VHF Radio and Antenna Locations?

A forum for discussing topics relating to MacGregor Powersailor Sailboats

Moderators: kmclemore, beene, NiceAft, Catigale, Hamin' X

adudinsk
First Officer
Posts: 335
Joined: Tue Aug 27, 2019 12:53 pm
Sailboat: MacGregor 26M

VHF Radio and Antenna Locations?

Post by adudinsk » Thu Oct 07, 2021 11:23 am

Looking at a new base station VHF/AIS/GPS radio
Wondering about the following:
1) I have a modified arch.. thats about 3' over my head. It has mounts for the antenna there.. is that a good spot... or should I mast mount.
2) What type of cable.. I was leaning to tinned LMR-400 (especially if mast mounted)
3) If I mast mount.. any comments.. suggestions.. or "watch out for.. this and that.."

Any brands anyone suggest?
Should I just use my hand held 5w unit?

chipveres
Engineer
Posts: 162
Joined: Sat Aug 11, 2012 12:53 pm
Sailboat: MacGregor 22
Location: Dania, FL

Re: VHF Radio and Antenna Locations?

Post by chipveres » Thu Oct 07, 2021 1:38 pm

A couple of things you may very well have already thought of: We didn't mast-mount our antenna because there are some bridges here we can just sneak under without an opening. Add the height of the antenna, and the banging might not break the antenna, but it would certainly break my nerves. Almost none of the "waterproof" antenna connectors are actually waterproof. PL-259/SO-239 types are brutally strong but not at all waterproof. You certainly need a mast-base connector for when you take the mast down. If you know what tinned LMR-400 is, you probably don't need my advice. Just use your best judgement.

Chip Veres
s/v Sand Dollar
"Always needs sanding, always costs some dollars."

User avatar
Highlander
Admiral
Posts: 5588
Joined: Wed Sep 21, 2005 8:25 pm
Sailboat: MacGregor 26M
Location: Maccutter26M 2008 75HP Merc. 4/S Victoria BC. Can. ' An Hileanto'ir III '
Contact:

Re: VHF Radio and Antenna Locations?

Post by Highlander » Thu Oct 07, 2021 2:05 pm

Here's my set up

Image

I have since also added an electric low tone trumpet horn up there also

from port side AIS, CEL booster S/B side TV , VHS

Hope this helps u out
J 8)

adudinsk
First Officer
Posts: 335
Joined: Tue Aug 27, 2019 12:53 pm
Sailboat: MacGregor 26M

Re: VHF Radio and Antenna Locations?

Post by adudinsk » Fri Oct 08, 2021 5:28 am

Nice! Highlander's boat is LOADED!

I am thinking just mounting to my arch as it is extended about 3' or so. 3db gain antenna...
There are warnings about RF causing 'harm" if to close to a person... any comments?
I guess for the 10 min / year that I transmit.. no biggie..
And if I am in trouble.. would not care about RF radiation... etc.
?comments?

Was considering the following VHF
Standard GX2400GPS Matrix VHF with AIS Receive GPS and NMEA2000

and the following antenna
SHAKESPEARE–Mariner 4200 3' 3dB VHF Sailboat Antenna

LMR-400 cable (have lots lying around.. so.. might as well)

Would like some sort of VHF/TV antenna.. still looking.. any recommendations ... ?

User avatar
Russ
Admiral
Posts: 6521
Joined: Thu Oct 11, 2007 12:01 pm
Sailboat: MacGregor 26M
Location: Bozeman, Montana "Luna Azul" 2008 M 70hp Suzi

Re: VHF Radio and Antenna Locations?

Post by Russ » Fri Oct 08, 2021 6:10 am

VHF is line of sight and height matters. Therefore powerboaters are jealous of our mast-mounted antennas. The problem is that our boats heal and therefore a sailboat mast-mounted antenna is usually a lower gain 3db antenna with a wider beam.

It also requires the mast to be up.

Many Mac owners go with lower mounted antennas because they often boat with mast down.

If you decide mast mount (I did) then you will have to get past the foam that is inside the top of the mast. There are many solutions to this if you search this forum. I was able to run a fish tape along to pull the cable.

More here
https://www.practical-sailor.com/marine ... sion-range


Image
--Russ

User avatar
Tomfoolery
Admiral
Posts: 6115
Joined: Tue Jul 05, 2011 7:42 am
Sailboat: MacGregor 26X
Location: Rochester, NY '99X BF50 'Tomfoolery'

Re: VHF Radio and Antenna Locations?

Post by Tomfoolery » Fri Oct 08, 2021 6:29 am

adudinsk wrote:
Fri Oct 08, 2021 5:28 am
There are warnings about RF causing 'harm" if to close to a person... any comments?
I guess for the 10 min / year that I transmit.. no biggie..
And if I am in trouble.. would not care about RF radiation... etc.
?comments?
If you look at the gain pattern in Russ's graphic above, standing under one means very little RF radiation straight down (or up). I wouldn't worry about it. Power boaters don't worry about it either, and they're usually using 9dB whip antennas, often with people around it. Better if above people, but I don't think it's actually a serious concern for such short exposures. We stick cell phones up against our heads, after all, and while they're low power, they're right next to our noggins (inverse square law).

My preference is for top of mast mounting, with 3dB antenna. The wider gain pattern is offset by the lower overall gain, but the wider pattern is better for heeling. Height is important, too, but going from 8 ft to 30 ft only gains a few miles range (theoretical) using line-of-sight calculators, assuming a 100 ft USCG antenna. BUT, a few miles can mean a lot when you're in trouble, either via clearer signal, or just being able to be heard at all.

