The counterpoise needs to be bare wire with separators at 4-6 inches for
the separation. We have tried making the counterpoise with 450 ohm window
line, which came up lossy. Operations improved with the discard of FCP
using heavy dielectric. Using zip cord would definitely be worse. FORGET
zip cord. Lossy, lossy, lossy.
Construct the FCP as if you were going to make it like 600 ohm open wire
line. Bare #12 and spacers. We have found that a spacer in the center
made from an 8 or 10 feet piece of 1.5 inch PVC water pipe, and and eight
and 14 inch pieces of half inch water pipe, placed at +/- 11, +/- 22 and
+/- 33 will separate the wires nicely with tension on the ends.
DO NOT use THHN and leave the insulation on. Water tends to bead on THHN
insulation. The extra water adds to the dielectric on the wire, and
detunes the FCP. We've already worked through that issue.
73, Guy.
On Wed, Dec 7, 2011 at 9:37 PM, <mstangelo@comcast.net> wrote:
> Guy,
>
> I'm looking at your antenna at W0UCe's website:
>
> http://www.w0uce.net/K2AVantennas.html
>
> Does the sections of the folded counterpoise have to be separated from
> each other or can they be adjactent to each other. I'm thinking of
> constructing one using zipcord for the FCP.
>
> 73,
>
> Mike N2MS
>
>
>
> ----- Original Message -----
> From: Guy Olinger K2AV <olinger@bellsouth.net>
> To: Jim Miller Waco Texas WB5OXQ <wb5oxq_1@grandecom.net>
> Cc: topband@contesting.com
> Sent: Thu, 08 Dec 2011 01:57:20 -0000 (UTC)
> Subject: Re: Topband: Best small space antennas
>
> Note: the following is not a theoretical or untested antenna. There
> are working antennas in the field using the folded counterpoise
> described below, scoring well in contests**, in use up to a year and
> more. Contest scores of the sort attained are not made using antennas
> with significant deficiencies or fundamental flaws.
>
> A miscellaneous end-fed inverted L or end-fed inverted U over an
> elevated 5/16 wave single wire folded counterpoise (FCP) will have
> good radiation from a small lot, with the ability to put out a strong
> signal not usually associated with small lots. In the simple
> implementation of this antenna (160 only), the length of the L or U is
> adjusted for zero reactance, usually resulting in a 50-60 ohm feed Z
> at resonance.
>
> There are NO radials. The main design point of the antenna is to
> minimize lossy currents induced in the dirt and confine TX signal
> current to the FCP and the radiating wire. This is a real, and lossy
> issue for a few short or miscellaneous radials. Enough of an issue to
> kill 15 dB.
>
> The radiating wire first goes up as much vertical as you can manage,
> then out as far as manageable, and then down if length is still needed
> to prune to resonance. The main point is to pick a feed point on the
> property that has your best vertical rise and then get the rest of the
> length for resonance however you can. For some properties this has
> meant putting extra angles in the up+over+down radiator. Some
> properties will not need the "down" part.
>
> The antenna uses a REQUIRED isolation transformer at the feed point
> because the counterpoise is NOT resonant, and the feed would really
> rather use the much lower Z but hugely lossy coax shield current as a
> counterpoise. The folds in the FCP are designed to maximally reduce
> counterpoise fields at the ground, reducing lossy currents in the
> dirt.
>
> The isolation transformer's leftover inductive reactance, a
> disadvantage in many applications, in this case helps to tune out the
> capacitive reactance of the FCP and reduces the length of the
> radiating wire needed to achieve simple resonance for the antenna.
>
> The counterpoise extends plus and minus 33 feet from the feed point,
> 167 feet folded into 66 linear feet occupied on the property. The
> middle 20 feet of the 66 should be straight, but either end can be
> bent away from the straight line to accommodate the property. Up 8
> feet or higher is recommended. Lowering the counterpoise increases
> the coupling to dirt, increasing losses.
>
> The isolation transformer uses the same physical components as a
> balun, but the unlike the balun there is NO connection of any kind
> between the primary and secondary windings. This is accomplished with
> twenty bifilar turns of double polyimide insulated #14 with teflon
> sleeving wound on an Amidon T300A-2 #2 material powdered iron toroid.
> One wire is the primary, and the other is the secondary. The low MU
> powdered iron toroid was picked over time to avoid heating, still
> provide required coupling, with other choices sometimes failing in
> spectacular fashion. We have no information of our currently-used
> winding method on the Amidon T300A-2 ever failing for any cause,
> though we would not expect it to survive a direct lightning strike.
>
> With the isolation transformer, the antenna and FCP is entirely above
> ground and not connected to anything else. We use a 5 megohm resistor,
> in parallel with a non-resistor lawn mower spark plug, from the FCP to
> ground as a static drain. The gap drains lightning induced voltage to
> protect the resistor, the resistor drains wind, snow, rain static.
> The resistor and gap protect the winding from a voltage puncture that
> will grow into a carbon track to ground.
>
> 73, Guy.
>
>
> **
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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