Slinky dipole

[N5DUX]

Well, gang, I just completed my Slinky Dipole.

I had heard of them, and seen them on ebay (http://search.ebay.com/slinky-dipole), but those guys are asking $30+!!! No way!

So I consulted our friend Google. Sure enough, there's someone with the plans. Maybe over-simplified and short on detail, but there's not much to the design either.
KG6IIR posted this howto (http://mysdhomevalue.com/album1_004.htm) on his site - I followed his directions to build mine.

I spent $2 per slinky @ Walmart, ~$3 for the PVC and eye hooks @ Lowe's and a couple bucks for the SO-239 from Radio Shack.
I used a 1" PVC tee, and 3 3/4" caps that fit snugly inside the tee. I figure this would look cleaner than the caps going over the tee. (just aesthetics)

Iif you're not in any hurry, you can order SO-239s from online for $1 (http://kg4ena.netfirms.com/back/nfoscomm/catalog/product_info.php?cPath=26_54&products_id=169), get the screw-on mount. The 4-hole is too big if you use the same 3/4" PVC caps that I did. I ended up trading a friend for his screw-on mount - he pulled it from an old, crusty CB.

I used a 1" PVC tee, and 3 3/4" caps that fit snugly inside the tee. I figure this would look cleaner than the caps going over the tee. (just aesthetics)

Haven't tried a QSO yet, too late right now for me, will prob give it a shot on 20m tomorrow morning after I hang it up outside.

http://img60.exs.cx/img60/356/slinky23zb.th.jpg (http://img60.exs.cx/my.php?loc=img60&image=slinky23zb.jpg) http://img60.exs.cx/img60/4227/slinky36mr.th.jpg (http://img60.exs.cx/my.php?loc=img60&image=slinky36mr.jpg) http://img59.exs.cx/img59/9623/slinky41es.th.jpg (http://img59.exs.cx/my.php?loc=img59&image=slinky41es.jpg)

For a little more info, check out this write-up by KD4CGA:
http://www.qsl.net/kd4cga/slinky.htm

[N5DUX]

If you're not too keen on the SO-239, you can always make a balanced line version:
Rather than putting on the 239 connector, you could put 2 screws on the sides of the insulator, then use the screws as tie-down posts for your twin lead.
I contemplated this when I first realized the 4-hold 239 wasn't going to play nice with the size end cap I bought.

Another idea I've seen, if you only have access to a 4-hole SO-239, is to drill 3 pilot holes on the sides of the tee. Get 3 zip-ties, and mount it like so (http://home.ptd.net/~rental1/so239d.jpg), using the 4th hole's corner as a solder point. (picture was taken from this ebay auction (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4672&item=5756381825), of which I am not affiliated with. Gotta give credit where credit is due!)

[kb2vxa]

Hi guys,

I saw a Boy Scout Special at the Timonium MD hamfest a few years ago where those little geniuses had it on a clothesline with pullys to support and adjust it. Unfortunately it was between a roof overhang above and over the roof of the tram station behind the building and fairly close to the wall, didn't work so well there. That sort of continuous loaded dipole usually is passable outdoors mounted clear of obstructions like on an upper story clothesline. I have seen other such clothesline antennas in stealth mode used by those with deed restrictions, nasty landlords and the dreaded "association". Frankly indoors isn't the way to go with any antenna but for some choices are limited.

Spot on, never buy what you can build!

[W3MIV]

Since you will not be able to absolutely guarantee the balance of each side of your Slinky dipole, I would suggest you add a choke to your feedline to control the inevitable RF on the outside of the shield that will result. This will help keep you from having RF bites and other problems at your rig.

[N9vdx]

I have run one of the slinky ant. and it worked great and wasn't that high up. The one I run did not have a choke on it, and the tuner handled it just fine on most all the bands. They are now adding the choke to the outside of the PVC. I think it is 13 turns, they come up in the center then out a drilled hole to rap the choke, then back in another drilled hole to the connection to the slinky. Works pretty well and it is cheap. Oh and I run RG 58X on the one I had up.

[K7KBN]

The ones I build with THESE (http://www.amazon.com/Slinky-Plastic/dp/B00000IZKY) don't work very well at all... http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif

[KC7UP]

They may have melted http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif
Curt

[ab8ro]

Quote[/b] (k7kbn @ Dec. 11 2007,14:11)]The ones I build with THESE (http://www.amazon.com/Slinky-Plastic/dp/B00000IZKY) don't work very well at all... http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif
You probably forget the fifty ohm resistor across the coax. The plastic ones need that because the molds aren't as perfectly circular as the metal ones are. Once you put the resistor in though you'll find that you have really wide bandwidth. For best results you need to get the slinky coils up high though.

