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: Antenna swr changing  (Read 1788 times)
KC8KTN
Member

Posts: 461


WWW

Ignore
« on: July 25, 2013, 11:36:19 PM »

Hello to all I have a ocf  w8amz 80 - 6 meters.

 http://w8amz.com/W8AMZ_OCF___WINDOM.html

The 80 meter side worked great. Swr was really low with my antenna tunner were really low 1.0-1.3.
Now all of a sudden at night I can not tune it in at all .
Durning the day the swr are good. This has been happening the last 2-3 weeks. Why durning the day sunlight it works great . At night swr,s really go bad. Ihave done nothing to the antenna.I have had the antenna up for 4 months now. On the other bands nothing has changed. Any sugestions. I am running an icom 718 at 100 watts.Thanks for any advice.. Everyone take care and be safe.  73s.   kc8ktn/chuck.
Logged
N4JTE
Member

Posts: 1157




Ignore
« Reply #1 on: July 26, 2013, 05:53:15 AM »

Somebody parking a motor home underneath it ?
Bob
Logged
K1CJS
Member

Posts: 6042




Ignore
« Reply #2 on: July 26, 2013, 06:28:16 AM »

It sounds like you've got a bad or a loose connection somewhere.  When it's warm and the materials expand, you've got a good connection (well, good enough) but when it cools, that connection loosens and you get the results you're getting.  Now the crappy part--it could well be a connection that you can't tighten, such as in a trap or other sealed part.  About the only way to see is to start tightening the connections you can get at, and if that doesn't solve your problem, to start replacing parts.

You could also contact the manufacturer and see if there is a reported issue with the antenna you have--sometimes that can cut your search time considerably.  As a last resort, if the antenna is still in its warrantee period, you could return the whole thing and get another.

Good luck and 73!
Logged
W1JKA
Member

Posts: 1765




Ignore
« Reply #3 on: July 26, 2013, 07:10:20 AM »

One of the many possibilities is night and early morning warm weather dew on grass and antenna wire. I have same symptoms on 30m. Same with early morning ice rime on wire in winter until sun melts it off. For me change in swr has no effect on contacts.
Logged
W5DXP
Member

Posts: 3613


WWW

Ignore
« Reply #4 on: July 26, 2013, 07:23:56 AM »

Now all of a sudden at night I can not tune it in at all.

Just a thought: A cold solder joint can cause that condition. Assuming the balun is a 4:1 voltage balun, it should show a low-resistance/short-circuit on an ohmmeter connected at the shack. If the resistance goes up at night there's probably a cold solder joint, loose connection, or broken wire somewhere.
Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KC8KTN
Member

Posts: 461


WWW

Ignore
« Reply #5 on: July 26, 2013, 09:02:46 PM »

Tried the antenna Friday night same conditions worked great low swr,s from 3.8-4.0. I was talking to some hams on 3.850 swrs were very low about 1.3. One of the hams said that using a automatic tuner which I have which is and ldg at-200 pro could be the problem of my high swrs from time to time. He said in his opinion that automatic tunners sometimes build up a charge and cause this issue. Maybe he is right. Tonight the weather and conditions are the same as last night when I was having my issues. I will keep trying it every night and see if it returns I will let evryone know on this post.. Thanks to all who gave me advice..Take care kc8ktn/chuck/   73s
Logged
KB6HRT
Member

Posts: 113




Ignore
« Reply #6 on: July 27, 2013, 07:47:58 AM »

Hi,
 Some antennas worl against ground for the match and most all antennas tuners work against ground, hence the ground lug on the back of your antenna tuner, if your ground is not as good as it could be then your antenna tuner will make a different choice to bring the SWR down as far as can but because of that it maybe different, check all your ground connections and your ground rod connections, that mak be the problem asso bushes near your antenna wind and time of the year can change things!
................73s..............kb6hrt
Logged
W5WSS
Member

Posts: 1744




Ignore
« Reply #7 on: July 27, 2013, 08:06:15 AM »

I have a LDG 200 pro and used it with a  same type of antenna from a summer cottage in Tennessee.
I never had a problem with the tuner suddenly changing.

The tuner operation is flawless relative to a stable antenna system.

You should look for something out and beyond it  changing that the tuner can only partially handle.

Is strain on the antenna hoist system where the connection at the feed point has been compromised?

I guess that the w8amz is wire and needs strain relief when hung from a tree with strain working to stretch stuff and where high humidity gets involved.
Logged
W3HKK
Member

Posts: 596




Ignore
« Reply #8 on: July 27, 2013, 12:07:38 PM »

My historical checklist from the school of hard nocks:

-loose or corroded coax connector- needs cleaning/tightening
-critters  ( or lawn mower) chewed coax outer jacket allowing water to enter - replace bad section.
-mechanical connection bad/loose- clean/tighten.
-bad coax jumper in the shack-replace.
-bad/loose/corroded antenna switch not making proper contact- clean/tighten.

DeOxIt is  great for cleaning coax   connectors, barrel connectors, etc
Logged
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!