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

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Grounding When Portable from Car  (Read 1296 times)
KA3QOT
Member

Posts: 29




Ignore
« on: August 09, 2008, 11:51:43 AM »

I often work portable from my car. My setup includes a Kenwood TS-570S(G) powered by an AGM sealed battery right next to it. I place both on the backseat of my car. My antennas include various hamsticks which are placed in a magmount on the roof of my car. I've worked reasonably well in this configuration.

Today, I tried to operate on 40m. Though I had a close-to-flat SWR, I received some nasty shocks when transmitting. This happened three times or so before I gave up. Occasionally, I've gotten tiny shocks but these were strong enough to make marks on my skin.

I am not using a ground, which I'm guessing may be the issue. How can I ground when operating? I usually operate from a park nearby and don't want to permanently install the radio in my car.

73,

Dennis KA3QOT
Logged
K0BG
Member

Posts: 10248


WWW

Ignore
« Reply #1 on: August 09, 2008, 12:10:35 PM »

The reason you're getting "bit" is because there are common mode currents flowing over the coax. This is a direct result of an in adequate ground plane under the antenna. Remember, what ever current flows in the antenna, must also flow in its ground plane.

The fact you are using mag mounts adds to the problem, as the coax shield is not connected to the body at a point directly under the antenna. Adding ground straps won't help the situation much.

You can use split beads to isolate the common mode currents, and turn the leakage into heating the ferrite. Or, mount the antenna directly on the vehicle.

Alan, KØBG
www.k0bg.com
Logged

KA3QOT
Member

Posts: 29




Ignore
« Reply #2 on: August 09, 2008, 12:49:54 PM »

Thanks, Alan, for the great advice.

Regarding split beads, should I go with a 43 or 77 mix? Also which diameter size and should I place them at the back of the radio? Anyplace you can recommend that sells them?

73,

Dennis
Logged
K0BG
Member

Posts: 10248


WWW

Ignore
« Reply #3 on: August 09, 2008, 02:19:21 PM »

You need to use Mix 31, and it needs to be on the coax very near the antenna. Just remember; if the choke isn't large enough, it will get hot enough to destroy the ferrite. So, use the 3/4 inch ID ones, and get as many turns as you can. If you can't get at least 10, use two beads.

Also, a choke just masks the real problem, and that's inadequate mounting.

Alan, KØBG
www.k0bg.com
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!