Antennas

[kew]

I have a really stupid question.

Left over from my CB days, I have a very good mobile antenna, similar to a Firestik.



From a PRACTICAL stand point, can that antenna be tuned for use on the 2 Meter band?

[RobertW]

Since CB is in the 27MHz area and 2 meter is in the 145 MHz area, I suppose you can cut that Firestick and use a SWR meter to see what you got, but it sounds pretty iffy to me.

[Toolman]

Ken....in one word....NO.

 That antenna can not even work on 10mtrs. without an antenna tuner and even then it would not be efficient. The take off angle of transmission used of out of band antenna's is the problem rendering it useless. That's where people have a missconception of antenna tuners to load the antenna to any frq. out of band.

 Best to buy an antenna intended for the band being used. Quality multi band antenna's operate very well albeit expensive. In some cases better than a mono band antenna......depending on if it's a 1/4 wave , 1/2 wave 5/8 wave etc.

 May I recommend the ARRL antenna handbook which will explain and may confuse, but non the less very infomative. I use it for gathering formula information on constructing wire antenna's to machining my own yagi's for HF or VHF-UHF work.
It also has a very good Smith Chart and velocity/gain loss factor chart for coax.

 Without that book I could never have made my own coils for 160mtr.s for a field day antenna.....double points for 160mtrs.

73,
WB6K

[Toolman]

Since CB is in the 27MHz area and 2 meter is in the 145 MHz area, I suppose you can cut that Firestick and use a SWR meter to see what you got, but it sounds pretty iffy to me.

 No it's top loaded....cut it off and then toss it in the trash.

[clint]

Yeah. What Mike said. NO.

[RobertW]

Since CB is in the 27MHz area and 2 meter is in the 145 MHz area, I suppose you can cut that Firestick and use a SWR meter to see what you got, but it sounds pretty iffy to me.

 No it's top loaded....cut it off and then toss it in the trash.

See, that's where the General and Advance tickets come into play.   

[clint]

Although come to think of it, in theory you could cut off all the heat shrink, unwind the copper coil, recalculate it for two meters, re wrap it. It has to be a correct turns ratio of helical wind to work. Cut of the several inches of fiberglass you won't need. re heat shrink it, and then it might work. But like Mike said, toss it in the trash.

[clint]

And that knowledge has nothing to do with being a General or Extra. And there is no Advance ticket anymore.

[RobertW]

And that knowledge has nothing to do with being a General or Extra. And there is no Advance ticket anymore.

See, I would have gotten that question wrong if it were on the test I took!        My understanding was that the upper classes had more to do with antenna theories, etc.

[clint]

Laughing...you are going to have to be punished

[Toolman]

I think his punishment should be to build a few antennas and it will all come together.

 I have the formulas on a note pad on my 18 element 2mtr. ohased stacked yagi's and 23 element 440 yagi's, for SSB work I've built.But we should make him suffer and figure it out on his own. 

 Then when he get's that down....lets let him make a 40mtr. dipole resonant in the middle of the band.


Ok...I guess it was his turn in the barrel.....sorry dude. But it is good learning experience.

[RennMan]

Never argue theory with electronics geeks...

[Toolman]

Never argue theory with electronics geeks...

 I agree....man.... stay away from them e-geeks.

I took special interest into antenna theory because it's more of a mechanical thing in the end for me. Especially machining parts for yagi's and when they work....oh...ya baby that makes me warm and fuzzy. Making the ultimate J-pole from the antenna book out of stainless and delrin kept my at work station going for years.

 I must admit, when I had problems with my amplifier I handed it over to the folks of a higher pay scale. I am not in that geekzoid zone that's for sure and I know my limits. I can hook it up and build the ACC connectors and change the tubes and that's about it.

[kew]

Thanks guys, like I said in my original post, "I have a really stupid question." But Hey, if you don't ask, you don't learn.

[clint]

Like Mike I reallly enjoy antenna building. It's more mechanical engineering than electronics and it's something even new hams can do with just a little help. When I was the Pasadena Radio Club prez I used to hold a J-Pole building clinic after each class got licensed so people could build their own antenna. J-Poles are really easy! Ther ARRL antenna book is big and expensive. It include some software for frequency and legth calcs that is quite useful. If you are going to seriously get into ham radio as a hobby -listen up all you new generals- you should the antenna book and the ARRL Amateur Radio Handbook.

[Wrightwood]

One step ahead of you over on Linnet Rd 

I have the software version of the ARRL antenna book and used it yesterday to print information regarding center feed antennas and flattop vs. inverted V dipoles.

Trying to learn what I can about the 90 foot broadband folded dipole antenna before installing it.

[RobertW]

It's a good thing John has a lot of property.  Here he is working on his new Antenna for DXing:

[Toolman]

I agree....the J-Pole is the best place to start for beginner antenna building. The copper water pipe solderes J was the first one I ever built. Then all my buddies wanted one.....jeesh it was a mass production. Not long after, a guy was selling them by the truck loads at the TRW swap meet so cheap the material almost broke even. He must have had imported help to build them. I think I still have a few in the garage if I haven't given them all away by now.

 I also agree that the new HF Generals should learn how to cut a wire dipole to resonant frq. Those formulas are covered in the NCT study guide. All it costs is the Balun and some wire....but then you can make your own balun also. Then there is the magical phenomena when you get it up in the air. You ask your self gee....I cut it to the formula, why isn't it resonate in the air?

I'll leave that for you to figure out

No helping Clint 

That looks like a 40mtr. mono band yagi at the top....jeesh those things are much bigger than the 40mtr. rotatable dipole I'm putting up soon. And is that a couple 20mtr. stacked phased yagi's for 20mtrs.  I think I'll stick with my KLM KT-34XA for a few more years.
 

[Wrightwood]

Bob - that stuff in the front yard is nothing!

You should see what's being planned for the backyard 

[lagomorphmom]

....I think I'll stick with my KLM KT-34XA for a few more years.

Darn straight, Skippy!

Another fun project we could do is a T-hunt antenna, although you can still do a lot with an HT and a cookie sheet!     [my turn to let folks figure THAT out!]

When I used to hunt with the Santa Clarita club they did a project with a pre-made instruction and materials kit for a mobile yagi. Simple stuff, just rod, pvc and wire. I stuck it through the sunroof of my Celica and had a 360deg template at the bottom. Worked great and got a lot of looks!     My friends that I went with had a quad that he made for their VW microbus, that looked pretty trick, too - got a lot of waves from little kids in passing cars    Of course, the trickest I've seen Toolman made, it's a nice little handheld yagi, that's another thought. I've been wondering about interest in T-hunts in town for awhile, I think I'll post a separate topic...