Oh, I know this might be obvious, but, you were using two coils of the same color, right?

Ok, silly question, I know.

[ai3v]

Quote[/b] (ab8ro @ Dec. 13 2007,02:08)]Quote[/b] (k7kbn @ Dec. 11 2007,14:11)]The ones I build with THESE (http://www.amazon.com/Slinky-Plastic/dp/B00000IZKY) don't work very well at all... http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif
You probably forget the fifty ohm resistor across the coax. The plastic ones need that because the molds aren't as perfectly circular as the metal ones are. Once you put the resistor in though you'll find that you have really wide bandwidth. For best results you need to get the slinky coils up high though.
<span style='color:green'>Oh, I know this might be obvious, but, you were using two coils of the same color, right?</span>
Ok, silly question, I know.
Also a lot of people mess up because they don't relize that the plastic slinkeys use the standard color code-just like resistors, for example on 160m you would want to use a brown then a blue then a black one.

Just tryin to help! #http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

Rege

[w8gtf]

Not to drag up an old topic, but I am in the process of building a slinky dipole.

I'm going to feed the dipole with ladder line, and connect it to my MJF-949D tuner. Am I going to see any problems with RF coming back into the radio? Do I still need a choke?

I'm really new to HF and using my antenna tuner. I just want to make sure I do it right.

[W4INF]

Not to drag up an old topic, but I am in the process of building a slinky dipole.

I'm going to feed the dipole with ladder line, and connect it to my MJF-949D tuner. Am I going to see any problems with RF coming back into the radio? Do I still need a choke?

I'm really new to HF and using my antenna tuner. I just want to make sure I do it right.

One great way to find out (and Im not be smart here...) is to try it and find out! Ive built I dont know how many antennas... Some work better than expected, some really sucked despite popularity, some worked even though every book written would say it should not work!

Antenna experimenting is an aspect of the hobby I enjoy a lot! I think from your description it should work fine.

You have 2 options:
1) Run balanced line into the shack and connect to the balanced feed of your tuner
2) Run balanced line to a 4:1 BALUN outside the house, then coax into the shack (This is always my choice).

Either way, in essence you will not have a slinky dipole, but a slinky doublet! Which is just peachy because now you have a good multiband antenna!!

Oh, and maybe a coax choke after the BALUN before it gets in the house, about 10-12 feet of coax in a 8 inch inside diameter coil.

GL & 73-
Andrew

[N9vdx]

I had trouble with some RF on one of them that I put up, and it was only on a couple of bands. I added the choke and all the problems went away. I'm not sure if it would be the same with the ladder line. But the 13 turns sure done wonders for the coax line.

[w8gtf]

I just got my antenna hung and played around with it a bit. I managed to tune it up to an SWR of 1.2 on the band I got to play with.

Here's a link (http://tim.midwestlost.com/gallery/Slinky_Dipole) to a gallery of pictures I took of the antenna. Once I finish testing, I plan to rebuild or make a new antenna that is built for outside (painting the Slinky's and using stainless steel hardware.

Thanks for all the input and advice in this thread. I suggest that anyone in a limited space to try this antenna, you may just be surprised.

[KD8HMO]

I havnt seen a real metal slinky in decades. Last I remember they brought out the plastic junk. Can you still buy a real one?

[w8gtf]

I havnt seen a real metal slinky in decades. Last I remember they brought out the plastic junk. Can you still buy a real one?

I got mine at Wal Mart for $1.94 a piece.

[W4INF]

A little more info there Tim, did it react as I anticipated? When fed with ladder line did it tune 'all' bands? If so you have a nice slinky doublet and I anticipate it will work good for you.

Let us know more details.

73-
Andrew

[w8gtf]

A little more info there Tim, did it react as I anticipated? When fed with ladder line did it tune 'all' bands? If so you have a nice slinky doublet and I anticipate it will work good for you.

Let us know more details.

73-
Andrew

Being as this is one of my first adventures into HF I have very little to compare it too. Also with fact that I'm waiting until the next time I see my girlfriends father (which will be about 2 weeks), for him to lend me an iCom 735 he's not using.

At this point, the only thing I have close to HF is an 11 meter radio I dug out of the bottom of the closet. That's what I tested it on and got a 1.2 SWR. I figure if nothing else, this should be decent for 10, 12, and maybe 15 meters.

