Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Radials required for by sea water use  (Read 1173 times)
F5VDM
Member

Posts: 11




Ignore
« on: April 09, 2013, 06:16:53 AM »

Hi

I have a 43 foot vertical for use about 3 metres from sea water.  My mobile antenna works brilliantly well by the sea, lots of DX is worked, but I want to try the 43 footer.  What do you recommend as radials (being as I'm so close to sea water?)  I don't practically see me putting out dozens, but guess that some should be present.  The location also has a hand rail/barrier which is about 1 mile long, I will also ground the antenna to this.  Any thought on radials?

BTW Match will be done by autotuner at the antenna base.

regards

Garry
Logged
W8JX
Member

Posts: 5479




Ignore
« Reply #1 on: April 09, 2013, 07:13:46 AM »

Fresh or salt water?
Logged

--------------------------------------
Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
KB4QAA
Member

Posts: 2275




Ignore
« Reply #2 on: April 09, 2013, 10:39:18 AM »

You can run radials to be in contact with the salt water, but there is no need to extend them very far into the water.  Remember that RF Skin Effect means that RF won't penetrate very deep into the water.

For good performance you will still need radials in the directions away from the shore.

How many radials you use always depends on your level of time, interest, effort.

In my opinion, eight (Cool 1/4 wave length radials (in your case around 3-3.5meters) provides a stabilized impedance and good basic pattern.

Have fun at the beach!  Bill
Logged
W8JX
Member

Posts: 5479




Ignore
« Reply #3 on: April 09, 2013, 12:18:09 PM »

You can run radials to be in contact with the salt water, but there is no need to extend them very far into the water.

True but it could effect the choice of materiel for radial.
Logged

--------------------------------------
Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
W4VKU
Member

Posts: 342




Ignore
« Reply #4 on: April 09, 2013, 01:14:14 PM »

I would be able to provide a first hand answer sametime next month after 8Q7 operation.
I have the Butternut HF6V-x with 12/17m coils all tuned up and marked. I ran 6 radials here in my backyard @ NC
to get an idea. I know the soil conductivity is going to be different, but the plan is to place it near the saltwater
line in both high and lowtide (3ft or so is the variance), meaning it is going to stand in water at times on a
6ft tubing that is driven down into the soil atleast 2plus feet. No breakers at the 8Q7 spot, since the reef extends
further out and appears to be a lagoon.

As the vertical is moved inland over a 1/4 wave, the signal strength starts to drop and at a 1/4wave point inland, it
again peaks up, but by not as much as when it is right near the water line. Then again, as you continue moving
inland, it drops even further. Hence the kicker is to keep it near the waterline at all times if possible. This is my
understanding based on reading some material about the best location to place a vertical.

Since many do not want to worry about the shifting waterline and tide pattern, the vertical dipole is used. Also the
vertical dipole is much better suited for a phased setup.

We are using #14 wire and durability past the operation is not a concern Smiley

73s
krish
w4vku
Logged
W5WSS
Member

Posts: 1652




Ignore
« Reply #5 on: April 10, 2013, 06:48:31 AM »

A flat plane radial system for a vertical that is 43 ft in length would be better served when the radials are as long as the vertical.

I presume you are mobile with the antenna nearby on a base mount? And where the antenna base feed point is just above the ground? If so

On the beach 3m from the actual shoreline I would roll out 4 43 ft radials In a + shape. and cover 3 JUST below the sand.
The 4Th radial will need a weight tied to the end to cast into the water and heavy enough to hold it in place. If I were being a perfectionist I would try to hold the radial just above the water level with the others but hey that's probably splitting hairs it is possible that one need not a radial in that direction.

I presume that this is an excursion to the shore? Salt water is hard on everything so do plan on frequent corrosion maintenance after each time you use it clean it off before storage.

Enjoy the contacts!
73


 



Logged
NH7O
Member

Posts: 126


WWW

Ignore
« Reply #6 on: April 10, 2013, 10:29:45 AM »

A local ham, at the beach on O'ahu, uses half wave long verticals, with a matching network at the base for the very high impedance. He just uses a ground stake into the sand, no radials at all. He gets out *very* well.
Logged
K0OD
Member

Posts: 2532




Ignore
« Reply #7 on: April 10, 2013, 11:10:36 AM »

Quote
"A local ham, at the beach on O'ahu, uses half wave long verticals, with a matching network at the base for the very high impedance. He just uses a ground stake into the sand, no radials at all. He gets out *very* well."

Hope no one, especially a kid in a swimming suit,  comes in contact with that 1/2 wave vertical. Very dangerous.

There is an Hawaiian station who has shown up on 60 meters running 50 watts to a 90' wire vertical 50' from the Pacific. Top was supported by a palm tree. Lord was he LOUD!  I think he just used a small ground rod.

He was many, many dB louder than any other KH6 I've heard on 60.


Logged
ZL1BBW
Member

Posts: 355




Ignore
« Reply #8 on: April 10, 2013, 06:33:58 PM »

We used to use a large as possible copper plate on the bottom of a boat, so it is s similar situation.  A good size 1 x 1 metre copper plate into sea water should provide a good earth, I would back that up with 4 radials and see how it goes.    Used to use the liners out of hot water cylinders for the copper plate, do not know if hot water cylinders still have the copper centre?
Logged

ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!