Those are great trial baluns, zapperman!

When you get one that you like, the most important thing to add is some means of moisture-proofing the open end of the coax, where it meets the twinlead.

Electrical tape alone is imperfect with most twinlead, because there's usually a depression on the twinlead between the two conductors, which prevents a good weatherseal.

I do have some twinlead here that really is flat -- no depression -- so perhaps I'll reserve that for balun lead-in from now on. :)

But with the regular stuff, a drop of hot-melt glue on each side can be used to level things somewhat before taping.

Or get some "coax seal" -- basically a very sticky tar-like substance -- and smear that all around everywhere. Perhaps some outdoor caulk might work well enough as a substitute.

Whatever one uses for that, use it sparingly, as its very presence will modify the line impedance. As does electrical tape...

Nothing is perfect, I guess! :)

New Coax Loop Balun works better than the PC board Balun inside the 91XG :

I had a TV in the attic with the 91XG directly feeding the DTVPal box (no amps). I found a channel that came in "OK" with DTVPal "numbers" going from about 65 - 75.

I made a balun with just over the 1 foot ruler length of RG-59. I cut off the black outer coating to make a just under 7" of shield (shooting for the middle of my available channels). This left about 2.75" on either end that I stripped off the white coating. Along with the Transmission Line RG-59, I just connected the ends of these to the antenna (of course, 2 wires are tied together, and the shields are all twisted together). Since I'm in the attic, I didn't bother with any electrical tape - only the shields twisted together hold everything together.

Now the "numbers" go from about 73 - 75. So, no improvement in the maximum "number", but it's far more consistent. Also, once I re-attached everything to drive the whole house (Pre-Amps, Distro-Amp, Rotor), the wife and kids are pleased with the whole setup.

What am I corrupting by just adding RG-59 length and not attaching Twin-Lead ??? I see all the 1/4 wavelength stuff, but this all seems rather inexact, and you have to "spread" out the wires anyway to reach the posts. Now that I have something better, I just have to wonder what better still could possibly be ?

I'm looking forward to the "Current-Coax-Loop" balun from MLORD !!!

I think that direct attachment, without any lead-in, is the best. And so do the thousands of ham radio operators who routine build these for their own antennas! Keep the unshielded ends as short as possible, ideally only a few millimetres long.

I've been quite busy with work and sunshine (two conflicting soaker-uppers of time) of late, and things are still heating up.

So nothing new from me on the balun front -- I'm just watching you folks do your stuff, and looking for any fresh ideas to steal!

I did design a UHF-65 yagi on Sunday -- 1m long with around 14dBi gain and a perfect 75-ohm match at the feed point. When I build it, there's going to be a balun requirement there. Either a 1:1 current balun by itself, or perhaps I'll replace the driver with a folded dipole again (for 300 ohm impedance) and then use a 4:1 coax-loop plus a 1:1 1/4W shield (current) balun.

Or maybe leave the yagi as 75-ohm, and try I0QM's 3/4W+1/4W T-loop style balun (http://www.i1wqrlinkradio.com/antype/ch11/chiave1828.htm), which is a 1:1 balun for a 75-ohm feedpoint. Substituting 75-ohm RG6/RG59 for his original 50-ohm coax, of course.

Cheers

.. you have to "spread" out the wires anyway to reach the posts.
Ahh.. all of the sources I have consulted on that, suggest that the only way to do it is to spread them at right-angles (90 degrees) out from the straight twinlead run. That way the "extensions" are more part of the antenna, than the feedline. And the feedline stays at 300ohms like it's supposed to be.

Not perfect, because in an ideal world those "extensions" should be made of (non-existant) tapered wire, as thick as the antenna hardware on one side, gradually getting down to the twinlead wire diameter at the other side where they meet the twinlead.

Cheers

I think that direct attachment, without any lead-in, is the best. And so do the thousands of ham radio operators who routine build these for their own antennas! Keep the unshielded ends as short as possible, ideally only a few millimetres long.

How do you that when the space between the two screws on my yagi is at least 5cm ?

Also, my third try of my balun was not good since I broke the great one:(

0% signal.

Back to zero, I will do a new one.
Thanks,

Quote:
I think that direct attachment, without any lead-in, is the best. And so do the thousands of ham radio operators who routine build these for their own antennas! Keep the unshielded ends as short as possible, ideally only a few millimetres long.

How do you that when the space between the two screws on my yagi is at least 5cm ?


Also how is the attachment best accomplished in between the phase lines on the bow-tie style, 1 1/4" separation, standoff 5" from reflector...

thanks

Yeah, this whole RF world is Black Magic. You take a hunk of coax and short out your antenna, and that's OK because it's some fraction of a wavelength. But I have great fear that one of the few hairs I have left will fall out of my head and without even touching anything will cause utter chaos !!!

