Can we please discuss BALUNs 300 Ohm to 75 Ohm in an easy to understand manner? - AVS Forum
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post #1 of 39 Old 11-11-2013, 12:10 PM - Thread Starter
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The Balun is a transformer used to balance an unbalanced transmission line, or to unbalance a balanced line.

With all the reading and research I have done on the subject of BALUNs I turn out to be more confused than I was before I started.

The discussions of integers of 2:1, 1:1, 4:2, 9:1 blah, blah, blah. Then we're stuck with some silly electrical engineer's algebra jibberish, that no one can understand, except for another electrical engineer.

BALUNs can be home made by configuring two pieces of enameled wire wrapped around a ferrite core, to create a transformer with a primary and a secondary winding. They can also be purchased already assembled in electronics stores.

Here is where discussions become complicated about store bought BALUNS. They never list on the BALUN or its packaging what the ratio is. Is it 2:1 or 1:1? No one can tell as far as I know, without cutting open the BALUN's aluminum casing to count the windings wrapped around the ferrite core.

Using an OHM meter to test continuity on the BALUN's 300 Ohm side to 75 Ohm side reveals different results on different BALUNs. For instance, in one test, the BALUN will show a ohm meter reading if the test probes are attached to the two 300 Ohm pigtails. However, no reading will result when testing the 75 Ohm side of the BALUN to the 300 Ohm side, nor will the shield side and the hot side of the 75 Ohm side of the BALUN show a test result.

Now on the other hand, another brand BALUN will test differently. Using an Ohm meter, a reading can be observed when applying the probes between the 300 Ohm pigtails and the BALUN 75 Ohm hot side. Why is this?

I have tested numerous BALUNs on home made television antennas and have found astounding results. No two BALUNs are alike!

One, can result very poor performance, while another can result in a 70% improvement!

The thing that baffles me the most is these things we call BALUNs are labled with nothing more than words such as TV matching transformer, or 300 to 75 matching transformer. Nowhere does these devices tell us what the ratio is on the transformer hidden inside the aluminum casing.

I have seen $1.00 USD priced BALUNs that perform better than a $10.00 one, or even a $20.00 for that matter!

So, the big question of the day here is how does one know a good BALUN from a poor one? How does one know what is inside the BALUNs aluminum can for a transformer?

There is nothing more aggravating than constructing an outdoor television antenna system that required placing in a dangerous area of a roof, only to find out the BALUN is a worthless piece of junk and has to be replaced! That's a lot of work for nothing.

So, (without all the engineer's algebra and numbers that mean nothing to the casual home television watcher that simply wants to set up a decent antenna system without having to take an electronic engineer's course in math) how does one know exactly, how to choose a decent BALUN that works best with a 300 Ohm antenna system? How can one tell a 2:1 from a 1:1 and realistically, what is best for home television reception? We're talking television here, not HAM radio! Now often, someone always has to bring up the ARRL HAM radio electronics and antenna hand books up. (Yeah, I have those) OMG, now we have to use that silly algebra jibberish I was talking about earlier, because the hand books talk about 2 Meters (a ham band close to VHF TV) one way or another those antennas do not tune well at frequencies at 213.0Mhz or below, nor do those BALUNs work for television frequencies without applying that engineer's algebra or integer jibberish to transform a HAM radio BALUN to work with VHF and UHF television broadcast bands.

I'll climb down off my soapbox for now, but it is my hope that sensible discussions in simple English can be had in this topic that will help those out there, who simply do not understand the hardcore technical stuff.

Bruce.

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post #2 of 39 Old 11-11-2013, 02:59 PM
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It is indeed good to know which type of balun works best for OTA reception. But would prefer to simplify the physics class and just recommend a certain brand name. Is the Channel Master version better than the matching transformer from RadioShack? All I need is a recommendation please. But a worthwhile topic for discussion.
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post #3 of 39 Old 11-11-2013, 06:06 PM
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Quote:
Originally Posted by MrBruce View Post


Using an OHM meter to test continuity on the BALUN's 300 Ohm side to 75 Ohm side reveals different results on different BALUNs. For instance, in one test, the BALUN will show a ohm meter reading if the test probes are attached to the two 300 Ohm pigtails. However, no reading will result when testing the 75 Ohm side of the BALUN to the 300 Ohm side, nor will the shield side and the hot side of the 75 Ohm side of the BALUN show a test result.

