I completed my DYI b4b antenna, and recive most HD channels, however I'm looking to squeeze more gain, should I attempt the DYI 1/2 wavelength balun, or just buy a balun.
Both. Making your own balun is dead simple, and cheap. Definitely worth it for the fun factor alone, and it ought to outperform just about any store-bought balun, for a single band.

But if you want it to work well across VHF-LO + VHF-HI + UHF, then buy one.

mlord:

for channels 10 to 42...

In another forum, Johnrmckee measured Philips Outdoor 4:1 Balun using
Agilent Network Analyzer and found only 0.6 dB (+/- 0.1 dB) Loss from
Ch2 thru Ch51. I hope he does some more.....

That's quite a bit lower in UHF band than what I measured (Dec 2004).

I tried building a balun out of coaxil for channel 33 (589) I calculated a length of 16.9 cm and connected it to my indoor reflectorless 4 bay.

It seemed work a bit worse then my current balun (philips from walmart) but there were a few issues that could of effected the result. are these big issues ?

1. 1 side of the u loop was not grounded ( i just taped the grounding wire down to the sheilding)

2. I left my other balun on while testing so I could just switch between the 2.

3. My home made one ran infront of the antenna while the phillips ran behind.

should I give my home made one another shot or stick with the philips.


also since this length is so short for uhf would it be better to make a "full length wave" balun or would that not work?

Thanks,

Aaron

Yeah, all three of those points are bad for the results.

Try again with a proper setup: only one balun connected, BEHIND the antenna, running vertically (not horizontally) behind the centerline of the antenna, proper grounding of the shield.

Cheers

In another forum, Johnrmckee measured Philips Outdoor 4:1 Balun using
Agilent Network Analyzer and found only 0.6 dB (+/- 0.1 dB) Loss from
Ch2 thru Ch51. I hope he does some more.....

That's quite a bit lower in UHF band than what I measured (Dec 2004).
Yeah, Im using one of those now, and it works well. But it is made in China so Im not surprised that one unit will vary greatly from another unit, maybe even from the same production line. Both you and Johnrmckee should test hundreds of them, heh.

and what about makeing a full wave lentgh balun?

i dont understand all the math behind it, just want to know if that would be more desirable then a half wave length balun.

In another forum, Johnrmckee measured Philips Outdoor 4:1 Balun using
Agilent Network Analyzer and found only 0.6 dB (+/- 0.1 dB) Loss from
Ch2 thru Ch51. I hope he does some more.....

That's quite a bit lower in UHF band than what I measured (Dec 2004).Just yesterday I picked up a package that contains both a traditional barrel balun (twinlead at 300ohm end into a barrel with female F-series coax end at 75 ohm) as well as a 90 degree balun with connection screws for twinlead at the 300ohm end and a press-on male F-series coax end at 75ohm, which unfortunately seems to have a rather flimsy centre conductor. I wonder if they measure the same loss?

http://www.user.dccnet.com/jonleblanc/images/philips-balun2.jpg

http://www.user.dccnet.com/jonleblanc/images/philips-balun1.jpg

^ Those will "work", but are extremely low quality. They are cheaper-made "clones" of already cheap transformer designs. :) Open up the non-cylindrical one to see what I mean. Also, I got a couple of packages of those (before getting $$ back) in which the cylindrical ones were defective, so measure them first (there should be some conductivity between the input and output).

cfraser that was exactly my intent when I bought them - I already have some CM baluns so I'm just going to open these ones up and take some photos. :)

^ Oh good! I'm dying to know what the insides of the cylindrical jobbie look like. I have to guess the core/wire is as small as in the other unit. The "original" Japanese versions of transformers that looked just like these were actually quite well-constructed inside, and the metal didn't have that greeny-gold color.

