RG-400 is VERY different from LMR-400. Among other differences, LMR-400 has a foamed polyethylene dielectric, which will allow migration of the center conductor. RG-142 is VERY close to RG-400, the difference being that it has a solid center conductor, which makes it harder to wind around a toroid. The stranded center conductor of RG-400 is easier to wind, its slightly higher loss is miniscule.
If I may suggest, leave the balun where you have it and re tune the antenna as necessary. This way the feedline will not be part of the the antenna or the tuning. Bob
Y'all are completely missing it, RG-303 is the the winding coax of choice. Copper clad, silver flashed solid steel center conductor with Teflon center insulator and a tight silver flashed shield. There is absolutely no need for a dual shield and besides it makes the winding more difficult. FWIW, this type is still susceptible to "cold creep" where the center conductor migrates through the Teflon. Projected time frame 25-30 years.
I was speaking of voltage and current ratings. They're pretty much identical. Great for balun and chokes. That's what DX Engineering had in their 10K plus baluns. RG400 I would take a pretty big ring toroid to wind LMR400 10-11 turns through it.
My choice would not be RG-303. A solid steel center conductor is easier to wind than solid or stranded copper? Also, seems to me that a single braided shield would have more unwanted coupling and be more susceptible to mechanical distortion than a double braided shield. No thanks.
Yes, but voltage and current ratings are not the only considerations. Look at the mechanical specs, maybe you'll see the differences. Those differences make it not so great for baluns and chokes, in my opinion. I'm not sure what you mean by "RG400 I would take a pretty big ring toroid to wind LMR400 10-11 turns through it". As I said, LMR-400 and RG-400 are completely different cables, I never advocated using LMR-400 to construct a balun.
A solid steel conductor keeps it's shape around the toriod much better. And if single braided shield would be a problem, then would a balun made of discrete wires be terrible? I'd say that discrete wires would even result in a better balun because of the symmetry.
Baluns made with coax and baluns made with bifilar windings are two different animals. Each has advantages and disadvantages, you're comparing apples to oranges.
It looks like only 40 meters was de-tuned, and moved lower in the band (indicating that the coax was 'contributing' to the antenna radiation). I've already done a coarse re-tune (shortening of the "hoop"), and it looks like I'm headed in the right direction. For those concerned about center conductor migration due to the tight turns on the toroid: yes, it probably will migrate; slowly and eventually. The outer insulation will also slowly deteriorate in the sun; eventually destroying the RG-8x coax. I may also eventually tire of the limitations of a vertical, and put up a beam atop a tower. Eventually. W2MC
Pretty much to me. I'm only worried about the Voltage potential. I don't use Baluns any longer. I just build a Link Coupled and let that be the transformer. I will use a 1:1 common mode choke using RG-400 for a fan dipole when I do this, but excuse me for not putting the -. I'm sure most readers will understand. The "have too", was left off the last comment. Let's do it this way, YOU would have to use one large ring toroid to wind 10 turns of LMR-400 or RG-8, etc... RG-400, RG-142 and as was mentioned 303 all good for Balun building, or just get 14ga enamel magnet wire and do that. If I do use a straight dipole, I will build an UNUN common mode choke and put together a T-Match and let that be the transformer. You can nit pick this all you want, I'm done. Too funny
The only fact in the link is that W8JI did a sloppy job. The crossover does produce different results even per his crude measurments.
Huge, the one in the video is comprised of two ~100 Ohms transmission lines in parallel to produce 50 Ohms while at the same time reduces the total of common-mode rejection in half. The same number with coax will be twice better as well as will heath the ferrite less compared to chokes wound with two wires. That is more pronounced if lossier materials like #31 are used.
They are exactly the same electrically. The only difference is that coax is easier to use and to maintain the correct impedance.
Hello everyone, Great to see all the talk on building and buying baluns/ununs/transformers! Like VK7HH, I too love to experiment with antennas. One place I found a while ago that helped me to homebrew my own working CMC reducer and my own working 4:1 balun was on YouTube where a gentleman named "Peter", who I think is from Germany or Austria, took the time to learn the English language and has produced several videos that are amateur radio related. Peter has a little trouble pronouncing words like "Balun" and "Series". He says "Balloon" and "Serious". If you can get past that and listen carefully you may learn a great deal from his videos. I give him credit for learning our language so he could help some of us. I have built several 1:1 CMC reducing baluns and 4:1 matching baluns as described by Peter and found they work great. I've used single FT240-43 and double (or stacked) FT240-43's. When using two cores I also use a little heavier PTFE wire. I have my own homebrew 160m OCF and 80m OCF dipoles using the 4:1 balun and at the entrance to my shack I use 1:1 baluns in the feedlines. I also use a 1:1 balun at the feed point of my 40m Full Wave Loop Skywire and my 75/30/20/17m fan dipole. Peter's goes by "TRX-Bench" on YouTube. I recommend watching his #100, #101, #105, and #131 videos about baluns. Here is a link for #100 to get you started. Using my RigExpert AA-600 analyzer and terminal resistance of 50 ohms for the 1:1 and 200 ohms for the 4:1 here are my charts showing the results of both a 1:1 and a 4:1 two core (FT240-43 x2) balun using 16ga Stranded silver plated PTFE wire. 1:1 Balun 4:1 Balun I hope you enjoy Peter's videos as I have. 73 to all and keep on experimenting! Jim
