Do You REALLY Need a Matching Transformer?

Here is a test of whether a Matching Transformer (Balun) helps improve your HDTV antenna's signal to the TV. This is important information for anyone who's making their own HDTV antenna, or even those people that are just curious about it.
Yes, I'm well aware that there is no specific "HDTV" antenna design, but the antenna industry has set the standard for using the term and definition, so don't blame me for following suit.
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[@ChristopherSobieniak]

Now you know what it feels to be old. We were using these 40 years ago.

[@douglasengle2704]

This was a fantastic real world test of Balun transmission line change. I lot of antenna sophistication ends up not making a lot of difference its so good to get some real world results!. There is more going on than just changing impedance between 300 Ω and 75 Ω transmission lines. The 300 Ω transmission line is treated as a "balanced" carrier transmission wave where half the wave is below a zero voltage reference and half the wave is above zero voltage reference. The idea is that at the receiver any radio wave interference to the transmission line will appear as a positive or negative constructive interference to BOTH negative and positive parts of the signal; whereas, the original signal would be very symmetrical. The non symmetrical part of the signal can then be greatly eliminated. 300 Ω transmission line is typically unshielded twin lead and it is best to put a slow twist into the line so any radio wave interference is applied somewhat evenly to both conductors. People have used unshielded 300 Ω twin lead in their attics as antennas in themselves. The 75 Ω transmission line is typically shielded unbalanced transmission line where the entire signal wave has been shifted so that the bottom of the wave that was below zero is not tied to a zero reference and the whole wave is considered to be above the zero reference. The typical 75 Ω shielded transmission line is coax cable with two very different conductors that do not act the same. This would make it a poor choice for a balanced transmission line because the two halves of the signal would be distorted from one another with the implicit reference to ground (actual ground). It is also much higher loss than the unshielded balanced transmission line. The shielding provides near total isolation from interference, but it also is thought to drain signal strength away to ground. The impedance of the transmission line can be thought of as the optimum ratio between voltage and current or R=E/I which in the physical conductor is set by the distance and dielectrics between the conductors. I have never gotten a good practical model for impedance matching. Impedance is dealing with energy storage and release due to magnetic (inductive) and electric (capacitive) fields. The reason impedance is referenced in Ω is that at certain frequencies it resembles an R=E/I relationship ship which is a physical ratio of voltage to current. That has relevance to the physical sizing of inductors and compactors. In radio electronics there is another meaning of high impedance in relationship to vacuum tubes (valves in Britain) in that they had relatively high resistance compared to later transistor electronic circuits and operated in at much higher voltages to produce similar output power in the hundreds of volts sometimes. A transmission line's termination needs to appear as a continuation of the transmission line or the signal will bounce due to a refraction change. The real problem with the signal bouncing is it will bounce off of other refraction changes and all that back and forth bouncing will cause distortion to the signal. There is also loss of signal with out a good impedance match because part of the signal is bounced backward. It is best practice is to have a strong signal booster right at the antenna so the antenna sees an ideal load on it and the signal booster can then provide a strong signal source to the devices using it. Ideally it would be best to over boost the signal at the antenna and have to cut the signal strength down at the receiver. If you use a passive signal splitter it cuts the signal strength down regardless if its ports are being used and more so for the number of ports it has. I've never seen an over booster signal not work on a TV. There is something else probably going on if that appears to be the case. High frequencies in the upper UHF can lose about 4 times as much strength as the lower frequency VHF TV signals on their way down from a roof antenna.

[@mrhoptoit7835]

Thanks Douglas for watching and giving such a thorough explanation. Very well written.

[@kensmith5694]

As a general rule, matching always helps. I get a "boat load" of TV stations with my attic antennas. They are directional so aiming of the antenna also matters a lot. If you are over about 30 miles from the transmitter, a directional antenna is best because it ignores noise coming from other directions.

[@RazorStrap]

Without a balun, the coax becomes part of the antenna elements and its placement/routing will likely affect signal and interference. Some small antennas that are marketed as VHF-High use the coax like this as the VHF-High element. Presumably so it can be marketed as a VHF-High antenna. Without an impedance matching transformer, a high impedance antenna (aprox. 300 or so ohms) is too high to effectively drive the lower impedance of 75 ohm coax cable. Thus the delivered signal is weaker. Impedance of an ordinary dipole antenna is supposedly close to 75 ohms and so 75 ohm coax can be directly connected. However, there is still the issue of balanced to unbalanced. So a 1 to 1 balun would be appropreate. Rather than 4 to 1 (300/75 ohm). There are some means of making a 1 to 1 balun with a length of coax. But these are usually narrow bandwidth and more suited for HAM systems etc.

