Can we please discuss BALUNs 300 Ohm to 75 Ohm in an easy to understand manner? - Page 2 - AVS Forum | Home Theater Discussions And Reviews
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post #31 of 85 Old 05-26-2014, 07:24 PM
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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.

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post #32 of 85 Old 05-26-2014, 07:29 PM
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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

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?

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post #33 of 85 Old 05-26-2014, 07:37 PM
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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.

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post #34 of 85 Old 05-26-2014, 11:31 PM
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Quote:
Basically I've replaced my balun with the Hal-Wave coax balun mention in an above post.
That's a typo; it should be Half-Wave.
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Thing is, it works far better than either of the two proper baluns I've used.
It works better because it is a very low loss balun.
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If they work this well normally why aren't more folks on this board using them.
1. Most people want to buy a balun instead of make one.
2. The transformer balun is a broadbad device covering more channels than the halfwave coax balun, which is cut for a narrow frequency range.
3. It is difficult to properly waterproof a coax balun; water will get in the ends of the coax.
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Is my situation a fluke?
No, you have created a balun that is optimum for your particular frequency range.

If you can not measure it, you can not improve it.
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post #35 of 85 Old 05-27-2014, 07:55 AM
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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. :cool:

 

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.

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post #36 of 85 Old 05-27-2014, 09:04 AM
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Originally Posted by IbzArtist View Post

... Not sure if I can but if an admin can delete those first two that would be greatly appreciated.

Click the "X" box in the lower left corner of your post. It is the one between the pencil/eraser and the flag.
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As far as weatherproofing wouldn't a $6 can of Home Depot Plasti Seal solve that problem?

A lot of sealants have previously been alleged to contain solvents that reacted unfavorably with the conductive surfaces.
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post #37 of 85 Old 05-27-2014, 11:56 AM
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Originally Posted by IbzArtist View Post

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.
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.
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post #38 of 85 Old 05-27-2014, 11:59 AM
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Originally Posted by AntAltMike View Post


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.

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post #39 of 85 Old 05-27-2014, 12:52 PM
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Originally Posted by tylerSC View Post


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.

 

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post #40 of 85 Old 09-18-2018, 10:25 AM
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is there a transformer that is better than the rest,


a brand, homemade, which one


want the best video quality and signal
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post #41 of 85 Old 09-18-2018, 04:51 PM
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There are many types of baluns, but the "best" one depends upon your application


general questions, get general answers

If you can not measure it, you can not improve it.
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post #42 of 85 Old 09-19-2018, 09:08 AM
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Originally Posted by IbzArtist View Post

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.
 

The fact that this works with the loop being 50 ohms shows that the loop impedance is not critical. Ideally the impedance of the loop coax should be the geometric mean between the antenna impedance (300 ohms) and the coax impedance being matched (75 ohms). The loop for a 300:75 ohm transformer/balun should be 150 ohms. But 150 ohm coax is not available. I used 93 ohm coax for the loop, Belden 9269, as a compromise.

Attached is an image of the transformer/balun I made. A couple of ferrite beads should be placed over the 75 ohm cable to improve the balun performance. The 2nd image is the insertion loss across the UHF TV band for two baluns back-to-back, comparing the coax balun to a typical ferrite balun. Divide by 2 to get the insertion loss for one.

When the repack is complete, it will be possible to make a coax transformer/balun with a few hundredths of a dB insertion loss for the entire UHF band.
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post #43 of 85 Old 09-19-2018, 02:34 PM
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what is the best transformer for ota local channels


best video quality
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post #44 of 85 Old 09-19-2018, 02:46 PM
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Originally Posted by Calaveras View Post
The fact that this works with the loop being 50 ohms shows that the loop impedance is not critical. Ideally the impedance of the loop coax should be the geometric mean between the antenna impedance (300 ohms) and the coax impedance being matched (75 ohms). The loop for a 300:75 ohm transformer/balun should be 150 ohms. But 150 ohm coax is not available. I used 93 ohm coax for the loop, Belden 9269, as a compromise.

Attached is an image of the transformer/balun I made. A couple of ferrite beads should be placed over the 75 ohm cable to improve the balun performance. The 2nd image is the insertion loss across the UHF TV band for two baluns back-to-back, comparing the coax balun to a typical ferrite balun. Divide by 2 to get the insertion loss for one.

