The "Slinky" Antenna

[kc8mln]

I came across a few "Slinky" antennas, some were end fed and others were dipoles......

Just wondered how well these work for shortwave recieve antennas........I was considering building one!

Also, does anyone have any links to good articles about building them, either the endfeed or dipole versions...

 

[LtDoc]

If I were desperate I think I would call the use of a 'slinky' as an antenna a last resort. They will probably 'work' on some frequency, but not well on any frequency. That depends a lot on just how it's put up. If it's outside subject to wind count on it being a 'variable' length thingy subject to how much it's disturbed by the wind. It amounts to one long loading coil that changes it's length and 'loading' as the wind blows. If that's suitable for your application then it should work fine.
They are a novelty, not any sort of adequate antenna. Unless you're desperate, of course...
- 'Doc

 

[radiokatz]

I've looked at several articles on these as well as youtube vids. They don't really seem to work all that well. But if you have the time to experiment, I suppose it could be a fun project & not that much money wasted.

Personally, I would rather put my time/effort/money into building a multi-band dipole.

 

[robertmac]

They work well for what they were intended for. That is slinking down a flight of stairs.

 

[ratboy]

I had a couple of slinky antenna for years. They worked great! One was two slinkies soldered end to end, and stretched out on a rope. It was 3 originally, but I had a nearby AMBC station that was strong enough that it caused problems on all my receivers, either adding a level of hash on lower freqs, or in the worst ones, causing audio to be heard in the background of almost every signal heard. Clipping one slinky off dropped the signal down enough to solve the problem, on my better receivers anyway. The other was a slinky dipole, with two slinkies on each side, put up into my attic. I had a new roof put on and the idiots doing the work went up there when they were replacing some of the plywood on the top of the house and cut it down, thinking it was "some kind of junk", and tossing it in the dumpster. I had a 60' dipole made up already, so I had them put it up for me, and it wasn't, and still isn't, nearly as good as the slinky antenna was. The longwire slinky was easily the best SW antenna I've ever had, easily beating the Alpha Delta Sloper I had in the past, and all the dipoles I've made. I have one of the ebay slinky antennas in the box and plan on getting it up this summer sometime. It looks to be very nicely made. If it lasts half as long as the one I made, I will be thrilled.

 

[kc8mln]

So far people on both sides of this issue are chiming in, some with positive support and others opposite....So, the verdict is still out I think, but in the spirit of amateur radio, lets further discuss this topic about building and using "slinky antennas"

 

[ka3jjz]

ratboy I had heard that these Slinkies do perform, as long as you stretch it out. I suspect that's what you have done. How did you feed it? Did you put a current balun or similar on it? I remember seeing one design many years ago that you had to create a choke (a few turns of coax) at the feedpoint, but I didn't get around to doing much experimenting with it.

Mike

 

[radiokatz]

ratboy,

How did you keep it from rusting to pieces being out in the weather like that? And, yes - let's keep the topic going. You're one of the few that I have heard of having good success with it.

 

[kc8mln]

If you spray paint the slinky and feel the metal from the outside elements that would protect to work the metal from rusting, that's what I read in a couple articles that if you are going to use it outside you have to spray paint it

 

[kc8mln]

ok, so I got my "slinky antenna" built last night and tried it out and it does perform super great! I was pulling in signals that I couldn't/wouldn't hear without the antenna. I used it inside and hung it from the ceiling on the 2nd floor of my home to try it out. I was able to hear shortwave stations across the bands, so my vote is a "YES" that these do work. It's not as good as an outdoor antenna, that I know, but it's a great, fast (and cheap) start!

 

[radiokatz]

I'm going to give this a try with my Grundig G6. I have used a long wire with it & had bad results, even worse than the whip. I'm curious to see if the slinky will perform better.

What radio are you using the slinky with, and what is the connector?

 

[nanZor]

LtDOC got it right - basically these antennas are usually untuned helically wound loading coils - essentially two HF "rubber ducks" back to back in a dipole configuration.

If you are going to transmit into them, you NEED a top hat or some form of disk at the ends unless you like setting your attic on fire from the huge rf-voltage present at the ends. At the very least run an extension of wire past the slinky.

There are way too many variables to judge with any accuracy how well an HF duck/dipole would work in a given installation. Often there is way too much inductive loading, so being able to short out some of the coil winding with jumpers is handy if the antenna is within reach.

Serious users will want to consult an ARRL handbook, and see the section about "Short Continuously Loaded Verticals", and obviously taking note that it applies to dipoles as well. (P. 6-28 of 20th edition)

 

[kc8mln]

For those who "missed" it earlier in the topic conversation AND that this topic posting is in the forum for RECEIVING antennas below 30mhz,...............this antenna is being used for RECEIVE ONLY for shortwave listening!!!!!!!!!!!!!!! You don't need a balun on a long wire receive antenna

 

[nanZor]

I didn't miss the topic description about RECEIVE ONLY antennas. I crossed the topic-line for a safety concern that sprung up.