Now on the other hand, another brand BALUN will test differently. Using an Ohm meter, a reading can be observed when applying the probes between the 300 Ohm pigtails and the BALUN 75 Ohm hot side. Why is this?
Some Baluns use isolation transformers and some use autoformers. If there is power injected (for amps) then an isolation type must be used or it will short out the power supply.
Quote:
I have tested numerous BALUNs on home made television antennas and have found astounding results. No two BALUNs are alike!

Bruce.
Probably so each company can patent their own item and avoid paying someone else royalties.

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Sturgeons Revelation: "Ninety percent of everything is crud."
My Thoughts: "A reasoned argument must share some basic common points."
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post #4 of 39 Old 11-11-2013, 06:11 PM
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A 300:75 ohm balun is a 4:1 transformation ratio. While other baluns are around for different applications, only this type is in common usage with TV antennas and 75 coaxial cable. A "matching transformer" for this use contains a balun, either wirewound or some kind of PCB. Depends on the designer.

Winegard and ChannelMaster make decent enough matching transformers. The ones from SummitSource labeled as "Eagle Aspen" are pretty good.
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post #5 of 39 Old 11-11-2013, 08:31 PM - Thread Starter
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Ahh! Very good! I have so far, contributors who are speaking common English that I think others can better understand.

I am a little dissatisfied with Radio shack's BALUN transformer which has the gold 75 Ohm coax connector. I switched out a cheaper Techtrionx brand for the gold one from radio shack and my signals have dropped by at least 26% and I was expecting an improvement. Here's the product from Radio Shack I speak of. http://www.radioshack.com/product/index.jsp?productId=2062049

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post #6 of 39 Old 11-12-2013, 07:53 AM
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yes, but ... the "impedance" ratio (300 ohm, 75 ohm) is the square of the turns ratio, so that balun has a 2:1 turns ratio. To sorta understand, assume an ideal transformer, no losses. For ease, I'll use small integers. If I put 2 volts into a transformer and the current is 1 amp, the "impedance is voltage/current or 2 ohms. If the output of this transformer is 1 volt and 2 amps , the impedance is 0.5 ohms. 2/0.5=4. Note that in this simplified example, the power on both sides is 2 watts. An engineer might talk about other things, phase relationships in particular, but I'm taking the simplified approach here,
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post #7 of 39 Old 11-12-2013, 09:54 AM - Thread Starter
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Quote:
Originally Posted by ProjectSHO89 View Post

A 300:75 ohm balun is a 4:1 transformation ratio. While other baluns are around for different applications, only this type is in common usage with TV antennas and 75 coaxial cable. A "matching transformer" for this use contains a balun, either wirewound or some kind of PCB. Depends on the designer.

Winegard and ChannelMaster make decent enough matching transformers. The ones from SummitSource labeled as "Eagle Aspen" are pretty good.

Okay, so what you are saying is that the best BALUN for outdoor television antenna applications should be a 4:1 BALUN? By the way, thanks for your input!
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Originally Posted by gbynum View Post

yes, but ... the "impedance" ratio (300 ohm, 75 ohm) is the square of the turns ratio, so that balun has a 2:1 turns ratio. To sorta understand, assume an ideal transformer, no losses. For ease, I'll use small integers. If I put 2 volts into a transformer and the current is 1 amp, the "impedance is voltage/current or 2 ohms. If the output of this transformer is 1 volt and 2 amps , the impedance is 0.5 ohms. 2/0.5=4. Note that in this simplified example, the power on both sides is 2 watts. An engineer might talk about other things, phase relationships in particular, but I'm taking the simplified approach here,

Okay, so what you are saying is that BALUN I posted a link to at Radio Shack's website is a 2:1 BALUN? Is a 4:1 a better choice for HDTV television antenna applications? If so, how does one know if it is a 2:1 or a 4:1? The description for that BALUN I posted above does not state the BALUN transformer's internal turns ratio. Also I wish to thank you for your input as well.

