80m Vertical on a Spiderbeam 12m Fiberglass Spiderpole

Note:  User feedback indicated that 6m for L2 is too long. 

It is probably more like 3.7 to 4m.  It is best to cut it 5m

and fold back a meter or so, then adjust for resonance.

THE MOST IMPORTANT  THING ABOUT THE CONSTRUCTION OF THIS ANTENNA is the choice of Top-Hats material. Weight and wind resistance are critical factors for the long-term reliability of this antenna.

• RADIATOR:
  • Cut the radiator wire 13m (42' 8") long.
  • The radiator is made of CQ-532 (AWG 18) wire.  This is about 1mm diameter.
  • Spiral the radiator wire down the pole about one turn per meter.  This balances the wire around the pole and reduces flopping in the wind.
  • Towards the bottom of the pole space the windings a little closer, such that the wire terminates at the connection box/plate.  Later you will use this extra wire for adjusting the resonant frequency.
• TOP-HAT WIRES: 
  • The Top-Hat wires are thinner, made of CQ-534 (AWG 26) wire.  It is VERY IMPORTANT to use thin wires for the Top-Hats.  
  • Cut the Top-Hat wires 6m (19' 8") long.  KEEP THE 4 Top-Hat wires EQUAL LENGTH.
  • Attach (and solder) the 4 Top-Hat wires to the top of the vertical radiator wire, insulate, and fasten to the very top of the pole with electrical tape and a uv-resistant cable tie.
  • Use a very lightweight INSULATOR such as the Spiderbeam Insulator on the ends of these wires.  We suggest using two insulators with about 10cm (4") of PVDF Monofil line between them, due to the high voltage on the ends of the top-hat wires.
  • Extend the top hat wires with PVDF Monofil Line.  This is very light weight line, yet has the strength and low wind resistance required for this application.  DO NOT USE ROPE.  When wet, it is too heavy.
  • Tie the extended Top-Hat wires to a ground peg about 10m to 15m or more away from the pole.  
  • The angle to the ground influences the required length of the Top-Hat wires. (more under Tuning).
• GUY ROPES: 
  • Use 2mm Kevlar Rope, guy in 4 directions at the 7m level.  This is at the bottom of the 8th segment, when counting segments from the bottom.
  • Tie these ropes to a ground peg about 5 or 6m away from the pole.
  • ALL guy ropes/lines should be fastened with a little slack in the line.  Do not over-tighten these lines. Normally the line should be sagging and not apply force to the pole.  It is only there to prevent the pole from bending too much in strong winds.
• RADIALS:  Use at least 8 to 10; that's enough for good performance, but 16 to 20 will be better.  Radials should be a minimum of about 10 to 12m long, and may of course be 20m long or longer.  All radials should be spaced symmetrically around the base of the pole.  It is not absolutely necessary that all radials be the same length.  It is better to have several short radials than fewer but longer radials.

Fundamentally the antenna will work simply by connecting a 50 Ohm coax to its feedpoint.

BETTER:  Insert a Common Mode Current Choke between the feedpoint and the coax.

All short, loaded vertical antennas on 160 or 80m tend to have a low impedance, and higher SWR.  If the SWR of this antenna is too high for your transceiver or linear, the easiest solution is to simply use a matchbox in the shack.

BETTER:  Insert a Hairpin Match at the feedpoint.  The Hairpin Match is very easy to build, costs less than $10, and will usually improve your SWR significantly.

With four  6m long Top-Hat wires and a 13m radiator, the antenna should initially be resonant too low in frequency. 

NOTE:  Feedback from one OM said he had to shorten the top-hat wires to 4m. We believe this was QTH-related, so begin with 6m.  You can always shorten them if necessary.

The antenna is tuned higher by shortening the radiator from the bottom.

Simply unwrap some of the wire, shorten the amount required, and adjust the pitch of the spiraling such that it terminates again at the feedpoint (the radial connection box/plate).

If you shorten the wire and it still resonates too low, you will need to shorten the Top-Hat wires.

In this case we recommend soldering some CQ-532 back onto the radiator, returning it to its original 13m length, and then shortening the Top-Hat wires by 50cm.  (That's about 20 inches).  If you do have to extend the radiator, insulate the solder joint well with heat-shrink tubing or good quality electrical tape.