Monday, April 21, 2014

Slinky dipole for 40m on balcony

My 10m wide balcony works fairly well for 20m but I wanted to try 40m. Good news, Australian Geographic stores carry very nice metal slinky's for $10 each so today I made up a balun and strung up two slinky's as a dipole.

A question: should the turns go the same way on both sides or should they be opposite? I have them in the same direction but it's not working very well.

With the slinky's extended to fill the available space I get a very good match but a little high in frequency for 40m.

This is an astonishingly good SWR and impedance for any antenna in my all-metal balcony, much better than what I get with the simple 20m dipole.

I can tune up on reasonable 40m frequencies, such as 7.146, with the Emtronic EAT-300 tuner but presumably co-ax losses are quite high.

As usual, I'm using about 10m of RG-174 thin coax to get from the balun, in through a window, to the transmitting position.

The windows here have soft rubber like seals and the thin coax will happily go through a closed window without much damaging compression.

Signal reception on 40m is disappointing, I've heard a few nets this afternoon but my CQ calls on 7.2 have gone unanswered so far.

It's a fine looking antenna but I don't think I should leave it out over night for fear of it blowing overboard and clobbering someone - leading to the breaking of another by-law no doubt.

This morning I had a pre-arranged contact with Stephen, VK2BLQ, who could certainly hear me OK, although no where near as strongly as you'd expect given our close proximity.

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