This is the perfect companion antenna for a POTA activation or any field HF operation. It operates 40m-10m and everything in between. The telescopic whip, tent stakes and guy tiedowns are all contained inside the 2" PVC tube. Add a tiny ATU-100 on a short piece of coax and you have a fully-tunable multi-band antenna.
MOTIVATION
This 40-10m compact antenna is intended for very fast setup and take-down with good performance on all bands. Everything you need (except the ATU and coax) is stored inside the 2' long 2" PVC tube.
THEORY
This OCFD vertical has an overall electrical length of about 22 feet which is the size of a typical "flagpole" OCFD. Since the impedance at the 20% feed point is about 450 ohms, a 9:1 UnUn is incorporated along with a good toroid-based common-mode choke. A battery-operated auto-tuner feeds the antenna's BNC connector. The antenna below the feed point is made with 7.5 turns of 1/2" copper foil tape wound around the PVC just to save height. This also keeps the PVC base low to the ground and easy to guy. WIth the ATU connected near the antenna, a 10W RF CW signal will trigger the tuner to tune up to that frequency where the resulting SWR is read out.
ELECTRICAL:
1 5.53m long, 14 section, stainless steel telescopic whip (eBay)
1 4.5' long section of 0.5" to 1.0" wide copper foil tape
1 ATU-100 with internal battery (w/UHF connectors) (eBay)
1 FT-240-31 ferrite core (Amazon)
1 FT-240-43 ferrite core (Amazon)
1 Common-Mode Choke (CMC), wound bi-filar, bi-sectional using 18AWG on Mix 31 core
1 9:1 UnUn, wound tri-filar using 18AWG on Mix 43 core (optional 100pF 3KV cap at input)
1 BNC bulkhead connector (round base, not square)
1 BNC right-angle adapter (to let the short coax jumper connect to the ATU on the ground)
1 3/8" ring terminal crimp style (crimp & solder)
A/R Different colored 18AWG stranded hookup wire (for CMC, TLT and leads)
WINDING DIAGRAMS:
Common-Mode Choke: www.pa9x.com/t... (3rd picture down)
9:1 UnUn TLT: vk6ysf.com/unu... (ignore the page title, it's a misnomer)
PVC (schedule 40):
1 ~24" long 2" tubing (creates the body of the antenna base)
1 2" cap (rounded top) (for the base)
1 2" plug (flat face) (for the reversible whip holder)
1 2" "T" (for mounting the CMC, TLT and BNC cap assembly)
3.25" 3/4" PVC pipe (onto which the CMC & TLT slide)
1 1" cap (rounded top) (holds the BNC bulkhead connector)
1 1" to 3/4" reducer (BNC cap goes over this)
1 2" to 3/4" reducer (mounts the 3/4 tubing supporting the CMC & TLT)
1 set of PVC glue primer and adhesive (to permantly attach all PVC parts)
HARDWARE:
1 3/8-24 threaded stub (~1" long) (to connect inside and outside unions)
2 3/8-24 female unions (one inside plug, one outside)
1 3/8-24 hex bolt (holds the ring terminal for the whip to the inside of the whip union)
3 ~1/2" OD screw eye & nut (for guy cord carabiners to hook to)
3 mini-carabiner clips (for clipping guy cords to the screw eyes)
3 CamEZ tensioners (to tension the guy cords near the tent stakes)
3 tent stakes (place about 2-3 feet from the base of the pipe)
3 3' sections of 3/16" parachute cord (guy cords)
1 2' long piece of 2.5" PVC heat-shrink tubing (goes over the spiral copper foil as protectant)
Негізгі бет K7RAW Self-Contained Off-Center-Fed Vertical Dipole (OCFVD)
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