Marine VHF whip performance on ham 2m ham bands?

[Jon Gauthier]

I haven't fired up EZNEC yet, but I was wondering how a standard 3dBi
marine whip would perform on the 2m ham bands. Since the marine
frequencies are 156.050-157.425 MHz, what could I expect at 144-148 MHz?

If it won't cut it, then does anyone have any recommendations for a
dual-band antenna (commercial or home-built)?

Jon

 

[Peter Bennett]

I haven't fired up EZNEC yet, but I was wondering how a standard 3dBi
marine whip would perform on the 2m ham bands. Since the marine
frequencies are 156.050-157.425 MHz, what could I expect at 144-148 MHz?

If it won't cut it, then does anyone have any recommendations for a
dual-band antenna (commercial or home-built)?

Jon

I've used a 2m antenna on the marine band with a marine hand-held,
with no apparent problems - it gives much better performance than the
hand-held's "rubber duck". (but I didn't check SWR)



--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

 

[Jon Gauthier]

My portable antenna for both marine and aviation use on 2 meter ham band for
a non-permanent install is to strip back 1/4 wavelength of coaxial cable
outer insulation, then push the braid back over the cable so I have 1/4
wavelength of coax center lead exposed and 1/4 wavelength of braid back over
the insulated portion of the cable, forming a sleeve dipole, then attach the
matching portable radio antenna connector on the other end. Fishing leader,
etc can be used to hang the antenna from an overhead supp-ort on the boat, a
tree limb when camping, etc. I Have used removable masking tape to tape the
antenna to the Plexiglas window in a rental airplane, etc. Works great. SWR
can be trimmed by starting long and working back to about 19 inches of braid
and center lead.
73
Doug K7ABX

I have the WAF to think about ;-)

Peter - I was asking the other way around - using my 2m ham radio
connected to the marine VHF antenna. I guess if the SWR is less than
something like 5:1, my Icom 706 won't shutdown...

Jon KB1HTW

 

[Peter Bennett]

Peter - I was asking the other way around - using my 2m ham radio
connected to the marine VHF antenna. I guess if the SWR is less than
something like 5:1, my Icom 706 won't shutdown...

Jon KB1HTW

I suspect that if it marine radio -> ham antenna works, then ham radio
-> marine antenna probably will also work - the frequencies are still
"pretty close".

Perhaps I should qualify things a bit - I primarily used the ham
antenna -> marine radio for receiving - I usually used a marine
fixed-mount radio with marine antenna for transmitting.


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

 

[Larry W4CSC]

If it won't cut it, then does anyone have any recommendations for a
dual-band antenna (commercial or home-built)?

Jon

Put using ONE antenna, dual band or not, out of your mind for the MARINE
and TWO METER radios, which CANNOT be PARALLELED on ONE antenna....(sigh)

The duplexer that would allow you to do this is bigger than a 4-cylinder
auxiliary diesel, its transmission and small fuel tank.....

Noone makes one....no market.

 

[Bruce in Alaska]

You could expect 3:1 or worse SWR unless you found a "dip" at certain
frequencies in the 2 meter ham band. I believe Morad makes a 2 meter version
of one of their marine antennas, however, their web site says "under
construction" when I checked it today. I usually use a Larsen (Radiall)
antenna on a boat for 2 meter ham band or VHF high band public safety
frequencies.
Do not try using a ham rig and a marine VHF radio on the same antenna, as
sooner or later you will accidentally end up transmitting into the other
radios receiver. Modified ham rigs on the marine band are illegal.
73
Doug K7ABX

Actually Morad has both a 146HD and a 146HD10db in their designs,
as I have one of each, of the original prototypes, that Eddie Zanbergen
gave me years ago. The 146HD is up on the roof of the cabin and the
146HD10db is in a tube out back waiting for the new "Retirement House"
to be constructed. All the designs for Morad antennas were first
tested in the associated Ham Bands next to the Maritime Mobile Bands.

