wire beam antenna?

[W5LZ]

"with six elements, this gives a "boom" length of 35.937 feet.(is this just a coincidence that it is so close to 1 wavelength at design freq.?)"
No. There are 5 spacing lengths,
5 X 20% = 100%. So it isn't really a coincidence. Just math. (Glad I ain't the only one who does things like that )

You might as well use the 14 ga. wire, 12 ga. won't have any benefits.

You're right, that "J" number is reactance, and it'll mean it will not be 50 ohms input impedance (lower than that). With it being mounted so close to the roof, I wouldn't even try to guess what the input impedance will be. Ought'a be manageable though.

Good luck.
- 'Doc

 

[loosecannon]

thanks doc,
i really appreciate you sticking with me through this.

you're right, not a coincidence. sort of...

when "designing" the beam, i was trying to decide what element spacing to use; and the info i read said that great performance is to be had using from .15 to .25 wavelength, with .36 wavelength producing maximum gain.
i kind of arbitrarily (sp?) chose .20 because i didnt have room for .25 spacing.
so, not a coincidence; i just didnt realize what i was doing. LOL
it was neat to notice though.

anyway, less than 50 ohms you say?
good!
hopefully it will be more than 20 so i can just use a coil across the driven element terminals to match it.
will also be coiling up the coax to use as a "choke balun".

still have no idea how to figure the coil dimensions.(at the terminals, not the coax)
using what i now know about the resistance and the reactance, is there a formula for figuring this out?

even the XYL thinks this is a cool idea, and she HATES my antenna projects.LOL

thanks again for all the help,
most likely will buy the wire this weekend and start cutting it up.
loosecannon

 

[W5LZ]

The coil. Until you know what the input impedance is you really don't have any way of knowing that size coil (reactance) you'll need. I don't have any recommendations about that, guessing isn't going to do much good. As I said, being near the roof is going to affect things, so see what you have to work with before worrying about 'fixing' it. Who knows, you might not have to do anything.
- 'Doc

 

[loosecannon]

good point doc!

i will post back on this subject once the antenna is built.

i sure wish i knew someone with an MFJ-259!
that would make this alot easier.
loosecannon

 

[Master Chief]

There has to be somebody on this forum who has a 259B in Vegas!

 

[C2]

Heck, I'd build one myself just to test and see what I get. My roof aint that long though, but I do have some nice equipment...

Maybe I'll make a 4-element with the elements bent at 90 degrees. I have an asphalt roof over a wood structure, and I can't imagine the soil would be that much different. However, my roof probably ain't as high.

I'll see what kind of wild hair grows this weekend.

 

[loosecannon]

MC, ive wondered the same thing about there being someone on here that lives in vegas.
if there is, i hope i dont insult them by saying that the majority of cb'ers in this town dont seem to use their computers as part of their cb hobby. i think they only go online to buy radios.
cb myths abound here, and you'd better not know something different or you'll create a fight.
to tell the truth i dont hang out with or even correspond regularly with the locals here. there are a select 2 or 3 that i will do radio work for, just because i think its fun.

if there is someone on here who lives in vegas, wassup?

C2, very cool, ill be very interested to learn what you end up with.
hey, what freq. is the CDX club using these days?
when this gets built id like to try calling on that freq. to get some reports.

thanks for the replys guys,
loosecannon

 

[Beetle]

I was born in Vegas and lived the first 22 years of my life there. You might ask around at AES - they might have an idea of some of their customers who might be able to help out.

My folks' house was at 711 South 6th. Now it's a law office, just inside the Las Vegas High School Historic District, so the house you see is the same architecture as it was 70 years ago (no, I'm only 63 but my folks lived there a few years before I came along).

On a visit to Vegas a few years ago, I dropped by the law office and walked in. The reception area is right where my bedroom was! I explained who I was and why I was so fascinated by "what they'd done with the place". She called the head legal guy and introduced us. Man, did HE have a lot of questions!

Using Google Earth, you can get so close you can see the individual shingles on the roof!

 

[loosecannon]

thanks for the reply beetle.

some people around here dont think anyone lived here 70 years ago.LOL

nice to meet an original.
if you're ever visiting town, send me a PM. im always up for a coffee break.

good idea about AES, i work about 2 miles from their store.
i wonder what its like to live in a town without one? LOL
loosecannon

 

[KingCobra_CDX882]

Hey..

if you really want a good wire antenna
why not give this a try

www.cd-corp.com/eng/cma/default.htm

that is ofcourse if you have the room for it (is not cheep either)

:shock: :colshd :mrgreen: :wow :rknrl eace

 

[Master Chief]

I was born in Vegas and lived the first 22 years of my life there. My folks' house was at 711 South 6th. Now it's a law office, just inside the Las Vegas High School Historic District, so the house you see is the same architecture as it was 70 years ago (no, I'm only 63 but my folks lived there a few years before I came along).

Beetle is really Bugsy Siegel (Bugsy.....Beetle.....both BUGS!) under the witness protection act! Dude, sorry I disagreed with you in the past! Please don't kill me!

 

[W5LZ]

'M.C.' ... You know, sometimes, you just ain't 'right'...
- 'Doc

 

[Beetle]

Master Chief, now that you mention Uncle Bugsy, let me relate a little personal stuff...

First: I retired today. 44+ years of more or less honorable and faithful service to king and country as a Navy civilian. Just got home.

Second: At the time Bugsy got himself whacked, he was a partner in the Flamingo Hotel in Vegas. His co-partner was a guy named Davie (aka Davey) Berman. The Berman family lived at 721 South 6th Street in Vegas, and as I said earlier, we lived at 711 - just three doors apart. Their daughter Susan was a playmate of mine, although she couldn't come to my place to play. The large men whom she introduced as her "uncles" were actually bodyguards for her and her mother Gladys while Dave was at work.

The story doesn't have a happy ending, though.

 

[C2]

Wholey Schnit, Beetle, I never would have guessed that you had ties to the mob. :shock: Sorry to hear about your playmate.

 

[loosecannon]

ok, 2 quick questions.

can i use this balun instead of coiling up the coax at the feedpoint?
http://www.rffun.com/catalog/antsup/2452.html

also, if you can visualize my antenna idea; where would be the best place to run the coax down the roof?
down the slope off the side between the driven element and the reflector?
or straight out the back, inline with the "boom".

i hope this makes sense.
should i even be concerned about this?
loosecannon