Antenna on my boat??
Nathan M. Hickson
I posted about this is rec.radio.cb and got no replys so now I'm
trying here...I need to put a cb in my 18 foot boat for the summer and I need
help with the antenna. The boat is all fiberglass except for a little
wood and some chrome railing around the outside. My problem is how do I
get a ground plane without any metal on the boat. Do I use the lake? My
idea would be to put a copper plate about 5 in by 5 in on the bottom of
the boat and run a hefty ground wire to the antenna ground. Would this
work...Would the lake be a sufficient ground...HELP...I dunno what to do
!!
Thanx a bunch,
Nathan Hickson
nhic...@walrus.mvhs.edu
--
"There are no mistakes, only opportunities to learn"
"I haven't lost my mind, I know EXACTLY where I left it!
Jeffrey Herman
>Hello all,
>
> I posted about this is rec.radio.cb and got no replys so now I'm
>trying here...I need to put a cb in my 18 foot boat for the summer and I need
>help with the antenna. The boat is all fiberglass except for a little
>wood and some chrome railing around the outside. My problem is how do I
>get a ground plane without any metal on the boat. Do I use the lake? My
>idea would be to put a copper plate about 5 in by 5 in on the bottom of
>the boat and run a hefty ground wire to the antenna ground. Would this
>work...Would the lake be a sufficient ground...HELP...I dunno what to do
>!!
Nathan - yes that will work fine. I sailed a boat from Hawaii to San
Francisco with using the ballast keel as the `ground'. It effectively
used the ocean as a ground plane. I used 20M daily and was given
great signal reports.
You'll want to epoxy the copper plate to your boat's bottom close to the
transom so you can run the wire up the stern - you don't want to drill
any holes below the waterline for the wire (although some do). No need
for a sacrificial zinc fitting if your boat stays in fresh water.
A quarter wave whip is your best antenna on 11M.
Jeff NH6IL
Guy West
If you have the height you could use one of the vertical dipole type antennas,
the ones with a fibreglass top section and metal bottom with the feed up through
the metal bottom. That type of antenna should not require a separate ground.
I have used a simple L-bracket bolted to the roof rack on my minivan to attach
a cut off Hustler CB whip for 10M band operation. It works after a fashion.
Grounding is a Good Thing, however from a practical standpoint,
if you can get the antenna to load and either don't have variations in vswr with
feed line position, or feed is tied down, then the antenna system should be
functional, not optimum, perhaps not even average, but often functional.
William Vaughn
>Jeff NH6IL
Nathan, Stop what you are doing and go down to the boat store and buy a marine
style antenna for your boat. Shakespere makes a bunch of different types and
they are real cheap.
William Vaughn vaug...@olympus.net "Just plain Bill."
Gary Coffman
>trying here...I need to put a cb in my 18 foot boat for the summer and I need
>help with the antenna. The boat is all fiberglass except for a little
>wood and some chrome railing around the outside. My problem is how do I
>get a ground plane without any metal on the boat. Do I use the lake? My
>idea would be to put a copper plate about 5 in by 5 in on the bottom of
>the boat and run a hefty ground wire to the antenna ground. Would this
>work...Would the lake be a sufficient ground...HELP...I dunno what to do
>!!
A 5 inch by 5 inch copper plate won't be much of a groundplane. You
should use something larger, like 5 *feet* by 5 *feet* copper plate.
The plate doesn't have to be very thick in fresh water, copper foil
tape may work well enough.
Probably a better idea though is to use a halfwave radiator so you
don't *need* any groundplane. That's an 18 foot whip on 11 meters,
and you'll need a matching network to match to the high base impedance,
but it won't need a groundplane at all. You can center feed it and
avoid the matching network, its center impedance will be close enough
to 50 ohms to satisfy your transceiver. A good mechanical arrangement
is to use aluminum *pipe* for the lower half of the element and thread
the coax *inside* the pipe up to the join. The join should be a PVC
coupling to a normal CB whip. Hook the shield to the pipe and the
center to the whip at the join, and you're in business. Watch out
for low bridges!
Gary
--
Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems | we break it. | uunet!rsiatl!ke4zv!gary
534 Shannon Way | Guaranteed! | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244 | |
Ross Alexander
>Nathan - yes that will work fine. I sailed a boat from Hawaii to San
>Francisco with using the ballast keel as the `ground'. It effectively
>used the ocean as a ground plane. I used 20M daily and was given
>great signal reports.
The problem here is that fresh water has a conductivity of about 20
mSiemens per meter, but salt water is far better - 5000 mS/m is
typical. Fresh water makes a poor groundplane, only marginally better
than typical loam soil. Salt water is about as close as one can ever
hope to get in practise to the theoretical infinite perfectly
conductive groundplane.
regards,
Ross ve6pdq
--
Ross Alexander VE6PDQ r...@cs.athabascau.ca,
(403) 675 6311 r...@auwow.cs.athabascau.ca
Jeffrey Herman
>
>Probably a better idea though is to use a halfwave radiator so you
>don't *need* any groundplane. That's an 18 foot whip on 11 meters,
>and you'll need a matching network to match to the high base impedance,
I wouldn't recommend this type of antenna for a small boat. The
base of the 18 foot vertical will be subjected to violent torquing
due to the severe motions which are always encountered on smaller
boats.
