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VHF w/ GPS reception problems?

Old 11-16-2016, 06:47 PM
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Default VHF w/ GPS reception problems?

My Bluewater 2150 has the radio flush mounted in the console glovebox. My current radio is 12 years old and the display is fried, so I want to replace with a unit with built in GPS so the distress button will work simply and reliably.

I haven't had any issues with reception on my chart plotter/fish finder when flush mounted, but do these radios tend to have reception issues when flush mounted in a console? I don't want to buy something and then have to figure out somewhere else to put it. Thanks.
Old 11-16-2016, 09:12 PM
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Your radio does not have an internal antenna, so mounting it in the dash will make no difference. The VHF antenna is a whip of some type that sticks up in the air Hopefully you have one somewhere?

The GPS antenna on the other hand is often built into the MFD. Even then, it usually doesnt reduce GPS reception enough to worry about when dash mounted.
Old 11-16-2016, 10:56 PM
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Originally Posted by Yrral3215 View Post
.... The GPS antenna on the other hand is often built into the MFD. Even then, it usually doesnt reduce GPS reception enough to worry about when dash mounted.
Gee I wish people wouldn't make statements like that based on little more than opinion and/or what else somebody reckoned that internal GPS is somehow exempt from the basics of signal reception, people might turn this myth into fact shortly
Old 11-17-2016, 12:49 AM
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Notice I said "usually doesnt"?

On the other hand, when was the last time you saw a report where a dash mounted MFD had poor GPS reception? There are - almost - no reports of problems when dash mounting modern MFD's unless they are inside a cabin on an aluminum boat.
Old 11-17-2016, 01:14 AM
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Originally Posted by Yrral3215 View Post
Notice I said "usually doesnt"?

On the other hand, when was the last time you saw a report where a dash mounted MFD had poor GPS reception? There are - almost - no reports of problems when dash mounting modern MFD's unless they are inside a cabin on an aluminum boat.
You are putting the wrong message across and then trying to justify your own comments, there is much more to this issue than many people want to acknowledge and "usually" isn't a word that should be highlighted in this case, gives a totally wrong impression so unless you can categorically deny there will never be an issue with an internal mount then my advice is best to simply say nothing.
Old 11-17-2016, 04:46 AM
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but do these radios tend to have reception issues when flush mounted in a console?
I think OP was talking of GPS reception of his VHF, not GPS reception of his MFD ....

If i am right:
When your chartplotter/fishfinder has GPS signal in the console your GPS VHF should have reception too. But to make sure you may try to put your smartphone inside the VHF cutout to see if the smartphone has GPS signal.
If so your GPS enabled VHF should have reception too as most of the GPS Enabled VHF radios have smartphone type GPS chipsets and antennas built-in.
Chris
Old 11-17-2016, 07:01 AM
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With any device that has an internal GNSS receiver, the ability of the device to receive signals from satellites will always be affected by the location and orientation of the device and its internal GNSS receiver antenna.

In the case of a VHF Marine Band radio transceiver that is flush mounted in the console of a boat, as long as the antenna of the internal GNSS receiver has a reasonably clear view of the sky most of the time, it should be able to get a position solution, but the actual outcome in any individual case depends on how it is mounted and where it is mounted.

There are usually about nine GPS satellites in view. To get a two-dimension position solution (latitude, longitude) only requires that three satellites be available. This suggests that two-thirds (six) of the satellites could be blocked from view at any one time, and as long as the other one-third (three) satellites were in view, a position solution would be possible. As I type this, I am sitting indoors, under a roof, with extremely limited view of the sky, and my iPhone has a GPS position solution with an accuracy of about 20-feet, and I just took it out of my pants pocket. These GNSS receivers work rather well these days.

However, that said, it should be duly noted that most GNSS receivers in smartphones are using a very big advantage: A-GPS. When you are on a boat, your GNSS receiver will be autonomous and will not have the advantage of A-GPS (Assisted GPS). Without getting into the technology, A-GPS allows a GNSS receiver to have a very much faster time to first fix than an autonomous GNSS receiver. The difference in time to first fix can be greater than ten minutes in comparing a receiver using A-GPS with an autonomous receiver, particularly an autonomous receiver with a cold start, that is, no current ephemeris data. I don't know how widespread A-GPS service is outside of the USA. In the USA it is just about universal with cellular telephone based devices.

