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: Poor signal in motor home with screwdriver  (Read 430 times)
KC0MQR
Member

Posts: 12




Ignore
« on: August 12, 2003, 05:14:22 PM »

I am posting this for a friend who has a Tarheel screwdriver on his mobile home. ( he does not have acess to a computer).

He has the screwdriver mounted on the trailer hitch but seems to have trouble getting out and tuning etc.
As the mobile home is mostly fiberglass he suspicions
the grounding. He has the antenna grounded to the frame and does not rely on the hitch mount as the sole contact for the ground.

Any suggestions as to ways to improve signal with this
set up.

John kc0mqr
Logged
K0BG
Member

Posts: 9868


WWW

Ignore
« Reply #1 on: August 12, 2003, 05:20:17 PM »

DC ground and groundplane are two different things. However, I don't think this is why he has poor results. Fiberglass or not, there are all sort of steel bracing and wiring which easily shield signals, add to losses, and generally mess things up.

The most important aspect of mounting mobile antenna is to keep the coil as clear as possible away from the body even on fiberglass vehicles (see aforementioned).

Not knowing what the RV looks like, it is hard to offer a solution as to mounting position, but sometimes the front bumper is a better bet if it keeps the coil clear.

Lastly, I don't know how he is matching the low impedance load to his 50 ohm output.

Alan, KØBG
Logged

WB2WIK
Member

Posts: 20603




Ignore
« Reply #2 on: August 13, 2003, 02:00:43 PM »

I've helped out a few local guys who have mobile homes/trailers and tried using HF verticals mounted to them.

In every case I can recall, the antenna (screwdriver or otherwise) worked far better when installed up high on the trailer, preferably the roof, but if not, on a side wall very close to the roof.  Almost none of them worked worth a darn when installed down low.

WB2WIK/6
Logged
WA4PTZ
Member

Posts: 528




Ignore
« Reply #3 on: August 16, 2003, 07:20:22 AM »

Another very common error that people make with a
screwdriver antenna is that they fail to insulate
the antenna from the mount. The entire assembly is
the antenna and if it is not insulated from the mount
then it is a short circuit. NO signal and high SWR.
Also, mounting it away from the vehicle helps too.
A few inches to 12 inches. Don't forget the physics of
moving and stopping objects. Many fiberglass objects
are made with an embedded wire mesh to add support.
This mesh is not grounded.
Good Luck and 73 - Tim
 
Logged
KB6HRT
Member

Posts: 111




Ignore
« Reply #4 on: September 06, 2003, 10:42:27 PM »

Hi,
If you are mounting the antenna on the Hitch you must be stationary when doing so. One could make an extenion for your antenna that is grounded and bring the antenna up so it is over the top of the motor home so the coil see's 360 degrees of the horison and you will get a lot better results also one can buy 2" metal duct tape and install raditals on top of the motor home to improve the ground plane. Tarheels now make a 6-80 antenna that is 54" tall when fully extended, which has only 18" of body to it which could be installed on the center of the motor home with 4 radils made from the tape which would work very well.  73s Hope this is of some value to ya.
KB6HRT a Tarheel antenna owner!
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!