My first real antenna for HF was a “Slinky Dipole“. I based it on a QST article, called “Apartment Dwellers: Slinky Jr. Dipole Antenna” (membership required to read), which I modified to suit my needs. I used a few 1/2″ wooden dowels with plant hooks to mount the antenna to my ceiling. It was stretched out to about twenty feet long, with wires hanging down on the ends to try to tune it on the 80m band.
The antenna worked somewhat on SSB. I was able to reach stations inside the US with reasonably decent results. On digital modes, I was able to reach Europe and Asia, occasionally, and most of the US.
Some notes:
- The antenna was about seven feet above my head when I was sitting down. So, I’m sure there was some RF exposure involved.
- I tried doing SSTV with the antenna at high power and burned out the finals in my radio. This is more of a note that you should not use 100W in high-duty-cycle modes.
- If you are not able to put up a straight dipole and follow the article exactly, you are highly directional. Even as a straight dipole, you’ll still be directional–but not as much as if you put it up at a 90-degree angle as the article suggests.
- If you can solder the connections to the slinkies — especially indoors —you’ll have better results. I used alligator clips that were crimped onto ladder line.
- Putting the antenna outside, and if you can raise it above the 1/2 wavelength above ground, will definitely produce better results. You should be able to stretch the slinkies out, which will increase the number of bands that you can use the dipole on. It should also improve the SWR on most of the bands.
Part of the use of the wires on the ends of the slinky is to short it out to make it resonant on certain bands. That didn’t seem to be as effective for me as I thought it would. You would attach the wire to each end with an alligator clip, and then attach the other end of the wire somewhere on the slinky. In theory, it would reduce the “length” of the antenna and make it resonant on the band you wanted. This becomes a hit-or-miss prospect. You have to try different points along the slinky in order to find the right spot for each band. And, depending on other conditions, the spot may move.
Making the antenna
Preparation:
The first step is to gather the materials that you will be using. I used two Slinkies from Amazon, 1/2″ wooden dowels from my local hardware store, along with the screws that connect the dipoles together, ladder line, and a balun to connect the ladder line to my coax. If you use a messenger line, you will want hooks (or poles) to hold it up in various places. You might also need ceramic (or plastic) insulators to hold the end of the dipole away from the hooks or poles.
Assembly:
The second step is to anchor your dipole centers to the rope or dowels. You want the slinkies spaced enough that they don’t touch, but close enough that you can solder the ladder line to them without extension wires. I used cable ties to secure them to the dowels. If you plan on using string or rope, you could tie the slinkies to it. Adjusting them may be more difficult if you do this.
Third, you will want to anchor the opposite ends of the slinkies to the dowels or messenger line. And if necessary, tie insulators on the end as well.
Next, you will want to solder your ladder line to the center points on the dipole. I would also recommend tying the slinkies together to minimize movement after you’ve soldered the line to them. Excessive movement, especially while you are mounting the dipole, could break the solder joints.
Finally, mount the dipole on the poles or ceiling, connect your coax to the ladder line, and start testing your SWR. This is the point where you can connect wires to the ends of the slinky and short the antenna out if necessary.
Testing:
If you have an antenna analyzer (or NanoVNA), this is the tool to use. If not, then you will want to use the lowest amount of power possible to check your SWR with your radio (preferably with a tuner/matcher). DO NOT TRANSMIT AT FULL POWER IF YOUR SWR IS GREATER THAN 2:1. Make adjustments and/or use a tuner to get your SWR below 2:1 before transmitting with high power.
Final notes:
This is a good starter antenna. You’ll move on from it, and that’s fine. I used it for about a year before I moved on to a folded dipole. It also serves as a good backup antenna in a pinch. And finally, remember a tuner doesn’t fix a bad antenna. It just makes your radio believe that it’s a good antenna, so your radio will put full power into it. You will still have losses between the tuner and the antenna. The hope is that by pushing full power out, it will overcome those losses to get your signal out. Nothing beats getting the antenna resonant where you want to use it.