[@mrhoptoit7835]

Really good information. Thanks for the comment!

[@w8lvradio]

Just my opinion based on my personal experiences, your mileage may vary and CAVEAT EMPTOR: A Balun is like the transmission in your car, it BALANCES the load to make for an EFFICIENT transfer of power. You NEED a balun for the efficient transfer of power, even here where we are dealing with picoamps! It WILL Make a difference in fringe reception. What's MORE, if you put an antenna up high, it's BEST to use 300 Ohm TWIN LEAD and bring that down into the house. (And don't forget the lightning arrestor!) I have observed PERSONALLY that SURE, you can use a PREAMP and use coax for this connection. But? You don't need the preamp at all, IF you use GOOD OLD FASHIONED 300 Ohm "TWIN LEAD" INSTEAD! This is a substantial SAVINGS in that you forgo the cost of a preamp, and even though it uses a so called "voltage injector" that is mounted INSIDE your house, you're just kidding yourself if you think that the preamp MOUNTED OUTSIDE which is where it MUST be to make any appreciable difference, will stand up well to weather, and that goes DOUBLE for coax outside, which eventually gets wet, no matter how well you seal it up, and that changes the impedance to something OTHER than 75 Ohms, and drops efficiency DRAMATICALLY! Now, INSIDE your home, you place the balun to switch over to 75 ohms for your actual TV connection. and with 300 ohm twin lead, you DO NOT AND SHOULD NOT place a balun on the mast. Why does this matter? Because TWIN LEAD is way way way more efficient than coax on any given length as compared to 75 Ohm coaxial cable. This is ESPECIALLY TRUE at VHF and UHF frequencies! You will STILL need a DISTRIBUTION AMP INSIDE THE HOUSE for the runs to the respective television sets.. again because of the loss of the coax INSIDE the house. This begs the question: Why not just run twin lead INSIDE the house to all of the TV's? The answer is that twin lead DOES NOT like to be run over or near runs of metal like pipe and duct work, indeed it will LOSE SIGNAL in these circumstances. If you use a metal pole as most of us do for your antenna mast? You MUST use FOUR INCH STANDOFFS MINIMUM to separate the coax from the metal pole/tower. In comparison to coax, you could theoretically run HUNDREDS OF FEET of Twin lead and have practically NO LOSS as compared to just 25 or 50 feet of coax! Back in the EARLY days of television, communities that were cut off from TV reception would put an antenna on a mountain and run...yes...you guessed it... TWIN LEAD to the bottom of the mountain. You would pay to be "hooked up' to the system, and this was the early "cable Pay TV" (using the term "cable" very genetically and loosely here! ;-)) USE PPE, AVOID FALLS, AND DON'T EVEN THINK OF MOUNTING AN ANTENNA NEAR ANY POWER LINES! People are KILLED installing antennas every year, don't be one of them! You MUST install the LIGHTING ARRESTOR to meet code and so you don't VOID YOUR HOME INSURANCE WARRANTY! Again, coax is lossy lossy stuff, that's why you see those inline "boosters" on the telephone poles all over your town, and even UNDERSEA CABLE has to be boosted MANY TIMES with VERY EXPENSIVE underwater boosters to make the trip to (and from) US/Canada and the UK for another example. All the Best! 73 DE W8LV BILL

[@mrhoptoit7835]

Thanks for the really good comments and advice, and thanks for watching

[@petermorton2869]

Having a balum makes all the difference to go with TV Antennas as you would pick up more signals from the TV Towers & also having an Excellent TV Antennas Kind Regards Peter

[@mrhoptoit7835]

Thanks for watching

[@jasonleekinney]

Thanks for posting.

[@mrhoptoit7835]

You're welcome

[@neilhardy8211]

Very thourough thank you for your hard work

[@mrhoptoit7835]

Thanks for watching my channel, Neil!

[@bobskie321]

It's much more evident in analog TV that using a 75 ohms coaxial cable an antenna with a matching transformer has better reception than without. A 300-ohm twin lead flat cable still needs a matching transformer not on the antenna but on the other end when you plug it into the TV.

[@mrhoptoit7835]

Thanks for the great comment!