When the repack is complete, it will be possible to make a coax transformer/balun with a few hundredths of a dB insertion loss for the entire UHF band.

is it possible to use the coax directly on the antenna instead of the twin lead -then-transformer-then-coax, the coax can be stripped at two points and wrapped around the insertion at the antenna.


second method, using a coax with one stripped and the other one with female connector, two of these stripped cables with the exposed ends inserted at the antenna directy, the female connectors are connected with a splitter to merge these two into one.
you have 2 coax - splitter - 1 coax


can either method work, reduce the loss in quality
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post #45 of 85 Old 09-19-2018, 02:58 PM
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Is this a joke?
Just get a balun from Walmart or Home Depot.
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If you can’t explain it simply, you don’t understand it well enough – Albert Einstein
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post #46 of 85 Old 09-19-2018, 05:01 PM
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Originally Posted by user7 View Post
what is the best transformer for ota local channels

best video quality
The problem is, you haven't given us enough information to give you a detailed answer.

What antenna will it be used with?

What are the OTA channels?

What does your TVFool report look like?

If you are not willing to give us any further information, get the Channel Master 94444, and good luck to you.

If you can not measure it, you can not improve it.
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post #47 of 85 Old 09-19-2018, 05:20 PM
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Originally Posted by user7 View Post
is it possible to use the coax directly on the antenna instead of the twin lead -then-transformer-then-coax, the coax can be stripped at two points and wrapped around the insertion at the antenna.
It is possible to connect the coax directly to the antenna terminals but there will be a mismatch and a loss of signal.
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second method, using a coax with one stripped and the other one with female connector, two of these stripped cables with the exposed ends inserted at the antenna directy, the female connectors are connected with a splitter to merge these two into one.
you have 2 coax - splitter - 1 coax
Your second method is even more complex and will cause even more loss of signal.
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can either method work, reduce the loss in quality
Your two methods will create more loss than the conventional method with a 4:1 balun matching transformer; keep it simple.

You still haven't told us what antenna you are connecting to the coax.

Are we going to have to pull each detail out of you, one by one, before we can give you an intelligent answer?

If you can not measure it, you can not improve it.
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post #48 of 85 Old 09-19-2018, 06:09 PM
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Originally Posted by rabbit73 View Post
It is possible to connect the coax directly to the antenna terminals but there will be a mismatch and a loss of signal.
Your second method is even more complex and will cause even more loss of signal.
Your two methods will create more loss than the conventional method with a 4:1 balun matching transformer; keep it simple.

You still haven't told us what antenna you are connecting to the coax.

Are we going to have to pull each detail out of you, one by one, before we can give you an intelligent answer?

my apologies,

looking to get as many ota channels as possible, even far distatant ones

have attached a copy of the tvfool report, a picture of the antenna, not the exact antenna, similar with twin leads
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post #49 of 85 Old 09-19-2018, 09:35 PM
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Originally Posted by user7 View Post
my apologies,
Thank you; apologies accepted.


I owe you an apology. I should have called to your attention the requirements listed in the sticky:
https://www.avsforum.com/forum/25-hd...-1st-post.html


I will study your information and come back after some sleep.

If you can not measure it, you can not improve it.
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post #50 of 85 Old 09-19-2018, 10:13 PM
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Originally Posted by user7 View Post
my apologies,

looking to get as many ota channels as possible, even far distatant ones

have attached a copy of the tvfool report, a picture of the antenna, not the exact antenna, similar with twin leads

Dr. Don should move this to the Sacramento local thread before it goes much further.

I'm also in the Sacramento market.

The pictured antenna is low VHF through UHF I think. A coax balun will not cover such broad range. Use a ferrite balun. Your signals are so strong that you don't need anything special. Stations other than Walnut Grove are in all sorts of directions. If you really want as many as possible you'll need a rotor to point the antenna in so many directions.
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post #51 of 85 Old 09-20-2018, 06:01 AM
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Is this a joke?
Just get a balun from Walmart or Home Depot.
Neither carries a matching transformer in their stores although you can order them from their web site.

If you need one "today", Lowe's is the only national store chain that has a balun that is carried in many stores.: https://www.lowes.com/pd/RCA-Outdoor...former/3724168 It's the same flimsy unit that Winegard has been putting on the RCA-branded stick antennas they build under contract for VOXX as well as using it on their own Freevision FDVHD30 antenna. For those in the Midwest, Menards also carries one or two matching transformers in their stores.