When on the water, the view of the sky is generally remarkably uncluttered by any terrain, so the only factors affecting GNSS reception are local factors on the boat itself. Even GNSS receivers inside a cabin will often work. One can also draw an inference from the popularity of VHF Marine Band transceivers with their own internal GNSS receiver; it they did not work in almost all installations, I am sure you would have a very large number of anecdotal reports about these failures.

Last edited by jhebert; 11-19-2016 at 08:51 AM.
Old 11-17-2016, 07:08 AM
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most of the time the VHF is linked in through the NMEA network and it relieves its position from the MFD. in that event you can mount the VHF any where you would like
Old 11-17-2016, 08:43 AM
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Sounds like you want a new VHF radio with an integrated GPS receiver. You have a very good chance that will work just fine mounted in the dash. I would go for it.


There have been several discussions on the benefits or not of an external GPS antenna/Receiver versus in internal GPS Antenna/Receiver with MFD's. No need for the debate here again. I choose to buy a new VHF radio with NMEA2K connectivity to take all the trouble of getting GPS and AIS working between my MFD's and VHF. Certainly another option for you to buy a VHF with NMEA2K so if either your MFD or VHF receiver have poor GPS reception at any time an external antenna can solve that problem for both applications.


Jim
Old 11-17-2016, 10:15 AM
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Originally Posted by Rolandt03 View Post
most of the time the VHF is linked in through the NMEA network and it relieves its position from the MFD. in that event you can mount the VHF any where you would like
This would be my choice; you already know your MFD has good reception so why not use it.

Or we could spend the day arguing about signal attenuation through fiberglass structures.
Old 11-18-2016, 09:48 AM
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Originally Posted by Kerry View Post
You are putting the wrong message across and then trying to justify your own comments, there is much more to this issue than many people want to acknowledge and "usually" isn't a word that should be highlighted in this case, gives a totally wrong impression so unless you can categorically deny there will never be an issue with an internal mount then my advice is best to simply say nothing.
Seriously? Well then, you must never give any advice at all on any subject - except for advice about not giving advice
Old 11-18-2016, 11:27 AM
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Originally Posted by jfwireless View Post
Sounds like you want a new VHF radio with an integrated GPS receiver. You have a very good chance that will work just fine mounted in the dash. I would go for it.

That's how I understood it. Like an Icom 324G/424G. I just bought one and had the same question but I think antennas have probably evolved over the past 15 years and are more sensitive to satellite signals. My plan is to try the in-dash mount without connecting to the NMEA 2000 backbone, and if reception is an issue I can connect it later. Same with the MFDs...see how they work and if it seems an antenna would help one can be added with relative ease.
Old 11-18-2016, 01:19 PM
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Originally Posted by Yrral3215 View Post
Seriously? Well then, you must never give any advice at all on any subject - except for advice about not giving advice
Seriously? So are you happy with a marginal (suspect at times) capability or would you prefer the best integrity possible?
Old 11-18-2016, 02:52 PM
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Originally Posted by Kerry View Post
Seriously? So are you happy with a marginal (suspect at times) capability or would you prefer the best integrity possible?
Im not sure why you are only picking on me when almost every one else has said essentially the same thing I have - the built in GPS antennas work just fine in the vast majority of installations.

In other words - "usually" they work just fine. Actually, 'usually' is probably conservative.

Cases where the built-in antennas DONT work are the exception to the rule.

