Building your own dipole

[mrstangblb]

What keeps me interested now is antenna theory and design, it's become one of my favorite aspects of this hobby. Anything or any facet of transmission design has become a passion for me over the past year. And bar none, I love digital modes (from voice to PSK/packet/etc). And despite the fact I have a row of 1500 watt linears (SS and tube) I have enjoyed the hell out of DXing on 30 watts or less (especially mobile). And without a doubt I love 20, 40 and 80 meters.

I'm curious - what's your recommendation for what antenna you would (or have) put up that's economical and would range over 20, 40 and 80 meters? I'm playing with all kinds of dipole and wire designs, but I'm curious what you think. I've got one simple double-14-gauge wire antenna out as a flat top dipole that is pulling a lot in, but it's only wire and no coax.

 

[acyddrop]

The cheapest solution is dipole fed with coax (pick your flavor coax). There isn't a lot to a dipole and works fantastically. On the other hand It's semi-directional (broadside to the antenna). So you're going to miss out on weak signals on the ends of the dipole to some degree. But it's the most econimical. Now if you want to string a single dipole out there, you're best bet is to tune it to be resonant on your lowest frequency and use a tuner to get a match on the other frequencies. This isn't an ideal solution because you're going to deal with loss in your coax and loss in the tuner, but it's an inexpensive solution. The other option is to create a single feed point system in the middle of your dipole and run 2 other runs resonant on the other frequencies. You don't need any fancy switching as the signal will choose to go down the resonant dipole run more or less automatically. You might find that feeding your dipole with ladder line is ideal as you're going balanced all the way, but again that is situational and coax is cheap and easy to contend with.

There are at least two additional options (especially if you have a small space, like I used to). The first is a vertical antenna. Verts are fun and they work really well provided you set them up right and provide a ground plane (I still use verticals that I built only now I have them phased for 40 meter use). There's two worthwhile ways in which to feed those. The first (and least expensive as you can homebrew it) is to have a tuner at the head end (your shack) and an UnUn at the remote end to handle matching to your vertical. This solution works ok but electrically it's not ideal. You can create a reasonably "efficient" wide band unun and that will work for you. You can create a very good Unun (better than you can buy generally) for about $30-50 in parts, but to make them work they are inherently lossy devices. The best way to feed a vertical is to use a remote antenna tuner and feed that with your coax from the shack. But when you start talking power (say 500 watts and up) this can become expensive quickly (a remote MFJ 1500 watt tuner is around $800 for example).

The best antenna I think you can use in a small space (and is generally a fantastic all around antenna) is a HEXX antenna. You can actually pick up the antenna from DX Engineering for around $550 or you can craft your own (which is a bit of a challenge but not impossible). Hex beams do of course require a rotator of some sort and they are directional with decent FtoB performance (Yagi's are still better if you have the room).

But the single best an most economical solution is a dipole as they are monkey simple to build, incredibly inexpensive, and perform like nobodies business.

I'm curious - what's your recommendation for what antenna you would (or have) put up that's economical and would range over 20, 40 and 80 meters? I'm playing with all kinds of dipole and wire designs, but I'm curious what you think. I've got one simple double-14-gauge wire antenna out as a flat top dipole that is pulling a lot in, but it's only wire and no coax.

 

[mrstangblb]

Re: What sparked your interest in ham radio?

That's for sure why I have worked with dipoles so much lately - I can afford them and they're fun when you hear everybody. It was a great sense of satisfaction working a $12 piece of wire last week into the Czech Republic, France, Poland and, last night, Croatia... And I have only been working with projects for a couple of months. I got my General class license a week ago Saturday, so I'm having FUN on my Uncle's old Kenwood TS-820, for sure!

------------

Barry
KK4RXN
Jeremiah 29:11-13 / John 3:16

 

[acyddrop]

It's hard to go wrong with a dipole as an antenna solution. You can even phase them to give you better peformance (this is of course cheaper the higher in frequency you go) and that can be quite fun as well. I know Bob Heil from Ham Nation (and Heil audio fame) use a phased dipole and swears by it's utility. I could see a phase dipole being really useful on very low frequencies but of course you'd need a lot of area at that point I might favor a purpose built vertical design over the enormous costs (in terms of sorting out your velocity and the distance between dipoles) of phasing a 160M dipole.

Right now I have a 160M 1/2 wave dipole up, strung between two ROHN 65G towers about 150 feet in the air. I also have a full wave 80M dipole and a full wave 40M dipole all fed by the same system. The 160M is run as a traditional flat top and the 80 and 40 are inverted V design. They all attach to the tower with PTFE insulators keeping everything in order (I had a lot of PTFE material sitting around and just turned some of it into insultors/tiedowns for the dipoles). I've created the 160M just because I could, but I spend the bulk of my time on 20 (at least until I get my Extra sorted out, now that I'm back in the US that'll be soon).

