Removing antenna from mast, good move?

[markbarendt]

Originally Posted by KP44

When an antenna is rated 3db gain, that can be confusing. Gain is the antenna's ability to direct or concentrate radio frequency energy in a particular pattern. There is no actual gain of signal energy. Our sailboat whip antennas are made to radiate more horizontally and less vertically. So 3db gain means the antenna throws twice as much energy where it is wanted; towards the horizon.

Use only the best connectors and use good marine coaxial cable like RG113. It is a one-time expense and worth doing right.

RG-113 has attenuation (loss) of about 2.5db per 100 feet.
RG-8x is 4.7db and RG-58 is nearly 6db.

The problem with any type of antenna gain is that it only improves the situation if the boat is sitting flat. Healing and pitching aim the stronger part of the waveform off into space or down into the water and you end up with less usable range and poorer signal reliability.

[transmitterdan]

Originally Posted by markbarendt

The problem with any type of antenna gain is that it only improves the situation if the boat is sitting flat. Healing and pitching aim the stronger part of the waveform off into space or down into the water and you end up with less usable range and poorer signal reliability.

For a short 3dB gain antenna you have to heel past 45 degrees to lose a lot of signal. In practice this isn’t a concern. The signal forward and aft isn’t much affected by heel.

[thomm225]

Originally Posted by 1camper

Ya, begs the question why put it there in the first place? I assumed it was factory but I could be wrong. The coax going thru the cabin top looks factory and old.

I have a Bristol 27 and my boat has a mast light mounted on that plate you are speaking of just above the spreaders. Maybe the PO modified yours for the antenna

My VHF antenna is mounted at the top of the mast

[1camper]

It certainly could've been modified. Is that light marked "bow light" on the panel?

[thomm225]

Originally Posted by 1camper

It certainly could've been modified. Is that light marked "bow light" on the panel?

No, the PO of my boat made up his own switch panel and put the switch there. I think he labeled it Nav Light

His home made panel has the wooden frame to the right in the photo

On the Factory Bristol Blue Panel the switches are Cabin Lights, Running Lights, Spare, Spare.

One of the spares is for the depth finder on my boat

[1camper]

Originally Posted by hamburking

I had an old antenna (and cable) at the top of the mast on my C&C25. The cable made a horrible noise at night, slapping around inside the mast. So I removed the antenna and cable entirely. Instead I used a handheld VHF. It worked much better than the old set/antenna ever did. Range was not an issue...it was mostly for calling marinas before entering, or bridges.

I removed a ton of unnecessary wiring and plumbing from the boat. Instead I used a few LED flashlights, handheld VHF, handheld GPS, etc. Kept the running lights of course.

Ya, that's been my approach so far. I pulled out the head, filled those holes and have a porti-potty for now. I kept the same fixtures but converted to led. I have the same panel as you do in this pic. I think that will go. I hate to do it because it's the only place that says Bristol Yachts.
Just wanting to think this out and change the best way that I can. I want simplicity but also a good deal of redundancy where I can. The price on GPS equipped radios w/AIS have really come down and it seems like a good way to go. Navigation will be handheld. As far as a distress call, Inreach or some spot device with sms messaging would be my choice for updating family and distress. Those have really come down in price as well.

[1camper]

Originally Posted by thomm225

No, the PO of my boat made up his own switch panel and put the switch there. I think he labeled it Nav Light

His home made panel has the wooden frame to the right in the photo

On the Factory Bristol Blue Panel the switches are Cabin Lights, Running Lights, Spare, Spare.

One of the spares is for the depth finder on my boat

Yep, that's my panel, except mine is not attach to the bulkhead currently. I have a circuit marked bow light I haven't tracked down. I thought I might change to circuit breakers..

[thomm225]

My VHF transmitting and receiving power through the mast Antenna is many, many times better than my hand held.

I have contacted the Sea Tow automated radio check at Little Creek from over 15 miles away plus. I was nearing Kiptopeke when I did this.

With the hand held, I'm lucky to get that at 5 miles

As far as GPS, my old one just failed so I ordered a VHF / GPS Hand Held for $162 and will see how well that works

I was going to go with the VHF/GPS/ AIS thru the Mast antenna but decided to wait until I actually cruise out of the Bay long distance. I won't be sleeping while sailing in the bay.........way to many obstacles and shipping traffic at times

The only time I have missed seeing a ship was at night and once when one was "hiding" behind one of the CBBT Islands then suddenly appeared in Thimble Shoal Channel moving quite fast

[bhclardy]

While I 100% understand the math- but as a HAM on 2m (which is right next door to Marine VHF) I find I can push out 100miles or more depending on conditions over land at 50 watts. (antenna height 6 ft above ground attached to vehicle). I can get 20 miles plus in valleys or other terrain depressions.

I am fascinated to experiment over water, i would actually expect that I could get out even farther given no obstructions. Tropospheric ducting is pretty uncommon on 2 M , not like 6 10 or 11 M. and ducting will get you 1000 mile skips when it happens.

Just wondering what practical experience people are having. even a low wattage radio with an antenna height of 40' should go way past 7 miles based on my experience

-73 KE5WQK
S/V Dragonfly

[RSB333]

I would always choose the top of the mast location, to increase line of sight and avoid interference from rigging. Is there a reason not to put antenna as high as possible?
rsb333

[transmitterdan]

Originally Posted by RSB333

I would always choose the top of the mast location, to increase line of sight and avoid interference from rigging. Is there a reason not to put antenna as high as possible?

rsb333

Above about 100 feet there is a diminishing return in coverage. But below that I think higher is better.

[S/V Illusion]

Originally Posted by RSB333

I would always choose the top of the mast location, to increase line of sight and avoid interference from rigging. Is there a reason not to put antenna as high as possible?
rsb333

No reason. Just misconception that the extra loss exceeds that of range enhancement with height. It’s largely academic as few masts are long enough to have any observable effect on either range of coax loss. The real reason to have an antenna on top is to preclude attenuation , detuning and interaction by nearly metals which, along with the effects noted, can distort radiation patterns.

[Freemind]

KP44,
Do you have a source for the 113 cable?
After searching I can only find 213.

Same thing?
Thanks

[carlwk3c]

Originally Posted by Cheechako

There have been times on crossings where the VHF needed to read quite a ways away to contact fellow crossers and having the antenna on mast top was a very good thing. But if you are satisfied with it only partially up the mast, I guess the 6 ft wont hurt you much.
Sailing Mexico, I heard VHF transmissions probably 150 miles at night at times. "skip" I guess. I was hearing boats anchored near Cabo and I was nearly at Mazatlan.

That’s a phenomenon called “tropospheric ducting.”

[stormalong]

Originally Posted by Freemind

KP44,
Do you have a source for the 113 cable?
After searching I can only find 213.

Same thing?
Thanks

I think KP44 meant RG213. I have been doing radio stuff for a long time and never heard of RG113.