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: Mobile antenna on plastic roof?  (Read 898 times)
KG6RCR
Member

Posts: 22




Ignore
« on: November 02, 2004, 07:40:11 AM »

I will be installing a little mobile rig into my '84 VW Vanagon Westphalia camper. These campers are of the "pop top" variety with little metal on the topside. Picture a van with the rear three-quarters of the roof removed and replaced with an inverted plastic bathtub. The forward 1/4 -- over the driver -- is still metal, but this is a cargo-carrying location. Putting an antenna there would get in the way of carrying luggage. Near as I can see, I don't have the kind of horizontal metal surface that mobile antennas are usually mounted on. My mount choices are: in the middle of the plastic poptop, or rain gutter mount. Either way, I reckon that the ground plane won't be what the mfgr had in mind. I'd appreciate hearing what others have come up with that works, especially Westy-owning hams. I'm planning on 440/2M/6M operation.
73's
Logged
K0BG
Member

Posts: 9879


WWW

Ignore
« Reply #1 on: November 02, 2004, 09:36:23 AM »

If my memory is correct, there is a small space on top of the fenders where one could mount an NMO or SO239 style antenna. Diamond and others make a colinear (6,2, and 440) with a SO239 connection which also could be used next to the hood. However, they're not too efficient, but some it better than none.

Alan, KØBG
www.k0bg.com
Logged

KG6RCR
Member

Posts: 22




Ignore
« Reply #2 on: November 02, 2004, 05:57:46 PM »

Fenders? Hood? on a Vanagon?

http://volksweb.relitech.com/tomc/vanagon/vanagon.jpg

:-) and 73!
Logged
K5LXP
Member

Posts: 4507


WWW

Ignore
« Reply #3 on: November 02, 2004, 09:19:00 PM »

I wouldn't worry about 6M operation, 2/440 are the bands you will do the most mobile activity with.  This issue is addressed often with public service vehicles like ambulances, and pickup truck campers made of fiberglass.  The solution is as simple as using contact cement to affix some inexpensive aluminum sheet to the underside of the camper top to serve as a groundplane.  Alternatively, self adhesive copper tape can be used.  Make it as big as practical, put your antenna in the middle of it and you're done.  You could also go with an end fed half wave design that can work without a groundplane, but being on the top of a van, clearance may be an issue with longer antenna models.

Mark K5LXP
Albuquerque, NM
Logged
K0BG
Member

Posts: 9879


WWW

Ignore
« Reply #4 on: November 03, 2004, 06:24:07 AM »

On the latest versions (not the old rear engine versions), at the edges of the hood where it meets the fender, there is a small space where an antenna could be mounted. I've personally never owned a VW bus, but I had a friend in Denver who did, and this is where he mounted his.

Alan, KØBG
www.k0bg.com
Logged

KG6RCR
Member

Posts: 22




Ignore
« Reply #5 on: November 03, 2004, 10:19:25 AM »

Oh, right. Vanagons were the '80's models, with the rear engine. (Before that, you had your "bay windows" in the '70's, and your "microbuses" in the '50's and '60's. All with rear engines.) The front-engine  90's version is the Eurovan. A matter of nomenclature and not anything you'd be expected to know unless you have a sufficiently wide masochistic streak to get into VW buses.
Logged
KG6RCR
Member

Posts: 22




Ignore
« Reply #6 on: November 03, 2004, 10:22:43 AM »

Thanks for the tips! The underside of the poptop is the ceiling to the living space. We were talking about painting sky and clouds up there . . . I wonder if there is a conductive paint we could spray on first as primer/groundplane.
Logged
KZ1X
Member

Posts: 3228




Ignore
« Reply #7 on: November 03, 2004, 04:53:15 PM »

It would be a straightforward matter to affix the aforementioned aluminum plate (steel would be OK too) and  to that glue an ordinary acoustic ceiling tile, trimmed carefully to fit.   This would cover the the ground plane plate, the antenna mount and the exiting coax, and also be relative benign-looking and quite inexpensive.

(Yes, of COURSE I have done this before.)

Your trick is to find a suitably thick piece of plate so an NMO mount will stay in it well, then relieve a hole large enough for the mount to stick through the fiberglass.  You'll need to use the right kind of sealer.

Recommended antenna is the dual-band Austin 500C.  Low-profile, forgiving of foreshortened groundplane, well-constructed, low cost.
Logged
KQ6Q
Member

Posts: 991




Ignore
« Reply #8 on: November 05, 2004, 10:53:36 PM »

I'd recommend against putting an antenna on the plastic roof  -you're asking for clearance problems in parking garages, not to mention water leaks.
Check HRO or Radio shack for gutter-clamp antenna mounts, and a 2/440 antenna on that mount, which you can leave in place. Pick an antenna that won't project much above the fiberglass top, to preserve your clearance.
Logged
KG6RCR
Member

Posts: 22




Ignore
« Reply #9 on: November 08, 2004, 07:31:38 AM »

That's a darn good point. This summer I watched while a friend drove his YL's camper-van through a drive-through at a bank and just about scraped the air-conditioner off the roof. Smashed it pretty good. So, yeah -- I do want to avoid having tall stuff on my Vanagon. Many thanks for saving me from myself!
73,
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!