How exactly would you tell someone that bit of information? Or should you just keep quiet and let them spend extra money and time over a 'problem' that they are very unlikely to have? Or do you think external antennas need to be installed in every single case?
Old 11-18-2016, 02:54 PM
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Originally Posted by Auburn1 View Post
That's how I understood it. Like an Icom 324G/424G. I just bought one and had the same question but I think antennas have probably evolved over the past 15 years and are more sensitive to satellite signals. My plan is to try the in-dash mount without connecting to the NMEA 2000 backbone, and if reception is an issue I can connect it later. Same with the MFDs...see how they work and if it seems an antenna would help one can be added with relative ease.
Exactly. The odds are very much in favor of the built in antenna working just fine. Thats especially true with the OP's type of vessel - a fiberglass center console - usually
Old 11-18-2016, 08:50 PM
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Thanks guys, I'm gonna go for it.
Old 11-19-2016, 02:20 AM
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Originally Posted by Yrral3215 View Post
Exactly. The odds are very much in favor of the built in antenna working just fine. Thats especially true with the OP's type of vessel - a fiberglass center console - usually
Oh good since when were people made of fibreglass Maybe the people could sit way way way down the back and steer with a forky stick.

You know there is not a lot of thinking people when it comes to some of the claims re internal GPS. People's perceptions are really minimal and lack total 24 hour concentration, people only see what people want to see and in the real world that is not a lot of the time.

Who is prepared to accept less? Who does want to be an exception to the rule? More so why do some want to be that exception?

All some people can do in places like this is advise what can happen, what could happen based on what has happened, what people do with that info is their own business, it's their boat, it's their problem but lets not have any crap about trying to justify unsubstantiated BS that somehow internal GPS is somehow exempt from reality.

Please feel free to accept the consequences of your own decisions, nobody is making you install a system with inferior capabilities,
Old 11-19-2016, 09:04 AM
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Originally Posted by Kerry View Post
...there [are] not a lot of thinking people when it comes to some of the claims re internal GPS....
I guess the people who think a GNSS receiver whose antenna is mounted internally in a device like a chart plotter or a radio will work must represent a large non-thinking segment of the population by your assessment.

It is certainly possible to invent circumstances in which a VHF Marine Band radio with an internal GNSS receiver with internal antenna might have reduced satellite reception. However, we have statistical data from the Coast Guard of the USA that 90-percent of the DSC distress alert transmissions made contained NO POSITION REPORT.

http://www.navcen.uscg.gov/?pageName=DSCSpecial

Since that data was taken before the arrival of radios with internal receivers, we have to conclude that radios without an internal receiver were NOT connected to an external receiver about 90-percent of the time.

This puts us in a difficult position. If we refuse to use a DSC radio with an internal GNSS, we are likely to be in a group in which nine of ten have no connection to a GNSS.

I think it is better to get a radio with an GNSS and hope that the internal GNSS will work at a higher rate than only one-time out of ten.
Old 11-19-2016, 09:26 AM
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Typically, VHF/DSC radios with 0183 GPS input have been mis-wired or not wired...one source quoted as high as 90% not receiving a usable GPS signal to the radio...That is a good justification for VHF radios having integral GPS receivers, I think.

Also, GPS receivers have improved dramatically over the decades I've been using them, both in terms of sensitivity and accuracy/precision (DOP). My first handheld GPS had a 4 or 6 channel receiver, and needed a clear sky-view...even tree canopy would defeat it. My current one ( a car model with "pedestrian mode" for hiking) will even get a usable signal inside a wood-framed house, and dense foliage is not a problem. And the earliest ones didn't even display on a map, just displayed a "bread-crumb" trail with waypoints.
Old 11-19-2016, 09:28 AM
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Originally Posted by Kerry View Post
Oh good since when were people made of fibreglass Maybe the people could sit way way way down the back and steer with a forky stick.

You know there is not a lot of thinking people when it comes to some of the claims re internal GPS. People's perceptions are really minimal and lack total 24 hour concentration, people only see what people want to see and in the real world that is not a lot of the time.
What the heck are you talking about?

but lets not have any crap about trying to justify unsubstantiated BS that somehow internal GPS is somehow exempt from reality.

Please feel free to accept the consequences of your own decisions, nobody is making you install a system with inferior capabilities,
Where did I - or anyone else - say internal antennas were exempt from reality? Do you not understand the definition of 'usually'?

Ok, so aside from all that - what exactly is YOUR advice for the OP? All you've done so far is complain about mine with nothing from you except 'shut up'.

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