There's more to it than just line-of-sight distances, as there is a little bit of diffraction that happens with UHF marine signals, and they actually will bend over the earth a bit (20-30% additional range is the figure I always remember, right or wrong). But height certainly helps.

https://www.easycalculation.com/physics ... stance.php

I have a hand held, which is limited to 5W I believe, and also an 'emergency' antenna that can sit on the deck and plug directly into the fixed VHF. I usually just use the hand held for no-mast operation, but the short backup is on the boat just in case.
Tom
Be seeing you . . .

pitchpolehobie
Engineer
Posts: 158
Joined: Wed Dec 18, 2019 8:46 pm
Sailboat: MacGregor 26X
Location: USA, OH

Re: VHF Radio and Antenna Locations?

Post by pitchpolehobie » Fri Oct 08, 2021 6:33 am

So I was considering a similar upgrade. I have an old basic VHF in my boat w a short antenna in the cabin from prev owner - works marginally I was going to run up a new vhf cable to the mast and get a new base unit but considering options and my use case (inland US, great lakes) I went with a good handheld radio the ICOM M94D has AIS and DSC. It has an AC and DC adapter to charge on the water. Used s week on the water and have been very happy w it. Obviously not the range of a mast top but with VHF towers by USCG its unlikelynto be an issue. :macx:

https://www.icomamerica.com/en/products ... fault.aspx

adudinsk
First Officer
Posts: 335
Joined: Tue Aug 27, 2019 12:53 pm
Sailboat: MacGregor 26M

Re: VHF Radio and Antenna Locations?

Post by adudinsk » Fri Oct 08, 2021 6:59 am

Very good points..
Prob will mount on the arch.. its easy.. and will work with mast down. (believe it or not.. did not think of that.. do not often run with mast down.. but am planning some trips next year to Rideau/Trent Severin canals..

Maybe will consider a 8' whip... at 3db

Thanks for all the advice...

(note self (not wife) ... spend more $$ on the boat...)


AD

User avatar
Tomfoolery
Admiral
Posts: 6115
Joined: Tue Jul 05, 2011 7:42 am
Sailboat: MacGregor 26X
Location: Rochester, NY '99X BF50 'Tomfoolery'

Re: VHF Radio and Antenna Locations?

Post by Tomfoolery » Fri Oct 08, 2021 8:13 am

adudinsk wrote:
Fri Oct 08, 2021 6:59 am
Maybe will consider a 8' whip... at 3db
Does anyone make such a thing?

Or are you funnin' with us? :|
Tom
Be seeing you . . .

chipveres
Engineer
Posts: 162
Joined: Sat Aug 11, 2012 12:53 pm
Sailboat: MacGregor 22
Location: Dania, FL

Re: VHF Radio and Antenna Locations?

Post by chipveres » Fri Oct 08, 2021 3:23 pm

I just ran Aduninsk's setup through the RF exposure calculator at ARRL.ORG You need to be at least 3 feet from your antenna while sending to be utterly safe. The health aspects of RF radiation have been greatly exaggerated because doom sells books and newspapers.

Chip V.

User avatar
dlandersson
Admiral
Posts: 3896
Joined: Fri Aug 27, 2010 10:00 am
Sailboat: MacGregor 26X
Location: Chicago metro, USA

Re: VHF Radio and Antenna Locations?

Post by dlandersson » Fri Oct 08, 2021 3:56 pm

Line of sight matters. If you can put it on your mast, it's a good idea. 8)
adudinsk wrote:
Thu Oct 07, 2021 11:23 am
Looking at a new base station VHF/AIS/GPS radio
Wondering about the following:
1) I have a modified arch.. thats about 3' over my head. It has mounts for the antenna there.. is that a good spot... or should I mast mount.
2) What type of cable.. I was leaning to tinned LMR-400 (especially if mast mounted)
3) If I mast mount.. any comments.. suggestions.. or "watch out for.. this and that.."

Any brands anyone suggest?
Should I just use my hand held 5w unit?

adudinsk
First Officer
Posts: 335
Joined: Tue Aug 27, 2019 12:53 pm
Sailboat: MacGregor 26M

Re: VHF Radio and Antenna Locations?

Post by adudinsk » Sun Oct 10, 2021 1:07 pm

I will look at ly arch next week... See what clearance I have.


Or maybe...put tinfoil on my head?
🤔

User avatar
Russ
Admiral
Posts: 6521
Joined: Thu Oct 11, 2007 12:01 pm
Sailboat: MacGregor 26M
Location: Bozeman, Montana "Luna Azul" 2008 M 70hp Suzi

Re: VHF Radio and Antenna Locations?

Post by Russ » Sun Oct 10, 2021 3:46 pm

If I had a nice arch, I'd probably put one on the mast and the arch. Redundancy and all that.
--Russ

OverEasy
Captain
Posts: 825
Joined: Mon Sep 28, 2020 11:16 am
Sailboat: MacGregor 26X
Location: NH SC
Contact:

Re: VHF Radio and Antenna Locations?

Post by OverEasy » Tue Oct 12, 2021 3:00 pm

:D :D Please Post picture of “tin hat” mod so we can copy it…. :D :D

Seem to recall that the ref radiation is also emanating from not only the antenna but also from the transmitter itself and the coaxial lead as well……. 🤔

adudinsk
First Officer
Posts: 335
Joined: Tue Aug 27, 2019 12:53 pm
Sailboat: MacGregor 26M

Re: VHF Radio and Antenna Locations?

Post by adudinsk » Wed Oct 13, 2021 2:30 am

I do have an EMF meter.. will see if that reads anything.. will check on a friends boat.

AD

Post Reply