Jeff NH6IL
William Vaughn
>In article <1994Jul12....@ke4zv.atl.ga.us> ga...@ke4zv.atl.ga.us (Gary Coffman) writes:
>>
>>Probably a better idea though is to use a halfwave radiator so you
>>don't *need* any groundplane. That's an 18 foot whip on 11 meters,
>>and you'll need a matching network to match to the high base impedance,
>....
Gary, go down to radio shack or your local marine/bait/hardware store and buy
a shakespere marine fold down whip for your cb.
Jeffrey Herman
>
>Gary, go down to radio shack or your local marine/bait/hardware store and buy
>a shakespere marine fold down whip for your cb.
This is the second time today that someone has made reference to
`buying' an item that can easily be built (the earlier item
was an antenna tuner). Gary's idea of a half-wave vertical is
excellent for a base station but might suffer under marine
conditions.
We shouldn't be so quick to direct someone to buy when we,
as amateurs whom are renowned for our skills of building something
out of nothing, can fabricate many station items ourselves.
If the original poster wanted to buy a ready-to-go antenna that
didn't require a ground he wouldn't have posed his question concerning
a below-the-waterline ground plate.
In general, the best choices of shipboard antennas are:
1. Halfwave wire dipole extending from a mast to the stern or another
mast (large powerboat or sailboat).
2. Halfwave vertical (heavy displacement ships, or powerboats operated
in protected waters).
3. Quarter wave vertical in conjunction with a below-the-waterline
ground plate (any vessel).
4. A random wire between masts, or mast and stern in conjunction with
a below-the-waterline ground plate (large powerboat or sailboat).
I wouldn't want the commercial fiberglass `compromise' CB antennas on
a boat of mine; my radio is my lifeline to the shore - I want to
make sure my signal is heard!
Of course, being an ex-Coast Guard Radio Officer I must in good
conscience say that one should/must have a VHF marine band radio;
the USCG has an excellent coastal/lake VHF radio system and have
radiomen listening 24 hours per day to channel 16 (156.80 MHz)
just waiting to assist you. The antenna of choice is a 5/8 wave
vertical; but a 1/4 wave ground plane atop a mast would suffice.
Jeff NH6IL
Gary Coffman
That's a good point, but probably more applicable to salt water
boating than to fresh water river or lake boating where large
waves are uncommon. I think the bigger problem would be bridge
and overhanging tree clearances. A couple of non-metallic stays
should reduce the torquing on the base, if that proved to be a
problem.
Bill Northup
I wanted to try out HF on the boat so I took the Hustler antenna off of my
truck and put it on the stern rail and used the keel as a ground. This has
worked far better than I expected on 10, 15, 17, and 20 meters.
I didn't work at all for 40 meters so I use an inverted V for that band.
--
--
Bill Northup PHONE: (508) 460-2085
Stratus Computer Inc. INTERNET: nor...@sw.stratus.com
55 Fairbanks Boulevard Packet: N1QPR@WA1PHY.#EMS.MA.USA.NA
Marlboro, MA 01752 Amateur Radio: N1QPR
Dave Kinzer
>
> I posted about this is rec.radio.cb and got no replys so now I'm
>trying here...I need to put a cb in my 18 foot boat for the summer and I need
>help with the antenna. The boat is all fiberglass except for a little
>wood and some chrome railing around the outside. My problem is how do I
>get a ground plane without any metal on the boat. Do I use the lake? My
>idea would be to put a copper plate about 5 in by 5 in on the bottom of
>the boat and run a hefty ground wire to the antenna ground. Would this
>work...Would the lake be a sufficient ground...HELP...I dunno what to do
You're ground plate idea will work, but commercial jobs for doing this
are usually slightly bigger, say a foot square. A freshwater lake
will provide the needed counterpoise, but not nearly as good as sea
water, thus the antenna performance will not be as good as possible.
It will probably work plenty good though.
If you want to avoid doing this you could get a fiberglass whip
antenna made for boats and a folding rail mount. No groundplane
is needed for this type antenna. I know some here will argue that
you should homebrew something, and I like fiddling with antennas
too, but you will be hard pressed to make something that is rugged
enough for the service. Besides, do you want to spend all your
time making antennas, or be out on the water. Summer is well
underway already, so get going!
-dave
William Vaughn
>In article <vaughnwt.2...@olympus.net> vaug...@olympus.net (William Vaughn) writes:
>>
>>Gary, go down to radio shack or your local marine/bait/hardware store and buy
>>a shakespere marine fold down whip for your cb.
