-6000 is a bit cheaper and it's basically an 8000 without WiFi.

Share this post


Link to post
Share on other sites

Is the xb-6000 nmea 2000 as well and does that matter?

edit: yeah it's both sorry for being so lazy

 

Edited by inneedofadvice

Share this post


Link to post
Share on other sites
Just now, IStream said:

The XB-6000 is a bit cheaper and it's basically an 8000 without WiFi.

Yes, the XB-6000 is about $200 cheaper, the same price as the yachtd gateway.

It is still $200 more than the em-trak package (active splitter and AIS transceiver).  I didn't know that the em-trak CEO was an asshole when I purchased my setup.  I'm not sure how much I would have let that influence my purchase.

XB-6000A ($489) plus splitter ($229) = $718 (cheapest Vesper, has an internal GPS antenna)

XB-8000A ($740) plus splitter ($229) = $969

em-trak sailor's package (B300 plus S300 splitter) = $550 (uses an external GPS antenna)

 

Share this post


Link to post
Share on other sites
Just now, inneedofadvice said:

Is the xb-6000 nmea 2000 as well and does that matter?

Yes, it is.

NMEA 2000 matters to me, because my Raymarine plotter (es78) doesn't copy AIS from NMEA 0183 to NMEA 2000, and so I can't see AIS on my i70 instrument displays without using a NMEA 2000 AIS transceiver.  How that matters to you will depend on the rest of the hardware on your boat.

I also hate NMEA 0183, so I'm happier with everything being NMEA 2000.

Share this post


Link to post
Share on other sites

So, ready to buy:

Vesper xb-6000 + splitter  - $141 more.

emtrak b100/s100 package - CEO is asshole.

Only other difference I can see is the external GPS antenna on the Emtrak. This hasn't been an issue for my chart plotter with internal antenna.

Decisions, decisions...

 

Share this post


Link to post
Share on other sites

I'd find the Vesper dealer(s) at the Toronto show and see if they can narrow the $141 delta.

Share this post


Link to post
Share on other sites

Turns out Hamilton Marine is not the Hamilton in Ontario Canada which makes that USD so that is a $430 difference. Makes for an easier decision. 

Share this post


Link to post
Share on other sites

Agreed. My personal rule of "try not to do business with assholes" isn't written in stone when the differential is huge. 

Share this post


Link to post
Share on other sites
On 1/24/2019 at 1:51 PM, inneedofadvice said:

Would it be recommended to skip the splitter and use a stern rail mounted separate antenna?

No, I would not recommend that. The splitter does have two disadvantages. First, it adds some loss. Second, you can't receive AIS data while you're transmitting. And mounting an antenna on the stern rail reduces feedline, which means less loss. But, the huge advantage of the splitter and antenna on the masthead is altitude. Range is greatly enhanced, especially if the AIS data you're trying to receive comes from a crewmember who went overboard and is now being tossed about in big waves.

Share this post


Link to post
Share on other sites

Just an FYI that Milltech Marine is having a Seattle boat show special on Vesper and other brands of AIS. The XB-6000A (no WiFi and no external GPS antenna) plus splitter is US$667.74. 

https://www.milltechmarine.com/

No affiliation except that I bought my Vesper gear from them a couple of years ago and was very pleased with their service both before and after the sale.

Share this post


Link to post
Share on other sites

Thanks for all the help on this. I went with the emtrak pkg as the price was unbeatable. ($668 is $900 CDN plus what they hit us to get it here). So no posting any more good deals so I don’t regret it ;-)

Share this post


Link to post
Share on other sites

If I recall, on the integrated vhf/ais in it's you can output the ais data to another device. So you aren't limited to receiving ais on the radio only. It been a while since I've done much of that stuff, so I could be wrong. I'm sure ull be corrected of I am. 

