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: W3EDP and grounding  (Read 5094 times)
2E0OZI
Member

Posts: 269




Ignore
« on: February 13, 2011, 02:27:53 AM »

G'day folks,

I have just put up a W3EDP that goes out the window, over the roof of my 2 storey house, and ends up 8 feet off the ground near my back shed. It has the traditional 17 foot counterpoise/wire leading off at right angles, this goes from the tuners ground terminal along 6 feet off the ground and terminates there. No coax involved anywhere.

I have no ground stake/earth - yet.

The question is; as I'm putting a ground stake in soon (next day or so) to what do I connect it to? The same terminal as the 17 foot counterpoise? Or the ground terminal of my tranceiver? Both? 

As it is it seems to be going OK - have made my first contacts on 40m in the Shetland Islands and in Hungary, plus a couple in Slovenia and Bosnia.... all with 10w SSB. But it certainly seems a pretty noisy thing. I expected it to be worse than my 20m dipole, but this worse?

all the best

Scott
Logged

Men can only be happy when they do not assume that the object of life is happiness.
George Orwell
2E0OZI
Member

Posts: 269




Ignore
« Reply #1 on: September 12, 2011, 05:04:18 AM »

Bought a 9:1 UnUn and will maybe hook the counterpoise to the earth post on it, and/or put in a ground stake directly below it with a radial or 3 or more. Problem is the radials will not be below the horizontal radiator of the antenna.
Logged

Men can only be happy when they do not assume that the object of life is happiness.
George Orwell
G6EGM
Member

Posts: 1




Ignore
« Reply #2 on: September 26, 2011, 01:40:47 PM »

Hi Scott,

in my experience the W3EDP is a good antenna but then again I was using it portable so in a quiet environment.

Have you considered a 4:1 Balun with the 17ft counterpoise connected to one leg of the balun and the 85 ft end to the other leg of the balun AND if that doesn't make it quieter then putting a choke between the ATU and the Balun. I find a choke does a wonderful job of quieting things down.

Kind regards

Dave
G6EGM
Logged
2E0OZI
Member

Posts: 269




Ignore
« Reply #3 on: November 19, 2011, 02:14:29 AM »

Hi Dave, yes something like that is part of the plan but a week ago I snapped my achilles tendon so everythng in life is postponed for a few months now. When I am mobile again I will move the unun up behind the chimney stack, hook up radial/counterpoises of bell wire, and make a choke as well.

all the best,

Scott
Logged

Men can only be happy when they do not assume that the object of life is happiness.
George Orwell
WB6BYU
Member

Posts: 13017




Ignore
« Reply #4 on: November 19, 2011, 09:21:46 AM »

The original W3EDP was NOT grounded.  Basically it was a combination of wire lengths that tube-type rigs
with a wide-range matching output matching network could feed some power into when it was plugged into
the back of the rig - which, at the time, may have had a balanced output with neither side grounded to the
rig chassis.

The "counterpoise" length was changed for each band to bring the total wire length close to resonance.
In this respect it was more like an OCFD, with the feedpoint close to the end.

In a modern installation with coax output, one side is earthed to the transmitter, and if that is connected
back to the mains earth it will form a much larger counterpoise/ground system than the 17' radial
by itself (especially on bands other than 20m, where the radial is resonant.)  That means that the whole
house electrical system is now part of your antenna, which isn't a good idea if you are trying to reduce
the amount of noise picked up!  So you really need a CURRENT balun of some sort between the rig
and the antenna feedpoint - or a rig with a balanced output.

Of course, any length of feedline (including that inside the balun) will change the impedances seen
at the transmitter.  With a good RF earth system that is effective on every band you may get a usable
SWR on 20m and perhaps 15m.  With the single radial wire (decoupled from the rig and mains wiring)
you are only going to get a reasonable match on 20m:  the SWR probably will be over 5 : 1 on most
other bands and over 10 : 1 on some even if you use a balun or UN-UN at the feedpoint.

It shouldn't really matter whether the radial runs under the wire or not - it changes the feedpoint impedance
a bit and varies the amount of radiation from the bottom end of the wire (depending on how it is installed.)

While 85' isn't a bad length for an end-fed wire, you need to provide a suitable earth return for each band
you are going to use.  One approach would be multiple quarter wave radials, for example, adding one each
for 15m and 10m to the one you already have for 20m.  (Running two radials per band in opposite directions
might be even better.)  A lead to an earth stake might work, though there are two common problems with
such an approach:  the length of the connecting wire, and high ground losses unless you also add further
radials across the ground.

If you aren't already using it with a wide-range ATU, you can get such a system to match with a 4 : 1 UN-UN
(not a balun) at the feedpoint.  That should give you a reasonable SWR on 20m, and the addition of a 27pf
capacitor in series should help on 15m.  (You can try a ~50pf variable with some means to short it out for
20m operation - possibly by bending the corner of one plate so it shorts when the plates are fully meshed.)


But it is important to understand how this differs from the original design, and why the original would have
worked better with the transmitters of its day than with modern rigs.
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!