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The K2AV FCP: 5/16 Wave Single Wire Folded CounterPoise
Efficient Low Band Counterpoise for Restricted Circumstances
Loss Avoidance Opportunities and Techniques for the Low Bands

We hope this web site will be a basket of tools for your successful use. Every ham station is different and only you will be able to determine any application to yours. But from years of correspondence, issues detected at one station often repeat at others. So you just might find unexpected opportunities.

The short and linear FCP was designed to reduce ground losses from inadequate radial systems beneath inverted L's and other vertical antennas. The FCP and Isolation Transformer allow us to get on Top Band and do well from a small building lot and other restrained circumstances. Other loss issues may be found and eliminated. We begin with the FCP, and then introduce the Pandora's Box of Loss Issues below.

The Single Drawing FCP Description

Before the FCP was published in 2012, W0UCE laid out this drawing of the FCP. Tried and true, it has quickly explained the FCP ever since. Some looked at this drawing once and went out and built it. And it worked. So we have placed it in our opening screen.

We have updated the drawing since 2012, also adding below.
**Please use the web site you are viewing now for all technical content and direction.**

to the the Single Drawing FCP Description:
(a) The drawing above and its dimensions are for 160m. For 80m use +/- 16.5 feet (+/- 5 m), keep 4 inch (100 mm) spacing between wires, for 40 m use +/- 8.2 feet (+/- 2.5m), keep 4 inch (100 mm) spacing between wires.
(b) Do NOT adjust FCP wire lengths to improve SWR. Changes add loss. SWR does not predict performance. See
(c) You can use other antennas above an FCP, but an inverted L is a common choice, practical and very effective when properly placed and tamed. See to find how you can get the maximum out of your inverted L.
(d) New: We now recommend a minimum FCP height of 8 feet (2.5m) if at all possible, better 10 feet (3m). See other important FCP placement considerations at
(e) You do not need a lot of spreaders between FCP wires. A 160 FCP only needs support at the center, at the two ends, and two spreaders between an end and the center. Keeping the number of spreaders low reduces dielectric material between FCP folds, reducing loss.
(f) The winding wire lengths only apply to a single T300A-2 or T300-2D core, or two stacked T300-2 cores. Alternate transformer configurations are discussed at
(g) Metric Dimensions, with harmless roundings to even metric numbers:
- The FCP is 10 meters from center to either end, 20 meters overall,
- at a recommended minimum height of 2.5 meters if possible, better 3 meters,
- the spacing between folded wires is 100 mm, and
- you may substitute locally available IEC wire size 4 sq mm for AWG 12. Exact AWG 12 wire is not required as part of the design. For the transformer's polyimide insulated AWG 14, we currently have no EU source for heavy polyimide insulated 2.5 sq mm copper and suitable matching standard wall teflon sleeving. If informed, we will include verified sources in our materials source listings.
(h) DO use an Isolation Transformer rather than a ferrite device at the feedpoint. Explained in Based on more than 250 FCP-related email thread or telephone consults 2012 through 2016, we only and very strongly recommend either a or commercial equivalent.
(i) If you must use a tower to support the bend of an inverted L, then see or depending on the size of your tower.
(j) To operate both 160 and 80 meters on the same L over FCP, see

The FCP "+" Project

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After Jack's FCP drawing and basic construction text, the rest of the FCP-related web site content exists because implementing FCP's exposed a Pandora's Box of RF loss Issues. Notably, eight green button topics treat inverted L issues. Remedying or designing around those losses exposed still more issues. "FCP+" is what we call a project that installs an FCP and remedies any other loss issues. RF Loss issues are treated in .

The "Plus" items are not required to make an FCP work. They just remove loss. The total loss remedy from a fistful of fraction of dB issues can approach the major remedy of the FCP itself. FCP+ sometimes produces an amplifier's increase in TX signal strength without the amplifier.

At a particular ham station, which RF loss issues actually exist varies wildly. RF Loss remedies, in individual stations with their individual situations, can range from easy to impossible. Issues are not in the list because we are convinced they exist at your station. We list them because the individual issues have existed and have been remedied at multiple FCP project sites. Any issue might exist and be fixable at your site. Certain issues have proven common, with a select few more likely present than not.

Reading while planning a station makes very best use of the Loss List, avoiding RF losses in the first place.

The Story Behind the Drawing

You can read the story leading up to Jack's drawing in the first four columns of the original May/June 2012 NCJ article. Note that portions of the article's technical content are no longer current. **Please use the web site you are viewing now for all technical content and direction.**

Are You Using An FCP?

Are you using an FCP? If so drop us an email at peerreview[at]k2av[dot]com and let us know about it and how you are doing. 73, The Committee.