Share this post


Link to post
Share on other sites
2 hours ago, Baldur said:

If I recall, on the integrated vhf/ais in it's you can output the ais data to another device. So you aren't limited to receiving ais on the radio only. It been a while since I've done much of that stuff, so I could be wrong. I'm sure ull be corrected of I am. 

You are correct. The SH unit has NMEA0183 out for AIS data.

Share this post


Link to post
Share on other sites
3 hours ago, IStream said:

You are correct. The SH unit has NMEA0183 out for AIS data.

So does my Link 8, both on N2K and 0186.

Share this post


Link to post
Share on other sites

Yeah, I thought I remembered doing the wiring to sendAIS output from a Standard Horizon (3200?) DSC VHF with the little AIS screen to my friends chart plotter and also to my fugawi on my laptop. And that would have been like 8 years ago. SO I would expect that most DSC and AIS capable VHF base units would be doing it by now. 

 

Share this post


Link to post
Share on other sites

SOTDMA experience ? 

My NAIS400 seems to be having issues, and if I will need to replace it, then popping in a more powerful, more frequent transmission would seem to be the way to go. 

 

the Emtrak looks to be a near swap: for size  https://www.milltechmarine.com/em-trak-B350-Class-B-SOTDMA-AIS-Transponder-_p_421.html

Share this post


Link to post
Share on other sites
16 minutes ago, LionessRacing said:

SOTDMA experience ? 

My NAIS400 seems to be having issues, and if I will need to replace it, then popping in a more powerful, more frequent transmission would seem to be the way to go. 

 

the Emtrak looks to be a near swap: for size  https://www.milltechmarine.com/em-trak-B350-Class-B-SOTDMA-AIS-Transponder-_p_421.html

That's because your NAIS 400 uses an Em-trak OEM AIS module. If you're having hardware issues with the 400, I'd think twice about going with Em-trak. 

Share this post


Link to post
Share on other sites

I'm going to scrutinize my connections etc first, and run diagnostics with proAIS2 to see if there's anything I can find first. The price seems to have dropped since 2016 when I procured the NAIS400. 

Share this post


Link to post
Share on other sites

FWIW, I've got a Standard Horizon GX2200 VHF/GPS/AIS receive as well as a Vesper XB-8000 AIS transceiver. Both had a receive range of about 10 miles until I replaced my masthead VHF antenna, swapped out my 25 year old RG8X cabling with LMR400UF up the mast and LMR240 within the boat, and eliminated several cable connections along the way. My receive range immediately increased to 30 miles for Class B transmissions and to about 50 miles for Class A.

As you well know, a radio is only as good as its antenna and cabling.

  • Like 1

Share this post


Link to post
Share on other sites

Cable sizing doesn't really affect receive performance, that's usually lousy connectors or dead coax. Hard to imagine you needed LMR400 and using LMR240 in the boat and LMR400 in the rig seems questionable. It's best to measure the total run and choose a suitable wire for that length. Using the ISAF requirement that you lose no more than 40% on transmit, LMR240 is good for 72 total feet and LMR400 is good for 130 total feet. 

 

Share this post


Link to post
Share on other sites
On 1/23/2019 at 10:53 AM, WoobaGooba said:
On 1/23/2019 at 5:32 AM, DDW said:

There are AIS tranceivers way cheaper than the Raymarine unit. As cheap as $200 on eBay. In a name brand quality unit, I'd go with the Vesper XB6000. For a few bucks more the Vesper XB8000 will also WiFi all your data (including instrument) to whatever you've got. Vesper quality and support are excellent.

Do tell re: these $200 Ebay deals!

+1 on the XB6000, but don't forget the splitter.  Puts you back in the $800 range.

+1 on Vesper support.  They are outstanding.

I'm loving my XB-8000. Wifi N2K data everywhere on the boat now is nice.

If anyone needs a Furuno FA-30 receiver I've got one under the floorboards somewhere...

