Need Help Building a dual band J Pole Antenna for 146/440

[quiksilver199324]

Hi i am a new amateur radio operator who wants to build an antenna for my house. I was looking at jpole plans and i was recommended the Construction Plans for the Model J146/440 at http://www.fwarc.org/Ant articles/J Pole Antenna.htm .It looks pretty simple, but i have a few questions.

I have never made a radio and i dont know how to mount it. is it neccessary to use the ubolt assembly and mount it to a pole, because i was thinking that i could bold the bracket directly into the the overhang of my roof right outside my room window. I know the antenna is supposed to be far away from other objects, and this spot is pretty far away from everything. My question is does the aluminum and ubolt that is used to attach it to a pole affect the performance of the radio, because i plan to use normal bolts and nuts.

Secondly, i was wondering where i attack the coaxial cable to the jpole. On the picture and discription at http://www.fwarc.org/Ant articles/J Pole Antenna.htm , there is no measurements for where to attach the coaxial cable.

Finally, my last question is how to i split the coax cable to attach to the radio. I have never done this and i was wondering how i split the sheild and center wire, how i attach it to the antenna, where i attach it, and if i use a splitter to do this.

One more thing. It says to test the swr readings to make sure it is adjusted correctly. How do i test this and what is this? thanks you

Thank you for all the help, and i am sorry these questions are stupid, but i am very new to amateur radio and i would appreciate the help.

-Peter

ps i fixed the links they should work now

 

[Beetle]

Peter - the links you tried to post don't work.

Google

jpole dual band

and you'll get lots of information, including http://www.n7qvc.com/amateur_radio/copper.html

 

[quiksilver199324]

The antenna that i would like to build is that one because i have easy access to solid aluminum and machine shops to build it. I just need to know where and how to attach the coax

 

[mackmobile43]

The antenna that i would like to build is that one because i have easy access to solid aluminum and machine shops to build it. I just need to know where and how to attach the coax

Just follow the instructions.

''The feed point also needed to be made simpler, so I elongated one of the mounting holes of a panel mount SO-239 fitting and inserted a stainless steel adjustable band clamp. This goes on the 57 1/2" long section of 1/2" tubing. A short 2-3/4" length of # 14 copper stranded wire is soldered to the center terminal to go over to the 19" section. I used another stainless clamp to attach this. ''

Then you can simply connect your pl-259.

 

[W5LZ]

quiksilver199324,
The thing about the attachment points for the coax is that it's variable. Depends on where the antenna is mounted and whats around it, which can have an affect on the antenna's input impedance. Moving the attachment points up/down changes that impedance match.
'mackmobile43' gave you a good starting point in the picture, about the same distance 'up' the two vertical parts as the distance between the two vertical parts. That's just approximate though! You'll need an SWR meter for making that adjustment. When you reach the lowest SWR point, stop adjusting. Doesn't matter is the SWR is exactly 1:1, just the lowest you can get it (1.5:1 or less is just fine). If you want to then solder/weld/whatever instead of using clamps, do so.

I've found that if you use a 'T' where the short thingy branches off the long thingy, then extend the long thingy below that 'T', that extending part usually will slip into a slightly larger mounting pipe just fine. May not be exactly straight up, sort of tilted, but unless that 'tilt' is extreme, it'll work just fine. If that 'extension' is something like 6" or a foot long, the weight of the antenna will keep it from being blown away by wind etc.
I've also found that a 2 meter 'J'-pole works just fine on '440 without doing anything special. 'Best' in the world on '440? Not really, but certainly good enough for most applications, and at the very least, it'll give you something to use for comparisons when you get something 'better'.
No idea exactly where to find them, but there are quite a few projects like this on the internet.
- 'Doc

 

[Moleculo]

You have a bunch of questions posted there so I'll try to point you in the right direction for each of them.

Construction of a 2m/440 J pole
Here are a few more links that have better pictures and good instructions. You can get some ideas on how to attach the coax better when you see some pictures:
Dual Band J-Pole
Copper Cactus J pole antenna - 2 metter 70 Cm dualband

Mounting the J Pole
It would be best if you attach it to a mast of some kind to get it up off the roof, at least a little. You really need to make the mast connection to the J pole non-conductive. You can do this with heavy PVC, a fiberglass rod, or even wood. Use the U bolts to attach the J Pole to the mast and then use something to bold to mast to the overhang of your roof. For my 220mhz J pole, I just used a wood dowel painted black (to protect from the sun) and just some metal strap and screwed that to the eave of the roof.

Attaching coax to the radio
Here are a couple of youtube videos that show you how to attach a pl-259 connector to both the thicker RG213 and thinner RG8x coax:
YouTube - PL-259 Installation Made Easy for RG8X
YouTube - PL-259 Installation Made Easy for RG213
Buy a few extra connectors and don't be discouraged when you screw up the first 5 of them and have to cut them off. Soldering these things on takes a little practice.

You asked about "splitting the coax" to attach to the radio. I assume you're asking this because your radio how connections for both 2m and 440. If this is the case, you need buy a 2m/440 diplexer and a couple of short jumpers. This will have a connection for 2m and another for 440 and also one for the antenna. If your radio only has one connection for vhf/uhf, then you don't need to mess with this.

Checking SWR
You need a SWR meter for 2m and 440. Something like this will work fine: SX40C DIAMOND I found and older one used for less. If you have some ham buddies nearby, ask them if they have one to borrow. In fact, ask them to show you how to set up and install the antenna and help with the coax connections once you get the antenna built.

I hope that helps a bit.

 

[Beetle]

Just a comment about those Ten-Tec soldering videos: 20 seconds of holding the iron on the connector is about 15 seconds too long. Don't try to use a little pencil iron when a large thermal mass is needed.