My Slinky Antenna Page

"The Slinkette"

by Aussiecbradio

First off, let me state I am not a radio technician, or an amateur radio operator or physics genius. All I can really tell you is that I have had an interest in shortwave radio on and off for over 25 years. My current living conditions don't permit an external antenna, so I have been plying with slinkies (yes, the toys you buy!).

The antenna I am about to describe to you has a theoretical resonance of 7.5Mhz, there is no special reason for this except that this is what I worked out from the length of the slinky. Chopping and changing to suit a particular frequency is great if that is what you need, but I really just need something that works over most of the spectrum.

What you will need:

Solder, Soldering Iron, Full loop lugs, Fine file or sandpaper, 300 Ohm to 75 Ohm TV style balun (you can get these cheaply), Glue Gun, 2 small slinkies (32mm diameter, mine were "Time the Toy man" brand, $2.99 ea) and a length of figure 8 flex or similar to run to your radio.

Start by carefully opening the TV balun. You should see a small ferrite winding inside. Remove this carefully, making sure to leave the 2 lugs in place that you will need to solder your lead-in to later on.

Bend about 15mm of a slinky at right angles, using the pliers to get a nice sharp bend. Slinkies usually have a a coating on them that doesn't let solder 'wet' them very well, you will need to file or sand this off. I have a miniature grinding tool that makes this job easy! When you have done this, try to put some solder on the slinky, if it doesn't 'stick' then you need to do some more grinding.

Remove the 75 Ohm round plug, to make hole for you to feed the lead in wire through.

	Feed your lead in through the hole, make a large, loose-ish knot in it so it wont slip back out through the hole, after soldering each wire to the respective solder pad.
This is how it should look from the front.
	Now glue it all up, and glue the back on to the balun case again. This stops the lead in wire falling out, makes the whole thing a lot stronger. You have just about finished.

One thing to remember is that this is not really meant to be a self supporting antenna. I recommend a putting a fishing line through the whole thing. The way you attach the antenna is something I will leave up to you.

A couple of other reminders:

1. This antenna is not intended for permanent outdoor installation. If you are going to do this I suggest you paint the whole thing because my research has suggested slinkies will rust.

2. How did I arrive at my 7.5MHZ ?ok: (32mm * PI * 97 turns = 9747mm = 31 feet) Total feet in wire 62. 468/62=7.5Mhz (roughly). No doubt there is some sort of fudge factor or reactance making things not quite right here, but close enough for a SWL like me. 62 feet of wire is physically only taking up about 20 feet of space in my somewhat limited apartment. Results are, tentatively, very good !

Enjoy !