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awetmore
Master Marine Consultant

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USA
1144 Posts

Initially Posted - 04/01/2012 : 17:55:57

I've search the archives extensively on antenna mounts, but still haven't quite found what I'm looking for. I'll start with the questions.

Does anyone have photos of how they've routed the antenna cable through the mast and to the radio? My radio is located by the companionway on the starboard side.

2nd question: How flexible are VHF antennas? A 3' antenna at the top of my mast is going to come with 1' of at least one bridge almost every time I go sailing. That makes me nervous.

I'm going to drop my mast in the next month or two for a variety of projects (new halyards and sheaves, new anchor and steaming lights, topping lift, deck plate) and have been thinking that I should run a VHF antenna up there too. My PO supplied a VHF radio and a long coax cable, but the antenna is missing. The easy option seems to be a rear pulpit mounted antenna (no drilling the deck, no height concerns), but I know that a mast mounted one will give me increased range (on the other hand I'm not sure that I need that range). So far I've just used a handheld.

thanks,
alex

Alex W
Seattle, WA
Express 37 "re-Quest"
previously owned 1984 Catalina 25 "Lutra"

Edited by - on

Voyager
Master Marine Consultant

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USA
5377 Posts

Response Posted - 04/01/2012 : 18:34:16

Alex
If you plan to do coastal cruising or offshore, a mast-top VHF antenna is required. On a lake < 12 miles wide, you do not need a mast-top antenna. If you have a spare antenna, and if you plan to drop the mast, go ahead and add one up there. It will bend over and bend back if you happen to touch the bridge, and will serve as a spare antenna in case the cable to your stern-mounted antenna fails.

Regarding a feed-through connector from the cabin-top for a mast-top mounted antenna, I've seen coaxial feed-through connectors for trucks and boats. This is probably your best bet. Once down below, route the cable down behind the mast post then into the bilge near the head. Another route would be along the port side cabin lighting cable all the way back to the power panel in the galley, then across the top of the quarterberth.

Another thought is to come in through the cabin top, then run the wire behind the starboard head bulkhead and follow the starboard side cabin lighting cables to the quarterberth.

For the stern-mount cable, I'd go in through the transom then run the cable along the centerline up on the quarterberth ceiling to the radio.

Edited by - on

waterbaby
Navigator

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USA
168 Posts

Response Posted - 04/01/2012 : 18:48:05

Alex,
We had a antenna is about 3' with the cable snaked down the mast and connected to a coax type fitting about an inch in front of the mast. We were told this was best so that we could disconnect it if we lowered the mast. From there it is lead over to the lavetory in the head and along the starbord side of the boat to the front near the companionway. we mounted it just over the front edge of the quarter bearth on the starboard side. We didn't do all this work so I can't really remember all of the details but the cable is hidden along the deck and hull joint. Hope this helps.

Edited by - on

awetmore
Master Marine Consultant

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USA
1144 Posts

Response Posted - 04/01/2012 : 18:51:36

The plans include coastal cruising up inside Puget Sound and the inside passage of Vancouver Island. I expect that we'll always been within 10 miles of land, and I know that we will be for the next year (where the farthest that we'll go is the San Juan islands in the north end of Puget Sound). Perhaps I should just get a stern-mounted antenna for now, and worry about a mast top one the next time that I drop the mast.

Edited by - on

aeckhart
Master Marine Consultant

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USA
1709 Posts

Response Posted - 04/02/2012 : 07:07:50

Alex,

I would think that Puget Sound and the San Juans are pretty heavily trafficked. I bet that on any given day there's at least one boat with a VHF within 5 miles of you. A rail mounted antenna would would probably be a safe alternative, especially if you have concerns about low bridge clearance.

Edited by - on

Drjohn71a
1st Mate

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USA
37 Posts

Response Posted - 04/02/2012 : 09:02:43

Alex,

Yes, when the conditions are favorable you will have many other boaters close, but my experience cruising the San Juan's was that when the weather and seas and currents all decided to fight it out, there was no one close to help. I'd go for the mast top, ESP. Since the islands have some blocking effect. John

Edited by - on

Voyager
Master Marine Consultant

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5377 Posts

Response Posted - 04/02/2012 : 17:11:49

Dr John
You are correct, VHF transmission is strictly line-of-sight meaning if there's a big hill between you and your target, you have a better chance hitting it with a mast-top antenna rather than a stern-rail one.

