there are many of the popular j-pole antennas described on the internet, most are either ribbon cable antennas for the 2m band, or quite elaborate copper/aluminium tube versions for 6 metres. i was unable to find a 6m ribbon cable one, so i set about making one. this antenna is based on the original 2 metre design by f c judd, g2bcx, which appeared many years ago in several publications.
these antennas were quite popular at one time, with the introduction of low cost multi-band commercial vertical antennas for 6m/2m/70cms they seem to be rarely used these days. for a low cost, "build it in minutes" antenna the ribbon cable j-pole or "slim jim" as it was known, is hard to beat. the antenna shown here includes a coaxial cable choke feed to remove rf currents from flowing on the outer of the cable. there are alternative methods of achieving the same decoupling, but wrapping a length of cable around a plastic tube is both low cost and easy to assemble.
materials required to build the antenna are :
1 off 450 ohm slotted ribbon cable, 4500 mm long. jsc part number 1318, or equivalent,
http://www.jscwire.com/ 2 to 3 metre length of rg58 coax.
120 mm x 43 mm diameter off cut of plastic waste water pipe, not critical.
coax plug/socket to fit rg58 coax.
3 off small cable ties (ty-raps).
assembly
begin by drilling a couple of small holes at each end of the plastic waste water pipe, these are to take cable ties to secure the coax cable. a hole size of 2 to 3 millimetres diameter should suffice. secure one end of the coax with a cable tie and wrap the rest round the pipe securing with the 2nd cable tie. the amount of coax and number of turns aren't particularly critical. form one end of the coax into short tails, fit a plug or socket of your choice on the other end.
carefully cut the ribbon cable to 4305 mm. solder a piece of spare wire across each end. measure 142 mm from one end and carefully remove the insulation. solder the coax tails to the ribbon cable at this point, see diagrams below.
on the side where the coaxial braid connects to the ribbon cable, measure 1380 mm from the bottom end and cut the wire, measure a further 80 mm along the ribbon and cut the wire again. remove the wire between the cuts. secure the coax to the ribbon with a cable tie as per the image below left.