After all of this, I still can't believe people buy these things I'm just dumb founded. I guess it's for people with more money than brains.


Becareful chasing DX can be addictive. I've gotten into mobile DX with the IC-7000 and a Scorpion antenna. Very very fun, and I'm still doing that with 100 watts or less. One day I'll add a linear to the mobile.

That's for sure why I have worked with dipoles so much lately - I can afford them and they're fun when you hear everybody. It was a great sense of satisfaction working a $12 piece of wire last week into the Czech Republic, France, Poland and, last night, Croatia... And I have only been working with projects for a couple of months. I got my General class license a week ago Saturday, so I'm having FUN on my Uncle's old Kenwood TS-820, for sure!

------------

Barry
KK4RXN
Jeremiah 29:11-13 / John 3:16

 

[mrstangblb]

After all of this, I still can't believe people buy these things I'm just dumb founded. I guess it's for people with more money than brains.

Be careful chasing DX can be addictive. I've gotten into mobile DX with the IC-7000 and a Scorpion antenna. Very very fun, and I'm still doing that with 100 watts or less. One day I'll add a linear to the mobile.

On that same little speaker wire dipole last night I couldn't break through any pileups, for sure... but the air cleared around 12:30 a.m., and I was able to break through to a fellow in Hungary on my TS-820. He gave me a 5-9, which I kind of doubt, but still - he heard me clearly and I heard him clearly. DXing really is a lot of fun! I was frustrated for a while because there were so many people calling to guys in Italy and other areas that couldn't hear me, and then finally I broke through to Hungary.

I have a really dumb question, though, acyddrop. I am researching dipoles like crazy and have read a LOT of how to construct them, but exactly how do you connect the coax to the middle of the wires in the dipole? I am really fuzzy on exactly how to construct that "T". As simple as you can put it, too, for this rookie! I am good and pretty handy, but I've only been doing this a couple of months.

I haven't ever soldered, but I'm ready to buy a decent soldering gun/iron to get started. I just need to know how to make the coax connection so I can get something other than just a wire dipole up and going.

 

[AK9R]

A very simple way to connect a coaxial cable to a dipole is to use a dog-bone insulator.

Attach the two wires of your dipole to the holes in the dog-bone (while holding the dog-bone horizontally, one wire would go in the left hole of the dog-bone and the other wire in the right hole). Pull the wire through the hole and wrap it around to make a loop through the hole in the dog-bone. Either twist the wire or use a split-bolt to make the connection mechanically secure. You should now have a long piece of wire coming out of the dog-bone that becomes one element of your dipole and a much, much shorter piece of wire that we'll use to attach to the coax.

Now, wrap your coax around the middle of the dog-bone. If you are using RG58, this works pretty well because the outside diameter of the coax will let the cable fit into one of the grooves in the dog-bone. Clamp the coax together so there's one loop around the dog-bone. A nylon wire-tie should work, but be careful to not make it so tight that you crush the dielectric in the coax. You should now have a long piece of coax coming off the center of the dog-bone which you'll run to your radio and much, much shorter piece that we'll use to connect to the dipole wires.

Strip the short end of the coax so that you have the center conductor separate from the shield. Twist the shield together to make a stranded wire. Now, solder the center conductor to one of your dipole elements using the short piece of the dipole that's hanging free from the dog-bone. Do the same thing with the shield and the other dipole element.

Attach the appropriate RF connector to the long end of the coax.

Attach dog-bones to the other end of each dipole element. Attach small diameter rope to these dog-bones. Pull each of the dipole up in a tree or other support (not live utility poles) so that the dipole is above ground and relatively horizontal. As you pull tension on the ends of the dipole, the center insulator with coax attached should rise up in the air.

Tune the antenna for resonance.

Have fun making contacts.

There are more elaborate center insulators that you can buy for making dipoles, but the coax-wrapped-around-the-dog-bone is about as simple and inexpensive as you can get.

 

[mrstangblb]

Sorry for the dumb question, but since I'm new to everything, it was a little hard to figure exactly what to do. Do you have any inexpensive sources for the dogbone insulators? And thanks for the great info!

 

[AK9R]

Just about any amateur radio store will have dog-bone insulators, wire, and coax. The Wireman's web site (The WireMan - Your source for coax, connectors, wire, baluns,and more!) is a little clunky, but he has everything you need.

