Baluns (Brands, Designs, Losses, DIY Loops, etc.) - Page 4 - Canadian TV, Computing and Home Theatre Forums

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post #46 of 811 (permalink) Old 2009-01-29, 03:02 PM
 
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For receiving, current and voltage baluns are pretty much interchangable. For large mismatches or Rf fields the current balun is preferred.
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post #47 of 811 (permalink) Old 2009-01-30, 11:42 AM
 
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Quote:
Originally Posted by stampeder View Post
Phillip Lee has cooked up a very low loss 300:75 balun (no idea of what the price point is):

http://www.tinlee.com/MATV_headend.php (scroll down to the MT-37X)
  • Thru loss .75 dB VHF, 1.25 dB UHF max
  • Return loss > 16 dB
How does its return loss compare to typical baluns?
has anyone actually used one of these, and if so can they verify that it's better (in the sense of lower losses) than the channel master baluns ?
it would be for use with a CM4228
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post #48 of 811 (permalink) Old 2009-01-30, 11:45 AM
 
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Originally Posted by mlord View Post
If you're interested primarily in UHF, then a very simple coax-loop 4:1 balun costs only a buck or two to construct, and will show about 0.5dB insertion loss across much of the the UHF television band.

That kind of proposition is hard to beat!

Speaking of which.. can any of you hams enlighten me further on the gamma match feed for a dipole? To me, it looks very much like a 1/2 wavelength loop balun in disguise.

Cheers
ah, I once tried to make one of these, and couldn't get it to work properly (in the sense that it was very lossy). Someone I know tried as well with similar experiences

Anyone make these commercially ?
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post #49 of 811 (permalink) Old 2009-01-30, 01:59 PM
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Quote:
I once tried to make one of these, and couldn't get it to work properly
Weird. These things are extremely simple to make, and very tolerant of small measurement errors. I wonder if you just wired it wrong or something?
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post #50 of 811 (permalink) Old 2009-01-31, 11:29 AM
 
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Originally Posted by mlord View Post
Weird. These things are extremely simple to make, and very tolerant of small measurement errors. I wonder if you just wired it wrong or something?
it worked but was lossy, meaning reception was worse than with a CM balun.
I used good quality RG6 and hooked things up exactly as per the instructions.
There's evidently some trick I'm missing
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post #51 of 811 (permalink) Old 2009-01-31, 01:30 PM
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Hybrid Balun design

This design is for a "better antenna-tuner balun" that "promises advantages over both voltage and current baluns" (their quotes):

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=12661 (link goes to a 6 page technical document in PDF format)

Anything in there for TV Antenna fans?

Last edited by stampeder; 2009-01-31 at 01:58 PM.
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post #52 of 811 (permalink) Old 2009-01-31, 01:52 PM
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Quote:
link goes to a 37 page technical document in PDF format
?? I only got 6 pages ? Am I missing some ?

My builds/plans (not the latest models) are located here.
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post #53 of 811 (permalink) Old 2009-01-31, 01:59 PM
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Sorry, I just changed it to say "6 pages" after I malfunctioned there...
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post #54 of 811 (permalink) Old 2009-02-01, 02:20 PM
 
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Originally Posted by holl_ands View Post
I reported on a handful of Balun loss "test" results here:
http://www.avsforum.com/avs-vb/showt...php?p=13581150
[Sometimes you have to use what you have available....]
To add to holl_ands's post, I emailed him about it at another forum in 2007, and when I asked him where to buy the RMS baluns that did so well in his tests, he was nice enough to tell me that "The RMS baluns date back to Warner Cable in the early 80's"
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post #55 of 811 (permalink) Old 2009-02-01, 02:55 PM
 
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Originally Posted by ppauper View Post
has anyone actually used one of these, and if so can they verify that it's better (in the sense of lower losses) than the channel master baluns ?
it would be for use with a CM4228
to partially answer my own question, I came across Tin Lee's web page a couple of years ago and got a quote (so the prices are out of date).
I was looking for a balun for a CM4228, which gets high vhf as well as uhf.
Maybe I've misunderstood their quote, but they offered to sell me a "MT-37X 0089",
and at the end of the quote, it seems that this is simply a channel master balun ???

--- their emailed quote from 2007----
low-loss 300 -> 75 Ohm matching transformer for TV
(VHF channels 6+ and all UHF channels, from the same antenna)
1.5dB to 2dB loss from 50MHz to 800MHz (VHF/UHF)
Channel Master 75/300 ohm Balun with weatherboot
Price / ea $8.00 plus $20.00 shipping and handling (plus taxes)
-----
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post #56 of 811 (permalink) Old 2009-02-01, 03:16 PM
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Wow, I didn't know that Tin Lee resold anything... maybe its a misunderstanding because the loss they quote is not the loss posted on the web site for their own balun model.
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post #57 of 811 (permalink) Old 2009-02-01, 03:51 PM
 
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Originally Posted by stampeder View Post
Wow, I didn't know that Tin Lee resold anything... maybe its a misunderstanding because the loss they quote is not the loss posted on the web site for their own balun model.
maybe it's the fact that I wanted high VHF as well as UHF that caused the problem.
The pdf quote definitely has their part number on the top and then the channel master specs on the bottom
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post #58 of 811 (permalink) Old 2009-02-02, 03:50 PM
 
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I recently enquire with Tinlee about their channel specific low-loss balun, in my case it was for VHF 13. The reply was it is better to use a generic balun because it has a lower loss than a channel-specific balun.

However they mentionned that the advantage of a channel-specific balun is less interference from other frequencies

the price quoted was $75CA, which is quite more costly than a generic balun which is usually $1 to $5
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post #59 of 811 (permalink) Old 2009-02-03, 08:26 AM
 
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I modeled a 4:1 balun using a halfwave of 75-ohm coax with the load centertapped and grounded. The load represents, for example, a folded dipole with its center electrically connected to the antenna boom and coax shield. Yagi antennas may use this configuration.



Mismatch loss at the band edges is twice as great as when the load is floating. I want to check the details of how the circuit analysis program models the transmission line, but if this result holds it provides a powerful incentive to insulate a driven element.





For reference, this is the floating-load model. Both models use a lossless transmission line. At UHF-TV frequencies the few inches of coax required for a halfwave balun should add negligible loss.

Brian
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post #60 of 811 (permalink) Old 2009-02-03, 11:50 AM
 
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the one that really bummed me out was this:
http://www.dlsus.com/catalog/product...roducts_id=458
>> Specifications
>> -Bandwidth: 5-900 MHz
>> -Insertion Loss: 0.7 dB
>> -Return Loss: 16 dB
>> -Impedance: Input 300 Ohm, Output 75 Ohm
>> -Balance Ratio: 30 dB

I emailed to get confirmation (again 2007) and couldn't get a straight answer
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