I'll be sure to post a follow up after I actually have some information to post.

[W4INF]

With a decent tuner, I would think it would be good for 80 - 10, but let us know what you find out.

Andrew

[AA7EJ]

Of course the main question would be – why do you want to do that?
Feeding dipole, even slinky one, with open wire ladder line is not a good idea.
In theory - the antenna feed point impedance and characteristic impedance of the feed line should match.
The “average” dipole has feed point impedance around 70 ohms – depending on many variables. The impedance of the ladder line can be anywhere from 300 to 600 ohms – primarily depending on wire size, distance and other factors.
That’s basic dipole.
If you modify that (likes of G5RV) and start using the feed line as radiating part of the system – than you get different story all together.

My take on this is - if the feed point of the antenna is "coax" friendly why bother with ladder line.
I am currently experimenting with extended Zepp antenna (5/8 wavelength radiator) and using 12:1 balun to feed it directly with RG58 coax.
Stay tuned for reports.

73 Vaclav AA7EJ

[W4INF]

EJ, actually there is a lot less loss with twinlead/ladder line which translates into more power to the wire. Also, there is other discussion about weather balanced line actually radiates, from my understanding it does not. that would make the balanced line section of something like a G5RV more of a tuning stub than a radiating section. Also traditionally a center fed coax wire antenna is realized as a 'dipole', and a center fed balanced line wire antenna is realized as a 'doublet', although the technical description of both is DIPOLE, any antenna with two wires. That would group the Windom into the same category. Traditionally, a balanced line fed dipole (doublet) will tune up multiband, and a coax fed dipole will more than less be for a resonant antenna. Additionally, a doublet actually works better when the legs are not of any resonant length as I can attest to personal experience (though the legs should be longer than the resonant length of the lowest frequency desired).

As always, YMMV.

Cheers,
Andrew

[ai3v]

Of course the main question would be – why do you want to do that?
Feeding dipole, even slinky one, with open wire ladder line is not a good idea.
In theory - the antenna feed point impedance and characteristic impedance of the feed line should match.
The “average” dipole has feed point impedance around 70 ohms – depending on many variables. The impedance of the ladder line can be anywhere from 300 to 600 ohms – primarily depending on wire size, distance and other factors.
That’s basic dipole.
If you modify that (likes of G5RV) and start using the feed line as radiating part of the system – than you get different story all together.

My take on this is - if the feed point of the antenna is "coax" friendly why bother with ladder line.
I am currently experimenting with extended Zepp antenna (5/8 wavelength radiator) and using 12:1 balun to feed it directly with RG58 coax.
Stay tuned for reports.

73 Vaclav AA7EJ

Hi Vaclav,

The ladder line will have much less loss when operated with a high VSWR,

This is the case when operating off resonance, i.e. the next band up or down!

Here is a Program that shows how much power you loose with mismatched lines.

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=12232

In some cases, going from coax to ladder line is the eqivilent to adding a amplifier.

73/Rege

[KD8FKP]

I have a couple of slinkys sitting here and was wondering how I would do this. I want to make a 10 meter antenna out of them. How would I connect the coax directly to the slinky. I thought of aligator clips. Would I connect the center line and the wire braided jacket to the slinky. Also would one slinky do it or will I need both. I seen the pictures for the slinky here, and would like to make the tee in the middle but how are the screws connected to the so connector.

[w7lpn]

The more you stretch it the better. Try to be equal on both ends, and a thin nylon inside to prevent the droop works well. I used 4 slinkies. Works great fromn 10m to 80m with the LDG-Z-100 autotuner & IC-730... good reports when the bands are good. $1.98 per slinky.
P.S. It seems to like the 4:1 balun better than the 1:1 and tunes faster and power power output. :D

[KC2LNB]

With a decent tuner, I would think it would be good for 80 - 10, but let us know what you find out.

Andrew

What is considered a decent tuner???.........Ron

[w8gtf]

I'm going to using an MJF-949C as a tuner. Still playing with it, but my YL is pregnant, so radio is on the back burner.

[KC2LNB]

I'm going to using an MJF-949C as a tuner. Still playing with it, but my YL is pregnant, so radio is on the back burner.

good luck on the new addision .Doctors have found out what causes women to get pregnant but the public has not been informed.yet......lol

[KC2LNB]

1.98 per slinky....I can't find one .here in N.J.....they might be outlawed like everything else.....LOL...send me 2 please ........