Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 23-09-2014, 08:52   #1
Registered User
 
Jon Neely's Avatar

Join Date: Aug 2009
Location: Cruising East bound to EU
Boat: Hans Christian 33
Posts: 283
PVC ssb antenna

I hope this has not been covered before and I did search. In my search I heard people mentioning the but not talking about if there are issues with them. I'm curious if I got 20ft of 3/8" PVC, painted it so it doesn't get UV chalky. then slotted it every 3 ft on one side thick enough for a zip tie to pull the inside wire snug against the backstay. Have 14g copper wire on the inside. Any issue with this? Seems like a poor mans GAM split lead to me. Tell me want you guys think. I just want something that is permanent but do sent cost a month in cruising funds.
__________________
Watch Our Adventure on a HC33 at youtube.com/c/sailingvesselprism
Jon Neely is offline   Reply With Quote
Old 23-09-2014, 15:27   #2
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: PVC ssb antenna

Jon,
I'm not completely clear on what you are trying to accomplish here...but it seems like you are trying to make a homebrew "GAM antenna"....

If that is the case, then yes, what you describe would work similarly to the GAM antenna....and that's actually not a good thing...

The GAM antenna (and your idea) couples a good deal of your transmit energy into the backstay / rig / mast / etc...and this can cause a whole host of problems on board, as well as providing at best an "average" antenna and at worst a truly horrible antenna....

Jon, just wondering why you do not simply run a wire from the transom / pushpit / stern rail / gunwhales, etc., up to close to the mast top, and use this as your antenna...
It has been used by many cruisers as an effective antenna, and is known around here as "An Alternate Backstay Antenna"....("btrayfors" has written about it and recommended it extensively for years...)

You can make it indestructible, by using SS lifeline wire....or you can place an insulated copper wire inside a rope, and hoist it aloft, etc...

Here is what I just got done writing in another thread...
Quote:
Originally Posted by ka4wja View Post
Option 2) Using standoff blocks and running it up the backstay. From what I've read this is not the best idea as some of the power will transfer to the backstay. But I've read conflicting posts about that. The reason I'd consider this is because it is the cleanest option.
-Although just about anything metallic can be made into an antenna and can be strung up in some fashion, to work to some extent.....what you are trying to achieve is the "best overall antenna" for the money / space, that you have...AND one that lasts and works WHEN you really need it to work...
For those reasons along, this is NOT a good approach...
Your first option is much better!!!
(not to mention the physical complexity / cost / maintenance / unreliability, etc....)

2. Is running the antenna up the backstay a bad idea? If so, why?
-Yes....(understand that while almost everything on-board is a compromise, this is one area where there is NO need to compromise, and every reason to avoid doing it wrong...)
a) There are a wealth of "bad" things that can happen....and no "good" things...
b) If you "choose" to load up your rig as an antenna (not a choice recommended by most), you can do so by simply connecting the AT-130 tuner's output to your backstay / shroud / stays / chainplates, etc....
And, save the $$$ of any real antenna....
(this approach does work to some extent, BUT....but is fraught with LOTS of problems, not the least of which is LOTS of RFI, both into other systems on-board and from other systems into your radio....all very bad!!)
c) If run your antenna wire (whether inside a rope, or not) up close to other stays (especially parallel to them) you end up coupling some of your transmitted energy into them rather than into the ether, and cause on-board RFI in the process....AND, on receive you can also find excessive amounts of RFI coming in on your antenna (where you CANNOT filter them out)...
Taken to the limit, this is the concept of the horribly-expensive GAM antenna....
d) There's a LOT more to this, such as shunt-feeding / slant-feeding verticals not being efficient/effective for multiband operation, physical complexity, RFI, systems failures, etc...how much do want to know??

Just keep your SSB Antenna away from as much other "stuff" as you can....and do not allow it to run parallel, in close proximity to other wires or long metal objects....
And, remember that the WHOLE thing IS your antenna, from the time it leaves the top terminal/insulator on the AT-130, it is ALL your antenna, so getting it in the clear and away from any other wiring / metallic objects is always recommended!!


Quote:
Originally Posted by Jon Neely View Post
I heard people mentioning the but not talking about if there are issues with them.

I'm curious if I got 20ft of 3/8" PVC, painted it so it doesn't get UV chalky. then slotted it every 3 ft on one side thick enough for a zip tie to pull the inside wire snug against the backstay. Have 14g copper wire on the inside. Any issue with this? Seems like a poor mans GAM split lead to me. Tell me want you guys think. I just want something that is permanent but do sent cost a month in cruising funds.
If you just want something that is permanent, anything will work...
But, if want something that is permanent AND works well across the HF bands, AND doesn't cause RFI issues on-board, your idea of a "poor man's GAM" antenna is NOT what I'd recommend!!

I recommend what works and works well...
As long as you keep the top of the wire a couple feet away from your mast top, run the wire down to a place on the deck / superstructure / aft rail / transom / push pit, etc. that keeps the whole wire (including what is inside the boat, coming off the top of the remote tuner) as far away from other metallic structures / wiring as possible....especially keep your antenna wire from running in close proximity to and parallel to other wires, stays, etc....
{BTW, I actually do have personal, real-world, experiences with shunt-fed / slant-fed / coupled vertical antennas (what the GAM is and what you inquired about)....and they are notorious for their issues....poor multiband performance, sporadic performance, difficulty in tuning, noisy, etc. as well as causing significant RFI issues and even in extreme cases equipment issues/damage...}


Please see this recent post...
SSB Antenna Length


I hope this helps...


John
s/v Annie Laurie
__________________
ka4wja 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
HF antenna Back Stay vs. Screwdriver antenna BocaIII Marine Electronics 34 13-04-2014 03:15
Old Shakespeake Antenna vs. New Shakespeare Antenna zboss Marine Electronics 2 21-08-2013 09:27
Gam split lead SSB antenna Sailaway08 Marine Electronics 7 02-03-2013 10:33
Rope Antenna for SSB Keegan Marine Electronics 5 17-06-2007 11:48
SSB Antenna - What we ended up with.... swagman Marine Electronics 4 09-02-2007 05:12



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 12:49.


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.