Here's an old article from QST about building dipoles:

http://www.arrl.org/files/file/Technology/tis/info/pdf/9106023.pdf

Here's another web site that describes the dipole building method that I posted:

AA5TB - The Dipole Antenna

 

[k3cfc]

Sorry for the dumb question, but since I'm new to everything, it was a little hard to figure exactly what to do. Do you have any inexpensive sources for the dogbone insulators? And thanks for the great info!

Put this in ebay ( Ham Radio Antenna insulators ) then choose what you want.

 

[AC2OY]

My dad was an MIT graduate in electronic engineering and a ham operator before I was born (back in the late 1950's). I grew up around both electronics and ham radio and that's what sparked my interest in ham radio overall. However, I didn't have the patience or the desire to learn code and while I could pass the general and advanced written without any real problems, I balked badly at 20wpm on morse code... So I never got licensed (this was back in the late 70s and early 80s). After my dad became a silent key, and I noticed that you could get licensed with no morse requirement I jumped on the opporunity.

What keeps me interested now is antenna theory and design, it's become one of my favorite aspects of this hobby. Anything or any facet of transmission design has become a passion for me over the past year. And bar none, I love digital modes (from voice to PSK/packet/etc). And despite the fact I have a row of 1500 watt linears (SS and tube) I have enjoyed the hell out of DXing on 30 watts or less (especially mobile). And without a doubt I love 20, 40 and 80 meters.

LOL If your really bored and you are in the New Jersey area and would like to help me erect a 80 meter dipole...I'll supply the.....and pizza!!!

 

[acyddrop]

Re: What sparked your interest in ham radio?

The dog bones are good you can also use a short length of PVC pipe about 10 turns of coax and some wire clamps and a couple of eye rings to construct the whole thing. All of that you can get at your local Home Depot or Lowes. Well maybe not the coax. And you will need a coax connector and 2 end caps for the PVC.

The soldering isn't to bad I recommend a PTFE insulated SO-239 if you're new so you don't obliterate the insulation. Don't listen to anyone trying to convince you a silver and PTFE insulated SO/PL-259 is expensive, they're not. I suggest RG-8X for your coil. If you want to get fancy you can make a very simple 1:1 BALUN but you don't need to.

Sent from my Funky EclipticRez v9

 

[acyddrop]

Re: What sparked your interest in ham radio?

I'm down for that, I'll PM you my number and my Skype info

Sent from my Funky EclipticRez v9

 

[902]

I use some scrap hardware store Lexan. Snap it into chunks (not even neatly), then drill two holes in it. Seems to work okay and has never broken on me, even after years. PVC might get crazed and brittle from UV radiation after years, but maybe the Schedule 40 PVC portions are more resistant.

Michael, I don't know when the next time I'll be back home visiting, but if you still need help when I am, I'm in!

 

[902]

I'm curious - what's your recommendation for what antenna you would (or have) put up that's economical and would range over 20, 40 and 80 meters? I'm playing with all kinds of dipole and wire designs, but I'm curious what you think. I've got one simple double-14-gauge wire antenna out as a flat top dipole that is pulling a lot in, but it's only wire and no coax.

When I was a Novice, and much through being a General, I had a 100' flat top antenna with a single wire feed coming up the side of the house from the downstairs window. Don't underplay your antenna! This was 1978/1979 and I have QSL cards from around the world using that antenna. I had to have a tuner, but that was a given.

Since you're interested in the lower bands, have you tried something like a B&W 90 ft. folded dipole? You don't have to spend their big bucks. You can buy the antenna materials from Buxcomm (a T2FD antenna) and make the same thing for a fraction of the cost. I use one in an NVIS configuration here and can work stations from literally every part of my state with usually good results. It's not meant to be a DX antenna (at least I haven't thought so), but it's wideband, usually doesn't need a tuner, and does a decent job if you want to get on 80/75, 60, or 40 meters. It'll do fine on 20 meters, too.

 

[elk2370bruce]

I have a really dumb question, though, acyddrop. I am researching dipoles like crazy and have read a LOT of how to construct them, but exactly how do you connect the coax to the middle of the wires in the dipole? .

So long as you using RG8 or similar cable (forget RG-58 especially from Radio Shack), a dog bone will do well. Solder the center conductor to antenna wire on one side of the insulator and the shield (the brass mesh) to wire on the other side of the dog bone. You can also replace the center dog bone insulator with a 1:1 current balun. I recommend the use of the balun rather than the dogbone insulator. Check yyour rig to see of you have an automatic "tuner) so you can keep your standing wave ratio (SWR) below 3.0 (as close to 1.1 as possible). The balun will set you back about 20 bucks but prevents nasty little shocks,

 

[n5sjs]

Barry,
Google 'Fan Dipole' for more ideas.
73,David/n5sjs

 

[acyddrop]

You can build a 1:1 balun for about $15 or less in parts, but if you can find a pre-built in that range you might as well buy a pre-built. If you're power output is minimal you can use less beefy parts for construction. A balun capable of max power (homebrewed) would set you back a bit more, because you'll want to take some precautions when setting it up. Basically you get stuck with some one off items (glass tape for example) that you can use to make a dozen baluns/ununs/whateverun's but it's pricy outlay (about $20 for a roll) for just one.