Here are pictures of a few ‘plug’ type baluns like stampeder purchased:
http://i726.photobucket.com/albums/ww264/chico3/IMG_7999.jpg


I wonder how this balun compares to the barrel type balun for loss? It appears to be a low loss design. It is from one of my clone antennas:
http://i726.photobucket.com/albums/ww264/chico3/IMG_8001.jpg
They are similar to the printed circuit board balun discussed here:http://www.digitalhome.ca/forum/showthread.php?p=875405&highlight=balun#post875405

Just yesterday I picked up a package that contains both a traditional barrel balun (twinlead at 300ohm end into a barrel with female F-series coax end at 75 ohm) as well as a 90 degree balun with connection screws for twinlead at the 300ohm end and a press-on male F-series coax end at 75ohm, which unfortunately seems to have a rather flimsy centre conductor.
Yep, the exact same package is sold in my local Wal-Mart for $3.99. As noted, its for indoor use only.


The "original" Japanese versions of transformers that looked just like these were actually quite well-constructed inside, and the metal didn't have that greeny-gold color.
Yeah, those are the ones to get. The more I spread the word about them, the more people who have tried them agree with me. They are very good, even though you have to weather proof them yourself. Unfortunately, the only good source is the local flea market. At least the price is right, as long as you make sure you get one that doesnt turn, heh. Look for "Made in Japan".

Can anyone answer the question i asked?

thanks

"
and what about makeing a full wave lentgh balun?

i dont understand all the math behind it, just want to know if that would be more desirable then a half wave length balun.

"

Yeah, all three of those points are bad for the results.

Try again with a proper setup: only one balun connected, BEHIND the antenna, running vertically (not horizontally) behind the centerline of the antenna, proper grounding of the shield.

Cheers
mlord:


does this apply the same way for the store bought baluns - does this mean place the balun (store bought) behind the reflector and antenna center structure, or is in the antenna structure , behind the phase lines OK (in the plastic ABS piping of my DYI antenna)


Also, when you say running vertically, I placed my store bought balun horizontally, (sideways, left to right say when looking from the front of the B4B) inside a cross piece of piping, actually inside the stand-offs for the phase lines, is this OK or should I drop it vertically behind the mast

In another forum, Johnrmckee measured Philips Outdoor 4:1 Balun using
Agilent Network Analyzer and found only 0.6 dB (+/- 0.1 dB) Loss from
Ch2 thru Ch51. I hope he does some more.....

That's quite a bit lower in UHF band than what I measured (Dec 2004).
the philips indoor transformer (the "cylinder", not the push-on) I had a good experience with:
when I used to have a CM4221, (the 4 bay bow-tie), the philips indoor transformer outperformer the CM balun the antenna came with (not a rigorous scientific experiment, and I didn't measure losses, but the reception was noticeably better on weak stations on my TV).
However, when I upgraded to a CM4228 (the 8 bay bow-tie), the converse was true and the CM balun the CM4228 came with outperformed that same philips indoor transformer.

Looking back, perhaps this is connected to the impedance of the antennas:
a CM4228 being two CM4221s connected togther,
so that the philips performed better at the impedance of the 4221 but the CM balun performed better at the impedance of the CM4228 ?

The "original" Japanese versions of transformers that looked just like these were actually quite well-constructed inside, and the metal didn't have that greeny-gold color.
Yeah, those are the ones to get. The more I spread the word about them, the more people who have tried them agree with me. They are very good, even though you have to weather proof them yourself. Unfortunately, the only good source is the local flea market. At least the price is right, as long as you make sure you get one that doesnt turn, heh. Look for "Made in Japan".


I have two quick questions:

Does someone have a picture of those Japanese balums?

Is it possible to make a Balum just for CH 13 VHF?

Thanks,

Intravino

Does someone have a picture of those Japanese balums?
When I take mine down, Ill try to take a picture.

Is it possible to make a Balum just for CH 13 VHF?

Yes, look back thru this thread for links.

Here are pictures of a few ‘plug’ type baluns like stampeder purchased:

Heh, three similar baluns, three different internal construction techniques.

^ The Japanese ones I have opened looked most like the two on the left: largish transformer cores, largish gauge wire. The "others" had tiny cores (smaller than the one on the right) with hair-thin wire...no wonder they are so fragile and lossy.

Re the CM422xHD antennas' baluns: they are built in now (and non-replaceable apparently), JIC you haven't seen one and I don't think the CM website pics made that clear *depending how you entered their site and what pic versions pop up*.

That PCB balun doesn't look too bad IMO. At least it's made on fiberglas board, which helps, unlike some others I've seen (but work OK indoors).