Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 16-06-2009, 09:36   #1
Registered User

Join Date: Jan 2009
Posts: 9
Standoffs - Antenna to Backstay Insulator

I asked this on another thread, but got no responses. (The GTO Wire)

We are redoing our tuner/backstay connection and looking for advice and/or ideas for stand-offs. We previously used pieces of hose, lengths of hose and I've been told you can put a shroud "cable" over the wire. I googled stand-offs and nothing that seemed applicable popped up. Any ideas appreciated. Sounds like a lot of you people are familiar with radio installations.

Thanks
__________________

__________________
Ramblin' is offline   Reply With Quote
Old 16-06-2009, 10:16   #2
Senior Cruiser
 
senormechanico's Avatar

Cruisers Forum Supporter

Join Date: Aug 2003
Boat: Dragonfly 1000 trimaran
Posts: 5,834
I'll probably start a flame war or something but here goes...

On our previous boat I only had one backstay insulator near the top.

After disconnecting the bonding wire from the chainplate, I fed it directly from the antenna tuner.

Nobody believed I wouldn't get shocked when transmitting, but although there's maximum current at the fed end, there's also minimum voltage there as well.

I proved my reasoning to several people by having a HAM friend talk on 20 meters while I stood at the stern while holding the backstay.

I demonstrated it by holding it from different heights from the deck to as high as I could reach without so much as a tickle.

The radio was an ICOM 735 barefoot, but running at full chat.

Over the years, I got lots of positive comments about my signal quality.

Think of an end fed antenna as working similarly to a bull whip. A lot of muscle is put into the handle end, but not a lot of speed.

The other end has enough speed to break the sound barrier, but not much "muscle".

I wouldn't even think of touching the upper end while transmitting!

Steve B.
__________________

__________________
senormechanico is offline   Reply With Quote
Old 16-06-2009, 10:22   #3
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,371
a piece of small hard plastic tubing with a notch in each end works well. Take a long tie wrap, wrap it around the back stay, pass it through the tubing and cinch it around the cable.... basically a loop with the cable at one end and the backstay at the other and the plastic tubing held in between...
__________________
Cheechako is offline   Reply With Quote
Old 16-06-2009, 10:33   #4
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,595
Images: 240
Rather than hose, I've always used rigid Nylon or PVC tubing, secured to backstay & GTO with a tie-wrap.
I cut the tubing with a drill (or rotary rasp), forming concave ends to cradle the wires.
Run the tie-wrap though the tube, around the stay, back through the tube, and secure around the GTO.
Attached Thumbnails
Click image for larger version

Name:	backstay standoff 2.jpg
Views:	574
Size:	7.0 KB
ID:	8582   Click image for larger version

Name:	backstay standoffs.png
Views:	2207
Size:	150.3 KB
ID:	8583  

__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 16-06-2009, 10:53   #5
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,371
Dont forget the dielectric grease on the backstay attachment area!
__________________
Cheechako is offline   Reply With Quote
Old 16-06-2009, 10:54   #6
Registered User

Join Date: Apr 2007
Posts: 718
Depending on frequency, antenna length and your ground plane system, the voltage at the the lower end feed point can be quite high. That's why there is a high voltage insulator on the tuner and why we use high voltage cable to connect to the backstay.

Eric
__________________
fairbank56 is offline   Reply With Quote
Old 16-06-2009, 12:07   #7
Senior Cruiser
 
senormechanico's Avatar

Cruisers Forum Supporter

Join Date: Aug 2003
Boat: Dragonfly 1000 trimaran
Posts: 5,834
I had a 3' straight copper foil to an external copper plate (not a dynaplate) and the output of the tuner was only 16" from the chainplate. I tried every frequency band I could legally transmit on (Advanced ticket) and never got even a tiny tingle. The radio covered 0.5/30 Mhz. but not include the 2 meter band. If it had, I'd not want to mess with the backstay under at those frequencies.

Steve B.
__________________
senormechanico is offline   Reply With Quote
Old 16-06-2009, 14:42   #8
Registered User

Join Date: Jan 2009
Posts: 9
Senormechanico, Cheechako, Gordmay and fairbank56, thank you all for your responses. All very interesting comments to digest. I've printed out the information and will give to the engineer on our vessel.

GordMay, thank you for the images, it looks like a very tidy installation. One question, on the image with the "little windows" describing the image, it shows the antenna cable connected to the backstay above the swage. In one of the many searches I have done, it was recommended you attach the cable to the smooth part of the swage rather than the wire backstay for a better connection. We were advised to strip the cable and attach directly to the swage and then wrap with waterproof tape (I'm assuming you put the dielectric grease on before the tape).

Sorry for all the questions, but on our last 6 years of cruising Mexico, our success with the radio was "hit & miss". We are trying to do a little better this time

Thanks again to all for your comments, it really helps.
__________________
Ramblin' is offline   Reply With Quote
Old 16-06-2009, 14:52   #9
Senior Cruiser
 
senormechanico's Avatar

Cruisers Forum Supporter

Join Date: Aug 2003
Boat: Dragonfly 1000 trimaran
Posts: 5,834
Another advantage of attaching the tuner to the chainplate (at least in my installation) was that it could be done with a standard ring connector under a chainplate ss nut fastener belowdecks. This had no environmental problems (salt, corrosion etc.) during the entire time I owned the boat.

