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: HF Antenna Loading Coil design  (Read 2062 times)
KF4OMY
Member

Posts: 15




Ignore
« on: December 29, 2005, 08:58:25 AM »

      I am looking for websites or information on HF Antenna Loading Coil designs/plans.  I would like to build a quality one for 40 meters, and want information on others experience with this.

Eric

KF4OMY
Logged
KA0GKT
Member

Posts: 555




Ignore
« Reply #1 on: December 29, 2005, 09:54:19 AM »

I did a quick search using the key words "Antenna Loading Coil" and came up with several resources.  Here's one:

http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/HiQCoil.htm

You can also do a search on this site, QRZ.com and the ARRL site.  

An older copy of the ARRL antenna book is a good resource as well.

Good Luck

73 DE KAØGKT/7

--Steve
Logged
K6AER
Member

Posts: 3524




Ignore
« Reply #2 on: December 29, 2005, 10:21:15 AM »


Is the vertical for the base station of for a mobile? I’ll make a guess it's for mobile operation.

Base loaded coil antennas perform very poorly and their feed resistance is hard to match. As a general rule you want the coil set about in the middle of the antenna in order to raise the feed current away from the base feed. Typical antenna heights on a mobile are limited by bridges so 13 feet is about as high as you can go. The larger the coil the higher the Q and the lower the loss in the coil.

Coils about 3-4 inches in diameter are about the norm. Wire size is about 14 or 12 gage with 20-35 turns depending on the length of the top whip. Most mast bottoms are about 54 inches. A typical 40 meter coil would be 14 gage insolated solid wire wound about 3 inch form (PVC) with 33 turns over a 10 inch length. Checking the resonance with an antenna analyzer will tell you weather to add or subtract coil turns depending on resonance. The longer the top whip the smaller the coil can be. Top whip size would be from 54 to 78 inches depending on mounting needs.

Base mounts for cars tend to be from bumpers or hitch mounts and mid mounts on trucks are common. With a 10-13 foot antenna you will probably have to have a polyfiber support line to keep the antenna from being bent way over while running down the highway. Most mounts are located at the rear of the vehicle in order to use the length of the vehicle as a RF counterpoise.

You will have a lot of fun operating HF mobile. With mobile operation the antenna is everything. Larger (longer) is always better.
Logged
K0BG
Member

Posts: 9879


WWW

Ignore
« Reply #3 on: December 29, 2005, 12:10:20 PM »

With respect to Mike's knowledge on the matter, there is far more to it than what he states, or even implies. I'll suggest a good place to start, and that is www.w8ji.com.

Tom has about 10 very good articles on the subject, and if anything is lacking it is a study of ground planes. I understand he is working on that one for later publishing. While some of the data is rather deep, it is nonetheless some of the best mobile antenna data on the net.

If you want a more practical view, visit my web site.

Alan, KØBG
www.k0bg.com
Logged

K6AER
Member

Posts: 3524




Ignore
« Reply #4 on: December 29, 2005, 12:24:11 PM »

Alan is right regarding the building and construction of HF mobile antennas but it can be done with a minimum of expertise if you are patient and don't mind doing a little experimenting. No design is 100% effective on the first iteration. Vehicle body size, construction material of the vehicle will effect the tuning.

With an antenna analyzer and a little research the task can be completed by anyone.
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!