Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 24-02-2014, 12:51   #31
Registered User

Join Date: Dec 2013
Posts: 209
Re: Rope Antenna for SSB

The term "antenna tuner" is wrong. The only way to tune the antenna is by changing its length.

Sent from my SCH-I415 using Cruisers Sailing Forum mobile app
__________________

__________________
wellin is offline   Reply With Quote
Old 24-02-2014, 19:10   #32
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: Rope Antenna for SSB

travellerw,
1) Be careful what you read...some of it might be misleading....
Quote:
Originally Posted by travellerw View Post
Ok.. I'm a complete noob, but have been doing tons of reading..





2) Seriously, though, you can use whatever you like...as long as it is conductive, you could probably get it to radiate!!! (I've used a vhf/uhf police scanner antenna on 10 meters and worked all over South America....and have used a piece of scrap wire, tossed out a window, laying on some shrubbery, to talk to guys all over Europe on 20m and 40m....all from Florida....but that doesn't mean they worked very well, nor that they'd be what I want to use on my boat...especially for safety/emergency comms!!)

But, the real questions are HOW WELL would it work, HOW RELIABLE it would be, and HOW LONG it would last??
Quote:
Originally Posted by travellerw View Post
I'm just wondering why you can't use a sloping wire encased in a sheath of some sort (to prevent corrosion) and held off the backstay with zip-tie and tube insulators. Kind of a cheap DIY GAM.
Not exactly sure of your intended design....but the "GAM" antenna has sporadic and unpredictable effectiveness, as it couples a significant portion of your transmit energy into the stay/rig (where some of that radiates)....so while "it works", it doesn't work as well as a "non-coupled" and/or insulated antenna does...
Further, feeding the stay directly (non-insulated, dc-grounded), also has sporadic / unpredictable results.....shunt-fed / slant-fed verticals (which I have a great deal of personal experience with), are usually okay antennas, but when multi-band operation is required, their effectiveness is compromised....meaning they are a compromise antenna, and don't work too well...
(again, doesn't mean they don't work....just that they don't work as well as a separate, isolated antenna...)

BTW, Bill T's famous "alternative backstay" antenna is a wonderful concept for those that have no backstay, and/or those who desire to not spend the $$$ on backstay insulators....
It is not a "compromise" antenna, works very well, and is not expensive at all....oh, and if you build it the way he suggests, it'll last a LONG time!!!
(permanent or semi-permanent, depending on how you build/install it...)





3) What "best" are you referring to???
Quote:
Originally Posted by travellerw View Post
Kind of a cheap DIY GAM. Seems like the best of both worlds (semi permanent and cheap)
Semi-permanent and cheap, are NOT my idea of "best"....just my opinion here, but "semi-permanent" and "cheap" seem to be compromises at best, and more likely the "worst" of both worlds....
And, of course, poor/compromised performance as well....
Some "best"....




I do hope this helps clarify things...

John
s/v Annie Laurie
__________________

__________________
ka4wja is offline   Reply With Quote
Old 24-02-2014, 19:33   #33
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
!!!

Wellin,
Yeah, "antenna tuner" isn't an accurate description of what remote auto couplers do..
Quote:
Originally Posted by wellin View Post
The term "antenna tuner" is wrong.
They couple the transmitter to the antenna, providing impedance matching without excessive loss across the entire HF spectrum..and a better description is "remote automatic antenna coupler"....
But...

But, I think we simply have to accept the nomenclature that has been accepted now for decades...even though "remote automatic antenna coupler" is the more accurate description, and is still used as the correct phraseology in the commercial world....in the consumer world / pleasure boat world / ham radio world, "auto tuner" or even just "antenna tuner" have become the defacto standard nomenclature for decades now.....heck, even Icom has been using this terminology for decades....





Here, you may need to modify your statement..
Quote:
Originally Posted by wellin View Post
The only way to tune the antenna is by changing its length.
This is not really the case....
As the way you "tune" an antenna is by changing its electrical length, not necessarily by changing its physical length....
And, by switching in/out inductors and capacitors, the "remote auto tuners" are not only coupling the transmitter to the antenna, they do in effect change the antenna's electrical length (not precisely, but in practice, that's what happens...have a look at the antenna currents as well as the circulating currents in the "tuners" as well, as these ARE part of the antennas here, and hence they are part of the antenna currents!!!)




Sorry to ramble on....
Bottom line:
Everyone uses the terminology "antenna tuners".....as long as you understand what they do, it doesn't matter what you call 'em!!




Fair winds...

John
s/v Annie Laurie
__________________
ka4wja is offline   Reply With Quote
Old 25-02-2014, 02:10   #34
Registered User

Join Date: Aug 2011
Location: Zeebrugge, Belgium
Boat: Jeanneau Voyage 37 ft
Posts: 254
Re: Rope Antenna for SSB

Hi TravellerW,

you have read John's technical answer I suppose.