I included the warning about transmitting into it "IF" you as an established amateur have that capability to protect YOU from inadvertently dumping a KW into your rx-only slinky by accident inside your home. All it would take is to forget to throw your antenna switch away from your slinky and set things on fire especially if your gear didn't break down first, and the antenna conveniently hidden near flammable materials at the ends.

It is also something that budding amateurs should be aware of if they are also SWL's, and decide to try their rx-only slinky antenna on transmit.

Moving on - for HF rx, while anything from a bedspring or shopping cart will work, a slinky has the disadvantage of being a huge narrow-band loading coil and may not be as efficient as just a plain piece of wire.

The hint was mentioned earlier about stretching the slinky until it no longer resembles a helical coil, but stretched so much that it resembles a slightly twisted wire for more efficiency - essentially removing or limiting the huge inductance. This I agree with on HF, especially when my tuner ran out of capacitance to deal with the normal slinky shape.

I have not personally tested it on AM BCB dx'ing, nor longwave where that much inductance might not be a hindrance.

One option that some may want to explore is not limiting the slinky to a vertical or dipole, but use it as a horizontal or vertical loop. That is also something I have never tried so it would be interesting to see how others fare in that department.

Aside from anecdotal evidence elsewhere, the ARRL chapter on these types of antennas provides good material for those that want to fine-tune an antenna like this even on rx-only.

 

[ka3jjz]

No worries, hertzian, we're back on track now.

In any case it might also be interesting to know where one would buy Slinkies anymore. As I understand it, at least some of the ones you see in toy stores like Toys-R-Us are plastic - so that won't work.

Another interesting question is how one would connect the Slinky to the coax, since it works as quite a decent heat sink. I don't believe the Slinkies are made of copper so there's also the long term question of joining dissimilar metals together. I think I read somewhere that there is a compound you can use to help make the joint and prevent a chemical reaction from trying to do this. Since I was fooling around with mine indoors, a couple of sturdy clip leads made the connection fairly easily.

Mike

 

[kc8mln]

The metal Slinky's are still availabe from Walmart for $3 and I am NOT using COAX because mine is built as a single Long Wire Antenna, so I have aligator clips on each end, one clips to the antenna and the other end clips to the slinky thats hung from my ceiling...

 

[majoco]

Without some support the steel ones tend to sag under their own weight after a while. I would hang them on polypropylene rope for support.

Anyone tried stretching it out/in to see if it can be 'tuned'?

I feel an experiment coming on, although it's getting a bit cold outside now....

 

[nanZor]

And I'd like to offer my apologies to kc8mln for coming on too strong like that.

Experimentation is key - heck I even use vertical ocfd's for scanning which are not exactly optimum either.

One thing gleaned from the text I referred to is that any sort of extension wire, stinger if you will, a feet beyond the end of a slinky will help lower the Q of the huge-inductance coil with capacitance in rx-only applications.

Where extensions or stingers are not practical, just merely adding drop-wires from the end(s) that don't get in the way of people/pets would be a useful addition. They would serve more as capacitors than being a major part of the antenna proper. At least a few feet or more if you have the room...

 

[Darth_vader]

"As I understand it, at least some of the ones you see in toy stores like Toys-R-Us are plastic - so that won't work."

The toy section at Fred Meyer also has them for something like $3. Grabbed one this PM so I could try turning one into an aerial, once I can get far enough away from the leading sources of shortwave RF noise pollution.

"I don't believe the Slinkies are made of copper"

They're not. I think they're made out of either aluminium or (stainless?) steel. I put the "stainless" in parentheses with a question mark because as a kid I left one outside in out lovely west-of-the-cascades Pacific Northwest weather, where it got rained on continuously for nearly two weeks. To this day it still hasn't shown any sign of rust, but that was also ~20 years ago. The materials have probably changed (read: cheapened) considerably since then.

 

[kc8mln]

I have tried mine on SW in both the horizontal and vertical (hanging from the ceiling ) positions and both seem to work very well for me as a RECEIVE antenna.

I did wanna test things out, so I measured the approx length of the slinky when stretched all the way out and then I cut a piece of stranded wire to approx the same length to compare the receive of either one and note if the slinky worked better or not (because the slinky has more wire in a shorter area since its coiled up as compared to just a straight long wire)........Results of my lil test showed that the slinky did perform a lot better than just a straight long piece of wire (in MY instance)

I then tried putting the "stringers" at the end of the slinky to see if that helped with receive....and I didn't notice any additional change with the addition of the "streamers (entra section of straight long stranded wire)", there wasn't much change...

I do use polypropylene rope to help support my slinky, when hung up, especially if hung as a horizontal.

The slinky's of today (as most everything else for that matter) IS made as CHEAP as possible! They aren't made of a high quality metal anymore and can be brittle if left exposed to the weather for a long period of time....for me, I use it indoors only.

So far, I like this setup as a neat and easy portable receive antenna and that I can use when I travel....My son has enjoyed helping and learning about it along with me, and he loves his SW receive project builder kit too, that we hooked this slinky antenna up to.