Canadian TV, Computing and Home Theatre Forums banner

Baluns (Brands, Designs, Losses, DIY Loops, etc.)

446K views 856 replies 132 participants last post by  Sev 
#1 ·
One thing I just realized about the value of these antennas is the fact that there is no BALUN signal loss. According to some articles that I read they state that you can lose more than half of the signal with a bad balun!

See - http://www.kyes.com/antenna/balun.html

So my hypothesis now is that it may be better to get a preamp with 300 ohm inputs rather than a 75 ohm input because this will eliminate the need for a signal stealing balun.

For this reason my SS-2000 works better than anticipated.

I have been wondering how to best tweak antenna setups to minmize all losses and maximize signal. My assumption is that an antenna is being used in conjuntion with a preamp for GTA viewers trying to get Buffalo stations.

I guess that you need the balun if you are not using a preamp.

I was wondering why my Winegard SS-2000 was working almost as well as a CM4221 with AP4700 preamp. When I looked inside the Wingard SS-2000 - see:
http://www.digitalhomecanada.com/forum/showpost.php?p=372939&postcount=87

I noticed that there was a preamp but no balun. The preamp was connected to the 300 ohm leads!

After doing some reading I learned something that appears to be common sense but I have not seen it discussed here.

If you have an antenna that has 300 ohm output then use a 300 ohm input preamp.

This means that if you have a CM 4221 you should not be using a CM 7777. With a CM 4221 or 4228 you should be using a Channel Master CM 0264 or Channel Master CM 064 preamp!

Match the antenna output and preamp input and eliminate the balun!
 
See less See more
#107 ·
I forgot to thank you for all the work you put in tracing out that circuit. It's interesting and nice to have.

I was just at Fry's a little while ago. They had a cheaper CM preamp ($30) I hadn't seen before. It has a gain of 13 dB, if I recall correctly, and a noise figure of 3.5 dB. The single 300-ohm input is via a thick, heavy-duty, captive balanced line a couple feet long that terminates in large spade lugs. The injector is a small satellite type with a cable shrink-wrapped at the power socket. The cable runs to a wall wart.

The more familiar CM preamp (I forget the number now but it's been discussed here) was $60.

Brian
 
#121 ·
balm said:
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.
 
#136 ·
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 ?
 
#124 ·
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
 
#135 ·
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
 
#126 ·
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.
 
#128 ·
Philips Baluns at Wal-Mart

holl_ands said:
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?



 
#129 ·
^ 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).
 
#131 ·
^ 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.
 
#133 ·
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".
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top