Baluns (Brands, Designs, Losses, DIY Loops, etc.) - Page 50 - Canadian TV, Computing and Home Theatre Forums

otadtvman · 2012-03-26, 10:23 PM

Wendell R. Breland has another suggestion for an outdoor balun:

Quote:

Originally Posted by Wendell R. Breland

Not for me. The Winegard TV-2900 balun uses twinlead for the 300Ω side so yo do not need to be concerned with wire spacing. It is also weather proof. MCM has a very similar product, part number is 33-040.

In low signal level conditions I prefer to use a λ/2 Coaxial Balun (that I constructed).

Has anyone recently tested the Winegard TV-2900 or MCM part #33-040?
Has anyone constructed their own Breland outdoor balun?
Using this design, how many inches (or mm) of Belden 1694A would be necessary for channels 7 to 51 such as with a Mclapp M4?

Thanks

ProjectSHO89 · 2012-03-27, 08:27 AM

See post immediately above...

roger1818 · 2012-03-28, 02:30 PM

I am looking at building a coax balun for channel 6 and found some interesting resources. First of all I found a 4:1 coax balun calculator that allows you to enter the desired frequency (85MHz in my case) and the Velocity Factor of the coax (assuming 0.66) and it will calculate the Half Lambda Coax Loop Length (45.8"). I will recalculate when I know the Velocity Factor of the coax I will be using.

4:1 coax balun design

Secondly I found a picture of a nice looking build technique. They don't look weather proof, but would be fine for my attic install (see the two on the right):

otadtvman · 2012-03-30, 11:39 AM

ProjectSHO89,

Thanks for alerting me to ADTech's test results.

otadtvman · 2012-03-30, 11:53 AM

roger1818,

Thanks for the balun caculator link & build technique photo - looks good. Was there also a close-up of the soldered connections? Weather proof: One could use a RS ABS enclosure as suggested by Wendell.

Is this balun technique appropriate for a channel 7-51 Mclapp M4?

ADTech · 2012-03-30, 01:28 PM

Half wave (coax) baluns have a very narrow frequency band in which they are efficient. They are best reserved for single-channel antennas.

Broadband ferrite core baluns such as I tested are the best compromise (generally) available for a wide range of frequencies in a single device.

stampeder · 2012-03-30, 02:19 PM

ADTech is precisely correct - use the right tool for the right job.

Also just a point to readers: a separate new baluns thread that was only a day or two old was merged into this existing one. If you've just joined in here in this thread please be aware that there is already a huge gold mine of info on baluns in this thread, so it is well worth the time to read through it for the best answers to your questions.

nezdepain · 2012-03-30, 06:19 PM

My coax baluns (cut for 521 MHz) work well on the entire UHF band for local signals and for more distant channels. They also perform well in the VHF band for local channels. I did some testing on a 50 miles distant VHF channel with fair results. The difference I could measure with my tuner, compared to a channel master balun, was maybe around 10% for that VHF channel. I would have to reconfirm this with more testings, but in any case, I don't consider their useful bandwidth range limited to a few channels.

roger1818 · 2012-03-30, 09:50 PM

Quote:

Originally Posted by otadtvman

Was there also a close-up of the soldered connections?

No, those are pictures for baluns you can buy and they aren't trying to show how to make them.

Quote:

Is this balun technique appropriate for a channel 7-51 Mclapp M4?

As ADTech said, they are best for specific channels. You might be able to get away with it in UHF only, where the wavelengths aren't as far apart (on a logarithmic scale) if your weak channels are near the centre of the band (or don't care about channels at the far end of the band). Similarly, you might be able to make one for a weak central VHF-HI station that will work with other VHF-HI stations, but it will likely only work for one or two VHF-LO channels.

ppauper · 2012-03-30, 10:52 PM

Quote:

Originally Posted by roger1818

No, those are pictures for baluns you can buy and they aren't trying to show how to make them.

I emailed that particular company a few years back, and they no longer sell those baluns

otadtvman · 2012-03-31, 12:36 PM

Quote:

Originally Posted by ADTech

Broadband ferrite core baluns such as I tested are the best compromise (generally) available for a wide range of frequencies in a single device.

Of all the broadband ferrite core baluns you tested, which one would be most appropriate for a ch 7-51 Mclapp M4? Thank you.

holl_ands · 2012-04-02, 11:19 PM

Quote:

Originally Posted by ADTech

Half wave (coax) baluns have a very narrow frequency band in which they are efficient. They are best reserved for single-channel antennas.

Broadband ferrite core baluns such as I tested are the best compromise (generally) available for a wide range of frequencies in a single device.

K6STI calculated loss of under 0.12 dB in a half-wave Coax Balun across FM Band:
http://ham-radio.com/k6sti/balun.htm

There are equivalent calculations for two 4:1 configurations in UHF Band in this thread:
Under 0.5 & 1.0 dB: http://www.digitalhome.ca/forum/showthread.php?p=874362

pfm1 · 2012-04-04, 04:17 PM

Typical commercial tv baluns are wound on some sort of a core material, most likely ferrite. But what I am trying to figure out is why not just a simple air core ? For a wideband uhf coil application do you think permeability is much to sweat about ? Because permeability is all about being able to wind less turns to get more inductance and I guess you don’t really need that much inductance at uhf. Plus using ferrite is a matter of matching the material with the frequencies it is used for otherwise core losses (u’ and u’’) at those frequencies could actually defeat the purpose of the core.

