Call Search

New to Ham Radio?
My Profile

Friends Remembered
Survey Question

DX Cluster Spots

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

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
Author Topic: Full length (lamda) wire yagi - as used by the Zuni (?) QRP contest group?  (Read 90 times)

Posts: 18

« on: October 10, 2019, 06:05:53 PM »

Greetings from Dhaka, Bangladesh, S21

Any tips on such an antenna?

Chris KF6VCI (can't log in any more with my old, too simple, password)

Posts: 18521

« Reply #1 on: October 10, 2019, 08:49:36 PM »

I have seen some designs that would qualify as a "full-wave yagi", though I don't know the details
of what the Zuni Loop Expeditionary Force actually uses.

Basically, you use a full wave driven element ("two half waves in phase") and add separate reflector
wires behind each half, with some spacing between them.  Because the parasitic elements are
colinear you can just use, say, 3 feet of synthetic rope as an insulator between them.

So, for example,  I can take the 40m doublet that I often use for Field Day, and behind it I can add
a pair of 20m reflectors with a bit of spacing between the ends.  That turns the doublet into a pair
of 2-element side-by-side yagis on 20m.  Feedpoint impedance is high, but that isn't a problem with
the ladder line feed that I use for the doublet.

Then I can add a 40m reflector behind the 20m wires to give additional gain on 40m.  That gives
gain on 2 bands.

You can use directors in place of reflectors in some cases, depending on your supports.

You can do the same thing with an Extended Double Zepp for a bit more gain, just by extending the
rope in the center of the reflectors.   But I've found that the EDZ pattern is a bit too narrow to cover
the whole East Coast of the US from here on the West Coast.

There is another sort of "full-wave yagi" (or longer), where you use a sloping wire one or more
wavelengths long, with a slightly longer reflector parallel to it and spaced behind it.  It isn't too
difficult to get a combination that gives (vertically polarized) gain on 20m and 15m, or 15m and
20m, but a tri-band combination requires some spacing trade-offs, especially for 3 elements.
I used a single sloping wire over salt water for Field Day years ago from Alaska, and it worked quite
well (at least for more distant stations), but  unless I have salt water handy a better use of the
required height would be for dipoles or other horizontally polarized antennas.
Pages: [1]   Go Up
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!