So, for now, if you plan to drop the mast anyway, but don't want to do major surgery installing the feed through on the cabin-top, go ahead and install the mast-top antenna for now, run the wire down through the mast and take it out the side. Then coil it up and tape over the end to protect the connector.

This way you will have it installed just in case you really need it. There will be plenty of time to install it properly as you wish once you get back.

Edited by - on

GaryB
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4304 Posts

Response Posted - 04/02/2012 : 18:32:15

Go with one of these (http://www.shakespeare-marine.com/antennas.asp?antenna=5018) and one of these (http://www.shakespeare-marine.com/antennas.asp?antenna=5228) and you can get the same height when you need it and not have to mess with the mast.

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9081 Posts

Response Posted - 04/02/2012 : 20:22:43

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Voyager
 ...VHF transmission is strictly line-of-sight...<hr height="1" noshade id="quote"></blockquote id="quote">Well, sort of... I've communicated clearly with another boat 3 miles away with 100'+ elevation of granite between us, where my antenna was on my hardtop and his was on his console. (The center of my 8' antenna is about 11' above the waterline.) VHF waves bend around obstacles the way water waves do, and they can bend over the horizon to some degree if the power and focus are adequate. An 8' (6dB) antenna focuses the transmission better on a horizontal plane and therefore reaches out better than a 3' (3dB) antenna, and might do about as well on the rail as the 3' does on the mast-head. The USCG antennas can receive and send transmissions to/from a handheld VHF at amazing distances, and to/from fixed antennas well over the horizon.

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Dave5041
Former Mainsheet Editor

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3758 Posts

Response Posted - 04/03/2012 : 07:33:50

An 8' on the rail has filled the need for many here and an awful lot of powerboats for a very long time. I chose a 3' masthead for long and short range coverage, but I don't have frequent overhead obstructions. Range to the very tall CG antenna won't be an issue with either approach, and modern receivers are so sensitive and have such high adjacent signal rejection that signal falloff from the flatter doughnut of a high gain antennae probably won't be much of an issue at short range when heeled. Keep a handheld in reach if it is - that would be cheaper than the Shakespeare package and provide backup.

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awetmore
Master Marine Consultant

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1144 Posts

Response Posted - 04/03/2012 : 12:48:23

Thanks everyone. I think I'll do an 8' rail mounted antenna for now, and worry about a mast mounted antenna down the line if we have issues with the rail mounted one. Keeping my height down is a big goal, and I just don't feel great going under low bridges with an antenna every time we go sailing.

All of my VHF experience is from kayaking where I'm using a 5W handheld radio 1-2' above the water line, so the radio on the sailboat is already going to have major advantages in comparison. On the kayak I'm mostly using it to monitor boat traffic when crossing shipping lanes.

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GaryB
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Response Posted - 04/03/2012 : 21:36:30

I gave a radio check to a guy last Friday using my Standard Horizon handheld. He was approx 3 miles from me and was coming in very strong. He said he could hear me loud and clear also.

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 04/04/2012 : 06:02:58

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by awetmore
 A 3' antenna at the top of my mast is going to come with 1' of at least one bridge almost every time I go sailing. That makes me nervous.
<hr height="1" noshade id="quote"></blockquote id="quote">

Survey the other boats in an around your marina to see how they're set up or better yet, ask those sailors that transit under this same bridge about there experience.

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Ape-X
Admiral

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USA
662 Posts

Response Posted - 04/04/2012 : 07:03:37

here's a interesting antenna question: I have regular coaxial cable: Can that be used for the VHF antenna, or is it a special cable?

Edited by - Ape-X on 04/04/2012 07:04:19

Dave5041
Former Mainsheet Editor

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Response Posted - 04/04/2012 : 09:15:37

Different cables have variations in impedance (like resistance) and signal loss, and signal loss can also vary by frequency in different cables. That means that a particular coax can have significant impact on your signal strength. Coax is defined by a letter+number designation that is imprinted on the cable and that can tell us if your cable is a reasonable choice.

