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: Help! 1 wire antenna, must have LOW swr and be fed by coax 160m and other bands  (Read 1375 times)
G7IVJ
Member

Posts: 82




Ignore
« on: April 16, 2013, 04:01:53 PM »


Dear fello hammers!

Thanks for the help in advance Smiley

I am going to be installing a wire antenna, I want to mainly use it for 160m and 80m, and not sure which type to install, my head is spinning !

Here is my situation, the feedpoint centre of the antenna will be 250 feet away from the shack, and I can only use coax from the shack to approx 150 foot towards the antenna, due to there are some buildings in the way that I have permission to clip the coax to, so I cant use open wire feeder as it will literally be tacked to the buildings for at least 150 feet

For the remaining 50 feet, I could still use coax or at that point I could change to feeder

Due to the long run, I think the antenna the coax is connected to needs to be resonant on th bands I want to use, if not resonant then there will be horiffic losses due to the long cable run, right ?

So my thoughts are installing a fan dipole for 160m, 80 and 40 so its resonant and therefore no high SWR and no real losses. Would you agree with that ?

I have approx 350 feet in a straight line to install the wire antenna on, so 160m dipole can easily fit.

I could install an end fed and get some good radials down, I could install a doublet but think thats not workable due to the coax swr and losses problem. I could install some loops as I have 350 x 350 foot space, but the first 150 foot must be coax fed.

I could get away with two coax runs to feed two antennas but the coax leads would be touching each other.

I could install two seperate fan dipoles on the same mast, on the same coax, that way I get 160, 80 and 40 on one, and 40 20 and 10m on the other, both on the same mast, on the same coax.

How about a multiband 160m to 10m trapped dipole, would that work ?

Any suggestions ?

What would you do in this situation ?

What I wwant is the best antennas for each band

73 from London
Logged
WB6BYU
Member

Posts: 13578




Ignore
« Reply #1 on: April 16, 2013, 09:32:19 PM »

First question:  do you want local or DX coverage on 80m and 160m?  What sort of height
do you have available?

For heights that are practical for most hams, you'll probably want vertical polarization for
DX and horizontal polarization for local NVIS operation.  That's why it is important to look
at desired coverage first:  it is quite possible to recommend an antenna that will meet your
requirements for SWR but be useless for your preferred operating style.  On the higher
bands where the antenna is 1/4 wavelength or higher, a horizontal antenna may be better
for DX (this also depends on your ground conditions, which may be poor in the middle
of the city.)

Yes, trap dipoles are quite practical, or for vertical polarization you can start with a
commercial trap vertical for 40m - 10m and add traps and extension wires running
up some support for 80m and 160m operation.  Or just put inverted "L" wires for
80m and 160m in parallel with the vertical feedpoint.

Loops can be used on harmonic operation with coax feed:  I had a loop up for
several years that had an SWR of 1.5 : 1 or better at some point on every band
160m - 10m (though this is easier for CW operators, especially in IARU Region 2
where the 80m phone band extends up to 4.0 MHz.)  There is an article about
such a "Figure-8 Loop" designed for NVIS operation on 80m and 160m here:

http://www.ycares.org/index.php?option=com_phocadownload&view=category&id=15:antennas


I'm sure we can find or invent a number of other options, but it will depend on your
desired coverage area.
Logged
G0VKT
Member

Posts: 64




Ignore
« Reply #2 on: April 17, 2013, 04:27:54 AM »

I envy the space that you have available!

If it were me I would consider an inverted L for 160 and 80. Then fan dipoles for the remaining bands.
You would have radials in place for the inverted L so experiments with other verticals on other bands would then be quite straight forward.

There are no problems running coax next to each other. Or you may consider building or buying a remote antenna switch. It will just come down to the most cost effective solution.
Logged
WA3SKN
Member

Posts: 5559




Ignore
« Reply #3 on: April 17, 2013, 05:36:17 AM »

Make a loop, the larger the better, the higher the better.  It does not have to be cut to frequency and feed it with ladder line to as close to the radio as practical, then use a 1:1 ferrite balun and coax to a tuner by the radio.  The loop does not have to be a square or triangle... it can have more than 4 sides, but keep it as open as practical.
73s.

-Mike.
Logged
AA4PB
Member

Posts: 13032




Ignore
« Reply #4 on: April 17, 2013, 05:47:58 AM »

Assuming you have a 100W class radio, I would (and do) use an SGC SG-230 remote tuner located on the ground at the antenna site directly feeding an inverted-L. It works great on all bands 160M thru 10M and provides a perfect match for the long coax feed line.
Logged
AD4U
Member

Posts: 2186




Ignore
« Reply #5 on: April 17, 2013, 05:53:44 AM »

I recommend either a commercial trapped dipole or a fan dipole.  If you use good quality coax, losses in 250 feet at the frequencies you want to use (160M-40M) should be low.

Dick  AD4U
Logged
G3RZP
Member

Posts: 4965




Ignore
« Reply #6 on: April 17, 2013, 08:55:27 AM »

Unless your 160m dipole is up at 80 feet plus, it will have a poor SWR anyway.

Logged
K8AXW
Member

Posts: 4002




Ignore
« Reply #7 on: April 17, 2013, 09:10:21 AM »

Have you researched the possibility of using a Windom antenna?  If you can use this antenna, you could eliminate that 250' feedline.
Logged
N4CR
Member

Posts: 1702




Ignore
« Reply #8 on: April 17, 2013, 01:16:50 PM »

First question:  do you want local or DX coverage on 80m and 160m?

Yes, this is quite a big deal. A lot of the aforementioned solutions will result in vastly different primary angles of radiation. If you are looking for DX on 80m and 160m, an inverted L with a strong radial system may be the easiest to achieve without a lot of height.

A 160 meter dipole just stops being almost all NVIS and ground loss when it's 40 meters in the air and really starts acting like a dipole with a figure 8 pattern and a reasonably low angle of radiation when it's up around 80 meters in the air. Getting a dipole 260 feet in the air is a daunting task. Even getting 130 feet in the air for stopping most of the 'under a 1/4 wave' ground losses is tough.

Which is why so many DX'ers on the low bands use verticals.
Logged

73 de N4CR, Phil

Never believe an atom. They make up everything.
N6AJR
Member

Posts: 9927




Ignore
« Reply #9 on: April 17, 2013, 01:25:29 PM »

first off, for hf, ( especially on the low bands) you can use coax all the way to the antenna.  the better the coax, the lower the losses, so lmr400 or at least rg8 u will work.  build your self a dipole ( or fan dipole)  for starters. This is very cheap.  get some 18 g wire, and stretch it out, and hook on side to the center and one side to the shield.  then try it, and go from there.  A large loop at 30 or 40 feet will also work ( preferably with an autotuner) or there are several verts that are cheap, and they work better with the radials.  contact a local club and see what they use, or just try  different home made  antennas.  have fun.
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!