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: Rain and Snow high SWR  (Read 587 times)
NK8A
Member

Posts: 24




Ignore
« on: March 23, 2008, 06:09:54 AM »

Thanks for all the help with my problem with High SWR when  there is dampness. I have found one problem. The s0239 connecters on my radio are shorted. I ruled out all the cables which were checked for shorts. Thanks again...73 ...Dave
Logged
K7KBN
Member

Posts: 2782




Ignore
« Reply #1 on: March 23, 2008, 07:38:07 AM »

How did you determine this?  Do you have a copy of your rig's operating or service manual?  You need a clear schematic of the rig.

What might appear to be a "short" to a multimeter at DC often appears as an open circuit at RF.
Logged

73
Pat K7KBN
CWO4 USNR Ret.
NI0C
Member

Posts: 2391




Ignore
« Reply #2 on: March 23, 2008, 08:17:05 AM »

I have observed a downward shift in the resonant points of narrow bandwidth top-loaded verticals in wet conditions.

I have observed it with the Cushcraft's MA8040V, and the Bencher/Butternut HF-2V with added top loading.  Cushcraft even has a note in their manuals concerning this.  

There was a discussion of this in the eHam TowerTalk forum about this: http://www.eham.net/forums/TowerTalk/5764


73,
Chuck  NI0C
Logged
K1BXI
Member

Posts: 812




Ignore
« Reply #3 on: March 23, 2008, 08:40:09 AM »

Your reading at the rigs SO239 using an ohm meter is normal for most rigs. Use a low ohm scale and you will see a reading of some sort due to the dc resistance of the devices in the input circuit. As said above, the ac resistance (impedance) is very high at rf frequency's.

Think of an rf choke and how it works and what the dc resistance is when measured and you will get the idea.

John.....K1BXI
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!