In article ,
Jon Gauthier wrote:

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

last boat i used a nice Diamond 2m/440 mobile antenna for my
Yeasu dualbander. the trick was the mount.

i bought a mounting kit containing (among other things)
a waterproof roof-mount UHF male that would
mate with the UHF female of the antenna base.
(an extra set of assorted O-rings came in handy, too.)

i then made an adapter to go between a standard marine
1"-14 mount from some bronze pipe fittings and a short piece
of 1.5 or 2" brass pipe acquired at West Marine.

the top was a pipe cap
which i drilled to take the UHF roof-mount which then transitioned
down to to the 1-14 with a reducer. the coax fed down through
the exit hole in the mount to the drip loop and back up
through the clamshell into the arch side where it was mounted.

after putting the adapter together i prepped and painted it with
several coats of white epoxy paint.

if i had a lathe, i would have turned down the fittings to
be both smoother and less obtrusive, and boring the cap
would have been easier than drilling it, not to mention
turning a flat on the top. but all told, the piece came
out fine - it worked great and nobody went blind looking at it.

there is a business opportunity, though, for someone to
make a line of mounts to put quality ham antennas on
1-14 marine mounts.

cheers,
-mo
N4NLN

ps - the same thing could certainly be fabricated from PVC,
probably with less effort, but i figured that the metal
would last longer. whether i'd live long enough to observe
the difference is an interesting question.

Jon Gauthier wrote in
:

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;

Larry W4CSC wrote:


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

Jon Gauthier wrote in
:

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....

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.


"Jon Gauthier" wrote in message
...
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