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post #8 of 39 Old 11-12-2013, 10:30 AM
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If it is called a TV balun there is a 99.99 percent chance it matches 75 to 300 ohms. A two to one turns ratio and four to one impedance ratio. The power loss is the result of imperfections of the real materials and construction quality of the particular balun. It is virtually never specified in a useful way by the manufacturer.
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post #9 of 39 Old 11-12-2013, 11:22 AM
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Quote:
Originally Posted by MrBruce View Post

......Using an OHM meter to test continuity on the BALUN's 300 Ohm side to 75 Ohm side reveals different results on different BALUNs. ....

Note that an ohmmeter measures DC resistance, wheras in this application one is talking about RF frquencies and impedances; the ohmmeter reading is not meaningful.
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post #10 of 39 Old 11-12-2013, 01:21 PM - Thread Starter
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Originally Posted by gring40 View Post

Note that an ohmmeter measures DC resistance, wheras in this application one is talking about RF frquencies and impedances; the ohmmeter reading is not meaningful.

Thanks for your input.

My reason for using the Ohm meter was to see over which of the four parts of a given BALUN were directly connected.

I have seen BALUNs where a reading can be obtained when placing the red and black ohm meter probes on both 300 Ohm pigtails. Obviously, the pigtails are part of one side of the transformer coil to which joins the two pigtails to create a complete circuit. At the same time, no reading can be observed if the meter was connected to the 75 Ohm side and the 300 Ohm at the same time. I do understand DC voltage at 1.5 Volts would not pass over the transformer to create a DC reading. I have however, found some BALUNs that actually allow DC to pass through the transformer. Now to my understanding here, as previously stated in this topic, that DC is allowed to pass to allow a RF power amplifier to be powered up.

In most antenna applications, a BALUN is placed on the television antenna's driven element and then a preamplifier is placed between the BALUN output and the downlead coax leading to the power supply located inside the house near the television set. So why would a BALUN be made as a passive device? Basically a BALUN is a transformer that corrects an impedance mismatch between a 300 Ohm antenna and a 75 Ohm coax cable. So I am a bit lost as to where a passive BALUN is at all useful. Even at the television side of things, the matching transformer would have to be placed between the amplifier's output and the television set's input.

Now, I can understand a coax signal splitter being manufactured as a passive device to allow DC to pass through to the antenna's mast mounted preamplifier, but not a BALUN.

Bruce.

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post #11 of 39 Old 11-12-2013, 11:52 PM
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A bunch of math would reveal that maximum POWER transfer occurs when the load impedance MATCHES the source impedance:
http://en.wikipedia.org/wiki/Impedance_matching

Since most TV Antennas have a Characteristic Impedance of about 300-ohms (in reality their SWR is NOT perfect), they need to operate into a 300-ohm load, which is the twinlead input on a Balun. Since the Coax (and Preamp and TV Tuner) impedance is standardized at 75-ohms, the Balun must TRANSFORM from 300-ohms Impedance to 75-ohm Impedance....which can readily be done with PASSIVE Components.

Nearly ALL Baluns for TV Antennas are 300-ohm to 75-ohm 4:1 "Transformers", with a few exceptions to this rule that use a 75-ohm to 75-ohm 1:1 "Transformer" or Coax Balun. Although a viable technique in the HF Radio Band, TV Baluns DO NOT operate as conventional Voltage Transformers, where the impedance ratio is the square of the wire winding ratio, because that technique can NOT provide the requisite Bandwidth (see Philips ECO6907.pdf App. Note below).

Modern Baluns typically use PAIRS of wires wound either in air or on Ferrite Cores as Transmission Delay Lines. PCB Baluns do the same thing via sinuous circuit board etches and "Coax Baluns" via different lengths of Coax. These Delay Lines have different delays so that when summed together they "Transform" from one impedance to another (unfortunately......it's all in the math).

Start with the Hal-Wave Coax Balun:
http://www.creative-science.org.uk/balun.html
http://n-lemma.com/calcs/dipole/balun.htm
http://www.k7mem.com/Electronic_Notebook/antennas/yagi_vhf_feed.html

The same Delay Line Technique can be used to form other Impedance Transformation Ratios:
http://yagi-uda.com/coaxial_balun.php

There are two commonly used methods in modern TV Baluns: Guanella and Ruthroff:
http://www.highfrequencyelectronics.com/Archives/Feb04/HFE0204_Sevick.pdf
http://home.earthlink.net/~christrask/TraskTLTTutorial.pdf