 

[elk2370bruce]

Barry,
Google 'Fan Dipole' for more ideas.
73,David/n5sjs

I constructed a fan dipole for 40-6 meters when I first upgraded to General. Cheap, effective, and easy to build. I use mine as my primary antenna and have neve regretted the time it took to build. Just take your time and do it right and the dx will roll in (depending on propagation of course). Go Fer It and enjoy the fruits of your satisfying labor.

 

[LtDoc]

A dipole is probably the simplest antenna around. The only 'biggies' are keeping the two 'sides' of equal length and using the 'right' length of conductors. That "keeping the two sides equal length" isn't a micrometer kind of deal, more like a "ruler" kind of deal, there's some 'fudge factor' in that "equalness" thingy. The higher you go in frequency the smaller that 'fudge factor' is, keep that in mind. At 80 meters an inch or two isn't going to make a humongus difference. At two meters that "inch or two" is a humongus difference. The "magic" numbers for antennas, '468' and '234' are on almost every license test (or all of them I've ever seen anyway). They will certainly get you into the 'ball-park' for any frequency you care to mess with. They are not -exact- by any means, there's some 'fudge factor' built in to them. They typically wind up just a little too long, which is certainly better than too short, right? You will have to 'tune' the thing anyway so starting too long means you won't have to 'add' more later (which would you rather do, cut it off or solder more on?).
Tuning an antenna always involves two 'parts', making it resonant and matching impedances. If you don't do both of those thingys then you really don't have a very efficient antenna. Matching impedances is a fairly 'common' thing, most people know about it, it usually means using an SWR meter. The resonance thingy is not as easily adjusted thing unless you have some expensive test gear or keep those "magic" numbers in mind. Those two thingys, SWR and resonance are typically adjusted by changing the length of the antenna. Unfortunately, changing the length for one purpose mis-adjusts the other. SWR/impedance matching has nothing to do with resonance and vis-a-versa. The important one is resonance, impedance matching just isn't that critical in the overall scheme of things. (I imagine that'll get some 'discussion', you think?? )
Have fun.
- 'Doc

 

[Token]

Barry,
Google 'Fan Dipole' for more ideas.
73,David/n5sjs

Yet another vote for a fan dipole. I have more than a couple antennas here, from dipoles to beams and dishes to Rhombics. And single band antennas with gain are awesome, but for a simple, multi band, no tuner for the bands covered, solution the fan dipole is a great, easy, and inexpensive thing.

I have a couple of fan dipoles up. Actually fan dipoles and inverted V antennas. My most used is one that has three bands on it, 160, 80, and 60 meters on a single feed. Just to show a friend it could be done on the cheap I built it using PVC for the insulators and wire from a hardware store, and except for the coax I bet I have less than $20 in that thing, even though there is almost 500 feet of antenna wire in it. The feedpoint is about 55 feet up and each band slopes down but on separate angles around the compass, all the legs of a fan dipole / inverted V do not have to go on the same bearings. Example the 160 meter portion slopes down with the wire on the 110 / 290, the 80 meter portion wire is on the 315 / 135, and the 60 meter is on the 345 / 165. There was some though given to that.

With this 55 foot feedpoint and end points at 12 or so feet the 160 portion is not a true inverted V, the angle is a bit too shallow. But it works well. The other two bands are proper inverted V’s. The bearing for the 160 meter wire was selected because I use this multi banded antenna primarily as a general coverage receive antenna for short wave. This antenna gives great coverage up to about 6 or 7 MHz, as might be suspected. What is surprising is that it actually works well all the way up towards 10 meters. At higher frequencies the 160 meter portion becomes pretty directional as it starts to become multiple wavelengths long. I selected the bearing the 160 wire is on to use this directionality, roughly pointing the lobes (which change angle with frequency) towards desirable target angles, it turns out I have some pretty good lobes towards Europe, South America, northern Asia, and the South Pacific.

Another good antenna that can be built on the cheap (except for the supports) is a full wave sky loop. I have one on 160 meters that works acceptably on all ham bands, and is a bit lower noise than a dipole or inverted V.

T!