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: "Fan" dipoles  (Read 637 times)
W4CBL
Member

Posts: 12




Ignore
« on: July 22, 2008, 05:47:27 PM »

I am about to construct a "fan" (multi-element, multi-band) dipole for portable/field day use.

The question I have is this: if using insulated radiators, do the elements have to be spaced apart? I mean, if the elements are electrically separated from each other by insulation, is their any reason that they could not be "ganged" together by wire ties?

It seems to me that this method would be easier to construct/install than the physically "fanned" method you see all over the internet.

Thanks!
Chris W4CBL
Logged
WB2WIK
Member

Posts: 20611




Ignore
« Reply #1 on: July 22, 2008, 06:05:05 PM »

Experimenters have tried that for decades.

Doesn't work.

You need to separate the wires physically as much as you possibly can.  6" is okay, 12" is better, 24" is better still.

No free ride, otherwise we could use flat rotator cable to make these -- and that's been tried a lot, with poor results.

WB2WIK/6
Logged
W4CBL
Member

Posts: 12




Ignore
« Reply #2 on: July 22, 2008, 06:13:33 PM »

Thanks.

I suspected that I was not the first to think of this, and that such close co-location would have harmonic or other effects, but I figured I would ask.

Thanks again.

73 de W4CBL
Logged
N6AJR
Member

Posts: 9910




Ignore
« Reply #3 on: July 22, 2008, 07:46:06 PM »

a few inches is minimum and more is better.  some folks like to put them in the "umbrella" or " astric" formation, with one north and south one east and west and the next caddy corner. this makes them a lot easier to tune too.

All in all its one of the cheapest, most effective a ham cn build.  good luck
Logged
WB6BYU
Member

Posts: 13336




Ignore
« Reply #4 on: July 23, 2008, 12:18:12 AM »

While such an antenna can work with close spacing, the problem is the
interaction among the elements when you try to tune it.  The ends of
each wire are particularly susceptable to this - you could try bundling
the wires together but leaving the last, say, 2 feet of each wire hanging
down out of the bundle.

Generally the farther the end of a wire is spaced from the rest of the wires,
the less the interaction when you are tuning them.
Logged
WA3SKN
Member

Posts: 5496




Ignore
« Reply #5 on: July 23, 2008, 04:12:56 AM »

We used to use ribbon rotator cables to make these antennas.  It is much better to have them spread apart... especially at the ends.
Radiates better, bandwidth better, matches better, etc!
Try and have some spacing between the elements!
73s.

-Mike.
Logged
K5DVW
Member

Posts: 2193




Ignore
« Reply #6 on: July 23, 2008, 05:37:47 AM »

I've build these kinds of dipoles out of ladder line with two bands per antenna. No issues at all tuning or using. I suspect that as you add bands it pays to have the ends separated more.
Logged
N0CGF
Member

Posts: 29




Ignore
« Reply #7 on: July 23, 2008, 10:22:22 AM »

I have built many of these over the years at different QTH's.  My experience is the same as WB2WIK and N6AJR have stated, the farther the distance the better.  I have feed them with 50 ohm coax and have not needed the Antenna tuner.  I have found the farther the distance apart the greater the SWR curve at my locations.  Can be frustrating to build, start with the lowest frequency dipole to tune, and work he way up.. I have been very happy with them over the years,,,,  73's N0CGF Dennis,,,
Logged
N0CGF
Member

Posts: 29




Ignore
« Reply #8 on: July 23, 2008, 10:30:58 AM »

I forgot to state that no antenna tuner was needed on 40 meters thru 10 meters but,, as common sense states the bandwidth is very narrow on 80 meters and the antenna tuner is needed there until the loss of the coax restrict the use..  I have mine separated at 6 inches apart for each band only for ease of mounting..,,,,,,N0CGF
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!