And for those who WANT to see the MATH squiggles, note the difference between a Conventional Transformer and a Delay Line Symbol (laid on it's side) and the important Frequency Compensation issues:
http://www.radio-kits.co.uk/radio-related/Linear_PA/ECO6907.pdf
http://www.vk1od.net/balun/index.htm

OUTDOOR TV Baluns usually have DC Continuity between the 300-ohm wire(s) and 75-ohm outer Coax connector in order to discharge the static electricity that builds up on the (ACTIVE ONLY) Antenna Elements due to wind passing across them (like shuffling your feet across a carpet)....which will ALSO protect the Balun against voltage arc-over, thereby avoiding user complaints. Whether there is DC Continuity between the two 300-ohm twinleads depends on choices by the design engineer such as how to use those pesky frequency compensation capacitors...or not...and the chosen interconnection between the Delay Lines.

Since the ACTIVE Elements are NOT connected to the grounded Mast, the leakage path through the Balun is the ONLY way to discharge static electricity buildup on those element. The PASSIVE Elements can (Optionally) be connected to the grounded mast, such as in typical Yagi designs, but if they "float" it's usually unlikely they will spark over due to the distances involved....probably...YMMV....

I as far I as can determine, the Philips and Channel Master OUTDOOR Baluns are known to be high performers....and indeed have DC Continuity between 300-ohm wires and 75-ohm outer Coax connector.
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post #12 of 39 Old 11-14-2013, 04:24 PM - Thread Starter
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holl-ands can I have your personal opinion on this particular BALUN?

http://www.radioshack.com/product/index.jsp?productId=2062049

Thanks for all the information you posted in your reply above.

Bruce.

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post #13 of 39 Old 11-15-2013, 05:52 AM
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Check out the post made by ADTech here. The four samples below have very similar performance to 600 MHz (Channel 40). Or you could get the CM balun and be done with it.

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post #14 of 39 Old 11-15-2013, 05:59 AM
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post #15 of 39 Old 11-15-2013, 08:52 AM - Thread Starter
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Quote:
Originally Posted by Wendell R. Breland View Post

The CM-94444 is available at Home Depot

Thanks for the link Wendell. The two customer reviews on this product place it at a 50/50 situation. One bad and one good. The bad review states that this item was not as good as another item an RCA brand BALUN. It does appear that this customer is using a BALUN on the receiver end and not at the antenna end. Although I must admit, I am not exactly sure either way, because the customer mentions indoor versus outdoor in his complaint.

I asked about the radio shack BALUN because I am currently using that BALUN on the 4-bay outdoor antenna I have and I noticed my signals went from a 50% signal reading to 40% which puts 3 different HDTV channels next to pixelization status or frequent audio dropouts which can be quite annoying. The signals to which I am having issues with are located at 288 True or 303 Magnetic.

Here's my TVfool, WVIT 35.1 Real is one station I have issues with here.

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46ae0bad93f7a6

I have one house that has a roof that is in the exact line of site of WVIT's tower, that is higher than my antenna, I have been trying to raise my antenna above this person's roof. The house is roughly 400 or so feet away to my west-north-west. Using Google Earth and locating WVIT's tower and using the ruler tool, I drew a line from Farmington CT. to my antenna here in Norwich. The line crosses right over this guys house. His house is built on a higher land mass that makes his roof an obstruction for me and I am not able to climb my antenna to see at which point it is finally over towering that house. Now, I do have WEDN real 9.1 Norwich West of here and WHPX 26.1 Real to my south-south-west of here. But I am not sure if either is causing over-load. I do use a in-line FM filter and an indoor amplifier, although removing the amp does not increase anything indicating an over-load of any kind. I simply believe having the right hardware at the antenna is the corrective procedure for me here. The choice of BALUNs seem to be the big issue. Same antenna, same amp and same receiver, changing the BALUN makes a big difference here.

This is why I bring this subject up in this topic. I have had numerous brands of BALUNs I also have several antennas setup up there on my roof. I do not use rotors to turn my antennas, they are all fixed in one direction and are selected via an indoor antenna selector switch. One antenna is pointed toward Boston Massachusetts the other towards Providence, Rhode Island. Those two antennas are on a different antenna mast from the Hartford CT. antenna.

Bruce.

