Notices

GPS Antenna's

Old 04-06-2003, 08:29 AM
  #1  
Member
Thread Starter
 
Join Date: Feb 2003
Location: Wellington, Florida
Posts: 93
Default GPS Antenna's

Which is better? Internal or External antenna's... Is there any benefit of one over the other? Any GPS recommendations? Thanks in advance
phisherman is offline  
Old 04-06-2003, 09:18 AM
  #2  
Senior MemberCaptains Club Member
 
Join Date: Mar 2002
Location: OFallon, Missouri
Posts: 340
Default GPS Antenna's

This has been a common question recently so a search will turn up some answers but basically an external antenna is needed if the head unit will be in an enclosed area without a clear view of the sky. The signal from the GPS satellites are weak and you want the best signal strength you can get. Not all enclosers are equal in blocking signal, fiberglass is far worse that canvas, so it depends on where you want the head unit.

My favorite GPS units are made by Garmin, the 182 is a nice unit.

23 Regulator (2002) F225
Montauk Joe is offline  
Old 04-06-2003, 03:11 PM
  #3  
Senior MemberCaptains Club Member
 
Join Date: Dec 2002
Location: Orlando
Posts: 3,997
Default GPS Antenna's

fiberglass will not block the gps signal. It's as invisible as canvas to the signal.
Sea_Dad is offline  
Old 04-06-2003, 03:23 PM
  #4  
Senior MemberCaptains Club Member
 
Join Date: Mar 2002
Location: OFallon, Missouri
Posts: 340
Default GPS Antenna's

I've have to disagree with you on that. I would never tell someone to mount a GPS with an internal antenna in a fiberglass electronics box or on a boat with a fiberglass T-top. While the signal may not be completely blocked, watch your signal strength bars fall as you move from uncoverred to covered.

quote:Originally posted by Sea_Dad:
fiberglass will not block the gps signal. It's as invisible as canvas to the signal.

23 Regulator (2002) F225
Montauk Joe is offline  
Old 04-06-2003, 03:36 PM
  #5  
Senior MemberCaptains Club Member
 
Join Date: Dec 2002
Location: Orlando
Posts: 3,997
Default GPS Antenna's

Fiberglass will not affect the signal strength of the gps. Metal most certainly will.I would venture that your all glass box and T-Top arent as all glass you may think they are.

I've yet to see a T-Top made from anything but aluminum by the way.
Sea_Dad is offline  
Old 04-06-2003, 07:37 PM
  #6  
Senior MemberCaptains Club Member
 
Join Date: Mar 2002
Location: OFallon, Missouri
Posts: 340
Default GPS Antenna's

Let me refine my post. GPS signal reception is line of sight. The clearest view of the sky will provide to best signal quality/strength and the greatest number of satellites. To some degree, any intervening material will lessen the strength and quality of the signal. The denser the material the weaker the received signal will be. This too applies to fiberglass. Most T-tops would not be considered thin fiberglass and certainly the supporting members being made of aluminum or stainless steel will truly block signals. Locating an antenna within an electroincs box would also not be considered thin fiberglass. Would you still receive a signal, probably. Would it be as strong as out in the open air, probably not. Would the unit function in good weather, probably. Is this an ideal location, no. As I suggested, one would have to test to see how much signal is lost and whether (in the judgment of the operator) this is acceptable. I believe my statement is still true, that a canvas top weakens the GPS signal less that a thicker fiberglass top.

23 Regulator (2002) F225
Montauk Joe is offline  
Old 04-06-2003, 08:42 PM
  #7  
Senior Member
 
Join Date: Feb 2001
Location: Australia
Posts: 3,562
Default GPS Antenna's

In essence the better reception will be one with a FULL clear 360 degree view of the sky above about 5 degrees above the horizon.

Generally anything less than that will/could/might have some restrictions and be a compromise depending (depending on many many things).

Basically an external (barring any obstructions) eliminates any maybe's and maximizes integrity capabilities and if one is considering WAAS then I wouldn't even consider an internal.

Cheers, Kerry.

I never get lost, everybody tells me where to go!
Kerry is offline  
Old 04-06-2003, 08:53 PM
  #8  
Senior Member
 
Join Date: Feb 2003
Location: L.I.Sound
Posts: 129
Default GPS Antenna's

If I were to purchase an internal antenna unit now and in the future installed a T-Top, would I be able to add an external antenna to the unit?
Say it was a Garmin 182c.
mudshark is offline  
Old 04-06-2003, 10:18 PM
  #9  
Member
 
Join Date: Feb 2003
Location: Cape May,NJ
Posts: 63
Default GPS Antenna's

Mudshark,

I have a 162 Garmin with internal antenna. I called Garmin and all I have to do is order the back for the external antenna unit. It's pretty neat how they do it. The internal back is held on with four screws and when you take it off the connector for the external antenna is already there. I would assume all there units are like that but I would call Garmin and check.


Ed
FUMoney is offline  
Old 04-07-2003, 06:44 AM
  #10  
Senior MemberCaptains Club Member
 
Join Date: Dec 2002
Location: Orlando
Posts: 3,997
Default GPS Antenna's

Mountak, I have a searay with the external antenna down in the cuddy cabin on a shelf. I has to look up through 1/2" fiberglass cuddy top to get any signal, yet it has no signal strength loss.

The closer you mount an antenna to a metal frame the larger the blackout zone behind the frame becomes. It's not the fiberglass, because the signal is a magnetic field, and fiberglass is simply not susceptible to it.
Sea_Dad is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread