Hello Guy and sorry for the very late reply,
I should have given more detail on my, admittedly poor radial system.
It is pretty sparse, consisting of only ~20 1/4 wavelength radials not
very well distributed. I'm sure that the poor radial system and
distribution account for the changes in bandwidth I saw when I installed
the ground screen. The reduction in bandwidth that I saw was ~10%.
Since the antenna is tuned for the low end of the band it was not a
problem, just an observation.
The current antenna is being replaced with a 57 ft DX-Engineering 80M
vertical. Assuming the weather cooperates this fall I plan on
re-installing the ground screen and adding additional radials to get me
up to 40-60 radials.
So back to my original questions. When using insulated radials, does it
make a difference if the ground screen is below or on top of the radials
and is there any need to bond the radials to the ground screen, besides
at the base of the antenna?
On 9/5/2011 4:03 PM, Guy Olinger K2AV wrote:
> Am I correct in reading your text to mean that you laid out FOUR
> twenty-five foot stretches of two foot wide chicken wire and that
> noticeably changed the bandwidth of the antenna? If that's not
> right, please enlighten me and ignore the following.
>
> From everything I can summon to evaluate that, honestly, it speaks
> poorly of the radials you already had installed, for whatever reason.
> In a good, dense radial system, the chicken wire should make no
> difference, particularly since you are talking about 1/10 wave chicken
> wire radials.
>
> Given your WAY better than normal experience with deterioration of the
> chicken wire, Try COVERING THE GROUND (e.g. dense) out to 25 feet with
> the chicken wire, using the same source and treatment of the chicken
> wire. Think quite a few of us would want to know what happens.
>
> Average of the stories I've heard about chicken wire on the ground
> were didn't last the year or gone with rust in two. Fairly quick
> degradation in over-the-air results. Some folks put it down new every
> August or September.
>
> 73, Guy
>
> On Sun, Sep 4, 2011 at 11:04 PM, Gary K9GS <garyk9gs@wi.rr.com
> <mailto:garyk9gs@wi.rr.com>> wrote:
>
> The timing of this topic couldn't be better. I was doing some major
> rework on my 80M vertical this weekend. The old style radial system
> consisted of radials made from insulated wire with a chicken wire
> ground
> screen layered on top.
>
> I've often wondered if it makes any difference if the ground screen is
> on top of the insulated radials or if the radials can be on top of the
> ground screen?
>
> Since the radials are insulated, should they be bonded to the ground
> screen anywhere besides at the base of the antenna?
>
> BTW..at my QTH in SE Wisconsin, the galvanized chicken wire
> survives the
> elements quite well. About three years ago I was at Home Depot
> and they
> happened to have a special on 25 ft rolls of 2 ft wide chicken
> wire. I
> figured, what the hell and bought 4 rolls. I also bought some
> galvanized steel "strapping" which consisted of a 4 foot long piece of
> ~1 1/2" flat stock with 5/16" inch holes every 3/4". I cut these
> into 2
> foot long pieces to match the width of the chicken wire, folded
> over the
> chicken wire several times and sandwiched the folded chicken wire
> between the two pieces of strapping and bolted the strapping ,
> with the
> chicken wire in between, together. Before assembling the
> "sandwich" I
> liberally gooped everything with Penetrox.
>
> Then I bolted the sandwiched chicken wire to my radial plate and
> rolled
> the chicken wire out on top of the insulated radials.
>
> Does it work? I can't answer that scientifically but I can say
> that the
> bandwidth of my antenna narrowed a little. Meaning I'm heading in the
> right direction.
>
> Today when I rolled up the chicken wire after three years it was
> almost
> like new, still shiny. Despite being in the woods, covered with
> grass,
> leaves twigs, etc and getting rained on and covered with snow
> every winter.
>
> On 9/4/2011 1:50 PM, ZR wrote:
> > ----- Original Message -----
> > From: "Herb Schoenbohm"<herbs@vitelcom.net
> <mailto:herbs@vitelcom.net>>
> > To:<topband@contesting.com <mailto:topband@contesting.com>>
> > Sent: Saturday, September 03, 2011 4:30 AM
> > Subject: Re: Topband: Fence "ground screen" instead of wire radials?
> >
> >
> >> On 9/2/2011 6:06 PM, Brian Machesney wrote:
> >>>> Thanks to NI0C for reminding me that this info was presented
> by NC0B
> >> Chicken wire or rabbit wire make an inexpensive alternative to an
> >> expanded copper mesh ground screen. Just roll it out in multiple
> >> directions from the tower base and tack it to the ground on top
> of the
> >> grass. The grass will grow through it in a short period and it
> will be
> >> invisible. that is easier than rolling up the sod for sure.
> The only
> >> problem is the connection but since the actual tower is most likely
> >> galvanized steel there isn't an issue of dissimilar metal just
> figuring
> >> out how to making a convenient connection via a galvanize steel
> bus with
> >> similar jumpers to the actual tower. Soldering is not possible
> and cad
> >> weld is expensive. Tinned copper braid jumpers with the proper
> >> preparation can work and galvanized steel angle brackets as well.
> >
> > I used 4' x 50' rabbit mesh (2x4") that was welded, then
> galvanized and then
> > plastic dipped for over 10 years at a prior QTH. It was
> purchased that way
> > at a garden store.
> >
> > Galvanizing is very easy to solder to with just normal rosin
> solder and all
> > I did was run some stranded #12 copper to the #6 copper ring at
> the base of
> > the shunt fed tower. A bit of spray autobody undercoating sealed
> the mesh
> > solder connections.
> >
> > Prior to this there were 60 radials, 60-135' long and
> performance was fair.
> > With the 4 sections of mesh on top of them it became a pileup
> buster and
> > contest winner.
> >
> > Carl
> > KM1H
> >
> >
> >
> >
> > _______________________________________________
> > UR RST IS ... ... ..9 QSB QSB - hw? BK
> >
>
> --
>
>
> 73,
>
> Gary K9GS
>
> Check out K9NS on the web: http://www.k9ns.com
> Greater Milwaukee DX Association: http://www.gmdxa.org
> Society of Midwest Contesters: http://www.w9smc.com
>
> ************************************************
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>
--
73,
Gary K9GS
Check out K9NS on the web: http://www.k9ns.com
Greater Milwaukee DX Association: http://www.gmdxa.org
Society of Midwest Contesters: http://www.w9smc.com
************************************************
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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