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post #16 of 39 Old 11-15-2013, 10:55 AM
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Quote:
Originally Posted by MrBruce View Post

The two customer reviews on this product place it at a 50/50 situation.

For me, I would trust ADTechs info above most.

One should make sure all the mechinical and electrical items are up to snuff when dealing with reception problems. IF water should ingress into a balun then its performance will be compromised so make sure there is no hairline cracks in the balun housing. The F connectors MUST be weather proof as well, for exterior use I use Thomas & Betts TSNS1P6, RG 6 Snap Seal Compression connectors and the Nut Seal. Some more info here.

As to antenna aiming, multi-path, co-channel interference, weak signal, etc., reception problems, IMO, without a spectrum analyzer, solutions are a crap shoot. See some results from a analyzer here.

An example:

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post #17 of 39 Old 11-15-2013, 11:05 AM
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Forgot to add: You MUST use a compatible tool to install the Snap Seal Compression connectors, example here.
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post #18 of 39 Old 11-15-2013, 06:08 PM
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My Dec2005 Balun & RF Combiner comparison tests are a bit out of date to be of much use for newer, hopefully improved Baluns.
But if you've resisted replacing an old, moisture degraded Balun, you might want to know what it did when NEW:
http://www.avsforum.com/t/381623/the-official-avs-antenna-and-related-hardware-topic/7830#post_13581150

And here's the test of the OUTDOOR Philips Balun, showing less than about 0.6 dB of Loss (even better than those tested by ADTech):
http://www.avsforum.com/t/798265/how-to-build-a-uhf-antenna/1710#post_15851345
http://www.avsforum.com/attachments/15540

I don't have any "opinions" on any Balun that hasn't been RECENTLY tested....

BTW: For those who may have trouble deciphering the Spectrum Analyzer display above:

The "MID" indicator says that 0 dB level is in the Middle on the vertical scale, with "2 dB /" per division,
so Loss hovers around 2 dB (give or take) on lower freqs and is quite a bit MORE in UHF Band.
However, note that ADTech's cited post indicated that Baluns were tested in Back-To-Back PAIRS, so
you have to divide by TWO to get the (sorta average) Loss of an individual Balun.

The "CTR", "500 MHz" and "Span 100 MHz /" indicator says that the bottom scale runs from "Zero" MHz
on the Left to 1000 MHz on the right, with 500 MHz in the middle, so top of New UHF Band (698 MHz)
is two division lines to right of center and the 174-216 MHz Hi-VHF Band is a bit below and barely above
the second division line from the left.
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post #19 of 39 Old 11-16-2013, 01:11 AM - Thread Starter
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Thanks for your input holl_ands.

As much as I love the AVS forums, one of the most annoying things about it, is the topics here go on for almost 250 pages and date as far back as 2006!

The technology on the first 100 or so pages is out of date and useless to use at this current time because so much has changed since the transition from analog to digital has taken place.

What really poses a problem is where one should start when reading through one of those topics and often the same information is repeated time after time, but nothing is current information. By the time you get to post number 2003, you lose interest in the whole 6400 post topic...Yawn! You get the point I'm sure.wink.gif

Let's take 300 Ohm to 75 Ohm matching transformers for instance. Since 2006 many BALUNs are long gone from todays market, however, no one has taken the time to do any up-to-date analysis on what is currently on the market.

I realize the OTA television market has dwindled for lack of public awareness that OTA TV still exists and that do to the ridiculous prices and limitations on imported OTA channels on cable TV, that OTA TV is cheaper than any pay TV service! Cable-Dish-Direct TV are nothing but price gauging money making schemes. They lost the intentions they originally made when the industry was started. The intent to bring hard to receive TV stations into the customers homes. Before satellite stations like HBO, ESPN, USA Network Etc. become available, cable TV companies built towers with the intent of bringing in OTA stations from over 250 miles away, sometimes even further than that. They had access to the best antennas and amplifiers out there. Now, you're lucky if you get all your local stations at all! Money! It's all about lining their pockets with money! You pay more for less every month that goes by!

Okay, now, back to what I said about the need for some people who have the equipment to make up-to-date analysis about todays current BALUN availability. If someone could update that information in this thread, it would most likely prevent do-it-yourself home antenna purchasers from having to read through hundreds and hundreds of pages in other topics looking for an answer on BALUNs when it can be found here in a topic of its own.

