Is this project to ambitious?

[Drafin]

I'd like to take this antenna , build it and add an element for CB reception as well as an element for the 40-50 mhz range. Come to think of it an element for MILAIR would not be bad as well.

Now , when it comes to building an antenna, I'm a complete newbie. I'm the first to admit it. But I am handy and from looking at the plans I know I can build it stock.

My question is

a. is adding elements for the 3 bands I mentioned a possibility

b. if so how and what lengths and angles would be required

I know it would probably be easier to just buy an antenna in the freq ranges I want but where is the fun in that?

Draf

 

[kb2vxa]

Not too ambitious but way too impractical. First of all you'll not solder a 9' CB element to an SO-239 with any hope of it staying vertical or not snapping the center sleeve. It gets worse, horribly worse when it starts looking like a Copper Cactus (Google it) made out of soft wire when that antenna is made from stiff copper tubing and it's only for VHF and UHF. I cringe when I think of what you have in mind. (;->)

OK you're a newbie and that's why KISS (keep it simple stupid) is so important. First of all forget about the CB part, a good old fashioned store bought antenna will do you justice. If you want to build a J Pole for VHF Lo Band go right ahead but don't louse it all up trying to figure out all those other elements. Now we get down to the VHF/UHF Copper Cactus, that's a practical idea being MilAir is nothing special sitting pretty in VHF to begin with. Last but not least are the plans you linked to, the most practical being you probably listen to 800MHz as well as VHF and UHF.

Here's an interesting point, once soldering is completed you can waterproof the up side of the connector with a glob of silicone bath tub caulk. (See where this is going?) Shove the coax up through the middle of a length of ordinary TV antenna mast, screw the connectors together and wrap with tape. Then slide it back, stand it upright and the antenna will sit neatly on top, the weight of the coax will hold it there without any other consideration. Just don't solder your fingers together and you'll do well young Jedi.

 

[rvictor]

As designed, that antenna appears intended to stand on the four radials serving as legs. If that's what you intend to do with it, I'd suggest something less flexible than the #10 or #12 solid copper wire for the radials.

Dick

 

[Drafin]

That's why I asked here. Thanks for the advice and tips.

I think I'll build the antenna I linked to and see where it goes from there.

CB is not a huge consideration as I rarely listen there, the 800mhz and VHF is my main concern. The others were after thoughts.

As for the standing on the legs, it wont have to. I am gonna attach it to an already attached mast that is on the top of the house. I just have to figure out how to secure it after I remove the obsolete dish that's there now.

Draf

 

[cassidy1190]

why do the elements curl at the tip?

 

[nd5y]

why do the elements curl at the tip?

So the sharp wire ends don't poke your eyes out or damage things when the antenna is used indoors. There is no electrical reason to make loops on the ends of the elements on an antenna like that.

 

[davidmc36]

I have built a few of those and they work very well as a multiband scanner antenna. I gave one away to my brother for his indoor use, just hang it from the rafters with a piece of string, and the last one I built I made with 5/32 piano wire and put it on a mast much like kb2 described but fastened it snugly to the top of the mast and put it at the top of my 40ft tower. It is going strong after three years. I did not use the SO-239 on the outdoor one though, I made a stronger base out of brass and phenolic (to insulate the center from the ground radials just as the SO-239 does) and drilled holes that were tight and pounded the ground radials in and then heated and soldered the whole thing so they would not loosen out. Silver solder is the best choice.

I have been very happy with each one I made using those dimensions. They give many-fold improvement over duckies or telescoping antennas that come with scanners, even if you can only get them a few more feet in the air than the stock antenna.

Great project to get you started making antennas and is easily and cheaply made.

Watch out for what type of SO-239 you get. Most I have seen have a nylon or teflon type insulator that will melt if you get things too hot, but I have seen some with phenolic insulators that will endure more heat.

 

[davidmc36]

As for the standing on the legs, it wont have to. I am gonna attach it to an already attached mast that is on the top of the house.Draf

As somebody mentioned earlier, you will not have any luck putting that outdoors made from the household copper wire. It is soft as butter and will be bent like a banana from very little wind.

 

[Drafin]

As somebody mentioned earlier, you will not have any luck putting that outdoors made from the household copper wire. It is soft as butter and will be bent like a banana from very little wind.

Couple of questions on the 5/32 piano wire.

Where did you find it in long enough lengths for the antenna?

How did you bend it?

How did you fasten the 800mhz and 450mhz elements?

Draf

 

[davidmc36]

Couple of questions on the 5/32 piano wire.

Where did you find it in long enough lengths for the antenna?

How did you bend it?

How did you fasten the 800mhz and 450mhz elements?

Draf

I got it at a hobby shop that sells radio control airplanes and the like. It is used for things like landing gear. They usually have it in 36" or longer.

You will want to use a cut-off wheel for trimming, it will put dents in things like diagonal cutters.

I heated it red with a propane torch to make the tight bends, you can only do very large radius bends with it cold.

The best way I could come up with was silver solder, if you had an acetylene torch you could braze it also. Regular solder does not stick well at all to the wire and I suspect would not last very long.

 

[rvictor]

You will want to use a cut-off wheel for trimming, it will put dents in things like diagonal cutters.

If a Dremel tool with cutoff wheel is not available, I suspect that one could file a notch at the intended cutoff point and snap it in two.

In either event, eye protection would be good.

Dick

 

[Drafin]

Didn't even think of using my Dremel and cutoff wheels...

May try that out.

Draf

 

[kb2vxa]

"As somebody mentioned earlier, you will not have any luck putting that outdoors made from the household copper wire. It is soft as butter and will be bent like a banana from very little wind."

Thanks for reminding me, the first VHF ground plane I made ended up like a pretzel. The next one I made using 1/16" brazing rod and it held up nicely. Er, piano wire is steel and difficult to solder, I suggest going with brass.

 

[davidmc36]

"As somebody mentioned earlier, you will not have any luck putting that outdoors made from the household copper wire. It is soft as butter and will be bent like a banana from very little wind."

Thanks for reminding me, the first VHF ground plane I made ended up like a pretzel. The next one I made using 1/16" brazing rod and it held up nicely. Er, piano wire is steel and difficult to solder, I suggest going with brass.

Bronze rod is a great choice for easier assembly, have seen others mention it. I will have to try it for my next project since I am pretty much out of decent lengths of piano wire. I made a replacement ground radial for a VHF antenna at work a while back and was not very happy with the strength, it sagged pretty bad after a year, but I think at 1/16 it just couldn't support itself. I'll try something a bit thicker for the next go.

 

[davidmc36]

If a Dremel tool with cutoff wheel is not available, I suspect that one could file a notch at the intended cutoff point and snap it in two.

In either event, eye protection would be good.

Dick

101% correct on both accounts.