Here's another fascinating HF antenna for limited or restricted spaces.
Thanks to Rudi (K7RAW) for this ingenious use of a "pool noodle" for a simple vertical helix antenna covering the 40 through 14 meter Amateur Radio bands.
As Rudi explains, this ultra simple HF antenna is ultra stealthy, requires no ground radial system, and is entirely portable.
If you can't see the video, please insert this title URL into your browsers search box: https://www.youtube.com/watch?v=7tky7p_x2mA.
Here are some comments from Rudi (K7RAW):
his is a BRAND NEW type of HF antenna for those with extremely limited space to setup a conventional antenna. It is derived from the Slinky Antenna but with a few upgrades. It is less than 1/5th the length of a normal dipole, yet performs similarly. No ground, radials, counterpoise, tuner or BalUn required. Just a coax feedline with a Mix 31 common-mode ferrite choke at the antenna end. It uses widely available ordinary parts which cost less than $25. It is easily scalable for other HF bands and can be used in vertical or horizontal mounting, including with other NoodleTennas on the same mast, acting like a fan dipole. On 10m the bandwidth is about 600 KHz below 1.5 and about 1 MHz below 2.0 I've made many contacts with it, getting good signal reports. You can build one in about 2-3 hours.
MATERIALS: (scale the lengths for other HF bands)
3" diameter (large type) 50" long pool noodle
40" of 3/4" schedule 1120 (thin-wall) PVC pipe
3/4" PVC "T"
3/4" PVC elbow
3/4" flat-top plug (smooth)
2" long 3/4" PVC stub ("T" to elbow)
6" long 3/4" PVC stub (for mast)
2' of coax (RG-8X, LMR240 or RFC240) with female BNC or UHF connector
https://www.ebay.com/itm/133481890997...
28' of 18 gauge stranded hookup wire
4 10" cable ties (2 at center, 2 at ends, 1 at bottom of the noodle)
TOOLS:
1/8" drill bit for center hole in PVC pipe
1/2" drill bit for BNC connector threads thru flat cap
7/8" wood bit (spade blade type) for hollowing out inside of cap
OPTIONS:
6 Snap-on ferrite beads (Mix 31) for common mode suppression on antenna end of coax
https://www.jpmsupply.com/Snap-It-Cor...
3/4-5 TPI tap for threading 1/2" x 3/8" PVC reducer to fit painter poles
https://www.ebay.com/itm/254642664421
Telescopic camlock mast (up to 31 feet high)
https://docadone.com/products/docapol...
Tripod that fits up to 2" diameter mast
https://www.ebay.com/itm/363482179344
Guy wire ring, tie-downs, adjusters & ground spikes
https://www.ebay.com/itm/114891585326
ASSEMBLY:
1) Mark the pool noodle every 1 inch with a Sharpie
2) Cut pool noodle into 2 sections, each 20" long
3) Drill 1/8" diameter hole at center of PVC pipe thru one side only
4) Slide both noodle sections onto PVC pipe leaving a 1" gap at hole
5) Divide the hookup wire into 2 pieces, each one 14' long
6) Thread both wires into hole and pull both to one end of PVC pipe
7) Strip coax back 1", solder each to coax and cover core and braid each with heat shrink
8) Drill PVC plug to fit coax connector (1/2" thru hole and 7/8" counterbore inside of cap to make thru hole wall about 1/8" thick)
9) Thread coax connector into one end of PVC "T" and out the side port
10) Insert 6" PVC stub to other end of PVC "T"
11) Attach 2" stub to elbow
12) Thread coax connector thru stub/elbow combination and attach to PVC "T" side port
13) Insert connector from inside of PVC plug and secure with its ring nut to flat outside
14) Insert PVC cap with connector onto PVC elbow facing away from noodle
15) Pull wires so that coax pulls all the PVC fittings can be joined together snugly
16) Slide both noodle sections together at hole in pipe
17) Pull wires perpendicular to noodle in opposite directions
18) Bring the up each wire onto the inner end of each noodle
19) Attach cable tie to each at inner ends of noodles to hold wire in place while winding helix
20) Wind one noodle with wire so that helix has even twist with 1" spacing between each turn
21) Wind other noodle with helix in the SAME WINDING DIRECTION as the other noodle
22) Tie off each wire at the outer ends of the noodles with cable ties
23) Adjust cable ties for for wire support at each end of each noodle with snugness
24) Trim off excess tails of cable ties
25) Connect to rig with good quality coax with at least 6 snap-on mix 43 ferrites at BNC-M end
26) Attach to mast at the 6" PVC stub
27) Raise the antenna and test with antenna analyzer
28) Trim both wires to the EXACT SAME # of turns until in resonance at the desired center frequency
Transcript
Follow along using the transcript.
Follow along using the transcript.
