Cruisers Forum

Join CruisersForum Today

  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
Thread Tools Search this Thread Rate Thread Display Modes
Old 11-08-2008, 15:20   #1
Registered User
Crak's Avatar

Join Date: Jan 2007
Location: Perth, Western Australia
Boat: Fountaine Pajot Athena 38
Posts: 61
Images: 5
Optimal length for radiating element ?????

I am about to install an insulator in my shroud for SSB operation and I am trying to decide what the optimal length should be "in my case".
I use pactor a lot on 80m & 40m and I also like to operate on 20m a lot, as well as all the marine frequency's. I realize the radiation pattern is not very good above 20m so I am not too concerned about frequency's above 20m, but I would like my antenna to be most efficient on 20m and below. To supplement this antenna I plan to build a vertical dipole for 20m operation and maybe some other dipoles for the higher frequency's. But as my shroud will be my permanent antenna I want it to radiate with maximum efficiency on 20m and below. I realize the longer the antenna is on frequency's below 30m the better it will radiate, but I am thinking if I optimise it for 20m the shortening in length will have minimum impact on the lower frequency's? I was thinking to make the radiating length of the shroud 42 feet (12.8m). I have an extensive ground system using resonant radial ground wires and an auto tuner. Would any body like to comment on what they think the optimal length my radiating element should be?
Crak is offline   Reply With Quote
Old 11-08-2008, 16:24   #2
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,047
Images: 4
42' sounds like ballpark, but it's very hard to say without modeling.

Might I suggest that you rig a temporary antenna made of whatever material you have readily available and try different lengths? You won't be able to duplicate what the shroud will be unless you remove the existing shroud and use comparable material (probably totally impractical), but you might get a close approximation by rigging the temporary antenna just forward, aft, or outside the shrouds, using PVC standoffs as necessary.

Certainly worth a try, I'd think.

BTW, I assume you're just gonna add ONE insulator at the top, and feed the shroud from the chainplate bolts belowdecks, right?

Good luck,



PS...nothing, but nothing will equal a 20m vertical dipole, so I hope you build and try one early on. If you have one, then you won't worry so much about 20m with the shroud -- which in any case ain't gonna be great -- and could optimize it for lower bands :-)

Be sure to check out this thread: Black Box Secrets - Revealed!

btrayfors is offline   Reply With Quote
Old 12-08-2008, 19:08   #3
Registered User
Crak's Avatar

Join Date: Jan 2007
Location: Perth, Western Australia
Boat: Fountaine Pajot Athena 38
Posts: 61
Images: 5
Hi Bill,
Thanks for your comments and it's good to know I am on the right track. (I think?)
Yes you are correct I plan to just install one insulator and feed the shroud above the lower turn buckle.
Although I plan on using a vertical dipole for serious 20m work, I would like to optimise the shroud for 20m for passage making, inclement weather and for when I am too lazy to rig up a temporary vertical dipole.
Crak is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Chain length schoonerdog Anchoring & Mooring 117 26-05-2008 06:49
What length boat? MaDouleur Monohull Sailboats 27 24-03-2008 08:56
Optimal Solar Array Wiring Keegan Electrical: Batteries, Generators & Solar 7 26-07-2007 11:53
Keel Length Alan Wheeler Monohull Sailboats 5 04-03-2007 11:00
Racor 500 Element Warning Pete the Cat Engines and Propulsion Systems 33 10-11-2006 02:55

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 15:07.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.