Most any VHF Antenna will work just fine on both 146 and 156, if
one is just trying to communicate, as SWR isn't really all that important
at frequencies that are horizon limited, and have Sufficent Power
(25 watts) to reach the Radio Horizon. A leaky dummy Load can
communicate a couple of miles at this frequency. Efficent coupling
into the ether at VHF Frequencies is relatively simple, when compared to
the MF and HF counterparts. The higher frequency, the less finiky, and
wider bandwidth, an antenna will operate over, for just communicating.
At the 25 Watt output power level, just about anything including a "Wet
Noodle" will communicate to the Radio Horizon at VHF Frequencies.
Ever wonder why you don't see a whole pile of "Antenna tuners" for VHF
Frequencies? It is because what little you would gain, by any tuning,
wouldn't show up by increasing the Radio Horizon in any meaninful way.

This isn't like your trying to do Moonbounce, or anything. It is like
going for 25 to 30 miles over water and looking at a Path Loss in the
high 80 or low 90 db's. Not a very difficult proposition in the radio
world.


Bruce in alaska

 

[Jon Gauthier]

Put using ONE antenna, dual band or not, out of your mind for the MARINE
and TWO METER radios, which CANNOT be PARALLELED on ONE antenna....(sigh)

The duplexer that would allow you to do this is bigger than a 4-cylinder
auxiliary diesel, its transmission and small fuel tank.....

Noone makes one....no market.

Larry, perhaps I wasn't specific enough in my description. I'm
definitely NOT trying to have both radios operational at the same time
on the same antenna.

What I was asking was, if I have a proper VHF switch (with the
unselected radio switched to a dummy load to prevent burning out the
finals if inadvertantly keyed), what kind of performance (SWR-wise)
could I expect out of a either a marine VHF antenna and a ham 2m radio,
or a 2m antenna and a marine VHF radio. Since you are a boater, I would
assume you would know how precious space can be on a relatively small
sailboat, and how expensive marine-grade equipment tends to be.

It was just a simple question. I'm not trying to act like a commercial
tower radiating multiple freqs from a single radiator for multiple
customers. I would have thought that being a licensed amateur radio
operator (Extra), one would not be such a reluctant elmer....

 

[Larry W4CSC]

What I was asking was, if I have a proper VHF switch (with the
unselected radio switched to a dummy load to prevent burning out the
finals if inadvertantly keyed), what kind of performance (SWR-wise)
could I expect out of a either a marine VHF antenna and a ham 2m radio,
or a 2m antenna and a marine VHF radio. Since you are a boater, I would
assume you would know how precious space can be on a relatively small
sailboat, and how expensive marine-grade equipment tends to be.

Oh, OK. On rec.boats.cruising we see a lot of radios parallel connected to
destroy each other's receivers......

To answer your question on SWR, "just awful" would be about right. 157 is
a LONG way from 145 in antenna resonance. Bite the bullet and put up two
antennas....both of them Metz is a great idea. Metz antennas could care
less about ground. They are end-fed half-waves with their loading
transformers buried in epoxy-filled PVC pipe pieces. Put the marine VHF on
top of the mast and the 2m antenna on the Metz bracket on the side of the
mast under the shroud so it doesn't get fouled in the sails. Bend the
bracket out so the 2m antenna on the side is about 30 degrees from vertical
which gets it away from coupling so hard to the mast....unless your mast is
non-conductive. The vertical separation of the two will keep the
transmitter from one blasting away the receiver of the other on 25w or 50w
powers. Never put them in parallel on top of the mast....bad idea.

The Manta 6 at:
http://www.metzcommunication.com/manta6.htm
is what the CG boats use. If you destroy it, Metz will simply replace
it...no hassles. It will talk to Jacksonville from Charleston at 55' up
the mainmast of an Amel Sharki ketch. Another Metz for the aux/emergency
VHF marine is at the top of the mizzen. Radios are Icom M-602 main and
Icom M-59 emergency, running off a separate DC supply. S/V "Lionheart"
wants not for comms...M-802 HF to AT-130 on insulated backstay to t-top on
triattic stay. Natural resonance is cut to 3.9 Mhz. I like 75M...(c;

The 2m antenna at:
http://www.metzcommunication.com/2-meter.htm
is the same antenna with its base loading transformer and whip length cut
for 2 meters instead of 157 Mhz. Same stainless construction, same
guarantee. The right angle brackets come with the antennas...

