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: using a 40 mtr vertical or 40mtr delta loop on 17 mtrs  (Read 1393 times)
KU7I
Member

Posts: 122




Ignore
« on: April 26, 2010, 09:08:01 PM »

I used a 40 mtr ground plane vertical back in the early 90's. It had six elevated radials all about 30 ft long or so. It was about 15 ft off the ground. A bonus was that it resonated perfectly on 17 mtrs and was a flame thrower on that band. Well, here we are in 2010 and I am thinking about putting up another vertical like this since I have moved since the last one was up. But I am curious to see if a 40 mtr delta loop mounted vertically with the base about 20 ft off of the ground would work about as well, especially curious to see how it would play on 17. The 40 mtr vertical is basically 5/8 wavelength on 17 which explains the low takeoff angle and generally great performance. Wondering if anyone has used a vertically oriented 40 mtr loop on 17? Lane Ku7i San Diego
Logged
K4SAV
Member

Posts: 1840




Ignore
« Reply #1 on: April 27, 2010, 09:04:19 AM »

A 40 meter 1/4 wavelength vertical with 1/4 wavelength elevated radials should resonant on 40 meters and close to 15 meters.  There should not be a resonance on 17 meters.  However it should work OK on 17 meters if you solve the SWR problem. 

There is a way to make a vertical resonate on both 40 and 17 meters, although it's a little tricky.  I hate to recommend this because of the common mode problem.  It's a little like creating a vertical version of an OCF antenna.  That would be to shorten the radials and lengthen the vertical element, something like six 25 ft wire radials and a 38 ft, 1 inch diameter vertical element.  Maybe that is what you had.  That should work OK on both bands. You will need a good feedline choke to keep the common mode currents off the feedline.   Another combination that works is four 25 ft radials and a 37 ft vertical element, all made from wire.  If the vertical element is not wire (maybe the vertical is a mast, you will have to modify both of those dimensions).

A 40 meter delta loop won't have a resonance on 17 meters, the SWR will be very high.  It should resonate close to even multiples of the fundamental, i.e., 40M, 20M, 15M, etc.  Worse yet, with horizontal polarization most of the signal will be directed up at a very high angle on 17 meters.  You could feed it with ladder line in the middle of a vertical side and that would be OK on 17 meters.

Jerry, K4SAV
Logged
ON8WW
Member

Posts: 7




Ignore
« Reply #2 on: November 11, 2010, 06:54:59 AM »

A 40 meter 1/4 wavelength vertical with 1/4 wavelength elevated radials should resonant on 40 meters and close to 15 meters.  There should not be a resonance on 17 meters.  However it should work OK on 17 meters if you solve the SWR problem. 

There is a way to make a vertical resonate on both 40 and 17 meters, although it's a little tricky.  I hate to recommend this because of the common mode problem.  It's a little like creating a vertical version of an OCF antenna.  That would be to shorten the radials and lengthen the vertical element, something like six 25 ft wire radials and a 38 ft, 1 inch diameter vertical element.  Maybe that is what you had.  That should work OK on both bands. You will need a good feedline choke to keep the common mode currents off the feedline.   Another combination that works is four 25 ft radials and a 37 ft vertical element, all made from wire.  If the vertical element is not wire (maybe the vertical is a mast, you will have to modify both of those dimensions).

A 40 meter delta loop won't have a resonance on 17 meters, the SWR will be very high.  It should resonate close to even multiples of the fundamental, i.e., 40M, 20M, 15M, etc.  Worse yet, with horizontal polarization most of the signal will be directed up at a very high angle on 17 meters.  You could feed it with ladder line in the middle of a vertical side and that would be OK on 17 meters.

Jerry, K4SAV

Jerry where is the best place to put the balun on a 40m deltaloop on the top or in de corner downstairs??

Dave
Logged
K5ACO
Member

Posts: 9




Ignore
« Reply #3 on: November 18, 2010, 03:19:26 PM »

My vertical (when tuned for 3.6mHz) works well on 17m
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!