Glad I found this topic. Recently I was having some odd reception issues and discovered it was a faulty balun. Being a DIY addict I decided to see if I could make a functioning balun. I used this design mentioned earlier in the post: http://www.creative-science.org.uk/balun.html I found another diagram of the coax balun but it's the same design.

After connecting it my quality of reception was significantly better. Signal drops were nearly gone altogether. This led me to believe making a balun out of spare coax was a better plan than purchasing one. Could any more experienced member shed some light on my situation. Honestly, it preforms far better than the WalMart/Radio Shack type baluns I was using in the past. Granted, I've read many posts elaborating on how they are the cheapest of the baluns you can use but for 10 mins of wire cutting, stripping and adding connectors I can see any reason to purchase a proper balun.

Were my results merely a fluke? Some insight would be greatly appreciated.

Quote:

Originally Posted by holl_ands 

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.

I have been currently using a home made Hal-Wave Coax Balun with great results. Far out preformed my previous balun which basically fell apart. Wal Mart purchase if memory serves me correct. Thing is, the coax balun seems more stable and has cut my "flickers" and other glitches to nearly zero.

Can anyone explain why this is and why more of the antenna DIY'ers here don't use them?

I've tried two posts and get "I don't have permission to post links...." so hopefully I can get this post up without hassle. Not sure why I can't post a link I copied from an above post but whatever....

Basically I've replaced my faulty balun with the Hal-Wave coax balun mention in an above post. Thing is, it works far better than either of the two proper baluns I've used. If they work this well normally why aren't more folks on this board using them. Is my situation a fluke? Since making the coax balun any "glitches" or other reception annoyances are almost completely gone. I'm a firm believer in "If it ain't broke don't fix it" but I just can understand why such a simple loop design out preforms the commercial baluns I've used.

Of course the two posts I thought didn't work are there now. (loudest Homer DOH! in history). I apologize for the multiple posts. I wasn't aware links had to be approved and assumed the posts simply didn't get posted. Not sure if I can but if an admin can delete those first two that would be greatly appreciated.

Honestly, I can't understand why anyone would want to purchase a balun that has a higher loss than one you can make yourself. I originally came to this topic from the "How to build a UHF antenna..." topic because after reading over 60 pages I have yet to see anyone mention making their own baluns. Seems like quite the logical step if you're building your own antenna from scratch. One comment I did read there is balun failure is the most common issue with antenna problems and I've found that to be very true. Of course I'm also using the Radio Shack, WalMart, Lowes or Home Depot variety which I'm sure are as cheap as they come. All supposedly "ourdoor" variety, yet even my most poorly constructed antennas seem to outlast the proper store bought baluns. Usually the female coax ends will literally just come loose and fall out. Not to mention most commercial type baluns have stranded wire to connect to the antenna. Those get brittle and break quite often.  I've gotten used to having to change them out once I start getting signal drops & most of my earlier DIY antennas were of the 2x4 plus coat hanger variety but they still end up outlasting the store purchased baluns.

Speaking from the DIY antenna direction the 10 mins involved in making the coax loop seems rather minor compared to the time spent in constructing an entire antenna. I have lots of spare coax and a trip to Home Depot etc. ties up at the least 30 mins.

As far as weatherproofing wouldn't a $6 can of Home Depot Plasti Seal solve that problem? Plus it always makes a good addition to the workshop.

I made my coax loop balun loosely based on one for RG8x cable. Worked for me but I've since found this handy calculator: http://n-lemma.com/calcs/dipole/balun.htm

Just for my own curiosity; Am I the only one using the coax loop type balun? If not, could anyone post their results with theirs?

Much thanks rabbit73 for your reply but after replacing 3 of my own baluns & my mother's balun on her "store bought" outdoor antenna I think I'm sticking with the coax loop for now.

Quote:

Originally Posted by AntAltMike 


Click the "X" box in the lower left corner of your post. It is the one between the pencil/eraser and the flag.
A lot of sealants have previously been alleged to contain solvents that reacted unfavorably with the conductive surfaces.

Mine only has the pencil & flag. No "X" at all.

Quote:

Originally Posted by tylerSC 


Where are you located in NC, and what market channels do you receive? I would consider using one of these custom baluns, but I am not that technically minded, and the instructions leave me a bit confused. Other than the general idea, as the mathematics and algorithms start to lose me.

My closest tower is less than 8 mi. I live in the NC 27248 zipcode. Counting the secondary channels, spanish language channels & religious channels I'm getting 26. Right now it's a very slapped together DB2 clone only 10-12ft off the ground. As far as the technical jargon I just used the RG8x measurement assuming it was close enough to the RG6 (appx 10-11in) I was using. That's the loop size. http://www.creative-science.org.uk/balun.html This is the best example of what I'm talking about as far as how to construct a coax balun. I would imagine I'm even more lost on the math & algorithms than you are. I would just give it a try and if it doesn't work, try another loop of a different length.

Honestly I was winging it. I feel like I just got lucky on the first attempt. I knew I was successful when my girlfriend stopped complaining about the signal going from full to nothing or general audio/video stuttering. Issues almost completely went away for the low cost of 10 mins of time. I'm also tired of replacing baluns. My shoddy constructed antennas should give out way before a manufactured balun but for me they don't.

A & B will be the connections to the antenna feed. I attached "U" connectors to A & B for a better connection to the antenna feed point. The copper middle wire will be connected to A. All braided shielding will be soldered together (if it's copper). If it's aluminum just twist them together tightly and use a wire crimp to secure.