Carbon Steel Whip

[Rosco-p-c]

I'm in the process of collecting components to build a 1/4 wave, 11 meter dipole for my attic. I ran into 1/8 diameter carbon steel rods plenty log enough to trim back. Are there any metalergical problems using carbon steel, like it can build and hold a magnetic charge? I've never seen it used and was wondering if there is a specific reason other than it deteriorates when out doors.

Thanks.

RJ

[muddy_udders]

My first guess would be oxidizing/rusting issues would be the reason it is avoided. Just a guess though.

[420Snowman]

HMMM, thats a great question actually. You can pretty much use anything conductive to make a good dipole, you would actually probably be better off building a simple one with some copper wire. I have a dipole in my attic for my horizontal side and it talks skip and locally VERY well and the SWR is flat. I purchased mine from a website and it cost me 30.00 with shipping, I think you could have that much into your project pretty quick with parts and labor. I will do a little searching on the carbon steel rod theory and get back to you.

Snowman

[Rosco-p-c]

I use these .125” rods for decorative steel projects and coat them with a thin clear lacquer that keeps them from rusting.
I’m using two 3/8 x 24 male threaded whip ferrules with the .100” holes drilled out to .140” to accommodate the .125” rods. A simple metal “U” bracket with a right angle SO 239 connector and a 3/8 x 24 threaded stud & coupling nut holds the two ferrules/rods at 180 degrees. Total cost is just under $20.00. If I have to use stainless steel rods, the price will go up about $5.00.

If I mount the “U” bracket so it can rotate on a wooden cross beam, the antenna can be pivoted vertical or horizontal as desired... more versatile than stretched wire.

If the set up works, I’ll try stepping up to two 102” X .187” rods for a half wave (but I’ll have to mount it out in the barn loft). I may have to MIG-Weld two shorter rods together end-to-end to get the length I need.

Some of my goal is to have a rigid centre-mounted antenna rather than a flexible wire one that has to be attached at both ends and kept taut with a lead suspended at the middle. The set-screw ferrules allow for some quick/easy length adjustment (about an inch and a half overall) without cutting.

[420Snowman]

WOW, you do have this all figured out!! Go for it, make it work, I want some pics when your done!!!

Snowman

['Doc]

I think it's more a mechanical thing than electrical. If you find that working with carbon steel is easy, and if you have the necessary lengths of it, why not?
Think about that 1/4 wave 'dipole' thingy again. If the total length of the antenna is only a 1/4 wave, an 1/8th wave on each 'side', then you are going to have SWR problems, it will be very difficult to match impedances with. If you mean a 1/2 wave dipole, a 1/4 w on each 'side', then it shouldn't be a problem at all.
- 'Doc

[Rosco-p-c]

OK Doc, you’ve got my attention.

My plan has been to construct a dipole antenna that has a total length of 102 inches, approximately 51 inches per side.
Is that not advisable?

[drdx]

Nope. A resonant dipole is usually a half wave total length at desired frequency. The dipole will need to be a 1/4 wave on each side to work, as doc mentioned, for happy feed. If it is 102 inches total, you've basically built a dipole for double the frequency of cb, or around 54 mhz, the 6 meter ham band, as it is half that size. Allow some extra length for tuning and/or come up with a hairpin adjuster or something so you can dial it in. If it is mounted in close proximity to other objects- like structures, it will need some tweaking to work. Antennas don't usually like to be right next to things and work right.

-drdx

[Rosco-p-c]

I think I've got it. Each side of the dipole needs to be the length of 1/4 wave, not the total antenna length. Guess that keeps me from going vertical in my attic.

Hey, I really appreciate you guys setting me straight. I need to pick up a book on basic antenna building/theory before going any further. Not giving up though... just regrouping.

Thanks.

RJ