Share this post


Link to post
Share on other sites
2 hours ago, Moonduster said:

Cable sizing doesn't really affect receive performance, that's usually lousy connectors or dead coax. Hard to imagine you needed LMR400 and using LMR240 in the boat and LMR400 in the rig seems questionable. It's best to measure the total run and choose a suitable wire for that length. Using the ISAF requirement that you lose no more than 40% on transmit, LMR240 is good for 72 total feet and LMR400 is good for 130 total feet. 

 

It was more the shitty old cable and connectors that were affecting receive performance, not the characteristics of the new stuff. Even if I'd done a one-for-one replacement of every connector and just used brand new RG8X, I probably would've gotten most of the benefit.

Question my choices of cable all you want, I had my reasons and they're still valid.

Share this post


Link to post
Share on other sites
11 hours ago, LionessRacing said:

SOTDMA experience ? 

My NAIS400 seems to be having issues, and if I will need to replace it, then popping in a more powerful, more frequent transmission would seem to be the way to go. 

 

the Emtrak looks to be a near swap: for size  https://www.milltechmarine.com/em-trak-B350-Class-B-SOTDMA-AIS-Transponder-_p_421.html

You can find the Garmin AIS-800 (which includes a splitter built in) for about the same price as that transponder plus the splitter. Of course if you already have the splitter then that's a good option. Keep in mind that the higher power means more battery power consumed, and given you're on a sailboat I don't think you'll benefit from the more frequent transmissions, since those only kick in when you're moving fast, as in > 23 knots. Some people debate the increase in transmit range from the extra transmit power (2w vs 5w) since VHF is line of sight and 2w can transmit to the horizon. A benefit of class B SOTDMA is that you can get one that sends message 27, which can be received by satellites. 

I'll probably go with SOTDMA and if so I'll get the Garmin, but this one also looks nice:

https://www.milltechmarine.com/AMEC-WideLink-B600-Class-B-SOTDMA-AIS-Transponder_p_392.html

 

Share this post


Link to post
Share on other sites
9 hours ago, Moonduster said:

Cable sizing doesn't really affect receive performance, that's usually lousy connectors or dead coax. Hard to imagine you needed LMR400 and using LMR240 in the boat and LMR400 in the rig seems questionable. It's best to measure the total run and choose a suitable wire for that length. Using the ISAF requirement that you lose no more than 40% on transmit, LMR240 is good for 72 total feet and LMR400 is good for 130 total feet. 

 

Isn't it a symmetric system? Same dB losses in TX and RX. Why wouldn't cable losses affect receiving?

10->30/50 miles is not about a small loss caused by cable size or a connector. There must have been a real problem. I got 10 miles AIS RX even with antenna inside the boat. 

Share this post


Link to post
Share on other sites

No. Transmission is about getting power from the output stage of the transmitter to the antenna with out much loss of power. Attenuation in the cable soaks up the power and it never gets to the antenna and so the radiated energy is lower.

Reception is a different beast. Here, the concern isn't power loss as there is no discernible power. During reception, the electro-magnetic field created by the transmitter is turned into a very, very small voltage on the antenna and the wire presents that potential to the receiver. The receiver has infinite impedance and no current flows in the cable; no current, no power. The resistance of the wire makes almost no difference at all.

The 10 vs. 50 miles is almost certainly bad connectivity from the antenna to the receiver. That's usually caused by corrosion.

Share this post


Link to post
Share on other sites
13 hours ago, George Dewey said:

You can find the Garmin AIS-800 (which includes a splitter built in) for about the same price as that transponder plus the splitter. Of course if you already have the splitter then that's a good option. Keep in mind that the higher power means more battery power consumed, and given you're on a sailboat I don't think you'll benefit from the more frequent transmissions, since those only kick in when you're moving fast, as in > 23 knots. Some people debate the increase in transmit range from the extra transmit power (2w vs 5w) since VHF is line of sight and 2w can transmit to the horizon. A benefit of class B SOTDMA is that you can get one that sends message 27, which can be received by satellites. 