It is really a bad idea (as is the GAM imho) to fix a well isolated wire so close to a backstay which is off course a very long conducting piece of metal.
You will either lose a lot of radiated energy into the backstay and/or have very unpredictable results from frequency to frequency.

If looking for simple, cheap and reliable, please go for the suggested "alternate" backstay antenna using either:
- a strong gauge insulated copper wire (less long-lasting)
- uninsulated SS wire (adding plastic/rubber hose tubing to the lower section about siix-8 feet up to protect your "innocent" crew from grabbing it when you are mumping SSB signales into the aether )
- copperclad insulated steel wire that is used a lot as wire for HAM wire antennas (I use it, sealed off the extremities and have no isuue with corrosion).(strong)

The other advantages of the so-called alternate backstay wire are:
- you can easily and cheaply change its length to obtain better tunable lengths
- usually you have easier-accessible space int the lazarette of storgae locker both sides of the cockpit where you can install the "remote antenna coupling device" (!) at the location where the alternate sloping wire comes down and thus keep very short the stretch of wire going underdeck to the "RACD" antenna lug.
- using a spare halayard you can if needed easily deploy it or bring it down for whatever reason (winter storage, etc).

Tip: lead it down from a spare halyard to an isolator attached to the top of the pushpit (taffrail). From there bring down the lower part of the wire (insulated here - or the usual GTO-15 wire) via isolator-standoffs along one of the vertical tubes of the pushpit and then through a waterproof through-hull connector to below decks.
See some pics of my system on:
ON3ZTT - Callsign Lookup by QRZ.COM

Success!

Jan
ON3ZTT
__________________
Goudurix is offline   Reply With Quote
Old 25-02-2014, 03:40   #35
Registered User
 
Albro359's Avatar

Join Date: Jun 2009
Location: Elyse is in Fiji
Boat: Amel Super Maramu 2000
Posts: 510
Re: Rope Antenna for SSB

It won't be any good.
Just like the GAM antenna, if your backstay is grounded the RF will be coupled to the backstay and , well, grounded , so your signal won't get out.
Just like those dinky little cable tie supports people put n their backstays to keep the antenna feed wire away from the stay...waste of time...it needs to be a metre or more away before it makes any difference.

get a proper insulated backstay...don't worry too much about the feed wire, mount the tuner as close as possible to the backstay, make sure you've got a GOOD ground for the tuner and you're away.

Cheers
Alan
__________________
See you out there ....... Alan S.V. Elyse
now http://svelyse.weebly.com
older http://voyagesofDIVA.weebly.com
Albro359 is offline   Reply With Quote
Old 25-02-2014, 11:59   #36
Registered User

Join Date: Dec 2013
Posts: 209
Re: Rope Antenna for SSB

I think the cheapest and simplest thing to do would be to buy a 3 masted square rigger and make dipole antennas for each yardarm tuned for each band. And put a 5 element beam on the tallest mast with a gyro-stabilized rotator platform.

Sent from my SCH-I415 using Cruisers Sailing Forum mobile app
__________________
wellin is offline   Reply With Quote
Old 25-02-2014, 14:41   #37
Registered User
 
travellerw's Avatar

Join Date: Jan 2014
Location: Martinique
Boat: Fortuna Island Spirit 40
Posts: 1,717
Re: Rope Antenna for SSB

I appreciate everyone's responses.. I choose my words wrong.. "Best" doesn't really apply to a sailboat, more like "Best Compromise".

I think its becoming clear to me. When the time comes, I will be using the "Alternative Backstay" method. An insulated backstay seems like a ton of expense for what you get.

I will continue to read and research, but I appreciate everyone's time.
__________________
travellerw is offline   Reply With Quote
Old 26-02-2014, 01:27   #38
Registered User

Join Date: Aug 2011
Location: Zeebrugge, Belgium
Boat: Jeanneau Voyage 37 ft
Posts: 254
Re: Rope Antenna for SSB

TravellerW,

value for money and DIY-wise, the best results will be obtained with vertical dipoles (one per target band); no need for tuner, no need for RF ground though a copper tape connection ro underwater bronze is always usefull to reduce receiving noise. Disadvantage: taking up and down the vertical dipoles / or having them permanently in less convenient locations for sailing

After that, indeed the "compromise" solution: alternate backstay, remote ATU. More expensive (needs good ATU like Icom, SGC); needs RF ground (as discussed). Advantage: good allband results; needs only 1 antenna system.

Success!

Jan
__________________

__________________
Goudurix is offline   Reply With Quote
Reply

Tags
antenna, ssb

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
USB GPS Antenna with OpenCPN? pillum Marine Electronics 7 16-10-2015 15:27
Garmin GA 28 Antenna Repair Help, Please macbeth Marine Electronics 2 12-07-2011 08:06
AIS Reception Issue twistedtree Marine Electronics 72 03-07-2011 04:57
FM Antenna Mounting allanpeda Marine Electronics 1 02-07-2011 07:09



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 16:23.


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.