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: 20M vert dipole for DX?  (Read 1056 times)
KA1J
Member

Posts: 174




Ignore
« on: December 03, 2012, 02:32:19 PM »

My antennae are 350' from the house, all ground mounted and connected to a radial base of 120 radials 130' long each. I have 160, 80, 40, 30 meter and vertical wires and a butternut HF9V in the center of the radial plate which I use solely for 20M. With this arrangement I can use the 160 inv-L for 10, 12 and 15M The 80 in-v works great for 17M. 20M though is only OK SWR-wise with the butternut. All the different antennae are switched in via an Ameritron remote coax switch. All the wires were erected by using a spud gun to get the wires/ropes over trees around the radial plate. the upward elements are mostly vertical except for 160m which has maybe 50-60' of vertical with the rest hanging on the tree tops.

I don't get out as well as I'd like with the butternut on 20M and my only interest is DX. I've been thinking of removing the butternut and making up a 20 meter dipole and shooting another rope over a treetop and hauling the wire to treetop level and having the lower part dangle free with fishing line attached to keep it from swinging. I'd have another 40' of coax needed to do this and the coax would not be running parallel to the ground but would be coming up at an angle from the remote coax remote terminal. Being in a forest setting, I can't erect a tower at this location. Having 1/2 the radials on a salt marsh (With the other 1/2 on the boggy ground in the forest) is too good to pass up so I need to work from this location.

Any problems with this or something I can do that would help? I was thinking perhaps 3-4 lower wires cut to 20m so I could angle them out more like a GP.

Thanks

KA1J
« Last Edit: December 03, 2012, 02:37:27 PM by KA1J » Logged
WX7G
Member

Posts: 6136




Ignore
« Reply #1 on: December 03, 2012, 03:18:53 PM »

I don't see that the vertical dipole will perform better or worse than the vertical.

Trees are said to offer greater loss to vertically polarized as opposed to horizontally polarized radiation. You might install a dipole or inverted-vee and compare.
Logged
K3VAT
Member

Posts: 731




Ignore
« Reply #2 on: December 03, 2012, 04:59:59 PM »

For 20M DX'ing and using a single horizontally polarized wire antenna, I recommend the extended double zepp mounted around 65 feet high.  The EDZ is nicely explained in the ARRL Antenna Book, Chapter 8, page 40.  It has gain (4.95dbi) and two nice low angled lobes and four others in a sort of cloverleaf configuration.  One can orient the EDZ to your target DX.  I've used this antenna on 40M (at 90') successfully to routinely work into Asia from Maryland.  You can verify this from modeling, but believe that the EDZ will have about 7db more than vertical dipole.  The existing radial field will enhance the EDZ also, especially if strategically positioned.

GL, 73, Rich, K3VAT
« Last Edit: December 03, 2012, 05:03:49 PM by K3VAT » Logged
KA1J
Member

Posts: 174




Ignore
« Reply #3 on: December 03, 2012, 10:10:46 PM »

Perhaps I didn't state the situation well. I have no supports other than tree branches to put my antenna in. None of the trees are more than 50 or so feet high so something taller is not possible. I have to work with what I can "erect" with a "spud gun" raising a dipole might be possible but I wouod have to shoot both ends over opposite branches and pull the ends tight to get a dipole up. My understanding is a dipole has directivity and since one antenna for 20M at 40' max here has to suit all directions, I don't expect a dipole is the best attempt for me to attempt.
Logged
K3VAT
Member

Posts: 731




Ignore
« Reply #4 on: December 04, 2012, 01:54:19 AM »

Perhaps I didn't state the situation well. I have no supports other than tree branches to put my antenna in. None of the trees are more than 50 or so feet high so something taller is not possible. I have to work with what I can "erect" with a "spud gun" raising a dipole might be possible but I wouod have to shoot both ends over opposite branches and pull the ends tight to get a dipole up. My understanding is a dipole has directivity and since one antenna for 20M at 40' max here has to suit all directions, I don't expect a dipole is the best attempt for me to attempt.

OK, got it.  Then if you're limited by height, get the Zepp as high as possible.  Anything over 35' will produce a low angled lobe that will work for most worldwide DX. IMHO, this arrangement will be superior to any other wire configuration (except perhaps a phased array, but don't see that is viable there at KA1J).  Perhaps another can provide a simple model to compare performance numbers.

GL, 73, Rich, K3VAT


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!