Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 01-10-2019, 15:30   #16
Registered User
 
Brian.D's Avatar

Join Date: Jan 2019
Location: Oceanside Ca
Boat: Lancer 27PS
Posts: 617
Re: Trying to find the perfect VHF antenna

The Glomex antennas look nice enough. However, I am not a fan of FME Connectors. With the pounding a boat can take in rough weather, there is a possibility (if remote) that the connector can work its way loose. I would say that PL-259 (UHF connectors) are time-proven to work. Just keep the whole connection water tight with dual wall heat shrink.

JMHO
__________________
Brian D
KF6BL
S/V Takara
Brian.D is offline   Reply With Quote
Old 01-10-2019, 16:50   #17
Registered User
 
CarinaPDX's Avatar

Join Date: Jan 2010
Location: Portland, Oregon, USA
Boat: 31' Cape George Cutter
Posts: 3,270
Re: Trying to find the perfect VHF antenna

The masthead VHF (my previous post) is a stainless whip with a PL-259 and I think pretty much ideal [it has a low SWR]. The AIS antenna is mounted on the radar pole aft and has the FME connector. The advantage is that the included cable can be routed through holes slightly larger than the cable, then connected in place without soldering/crimping a PL-259 (and the FME connector was installed at the factory). Given how badly so many people do making up a PL-259 this is a reasonable approach. I think it best to have an AIS antenna tuned to the AIS frequencies, and this was what was available at the time. Again, I would prefer a stainless whip, and for me the PL-259 would have been fine if it was available, but the AIS tuning was paramount. As it was I installed it while at anchor, standing on the pushpit and stretching up to assemble, so I was happy with it.

Many years ago the first generation of ethernet used coax cables and PL-259 terminals. My brother did a lot of networking and was often called in to troubleshoot; short answer: it was (almost) always the lousy install of the PL-259's that was to blame - even crimped ones. Unfortunately while it was easy to find - that was the first place to look - IT guys don't like to hear their problem was of their own making, with such an apparently simple task.

Greg
CarinaPDX is offline   Reply With Quote
Old 01-10-2019, 17:03   #18
Registered User

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,420
Re: Trying to find the perfect VHF antenna

We use a short stub antenna. It has less dB but better angles.


b.
barnakiel is offline   Reply With Quote
Old 02-10-2019, 02:36   #19
Registered User

Join Date: Sep 2018
Posts: 63
Re: Trying to find the perfect VHF antenna

I got fed up dealing with masthead antenna problems, so I mounted a 3 ft fibreglass GLOMEX VHF antenna on the stern railing. I'm not an engineer, but I figured the very short cable run would compensate for loss of height, and any issues with corrosion or dodgy connections would be easier to fix.

I use this antenna both for R/T and AIS reception, and haven't noticed any difference in range from having it mounted much lower down. In fact, I regularly receive AIS data from vessels over 50NM distant.

AGE OF SAIL - Home
psp2psp2 is offline   Reply With Quote
Old 02-10-2019, 02:42   #20
Registered User

Join Date: Jan 2017
Location: Irish Sea
Posts: 1,321
Images: 7
Re: Trying to find the perfect VHF antenna

Quote:
Originally Posted by psp2psp2 View Post
I got fed up dealing with masthead antenna problems, so I mounted a 3 ft fibreglass GLOMEX VHF antenna on the stern railing. I'm not an engineer, but I figured the very short cable run would compensate for loss of height, and any issues with corrosion or dodgy connections would be easier to fix.

I use this antenna both for R/T and AIS reception, and haven't noticed any difference in range from having it mounted much lower down. In fact, I regularly receive AIS data from vessels over 50NM distant.

