50 ohm full wave loop

[Buffalo]

Got lucky. First cut 36’8” was dead on. I knew it was going to be narrow banded but not bad at all. 1.5 on 26.965 and 27.9. 13’ AGL at the moment on a test pole. A couple of checks today (DX) it performed better than my 2016 which is 32’ at feed point. Could have just been conditions which were up and down it a heart beat!! At any rate it performed rather well. 1:1 current Balun at feed point.

 

[sp5it]

Full wave loop 50 Ohm? Interesting
With 1:1 balun? Even more interesting.
Mike

 

[Henry HPSD]

Hello Mike,

Yes sure is !
There are a couple ways to make full wave loops 50 ihms :

https://cb-antennas.com/?page_id=802

And another (rectangle)

https://cb-antennas.com/?page_id=1662

But im sure there must be other ways...

That "improved bamby" is quite frequently seen with activations on 27 MHz.
I have one in the car just rolled up...with a wire spreader in the middel..and if needed i can put it up anywhere....
Lots of fun !

 

[Buffalo]

Wow great site Henry. I’m wondering how I didn’t stumble across it before now. Loops are new to me but it seems as the sides of most shapes are elongated the impedance drops and the gain increases.

 

[Henry HPSD]

Hello,

Thank you...
the site is still work in progress, i finally did some work on it lately hi.

And yes, it depends on the "aperature" of the antenna...which is kinda like its "size" (but not the same). ...its like "its effective size"..

The impedance also depends on location, just think of a folded dipole fed at the center... thats roughly 250..300 ohms.... though it is very stretched...ps that has less gain again...but still is a full size loop

Keep up working on those projects !...lots of fun building your own antennas !

Kind regards, H.

 

[Buffalo]

I found it. Here is where I came across the idea of a 50ohm loop. I had enough junk laying around and had to try it.

Theory of Full Wave Loops – Practical Antennas

practicalantennas.com

 

[Buffalo]

Never even took the time to double check it this way. Was just using swr meter on the radio. Didn’t actually hit the frequency I calculated it for (27.4) but close enough.

 

[Crawdad]

.lots of fun building your own antennas !

Absolutely positively!!!!!!!!

 

[Buffalo]

Well, the antenna was sitting on the ground up until yesterday waiting on me to decide where and how I was gonna put it up permanently. In the morning yesterday, something went wrong with my four element being SWR jumped up to like 1.9. Checked everything and it seems something funny with the antenna I switched the coax out. Bypassed everything.
Lightning arrestor jumpers meters coax ETC. So I took the beam down so I could work on it and figure out what the heck is going on. Put the wire antenna up in its place, and had a great contact for about 10 minutes this morning with a guy on a robin CB radio in the Canary Islands. It was one of those contacts you wish you had recorded.

 

[murdog]

Buffalo, can you post length of top , fiber glass to support ?

 

[secret squirrel]

Awesome work.

 

[Buffalo]

Buffalo, can you post length of top , fiber glass to support ?

Top and bottom support arms are 6’ fiberglass driveway markers. I cut the pointed tips off, put marine shrink tube on the ends to take up space so the 3/8. Push to fit elbows I used on the corners would lock on. I only have an estimate for the top and bottom length. A little over 6 feet. The total length is 36‘8“ with 14 gauge wire that is insulated. Sorry I don’t have the exact number for you.

 

[BC Coyote]

Buffalo, can you post length of top

The lengths of the sides shouldn't matter with a full wave 11 meter loop like that. I've seen and used full wave loops that were all kinds of weird shapes.......so long as it's roughly a loop and it's total length is 36 feet (or a wee bit more).
The height is important.... It needs to be at least 36 feet above ground otherwise its radiation angle will be much too high for 11 meter propagation.

You don't need a balun for a full wave loop, though you could use a 1:1 If you're worried about CMC's. Impedance of the loop is close enough to 50 ohms.

Rules that apply to full wave loops DON'T always apply to other kinds of wire loops. For example, on a delta loop the lengths of the sides, and the corresponding corner angles are critically important as the shape of the delta is a major influencer of the impedance present at its base.

Great to see people experimenting with homebrew antennas! It's one of my favorite parts of the hobby!

 

[murdog]

Top and bottom support arms are 6’ fiberglass driveway markers. I cut the pointed tips off, put marine shrink tube on the ends to take up space so the 3/8. Push to fit elbows I used on the corners would lock on. I only have an estimate for the top and bottom length. A little over 6 feet. The total length is 36‘8“ with 14 gauge wire that is insulated. Sorry I don’t have the exact number for you.

OK thanx Buffalo and BC Coyote.

 

[Buffalo]

The lengths of the sides shouldn't matter with a full wave 11 meter loop like that. I've seen and used full wave loops that were all kinds of weird shapes.......so long as it's roughly a loop and it's total length is 36 feet (or a wee bit more).
The height is important.... It needs to be at least 36 feet above ground otherwise its radiation angle will be much too high for 11 meter propagation.

You don't need a balun for a full wave loop, though you could use a 1:1 If you're worried about CMC's. Impedance of the loop is close enough to 50 ohms.

Rules that apply to full wave loops DON'T always apply to other kinds of wire loops. For example, on a delta loop the lengths of the sides, and the corresponding corner angles are critically important as the shape of the delta is a major influencer of the impedance present at its base.

Great to see people experimenting with homebrew antennas! It's one of my favorite parts of the hobby!

In this case with a rectangular loop, a two to one ratio, sides to top and bottom results in 50 ohm impedance at the feed point!!! Still using the thing and it works great. Probably the simplest antenna I ever constructed. Pretty well tuned right out of the gate didn’t have to cut anything.