Edited by - on

JimGo
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Response Posted - 04/04/2012 : 09:26:42

Dave, how do you know if the coax is "right" for this application? That is, do you know what letters/numbers are appropriate?

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awetmore
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Response Posted - 04/04/2012 : 09:49:26

My marina has 10 boats or less, and I think I have the highest mast except for a C-27 which seems to be abandoned (it has a forsale sign, no sails installed, and I've never seen the owner at the docks despite being there almost every day myself). I don't think that any have VHF antennas at the top of the mast, but I'll double check tonight.

The next tallest boats are a couple of Thunderbirds with the same height mast as my tall C-25, but a lower deck height.

There are actually 3 bridges that I need to worry about, with heights over water of 46' (Montlake Bridge), 42' (University Bridge), 44' (Ballard Bridge) and we're already too tall for the Fremont Bridge (30'). Clearance is at the fairly narrow center section and drops off around there. So a 3' antenna bringing my clearance up to around 40' would mean that I'd have to motor instead of sail under the University Bridge (the closest to my slip) to make sure that I stay under the center. Maybe I'm more concerned about this than I need to be. It is the low bridge in this photo (the high one is I5 and has no clearance issues):

This isn't a one time choice, I can always drop the mast later and add an antenna if I don't like how the rail mounted one works out.

Edited by - on

Stinkpotter
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Djibouti
9081 Posts

Response Posted - 04/04/2012 : 11:38:55

If you have significant currents under those bridges, I'd suggest that sailing through there could be dicey. Your tacking angles can change dramatically, which could quickly put you in a bad place relative to those arches. Also, other traffic may be restricted in maneuverablity and, if moving down-current, not able to avoid you as you're trying to get under the middle of the bridge. From what I see, I would only motor through there.

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Dave5041
Former Mainsheet Editor

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Response Posted - 04/04/2012 : 13:17:46

RG-58, RG-8X, RG-84 and RG-213 Of these, use the cable with the largest diameter that you can easily route for the least loss. Other 50 ohm coax will work, some worse and a few better than these, but these are all readily available. I use 8X and that probably only sucks about a third of my power. I don't know if RG-84 is still available or if it has been totally replaced by 213. 213 would be the lowest loss, but it's almost 1/2 inch in diameter. Use as few connectors as possible and don't splice it. I have 4 connectors, one at the radio and antenna and one on each side of the through deck

edit: and don't force a tight bend.

Edited by - Dave5041 on 04/04/2012 13:22:09

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
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Response Posted - 04/04/2012 : 13:28:11

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by awetmore
 There are actually 3 bridges that I need to worry about, with heights over water of 46' (Montlake Bridge), 42' (University Bridge), 44' (Ballard Bridge)...So a 3' antenna bringing my clearance up to around 40' would mean that I'd have to motor instead of sail under the University Bridge (the closest to my slip) to make sure that I stay under the center.<hr height="1" noshade id="quote"></blockquote id="quote">

Now I've never actually measured the above the water height of the masthead, but if we take the "I" dimension of a tall rig (31') add say 4' to the waterline we get an approximate height of 35'. Then add a 3' foot antenna and you're at 38' with four feet to spare.

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Davy J
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Response Posted - 04/04/2012 : 13:34:34

Just be glad you don't have to lower your mast every time. I have a whip antenna that resembles this:

It has some flexibility, because I see it shaking around once my mast is lowered.

Here is a suggestion, take a short piece of 1/2" PVC pipe, two sail slugs, two hose clamps and a three foot section of wire or maybe coat-hanger. Use the hose clamps to clamp the sail slugs to the PVC, duct tape the wire or coat hanger to the PVC. Then raise the device to the top of the mast, transit the bridge a few times and see if you hit it.

I use a similar device to hang a couple of CDs at the top of the mast to keep the birds off. I'll take a photo of it later today so you can get an idea of what I'm talking about.