>I wouldn't want the commercial fiberglass `compromise' CB antennas on
>a boat of mine; my radio is my lifeline to the shore - I want to
>make sure my signal is heard!
>Of course, being an ex-Coast Guard Radio Officer I must in good
>conscience say that one should/must have a VHF marine band radio;
>the USCG has an excellent coastal/lake VHF radio system and have
>radiomen listening 24 hours per day to channel 16 (156.80 MHz)
>just waiting to assist you. The antenna of choice is a 5/8 wave
>vertical; but a 1/4 wave ground plane atop a mast would suffice.
>Jeff NH6IL
Jeff, buddy. We are talking about a "CB" antenna here. Why waste time on the
silly thing. Being an ex CG radio officer you are probably aware that the
coast guard does not monitor CB radio any longer. If there is a CB radio in
the comms room the radioman(person) has the gain and volume turned all the way
down. Being an ex CG radio officer how many times have you lost a person who
had a cb and had to relay thru someone who had a VHF? I suggested that he buy
one because they are cheap and he won't get that much better performance
anyway. Those vhf antennas you have for your boat, did you make them yourself
or did you buy one of those compromise fiberglass ones?
Jeffrey Herman
I wrote:
>>Of course, being an ex-Coast Guard Radio Officer I must in good
>>conscience say that one should/must have a VHF marine band radio;
>>the USCG has an excellent coastal/lake VHF radio system and have
>>radiomen listening 24 hours per day to channel 16 (156.80 MHz)
>>just waiting to assist you. The antenna of choice is a 5/8 wave
>>vertical; but a 1/4 wave ground plane atop a mast would suffice.
>
>>Jeff NH6IL
>
>Jeff, buddy. We are talking about a "CB" antenna here. Why waste time on the
>silly thing. Being an ex CG radio officer you are probably aware that the
>coast guard does not monitor CB radio any longer. If there is a CB radio in
>the comms room the radioman(person) has the gain and volume turned all the way
>down. Being an ex CG radio officer how many times have you lost a person who
>had a cb and had to relay thru someone who had a VHF?
Why do you think I suggested getting a VHF radio? Sheesh. But, here in
Hawaii our fishing fleet operates on CB channel 19, so one's best bet
is having both a CB and a VHF radio here.
Whatever lake the original poster is operating on might be so small
that there is no VHF marine system in operation there. So, if his
comms are entirely dependent upon his CB radio then he'll want the
best possible antenna. It's possible the lake has a REACT monitor
listening on channel 9.
>I suggested that he buy
>one because they are cheap and he won't get that much better performance
>anyway. Those vhf antennas you have for your boat, did you make them yourself
>or did you buy one of those compromise fiberglass ones?
We're talking about a wavelength of 11 meters - commercial antennas
at this wavelength are all compromises (unless they're half wave
length).
On the VHF marine band the wavelength is less than 2 meters so
the commercial antennas are not compromises; they even provide
a certain amount of `gain' from their lower angle of radiation.
I use a homebuilt 1/4 groundplane atop the mast of my sailboat for
my VHF radio. You want a high angle of radiation off a sailboat
antenna because the wind acting on the sails keeps the boat heeled
over at sometimes drastic angles! Even with the sails down the
boat is subject to a rocking motion due to ocean swell, so
again one would still want an antenna with a high angle of radiation.
I think we've beat this topic to death.
Jeff NH6IL
Steven S. Dimse
:
: I posted about this is rec.radio.cb and got no replys so now I'm
: trying here...I need to put a cb in my 18 foot boat for the summer and I need
: help with the antenna. The boat is all fiberglass except for a little
: wood and some chrome railing around the outside. My problem is how do I
: get a ground plane without any metal on the boat. Do I use the lake? My
: idea would be to put a copper plate about 5 in by 5 in on the bottom of
: the boat and run a hefty ground wire to the antenna ground. Would this
: work...Would the lake be a sufficient ground...HELP...I dunno what to do
: !!
If the railing is greater than 1/4 wavelength (108 inches for CB) it
would work as a ground, but less than ideal and would likely cause some
directionality to the antenna pattern. If you try this route, you must
be certain that the railing has a good solid connection to all parts of
itself...electrical connection that is, not mechanical. Depending on the
contruction of the railing, that may mean putting a wire across all the
mechanical connections.
Using the lake as a ground plan would work great...if the lake is the
Great Salt Lake. Unfortunately, radio waves are not reflected well by
fresh water. Also, you would need a much greater area of connection than
5 inches...there is a commercial product called DynaPlate that provides
several square feet of effective surface area in a small package by
using a rough surface.
Another possibility would be to make your own ground plane...attach
several 108 inch or longer wires to the base of the antenna, run them as
straight way from the base as possible. This is probably your best
alternative.
Good luck es 73 de Steve
KO4HD @KB4GCZ.#EYW.FL.USA
sdi...@umbio.med.miami.edu