Steve B.
__________________
senormechanico is offline   Reply With Quote
Old 16-06-2009, 18:07   #10
Registered User

Join Date: Jan 2005
Location: Seattle area (Bremerton)
Boat: C&C Landfall 39 center cockpit "Anahita"
Posts: 1,076
Images: 6
Seniormechanico

My experience has equaled that well stated by Seniormechanico. There is every disadvantage in paralleling the GTO feed line with a grounded backstay lower "stub" the radiation pattern will be poor when compared with driving the backstay from inside a lazarrette directly.
__________________
"I don't think there'll be a return journey Mr. Frodo". Samwise Gamgee
Rick is offline   Reply With Quote
Old 16-06-2009, 18:19   #11
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,595
Images: 240
Quote:
Originally Posted by Ramblin' View Post
... on the image with the "little windows" describing the image, it shows the antenna cable connected to the backstay above the swage. In one of the many searches I have done, it was recommended you attach the cable to the smooth part of the swage rather than the wire backstay for a better connection...
I cannot claim to be an authority on antena installations; but your comments sound right to me. On general principles, I'd expect the smooth, solid swage to make a better connection.
I'd defer to BTrayfors, Rick, Seniormechanico, or any of our other real experts, on this one.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 16-06-2009, 18:57   #12
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Well, here's where we get squarely into the realm of emoting rather than pontificating based on solid RF radiation principles.

I, too, am an affectionado of the "feed the chainplate" view. In fact, I just counseled a client with a 44' catamaran to install a single insulator high up on the topmast shroud, and we'll feed the thing from the chainplate belowdecks. Neat, efficient, protected from weather, easy to implement, etc., etc.

However, this won't work in every case. Most insulated backstay antennas -- or "alternate backstay antennas", like mine --- are fed via a GTO-15 wire run from the tuner belowdecks thru a waterproof deck fitting and up to the backstay. If you take this route, you'll be well advised to use some sort of standoff insulators for the GTO-15 wire. I've found that the best way to do this -- for me and my clients -- is to use 5/8" solid nylon rod. Cut into 2" lengths, drill a hole lengthwise thru the bar, and use plastic wire ties to hold the insulator in place. No need to cut grooves. Works fine, looks neat, and is inexpensive. The 5/8" solid nylon bar is available from US Plastics, among other sources.

I am also a believer in not worrying too much about the potential for RF burns. As an old ham who's built many rigs and experimented for many years, I KNOW what RF burns can be like. Stick your fingers in the final coil of a transmitter....yeah, that can be dangerous. Burns from the bone outwards.

BUT....at the power levels used on a boat, and with the typical backstay installation, it's unlikely anyone's gonna get an rf burn. Even if they happen to be hanging onto the backstay while someone is below transmitting, at most they'd feel a tingle and would damn well remove their hand quickly before any damage was done. Ditto for the RF ground systems, e.g., toerails or lifelines. IMHO, this just isn't a problem. Sorta like worrying about the varnish job when the ship is sinking :-)

Bill
__________________
btrayfors is offline   Reply With Quote
Old 18-06-2009, 20:49   #13
Registered User
 
Aparrotwind's Avatar

Join Date: Dec 2007
Location: It was...Portland, Oregon
Boat: Maple Leaf 42 - WINDFALL
Posts: 44
Images: 1
I just installed our new ham with backstay for antenna, but while in the harbor I cant seem to pick up much. I have an automatic tuner and copper foil under the waterline - grounded to the motor mount. Will I get better reception out on the open water? Or do I have other problems that need be addressed?
__________________
Sailing...the cure for Land Sickness!
Aparrotwind is offline   Reply With Quote
Old 19-06-2009, 04:37   #14
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Reception in marinas is generally bad. Too much interference from other boats, marina equipment, etc.

Re: your copper foil, usually it's a better bet to run it to the nearest bronze thru-hull, not otherwise connected to the boat's grounding systems. You get better grounding this way, and less potential for radio frequency interference (RFI).

Also, what you hear is very much dependent on propagation, frequency, and time of day. Try getting WWV or WWVH on 5mHz, 10mHz, 15mHz. Also, try tuning the different ham bands....mostly 40 and 20 meters during daytime, and 75 meters at nite.

Also, try reducing onboard interference by turning off all AC and DC equipment on board while listening, then slowly turn each on and see if you hear any interference. Motors, computers, and digital devices are notorious. Inverters, frigs, etc. can play havoc with HF reception. On my boat, I found that a digital voltmeter was causing a lot of interference.

Good luck,

Bill
__________________
btrayfors is offline   Reply With Quote
Old 19-06-2009, 19:58   #15
Registered User
 
Aparrotwind's Avatar

Join Date: Dec 2007
Location: It was...Portland, Oregon
Boat: Maple Leaf 42 - WINDFALL
Posts: 44
Images: 1
Thanks Bill, I'll try rerouting to a thru hull fitting this weekend and see if my reception gets any better. The boat beside mine gets a lot better reception so I know I have some issue(s) going on. I appreciate the feedback.
__________________

__________________
Sailing...the cure for Land Sickness!
Aparrotwind is offline   Reply With Quote
Reply

Tags
antenna, backstay insulator

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Best Lightning Insulator? sneuman Electrical: Batteries, Generators & Solar 24 24-11-2009 08:39
Do I need running backstay? Acadia Deck hardware: Rigging, Sails & Hoisting 2 01-12-2008 20:16
help with broken backstay johneri1 Deck hardware: Rigging, Sails & Hoisting 20 05-08-2008 21:15
Backstay Must Come Down - But How?? markpj23 Deck hardware: Rigging, Sails & Hoisting 27 25-05-2008 07:18
Backstay Antenna Full Lenght (No Isolators) Patrick_DeepPlaya Marine Electronics 7 05-05-2008 01:50



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 06:52.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.