AGE OF SAIL - Home
If you use a decent cable (even r8x, shipped with many decent vhf antennas) you'll hardly loose anything. It's the broken connectors and wet foam dielectrics that kill your traffic.
AIS goes further (don't ask me why...), but voice is usually line of sight. That's why I'll put my separate AIS antenna on the stern, likely on the radar pole:

__________________
Useful as a fireproof bottom paint...
GTom is offline   Reply With Quote
Old 02-10-2019, 12:08   #21
Registered User
 
powsmias's Avatar

Join Date: Apr 2014
Location: Jersey
Boat: Bristol 35.5
Posts: 485
Re: Trying to find the perfect VHF antenna

home depot runnin a sale on this one now
https://www.homedepot.com/p/Tram-AIS...b2XGvlfwt-5IeI
__________________
www.eddiethelock.com
powsmias is offline   Reply With Quote
Old 02-10-2019, 13:02   #22
Registered User
 
S/V Illusion's Avatar

Join Date: Oct 2007
Location: Lakewood Ranch, FLORIDA
Boat: Alden 50, Sarasota, Florida
Posts: 3,467
Re: Trying to find the perfect VHF antenna

Quote:
Originally Posted by barnakiel View Post
We use a short stub antenna. It has less dB but better angles.


b.
Line of sight is line of sight. No amount of additional power can compensate for the reduced line of sight which occurs with low antennas. And no stub antenna is an efficient radiator or affects radiation angle in any way. Marketing is so adorable.
S/V Illusion is offline   Reply With Quote
Old 02-10-2019, 13:04   #23
Registered User

Join Date: Jan 2017
Location: Irish Sea
Posts: 1,321
Images: 7
Re: Trying to find the perfect VHF antenna

BTW anyone selling antennas with N-type connector on the Northern hemisphere? The only one I saw so far was in New Zealand.
__________________
Useful as a fireproof bottom paint...
GTom is offline   Reply With Quote
Old 02-10-2019, 16:26   #24
Registered User

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,420
Re: Trying to find the perfect VHF antenna

Quote:
Originally Posted by S/V Illusion View Post
Line of sight is line of sight. No amount of additional power can compensate for the reduced line of sight which occurs with low antennas. And no stub antenna is an efficient radiator or affects radiation angle in any way. Marketing is so adorable.

This:


SMALL/VHF - Banten


at 10m, matched with the fat cable.


What is my problem? Talk to me.



Or do you sail a cruise ship with stabilizers?


My boat will heel 25-30 degs on a regular basis. Think of a small and narrow double ender in trade winds.


Rx.


?


Cheers,

b.
barnakiel is offline   Reply With Quote
Old 02-10-2019, 16:38   #25
Moderator and Certifiable Refitter
 
Wotname's Avatar

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,301
Re: Trying to find the perfect VHF antenna

Quote:
Originally Posted by psp2psp2 View Post
...... I'm not an engineer, but I figured the very short cable run would compensate for loss of height,
Height trumps power!
1 watt at 10 ft is way way way better than 10 watts at 1 ft etc. Obviously you need a bit of both though

Quote:
Originally Posted by psp2psp2 View Post
.
and any issues with corrosion or dodgy connections would be easier to fix.
..........
This is very very true!
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Old 02-10-2019, 19:59   #26
Registered User

Join Date: Sep 2017
Location: Langley, WA
Boat: Nordic 44
Posts: 2,501
Re: Trying to find the perfect VHF antenna

Avoid LMR400. Not only because of the foam dielectric, because LMR400 uses aluminum conductors and the center wire is not stranded. The center wire in copper clad so it can be soldered but despite appearances it is aluminum. The shield cannot be soldered - a crimp connector must be used. A proper crimping tool is about $50. Apply that money towards rg-213.

A good source of tinned rg-213 is Davis RF. No affiliation, just a happy customer.
stormalong is offline   Reply With Quote
Old 24-11-2019, 12:42   #27
Registered User
 
TreblePlink's Avatar

Join Date: Aug 2017
Location: Kentucky
Boat: 1969 Rhodes 28'
Posts: 307
Re: Trying to find the perfect VHF antenna

Antenna brand or type doesn't matter much. Height is everything at VHF, so it belongs at the masthead if you want best range. As has been mentioned, most problems are connector and corrosion related. I use teflon rg58/u - I forget the exact nomenclature. 18 meters does introduce some loss, but in the overall scheme of things, not much. If you have range issues, and the antenna LOOKS ok, the first thing to check is standing wave ratio - "SWR." You do this by inserting the meter between the radio and the antenna transmission line. Meters can be had on ebay for $30, or can be borrowed. You should see less than 2:1 on channel 16.