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post #52 of 85 Old 09-20-2018, 08:22 AM
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Quote:
Originally Posted by user7 View Post
looking to get as many ota channels as possible, even far distatant ones

have attached a copy of the tvfool report, a picture of the antenna, not the exact antenna, similar with twin leads
Quote:
Originally Posted by user7 View Post
what is the best transformer for ota local channels
Calaveras is correct, you will need a ferrite core balun for your VHF/UHF antenna with 300 ohm output terminals.

The "best" ferrite balun was the original Channel Master 94444 outdoor balun. It is no longer being made and is hard to find. PCT International now owns the Channel Master name and intellectual properties. They are now selling a redesigned balun with the SAME model number. They did a similar marketing trick when they redesigned the original CM7777 preamp. The impression they gave was that they were trying to trade on the good reputation of the original version for the redesigned version. That didn't sit too well with those of us that give reception advice, because we had to ask: which 7777 do you have?

Some sellers are using the photo of the original balun, but send the new balun.

This is what the new balun looks like:



This is the superior original balun:



I found some of the original Channel Master 94444 baluns and was able to make measurements of three different baluns. I connected two of each, 300 ohm to 300 ohm, and measured the loss at three frequencies in the UHF band.



For the first measurements, I used a Blonder Tongue HAVM-1UA Frequency Agile Modulator as a stable signal source, and a Sadelco Signal Level Meter. The modulator puts out an analog signal; I used the video carrier for each channel.

To make a measurement, I first connected the modulator to the meter with an F-81 adapter and took a reading. I then substituted the balun pair for the adapter for the second reading. If the loss of each balun is the same, then the loss of one would be half of the pair connected together.

There was an attenuator at the output of the modulator and at the input of the meter to try to keep the line "flat" (low SWR).



The Original Channel Master 94444 is clearly the best.

When I was making the measurements of the New CM balun, I noticed the loss readings would vary according to the position of the 300 ohm wires between them. I decided to cut the wires to 2-1/2" before removing the insulation to see of it would make any difference.



I then made measurements of this modified balun:



The loss was reduced and was much less affected by the position of the wires. The long wires formed a transmission line of indefinite impedance.

If you use the new CM balun, I suggest you keep the wires short.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 09-20-2018 at 08:29 AM.
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post #53 of 85 Old 09-20-2018, 09:47 AM
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Originally Posted by Calaveras View Post
Dr. Don should move this to the Sacramento local thread before it goes much further.

I'm also in the Sacramento market.

The pictured antenna is low VHF through UHF I think. A coax balun will not cover such broad range. Use a ferrite balun. Your signals are so strong that you don't need anything special. Stations other than Walnut Grove are in all sorts of directions. If you really want as many as possible you'll need a rotor to point the antenna in so many directions.
Thank you for suggesting the ferrite balun and the rotor
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Originally Posted by ProjectSHO89 View Post
Neither carries a matching transformer in their stores although you can order them from their web site.

If you need one "today", Lowe's is the only national store chain that has a balun that is carried in many stores.: https://www.lowes.com/pd/RCA-Outdoor...former/3724168 It's the same flimsy unit that Winegard has been putting on the RCA-branded stick antennas they build under contract for VOXX as well as using it on their own Freevision FDVHD30 antenna. For those in the Midwest, Menards also carries one or two matching transformers in their stores.
Thank you mentioning the link for the balun
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Originally Posted by rabbit73 View Post
Calaveras is correct, you will need a ferrite core balun for your VHF/UHF antenna with 300 ohm output terminals.

The "best" ferrite balun was the original Channel Master 94444 outdoor balun. It is no longer being made and is hard to find. PCT International now owns the Channel Master name and intellectual properties. They are now selling a redesigned balun with the SAME model number. They did a similar marketing trick when they redesigned the original CM7777 preamp. The impression they gave was that they were trying to trade on the good reputation of the original version for the redesigned version. That didn't sit too well with those of us that give reception advice, because we had to ask: which 7777 do you have?

Some sellers are using the photo of the original balun, but send the new balun.

This is what the new balun looks like:



This is the superior original balun:



I found some of the original Channel Master 94444 baluns and was able to make measurements of three different baluns. I connected two of each, 300 ohm to 300 ohm, and measured the loss at three frequencies in the UHF band.