Edited by - on

WindyLegacy
Deckhand

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USA
23 Posts

Response Posted - 04/04/2012 : 15:05:16

Does anyone run a nice handheld instead of a mast-mount and fixed mounted radio? I'm asking because I'm trying to keep some cost down and have been told by my service manager that around the river inlets on the Chesapeake, both cell phones and a handheld is all you'll ever need for the day cruising/coastal cruising.

I also like the idea of not having to do a hard install

Thoughts?

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Davy J
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1511 Posts

Response Posted - 04/04/2012 : 15:44:22

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Does anyone run a nice handheld instead of a mast-mount and fixed mounted radio?<hr height="1" noshade id="quote"></blockquote id="quote">
I rarely turn on my fixed mount VHF radio. I keep a handheld in a drink holder in the cockpit. I sail in Tampa Bay 98% of the time and also have Coast Guard sector St Petersburg close by. However, as others have pointed out, if you will be offshore, or hampered by obstructions, you will want a high mounted antenna

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Stinkpotter
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Djibouti
9081 Posts

Response Posted - 04/04/2012 : 19:08:08

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by WindyLegacy
 ...I'm trying to keep some cost down and have been told by my service manager that around the river inlets on the Chesapeake, both cell phones and a handheld is all you'll ever need for the day cruising/coastal cruising.<hr height="1" noshade id="quote"></blockquote id="quote">One way or the other, get a handheld. In an emergency, you should have a battery-powered unit. Then see how it does in your area. On the Chesapeake, I'd be pretty confident that the USCG will pick up your handheld, and there are enough other vessels within range almost anywhere. Sea Tow does automated radio checks, playing back your transmission. Around here, it's on Ch. 27, and they tell you where they're receiving and replying from (along with a little commercial). Their website also shows their radio check locations.

Edited by - Stinkpotter on 04/04/2012 19:12:50

delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 04/04/2012 : 19:56:49

Alex,
Have you measured to the top of your mast? It's quite easy to run a fiberglass measuring tape up your mast so you know exactly how high it is from the deck. Then you can measure down to the waterline to get an overall height. My tall rig is 38'-10" to the top of the 3' whip antenna to the waterline. Obviously yours is going to be different from a C-250, but running the tape up the mast will give you a very good idea of your overall height even if you have to estimate from the halyard sheave to the top of the truck. I would think that the Fremont bridge at 30' is the only one you have to worry about, but please don't take that to the bank. I don't know how tall a C-25 TR tops out at, but here's an estimate. If I remember correctly, the C-25 TR mast is a 30' extrusion, and my deck to waterline height is 3'-4". If yours is similar and since it used to be parked right next to mine, I think it is, then your overall height is roughly 34'-35'. The other three bridges will give you some pucker factor, but you should clear with feet to spare even if you put a 3' whip antenna up there.

I keep all measurements like this on my phone so I can refer to them quickly if I need them.

Edit: found [url="http://www.catalina-capri-25s.org/forum/topic.asp?ARCHIVE=true&TOPIC_ID=16710"]this thread in the archives[/url] while looking for C-25 mast height.

Edited by - delliottg on 04/04/2012 20:00:59

awetmore
Master Marine Consultant

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USA
1144 Posts

Response Posted - 04/04/2012 : 21:43:31

Thanks David.

I did measure our mast when I first got the boat. The mast is 31', it is about 35'6" or 36' to the top of the windex at the top of our mast. A 3' antenna would get me up around 38 or 39', which keeps me safely under the 42' University Bridge, but keeps me at a narrower center section of the bridge. That's fine under power, but doesn't leave a lot of room if we are off center.

I checked and many of the boats down at my slip do have mast mounted antennas, but most have been knocked around and are no longer standing vertically. I'll have to ask the owners what happened there. The straight ones were on a Thunderbird (it was a shorter antenna integrated into a Windex) and a 24' boat with a much shorter mast than the T'Bird or C-25 TM.

I guess I'm coming around to mast mounted, especially now that I've looked up the manual for the Blue Sea Cable Clam.

Edited by - awetmore on 04/04/2012 22:02:32

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