Search results

I see it referred to as a 1:1 coax loop balun elsewhere. 1/4 wave and 3/4 wave sections, VF corrected.

This is the one I used. It's been spot on so far. Used it on simplex and the usual repeaters with great results. Haven't been able to get it in the air yet, tested on a camera tripod. https://3g-aerial.biz/en/online-calculations/antenna-calculations/dl6wu-yagi-uda-antenna-online-calculator

A little fun with some 8awg ground wire and a (surprisingly straight) 1/2 x 3/4" furring strip. Swept well and works great. I call it Jacob's Ladder.

Oh man thanks, great info and I appreciate you taking time to post that. Impedance and SWR was initailly balun only into 50 ohm load with impedance around 45-46 ohms and SWR 1.25 and once assembled with antenna, pretty close to the same results. I may be calling it a 1:1 balun mistakenly. Here...

A little more research leads me to think that wasn't the correct way to test the balun. The antenna works great though. I'm building a 12 element now and I'm just going to use the calculated measurements and see how it works. If anyone can give me insight on how to properly test a 1:1 UHF coax...

Well I cut all that extra shield off that I twisted together as i imagine that skews something, connected a 50 ohm load (that's used for calibrating my vna) across the feed and ended up snipping about 1/8" off the 1/4 wave section and about 3/8"off the 3/4 section. Got it real close to 50 ohms...

I figured it out. Best antenna I've made so far.

I'm going to start experimenting with GMRS Yagis and so now I'm building my first balun ever. The plan I'm using calls for a 1:1 coax balun using a 1/4 and 3/4 wave sections. Am I correct that I can connect a 50 ohm load across the leads and check impedance on my nanovna and adjust? I went ahead...

Appears in this configuration I actually built a Sperrtopf antenna. Difference being Sperrtopf is fed through bottom, (easier to experiment) where as Topfkreis feeds through side (get it right the first time). It's working really well.

Check this out. Think I'll hook it up and give er a shot. Lol and holding the ground to the tube with my thumb.

Not sure about any of that as I'm very new to this but it appears the inner diameter of the (1/4 wave) outer tube (D) to the outer diameter of the (3/4 wave overall) inner tube (d) should be as close to 50 ohms as possible calculated the same as coax cable. Only info I can find shows formula...

Antenna. I stumbled onto the design looking at J-poles and was intrigued. Internet search of topfkreis antenna shows a few results.

Man this one is a challenge. First attempt was resonant at 375mhz. I just learned about K factor, made some adjustments, closer at 410mhz now. I think the feedpoint is throwing me off at this point. I've modified it to be temporarily adjustable. I'll get there...

Found some 1/4 and 3/8 OD and 1" ID copper tubing. Shined up nice. It'll be my first attempt at a Topfkreis build. Hoping I can get that impedance close.

Updated version and the resulting sweep.

Still had to trim it, then added a tail to the reflector. Not afraid to admit no clue as to what that does but it made the Smith chart happy and this little rig just had a good contact on a repeater 28 miles out on that little Retevis and me holding the antenna inside our living room. 3 degrees...

I had good (lucky) success with an 11 meter version I built and I like the 50 ohm feed but yeah, a yagi might make more sense. I'm just having fun building these. I have no formal education on this stuff but I can follow directions. The nanovna sure helps.

I'm a little slow and just noticed the vertical polarization I referred to is for the eznec model and has nothing to do with dimensions. So moxgen and the online calculator are showing different results. Hmm

Thank you! The link you shared has indeed been the closest so far but my results differ. I suspect it's because you were able to choose vertical polarization (thank you). I'll be using the specs from your results but for comparison, here are mine.