For the primary a few (10?12?) tightly wound turns in half to one c.m. coil diameter should be good I guess. The secondary can be 3 turns interleaved with the primary winding across its length.
Has anyone ever tried an air core balun for a 300:75 transformer like that ? Would this work ? If not can anyone please explain me why ?
Thanks.

Xauto · 2012-04-04, 04:30 PM

pfm1: Yes it will work. If you read #735 of this thread. That is what I did, but the turns need to be 2:1 not 4:1.

Note this is not a true balun. It is more like a 1/4 wave length matching section. Two 1/4 wave length sections can be combined to make
a balanced transforming unit.

pfm1 · 2012-04-04, 05:19 PM

yes and I was referring more to a "transformer", as in inductive coupling with no core involved.

btw, can you tell anything about the bandwidth of that balun ? how wide or narrow might it be ?

2012-03-28, 02:30 PM	#738
roger1818 Veteran Join Date: Apr 2006 Location: Ottawa (Stittsville), ON, OTA (Radio Shack Omnidirectional Antenna and 5Y6S in Attic), MythTV HTPC Posts: 5,605	I am looking at building a coax balun for channel 6 and found some interesting resources. First of all I found a 4:1 coax balun calculator that allows you to enter the desired frequency (85MHz in my case) and the Velocity Factor of the coax (assuming 0.66) and it will calculate the Half Lambda Coax Loop Length (45.8"). I will recalculate when I know the Velocity Factor of the coax I will be using. 4:1 coax balun design Secondly I found a picture of a nice looking build technique. They don't look weather proof, but would be fine for my attic install (see the two on the right): __________________ Link to my TVFool results is in my profile Homepage URL. I suggest others do the same.

2012-03-30, 02:19 PM	#742
stampeder OTA Forum Moderator Join Date: Jan 2005 Location: North Delta, BC (96Av x 116St) Posts: 23,338	ADTech is precisely correct - use the right tool for the right job. Also just a point to readers: a separate new baluns thread that was only a day or two old was merged into this existing one. If you've just joined in here in this thread please be aware that there is already a huge gold mine of info on baluns in this thread, so it is well worth the time to read through it for the best answers to your questions. __________________ New To OTA? OTA FAQ & Knowledge Base OTA Antenna Chart 8.2

2012-04-04, 04:17 PM	#748
pfm1 Rookie Join Date: Apr 2012 Posts: 2	Simple air core balun ok as 4:1 TV antenna transformer ? Typical commercial tv baluns are wound on some sort of a core material, most likely ferrite. But what I am trying to figure out is why not just a simple air core ? For a wideband uhf coil application do you think permeability is much to sweat about ? Because permeability is all about being able to wind less turns to get more inductance and I guess you don’t really need that much inductance at uhf. Plus using ferrite is a matter of matching the material with the frequencies it is used for otherwise core losses (u’ and u’’) at those frequencies could actually defeat the purpose of the core. For the primary a few (10?12?) tightly wound turns in half to one c.m. coil diameter should be good I guess. The secondary can be 3 turns interleaved with the primary winding across its length. Has anyone ever tried an air core balun for a 300:75 transformer like that ? Would this work ? If not can anyone please explain me why ? Thanks. Last edited by stampeder; 2012-04-05 at 02:15 AM. Reason: Yep, this is the correct thread :)

2012-04-04, 04:30 PM	#749
Xauto Join Date: Sep 2008 Posts: 487	pfm1: Yes it will work. If you read #735 of this thread. That is what I did, but the turns need to be 2:1 not 4:1. Note this is not a true balun. It is more like a 1/4 wave length matching section. Two 1/4 wave length sections can be combined to make a balanced transforming unit. Last edited by Xauto; 2012-04-04 at 05:03 PM. Reason: Add info. about 1/4 wave

2012-04-04, 05:19 PM	#750
pfm1 Rookie Join Date: Apr 2012 Posts: 2	yes and I was referring more to a "transformer", as in inductive coupling with no core involved. btw, can you tell anything about the bandwidth of that balun ? how wide or narrow might it be ? Last edited by pfm1; 2012-04-04 at 05:35 PM.

2012-03-27, 08:27 AM	#737
ProjectSHO89 Join Date: Nov 2009 Posts: 296	See post immediately above...

2012-03-30, 11:39 AM	#739
otadtvman Join Date: May 2010 Posts: 100	ProjectSHO89, Thanks for alerting me to ADTech's test results.

2012-03-30, 11:53 AM	#740
otadtvman Join Date: May 2010 Posts: 100	roger1818, Thanks for the balun caculator link & build technique photo - looks good. Was there also a close-up of the soldered connections? Weather proof: One could use a RS ABS enclosure as suggested by Wendell. Is this balun technique appropriate for a channel 7-51 Mclapp M4?

2012-03-30, 01:28 PM	#741
ADTech Join Date: Oct 2010 Location: Antennas Direct Tech Support - St Louis Posts: 211	Half wave (coax) baluns have a very narrow frequency band in which they are efficient. They are best reserved for single-channel antennas. Broadband ferrite core baluns such as I tested are the best compromise (generally) available for a wide range of frequencies in a single device.

2012-03-30, 06:19 PM	#743
nezdepain Join Date: Nov 2010 Location: Québec, QC Posts: 313	My coax baluns (cut for 521 MHz) work well on the entire UHF band for local signals and for more distant channels. They also perform well in the VHF band for local channels. I did some testing on a 50 miles distant VHF channel with fair results. The difference I could measure with my tuner, compared to a channel master balun, was maybe around 10% for that VHF channel. I would have to reconfirm this with more testings, but in any case, I don't consider their useful bandwidth range limited to a few channels.

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