I'll probably go with SOTDMA and if so I'll get the Garmin, but this one also looks nice:

https://www.milltechmarine.com/AMEC-WideLink-B600-Class-B-SOTDMA-AIS-Transponder_p_392.html

 

I have the splitter installed,  so a swap into the same space in my elecronics bay has a certain value, it looked as though the plug might even be the same... 

the Satellite reception is nice, though I am currently not offshore, and I doubt Lioness would ever do 20 kts+ without being on a trailer. 

 

Share this post


Link to post
Share on other sites
4 hours ago, Moonduster said:

No. Transmission is about getting power from the output stage of the transmitter to the antenna with out much loss of power. Attenuation in the cable soaks up the power and it never gets to the antenna and so the radiated energy is lower.

Reception is a different beast. Here, the concern isn't power loss as there is no discernible power. During reception, the electro-magnetic field created by the transmitter is turned into a very, very small voltage on the antenna and the wire presents that potential to the receiver. The receiver has infinite impedance and no current flows in the cable; no current, no power. The resistance of the wire makes almost no difference at all.

The 10 vs. 50 miles is almost certainly bad connectivity from the antenna to the receiver. That's usually caused by corrosion.

RF signal loss of a cable  is expressed in dB/m. It's not a function of power and the loss is the same (in dB) for receiving and transmitting.

Share this post


Link to post
Share on other sites
8 hours ago, LionessRacing said:

I have the splitter installed,  so a swap into the same space in my elecronics bay has a certain value, it looked as though the plug might even be the same... 

the Satellite reception is nice, though I am currently not offshore, and I doubt Lioness would ever do 20 kts+ without being on a trailer. 

 

Right, so you could also save yourself a few bucks and go with the older class B standard, unless you want the higher power. If you're not offshore, you probably don't need that either, especially if your antenna is at your masthead. Just a suggestion.

Share this post


Link to post
Share on other sites
4 hours ago, Joakim said:

RF signal loss of a cable  is expressed in dB/m. It's not a function of power and the loss is the same (in dB) for receiving and transmitting.

Joakim is exactly correct.

Share this post


Link to post
Share on other sites

Yes, exactly ... the wire is the wire. But stating the obvious does not answer the question at hand.

When the current is zero, the attenuation of power doesn't matter.

The effects of conductor for receiver are much different than for transmitter.

 

Share this post


Link to post
Share on other sites

The issue is not strictly signal strength but signal to noise ratio, which is why dB is the appropriate measure whether transmitting or receiving. If the dominant noise source is the radio itself rather than environmental noise and you lose 20 or 30dB due to poor connections or water infiltration in your cabling, you may fall below the minimum SNR needed to make a received signal intelligible. That same loss will reduce your transmission range but someone nearby will still receive you just fine because the poor connection doesn't increase the amount of noise you transmit.

Share this post


Link to post
Share on other sites
8 hours ago, Moonduster said:

Yes, exactly ... the wire is the wire. But stating the obvious does not answer the question at hand.

When the current is zero, the attenuation of power doesn't matter.

The effects of conductor for receiver are much different than for transmitter.

 

Doesn't cable loss mean that the amplitude of the signal is lower at the receiver end than at the antenna end? The receiver has a lower limit for the amplitude it can detect. My VHF specs show 0.5 uV as the lower limit.

How is receiver cable loss different from receiver antenna gain or antenna altitude giving higher signal?

I don't think noise picked up by the antenna is the limiting factor typically. If it was, having a better antenna and cable would not help receiving.

All papers I have read about transmission path between RF TX and RX sum the gains and losses symmetrically to get the total dB loss of the system. 

 

Share this post


Link to post
Share on other sites
On 5/17/2019 at 5:50 PM, Moonduster said:

When the current is zero, the attenuation of power doesn't matter.

The attenuation of power doesn't matter. The attenuation of signal on the other hand, does.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now