I have spent my career doing communications and antenna work.
TreblePlink is offline   Reply With Quote
Old 24-11-2019, 12:54   #28
Registered User
 
Auspicious's Avatar

Join Date: Jun 2003
Location: Chesapeake Bay
Boat: HR 40
Posts: 3,651
Send a message via Skype™ to Auspicious
Re: Trying to find the perfect VHF antenna

Nothing is perfect. I like the Metz Manta for many reasons.

Quote:
Originally Posted by stormalong View Post
Apply that money towards rg-213.
I like RG-214. Double shielding. Remember to isolate the antenna bracket from the mast to avoid ground loops.

Quote:
Originally Posted by TreblePlink View Post
Antenna brand or type doesn't matter much. Height is everything at VHF, so it belongs at the masthead if you want best range.
AND NOTHING ELSE UP THERE. Separate AIS antennas (recommended), cellular, satellite, WiFi - all belong somewhere else. Spreader, pole, backstay, where ever but not at the masthead.

I like the Daiwa CN-801 cross needle meter which works on both HF and VHF.
__________________
sail fast and eat well, dave
AuspiciousWorks
Beware cut and paste sailors
Auspicious is offline   Reply With Quote
Old 24-11-2019, 13:47   #29
Registered User
 
CarinaPDX's Avatar

Join Date: Jan 2010
Location: Portland, Oregon, USA
Boat: 31' Cape George Cutter
Posts: 3,270
Re: Trying to find the perfect VHF antenna

While we all agree that antenna height and line-of-sight is more important, I don't think we should dismiss the importance of reducing cable losses (or obsessing about it either). RG-58 has about a 6dB loss over 100ft at marine VHF frequencies, and RG-213 has less than 3dB loss. The 3dB difference is a halving of signal strength. So a 100ft run from radio to antenna with 25W output will result in roughly 12.5W for RG-213 and 6.3W for RG-58 (about what a handheld puts out). At the margins of the range this does make a difference, although less than it may appear, as it is stated in decibels because the radiated power is an inverse square of the distance, not a linear relationship. Having that little bit of extra range is what a good install is all about, and entails both height and low cable loss.

Greg
CarinaPDX is offline   Reply With Quote
Old 24-11-2019, 13:50   #30
Registered User
 
TreblePlink's Avatar

Join Date: Aug 2017
Location: Kentucky
Boat: 1969 Rhodes 28'
Posts: 307
Re: Trying to find the perfect VHF antenna

Quote:
Originally Posted by Auspicious View Post

I like RG-214. Double shielding. Remember to isolate the antenna bracket from the mast to avoid ground loops.

RG-214 is certainly low loss.



But I have never heard of isolating the antenna bracket from the mast. Is there a reference advocating this? The mast and stays form part of the antenna and can't be ignored. Some "no ground plane required" antennas can work with just the coax outer conductor forming the "other half" of the dipole, but most mast top antennas need the stays and or mast connection. From a lightning protection standpoint (nearby, not direct mast strike where not much helps) bonding at the top and close to the base is best.


All metal near the antenna affects the pattern. In a previous post I showed a typical effect on the vertical field due to induced mast and stay currents:

http://www.cruisersforum.com/forums/...-193349-2.html
TreblePlink is offline   Reply With Quote
Reply

Tags
antenna, vhf

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

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 Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
"What makes the perfect boat woman...perfect" Celestialsailor Our Community 221 10-10-2017 10:38
Can AIS Share VHF Antenna with Existing VHF Radio ? cool2848 Marine Electronics 18 24-04-2013 08:56
Perfect Boat or Perfect Place? Hanna&Chris General Sailing Forum 22 08-10-2009 19:27

Advertise Here


All times are GMT -7. The time now is 11:45.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.