[@dhansel4835]

You are converting 300 OHM to 75 OHM which gives you a balanced load. If you ever run a multi-output splitter you need to buy some 75 OHM terminating resistors and put on the ports you don't have a TV hooked to.

[@mrhoptoit7835]

Thanks for making a good point. Keep watching!

[@lenywilliams7765]

Ok, now that reception is for TV ! I'm curious about the signal for FM radio? Can this work for that too ?

[@stereomann83]

it might pick up some stations but the antenna he used is for uhf and FM uses Vhf. a pair of rabbit ears would work for FM

[@kensmith5694]

Yes, a balun does work for FM radio. If you make the classic folded dipole FM antenna out of some twin lead or just hook up to a TV antenna, the matching still helps if you need to run coax to the radio.

[@debojitacharjee]

*WHY NOT RABBIT EARS?*---why you didn't include the two rabbit ears antenna with this one? I need to make one antenna like this one but with two rabbit antennas to make it a complete tool. But I wanna know how to connect the two antennas with the UHF loop antenna. Do you have any idea?

[@mrhoptoit7835]

Often the UHF loop shares the same connection as the rabbit ears - try connecting them together, one on top of the other.

[@debojitacharjee]

@@mrhoptoit7835 You mean both the loop and rabbit ears antennas should be in parallel connection with the input of the balun?

[@mrhoptoit7835]

Yes.

[@debojitacharjee]

@@mrhoptoit7835 I don't think that way the loop antenna will work with the rabbit ears. I think the rabbit ears need to be connected to the output of the balun.

[@mrhoptoit7835]

There are situations where connecting the antennas together will not work well. I always recommend at least trying it first. If it doesn't work for you, attach both antennas to their own balun, run equal lengths of coax from them to a combiner/splitter, and then run your coax to your TV.

[@luigitesla724]

Very well I from Mexico

[@mrhoptoit7835]

Thanks for watching!

[@jeffdwyer6105]

I agree with your conclusion but your testing was totally unscientific .. BALUN stands for Balanced-UNbalanced its to match a balanced antenna (TV) made up of horizontal parasitic elements and dipole driven elements to an UN-balanced coax cable ... , in other words they haven't fundamentally changed from the old Analog days , there is no such thing as a HDTV antenna . A balun can also match different impedances because its a transformer . ....The new digital channels are all in the UHF range which has the greatest cable losses , the most important issue with reception is the cable . Always use the shortest run , use high quality double shielded cable . Digital signals are easily interrupted by interference .

[@mrhoptoit7835]

Thanks Jeff for your great feedback. As I stated, I am not an Electrical Engineer, just a hobbyist that enjoys building and testing TV antennas. Its really great that a person like yourself with a lot more knowledge on these matters took the time to watch my video (even with it's simplistic methodology) and agrees with my conclusion! Thanks again.

[@mrhoptoit7835]

Thanks for the great comments, Ed. I actually do know the definition and theory behind baluns. My video was meant to be quick, entertaining and non-technical. If anyone wants a thorough understanding of baluns, I recommend watching David Casler's video on the subject. You are also absolutely correct that there are no ACTUAL HDTV antennas. Saying "HDTV antenna" simply lets most people know that yes, it will pick up a signal that your HDTV can use. I appreciate you watching my videos and I hope yours and Jeff's comments help answer questions that I did not cover. Thanks for your support and please keep your comments coming!

[@mrhoptoit7835]

@Ed Baumann no problem Ed. I just wanted to clarify. I deliberately keep my videos non-technical as that appeals to the majority of my viewers. They just want the instructions, not the theory. I really do appreciate your comments. Its great that I have some more tech minded viewers.👍

[@RazorStrap]

I'm sure you know this but just to clarify for those who may not. A balun is not necessarily an impedance matching transformer, and an impedance matching transformer is not necessarily a balun. Most mass-produced TV matching baluns/transformers have both functions incorporated. There are BTW actual HDTV antennas. An HDTV antenna is an antenna that is connected to an HDTV. Thus, it is an HDTV antenna. ;) Otherwise, it is just an antenna.

[@mrhoptoit7835]

Great comments! Thanks, RazorStrap for watching my video.

[@williammason8053]

Night and day 👍🙌☔🆓

[@wolfcanine100]

i only use those for converting rabbit ears to modern input on old tv sets really useless on anything new

[@musovk3735]

This is not real balun. Open it and you will see that nothing insid

[@mrhoptoit7835]

Thanks for watching