Is anyone willing to attempt that? I would sure read the results with interest. wink.gif

Bruce.

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post #20 of 39 Old 11-16-2013, 03:05 AM
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Customer reviews of passive reception components aren't worth a whole lot. I once troubleshot a system that worked better with what was a technically inferior balun than it did with any better one because the inferior balun rolled off the strong local channel 48 and 50 signals so the preamp developed less intermodulation distortion. I once wound up with egg on my face when I (temporarily) replaced an old Radio Shack antenna with a similar Winegard one that had a slightly larger UHF section but didn't perform as well for that customer. The reason for that was, the Radio Shack UHF section was so poorly designed that it had less gain throughout the UHF band EXCEPT for a narrow frequency range that included the weakest channel (22) that this customer prized most highly. Since she wasn't willing to spend the price of a larger UHF antenna, I just reinstalled her old antenna and crossed her off my future customer list. In multipath signal environments, one antenna may perform better than another just because an off-axis null more fortuitously rejects an offending, multipath reflection.

Is MrBruce using a preamp? If he is, his two relatively strong channel 9 and 26.signals could be overloading it, and in that case, he might benefit from notching them down. Channel 9 can be reduced economically with a channel 9 Jointenna (commonly available now for about $6), or the UHF and VHF can be split before the preamp, with the VHF routed around it. Weakening 26 could probably best be done with a hand tuned Winegard UT-2700 notch filter.
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post #21 of 39 Old 11-16-2013, 03:26 AM
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Originally Posted by holl_ands View Post

A bunch of math would reveal that maximum POWER transfer occurs when the load impedance MATCHES the source impedance:
http://en.wikipedia.org/wiki/Impedance_matching

I mentioned that here a decade ago, when tuned, half wave baluns were being touted. I wondered at the time how much of the benefit of that match would be offset by the impedance mismatch, but no one further commented on that. Have you or has anyone compared the theoretical and actual benefit of a half wave balun formed by matching the extra length of the center conductor to the wavelength and conventional matching transformers?
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...as far I as can determine, the Philips and Channel Master OUTDOOR baluns are known to be high performers....and indeed have DC Continuity between 300-ohm wires and 75-ohm outer Coax connector.
Not related to this user's situation, but the ones with continuity cannot be used back-to-back for ground loop isolation for that reason. I remember that since all the push-on baluns that were tested here some time ago in fact isolated the input from the output, the popular choice for home-made isolation transformers was to couple a push-on balun with a more conventional looking one, which was very convenient because the push-on baluns had screws for the 300 ohm connection. A word of warning, however: really old Radio Shack push-on baluns were intended for FM radio use and BRUTALLY rolled off anything over about 500 MHz.
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post #22 of 39 Old 11-16-2013, 06:08 AM
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Quote:
Originally Posted by holl_ands View Post

I don't have any "opinions" on any Balun that hasn't been RECENTLY tested....

A ½λ coaxial balun should have very little insertion loss. The negative is it has less bandwidth than a well designed ferrite core balun. IIRC, Antennas Direct uses a PWA style ½λ balun on some of their products.

In the early days of ATSC I used a homemade ½λ coaxial balun with a Winegard PR-9032 to receive the very low power ATSC transmitters.
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post #23 of 39 Old 11-17-2013, 11:06 AM
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K7MEM's Convenient Half-Wave 4:1 Balun Calculator:
http://www.k7mem.com/Electronic_Notebook/antennas/yagi_vhf_feed.html

K6STI MODELED a simple Coax Coil 1:1 Common-Mode Balun as well as a Half-Wave 4:1 Coax Balun, showing low Loss across FM Band....but model is for a ZERO LOSS Coax and NOT an actual measurement:
http://www.ham-radio.com/k6sti/balun.htm
The results should also be fairly typical in the Hi-VHF Band....but I would like to see a better model for the distributed capacitance (AND Measurements) for one designed for wider bandwidth UHF Band. And they are ONLY applicable to one Band at a time and would not be appropriate for either Hi-VHF/UHF Combo Antenna....or even a Ch2-13 VHF Antenna.....and would require HUGE Lengths of Coax for a Ch2-6 Lo-VHF Band Antenna.
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post #24 of 39 Old 11-24-2013, 03:08 PM - Thread Starter
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Reading back through this topic I see we went back to what any topic like this usually does, HAM radio.