I had the marine VHF on a 16' Sea Ray Sea Rayder fast jetboat using its
angle bracket bolted through an existing bolt in the bow, beating and
jumping waves, from 1997. The guy who bought my boat is still using it on
the Icom M59 I installed. Still works great, even though it is regularly
drown in seawater salt....(c; The antenna has survived 3 coaxes, which got
eaten away connected to the bottom of it. Quite a testimony for Metz...(c;

 

[Jon Gauthier]

Oh, OK. On rec.boats.cruising we see a lot of radios parallel connected to
destroy each other's receivers......

To answer your question on SWR, "just awful" would be about right. 157 is
a LONG way from 145 in antenna resonance. Bite the bullet and put up two
antennas....both of them Metz is a great idea. Metz antennas could care
less about ground. They are end-fed half-waves with their loading
transformers buried in epoxy-filled PVC pipe pieces. Put the marine VHF on
top of the mast and the 2m antenna on the Metz bracket on the side of the
mast under the shroud so it doesn't get fouled in the sails. Bend the
bracket out so the 2m antenna on the side is about 30 degrees from vertical
which gets it away from coupling so hard to the mast....unless your mast is
non-conductive. The vertical separation of the two will keep the
transmitter from one blasting away the receiver of the other on 25w or 50w
powers. Never put them in parallel on top of the mast....bad idea.

The Manta 6 at:
http://www.metzcommunication.com/manta6.htm
is what the CG boats use. If you destroy it, Metz will simply replace
it...no hassles. It will talk to Jacksonville from Charleston at 55' up
the mainmast of an Amel Sharki ketch. Another Metz for the aux/emergency
VHF marine is at the top of the mizzen. Radios are Icom M-602 main and
Icom M-59 emergency, running off a separate DC supply. S/V "Lionheart"
wants not for comms...M-802 HF to AT-130 on insulated backstay to t-top on
triattic stay. Natural resonance is cut to 3.9 Mhz. I like 75M...(c;

The 2m antenna at:
http://www.metzcommunication.com/2-meter.htm
is the same antenna with its base loading transformer and whip length cut
for 2 meters instead of 157 Mhz. Same stainless construction, same
guarantee. The right angle brackets come with the antennas...

I had the marine VHF on a 16' Sea Ray Sea Rayder fast jetboat using its
angle bracket bolted through an existing bolt in the bow, beating and
jumping waves, from 1997. The guy who bought my boat is still using it on
the Icom M59 I installed. Still works great, even though it is regularly
drown in seawater salt....(c; The antenna has survived 3 coaxes, which got
eaten away connected to the bottom of it. Quite a testimony for Metz...(c;

Sorry, had a grumpy morning. The Metz looks like it would fit the bill.
Wonder how it would standup on the port spreader? Just gotta see if I
can shoehorn another RG-8x throught the compression post and mast step.
I know I'll never be able to fit the Belden 9914F I have lying around...

Jon KB1HTW

 

[Larry W4CSC]

can shoehorn another RG-8x throught the compression post and mast step.
I know I'll never be able to fit the Belden 9914F I have lying around...

All my antennas are run with military surplus RG-58A/U. The mast is 55'
and the base of it is around 35' from the VHF at the nav station, as the
cable is run. It hears and transmits great, even on 1 watt. You don't
need the fancy cable to get to the horizon with a 50' antenna...(c;

I do like 58A with its flexible, stranded center conductor....

 

[Jim Pook]

Hi Jon:

I see a number of people have replied to this posting, but I think they may
have missed the main point of your question.

The only thing I'm not clear on is are you planning to use the marine
antenna for both ham and marine radios? Or will it only be used for the ham
radio?

Also, is the antenna a metal whip or a fiberglass whip?

If the antenna is a metal whip with a loading coil, then it should be easy
to clip the end off of the tip of the metal rod to tune it to the higher
frequency. (higher frequency = shorter antenna). If your antenna is
fiberglass, then I guess that you would be out of luck.

If you are planning on using one antenna for both radios and switching back
and forth, then I would decide which is the most important radio and tune
for it, OR tune it half way between for a comprimise on both radios. Keep in
mind that you will have to use a switch box or disconnect and reconnect the
radios as needed.

The simple thing to do would be have two antennas - one for each radio, and
tune appropriately.

Good luck.