How do you that when the space between the two screws on my yagi is at least 5cm ?
See post #364 (http://www.digitalhome.ca/forum/showpost.php?p=958092&postcount=364) above for the detailed explanation.

But again, whatever works is most important!

I'm trying to make one of these DIY baluns, but having difficulties soldering the braids, and the RG6 conductor...

I tried to follow the tips in the solder thread but to no avail.

I twisted the braids, and heated them up with a torch, then I tried applying rosin core solder (lead free - Tin/copper/silver alloy, .032"), and instantly the solder melted and beaded but seemed to fall off almost as fast. Cannot get it to go around and stick. Also the copper conductor, braids, turned brownish, needless to say the twist did not hold.

Am I overheating, using the wrong solder?

Wrong cable? Is it *really* a copper braid? I haven't got any RG6 here with a copper braid, so I use RG59 (w/copper) instead for the baluns.

Oh, and find some *real* solder, the kind with lead in it.
MUCH MUCH MUCH easier to work with!

Balm,

Lead-free solder melts between 350-400C while leaded solder melts between 250-300C. This is why mlord says it is easier to work with. However, lead is toxic. I don't use it.

I see that you use a torch which likely oxidizes the copper braid. Copper oxide is a bad conductor, so that's not very good. Do you have access to a 45W iron (or higher wattage)? The iron won't oxidize your braid and will distribute the heat more evenly in the material to solder. Addison has a 60W iron for $15.99.

You can use zip-ties to hold your twist in place, so as to not place strain on your solder. You can see the picture in my post (http://www.digitalhome.ca/forum/showpost.php?p=954150&postcount=319).

STL

Thanks Mlord / STL,

Im now using the 50/50 rosin core (leaded). And yes it is much easier to solder with, but still had to add flux. It seems with the torch, you are correct, it literally burns the braid, hence browning color, and you must work very fast otherwise you have to keep heating.

I had considered the electric irons, but was told that to heat up the wire conductor portion its better with a 200 watt iron.

Anyway I finished 2 baluns, the solder held, but I cant trust I didnt damage the copper.

Too bad I was at Addison today for other supplies, in the west island the strongest ive seen is 40 watt...

My main soldering station is a 50watt Weller. I solder everything except plumbing fixtures with it. :)

And more flux just about never hurts! I apply extra flux to everything.

Cheers

will this be the silver bullet :o

http://s638.photobucket.com/albums/uu110/stanicet/?action=view&current=IMG_0307.jpg

That looks very much like the one I built. Over the weekend, I'll try to get a picture, but mine has the braid "split" into top and bottom, and I made "hooks" at the end of the 2 wires, and all 3 cables touch (to keep the spacing short). Also, no solder and no tape.

Dunno. The ideal length for that piece of twinlead, measured *after* hooking it up at each end, is 1/4 wavelength (half the length of your coax loop). Or any nice even half multiple of that (I think).
I've been meaning to come back and correct myself here for a while now, so here goes:

The important number is, any odd multiple of 1/4 wavelength. So 1/4W, or 3/4W, or 5/4W, etc..

Cheers

I left .75" of bare conductor past the end of the cable on my DIY balun loops - I split the gap distance (1.5") between the 2 phase lines on the bow-tie.

Is this too much bare conductor, I will make sure though to come into the feed point perpendicular...

Dunno without a photograph. But it sounds okay.

Cheers

In getting a brand new 91XG antenna, should I replace the balun to get better performance? Which balun is recommended and is it easy to do?

In getting a brand new 91XG antenna, should I replace the balun to get better performance? Which balun is recommended and is it easyPlease see my post # 362. Replacing the factory with the coax-loop balun seemed to work better for me. I have to point out that I live in FLORIDA, and the weather affects things immensely, as well as often. It's quite possible that there were coincidences at hand when I made my evaluation.

When you take apart the factory balun, be sure that you remove the nut that holds the F-connector in place (as well ass the rubber seals around the dipole). It's quite easy. I did NOT use twin-lead - I just made my balun so that the center-conductors reached the posts (trying to make a perpendicular connection).

My post #313 had pictures:

http://img268.imageshack.us/img268/5223/img0532u.jpg
http://img88.imageshack.us/img88/9530/img0533v.jpg
http://img249.imageshack.us/img249/7820/img0535.jpg

I took more pictures, but I'll have to get them at lunch.

Sorry, this is a little off-subject, but concerning 91XG:

There is indication that the 43XG is just a 91XG without the third beam. That's not quite true. The 91XG has a PC board balun, with the 43XG having a "traditional" balun. The lengths and number of directors are different too.
You see, I originally bought the 43XG to make sure it would fit in my attic. Then I wanted to "stack" or "gang", so I wanted another, but opted for the 91XG because it was only a little more and had a better mast mount. Things are working out well for me though.