It appears that if I wanted to become a HAM radio operator, I would have a wealth of information in regards to constructing a decent antenna.

The Ham band frequencies--although close to VHF lo and high-- are not resonant at 174-- 216.MHz nor are they close with 470--698 MHz UHF.

Using those silly HAM radio related calculations does not leave one with decent results with SWR on the television broadcast band.

Many years ago, before cable TV, there was more homes--owning a television set-- using an outdoor television antenna than there was HAM radio operators using a ribbon wire antenna for communications. Since the odds are 99 to 1, I still can not understand why a simple BALUN for use in television reception is totally misunderstood and lacking in information than a BALUN for HAM radio use.

The technology of television reception is more common place in America then HAM radio is, almost every American home has a television set in it. Yet still, research regarding this technology is limited to how to make an antenna for HAM radio transceivers. I still can not grasp the lack of information on this subject.

Bruce.

DTV DX Fanatic
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post #25 of 39 Old 11-24-2013, 04:10 PM
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Most of us have no reason to care about our baluns. Digital TV tuners function well with inputs varying in signal power by over 80dB. The liklihood that a person can ascertain a balun construction that gets him a dB or two of improved performance at his problem frequency that pushes his reception efficiency from unacceptable to acceptable in minuscuule.
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post #26 of 39 Old 11-25-2013, 09:31 PM
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A good portion of HAM radio operators do it because they like to understand and build electronics.
The VAST majority of the people who want a television balun, just want to watch TV.
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post #27 of 39 Old 11-26-2013, 05:08 AM
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Good discussion topic, though.
I guess someone could do some experiments with the different types of baluns.

Personally, I've been wanting to find time to play with some ideas on higher power handling baluns for FM radio reception....wondering if the thousand or so high-powered FM stations in our market (at least, it seems like that many) may be overloading the balun core, and masking some weak FM signals.

Ken English, Sr. Engineer, KSL-TV.
"The postings on this site are my own and don't necessarily represent the Company positions, strategies or opinions."
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post #28 of 39 Old 03-19-2014, 09:02 AM
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What would be better?

I had recently replaced an old TV antenna for my folks. I have all new quad-shield RG-6 running down from the antenna into the cellar, where the signal then runs to their set.

Problem is that my father made use of some old RG-62 cable back in the day when their home was wired for CATV, and ran it through the house. This is the distribution cabling. I am beginning the think that I might be getting two sets of reflections in the line because of impedance mis-matching. Pulling new RG-6 may be a problem due to insulation and other modifications made in the past 30 years. However, there is some abandoned 300-ohm twin lead running parallel to the coax.

Would I have better reception results by going from 75 ohm (antenna feed) to 300 ohm (distribution) then back to 75 ohm (at the set), then using that RG-62 as a distribution line?



Cheers!
-Doug
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post #29 of 39 Old 03-19-2014, 11:41 AM
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Me thinks you worry too much....

RG-62/U impedance is 92-ohms, which results in only a 1.2 SWR when terminated into 75-ohms.
Tuner specs that I've seen disclosed are "typically" as high as 3:1 and sometimes higher.
So there is only minimal difference between using 92-ohm and 75-ohm Cox.
Indeed, if the Tuner Impedance is HIGHER than 75-ohms, the match is actually BETTER.

Bear in mind that a 1.2 SWR is a Mis-match Loss of ONLY 0.04 dB (and 2.7 SWR is only 1.0 dB).

Of course if you ran new RG-6 through out the house, cable losses would be reduced.
But if you are using a Preamp or Distribution Amplifier prior to the internal runs, the difference would be inconsequential and would ALSO present a much better match to a 75-ohm source impedance than the typically poor SWR coming out of the Balun (which simply reduces the Antenna SWR curve by a transformation factor of 4:1).
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post #30 of 39 Old 03-19-2014, 11:48 AM
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I wonder if antennas with a PCB balun box work better with weak signals than an antenna that requires the 300ohm-75ohm matching transformer type balun? That is a key difference in an Antennacraft HBU-33 antenna and a Winegard 7696 antenna, which are otherwise somewhat similar. Does the balun type really make much of a difference?
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