For the first measurements, I used a Blonder Tongue HAVM-1UA Frequency Agile Modulator as a stable signal source, and a Sadelco Signal Level Meter. The modulator puts out an analog signal; I used the video carrier for each channel.

To make a measurement, I first connected the modulator to the meter with an F-81 adapter and took a reading. I then substituted the balun pair for the adapter for the second reading. If the loss of each balun is the same, then the loss of one would be half of the pair connected together.

There was an attenuator at the output of the modulator and at the input of the meter to try to keep the line "flat" (low SWR).



The Original Channel Master 94444 is clearly the best.

When I was making the measurements of the New CM balun, I noticed the loss readings would vary according to the position of the 300 ohm wires between them. I decided to cut the wires to 2-1/2" before removing the insulation to see of it would make any difference.



I then made measurements of this modified balun:



The loss was reduced and was much less affected by the position of the wires. The long wires formed a transmission line of indefinite impedance.

If you use the new CM balun, I suggest you keep the wires short.
really appreciate you going over the posted information to determine the best setup. Thank you very much.

when you say keep the wires short, is it the wires on the balun, snip them short
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Originally Posted by user7 View Post
really appreciate you going over the posted information to determine the best setup. Thank you very much.

when you say keep the wires short, is it the wires on the balun, snip them short
Yes, that is correct. Of course, you will only need one balun to connect the coax to your antenna; I had to use two to make a measurement of losses.



Your local signals are very strong. If your antenna is in the clear with no trees or other objects in the signal path, you will not need, and should not use a preamp. If your antenna is aimed SSW, a preamp and your tuner will be overloaded.

I made an estimated report of your FM signals. They are not strong enough to interfere with TV reception.
http://www.fmfool.com/modeling/tmp/c...5/Radar-FM.png

Because of UHF Repack by the FCC, there will be channel changes in your area. You will need to rescan.
https://www.rabbitears.info/market.p...&callsign=kmax

https://www.rabbitears.info/repackch...h=&lss=&status=

The changes will happen during Phase 9, 3-14-2020 to 5-1-2020
https://www.fcc.gov/about-fcc/fcc-in...ition-schedule

https://www.commlawcenter.com/2017/0...deadlines.html
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If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html

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post #57 of 85 Old 09-20-2018, 01:42 PM
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I summarized Actual Measurements of Balun Insertion Loss here:
https://www.digitalhome.ca/forum/186...ml#post3039322
https://www.digitalhome.ca/forum/81-...ml#post2075514

The PHILIPS OUTDOOR 4:1 BALUN, measured in 2009 by johnrmckee, was only 0.5 to 0.9 dB, considerably better than ANY other Balun. I recommend a RETEST to see if CURRENT Philips Baluns remain as good a choice. And it wouldn't hurt to RETEST the RCA OUTDOOR Balun (and whatever else is popular) as well.

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Quote:
Originally Posted by rabbit73 View Post
Yes, that is correct. Of course, you will only need one balun to connect the coax to your antenna; I had to use two to make a measurement of losses.



Your local signals are very strong. If your antenna is in the clear with no trees or other objects in the signal path, you will not need, and should not use a preamp. If your antenna is aimed SSW, a preamp and your tuner will be overloaded.

I made an estimated report of your FM signals. They are not strong enough to interfere with TV reception.
http://www.fmfool.com/modeling/tmp/c...5/Radar-FM.png

Because of UHF Repack by the FCC, there will be channel changes in your area. You will need to rescan.
https://www.rabbitears.info/market.p...&callsign=kmax

https://www.rabbitears.info/repackch...h=&lss=&status=

The changes will happen during Phase 9, 3-14-2020 to 5-1-2020
https://www.fcc.gov/about-fcc/fcc-in...ition-schedule

https://www.commlawcenter.com/2017/0...deadlines.html

a matching transfromer that can do 75 to 300, can it doo 300 to 75
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Quote:
Originally Posted by user7 View Post
a matching transfromer that can do 75 to 300, can it doo 300 to 75
A balun matching transformer is also called a 4:1 balun for a 300 to 75 ratio. They usually can work in either direction. In my tests, the left hand balun of a pair is doing 75 to 300 ohms; the right hand balun is doing 300 to 75 ohms.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html
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post #60 of 85 Old 09-20-2018, 06:59 PM
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great work

Quote:
Originally Posted by rabbit73 View Post
A balun matching transformer is also called a 4:1 balun for a 300 to 75 ratio. They usually can work in either direction. In my tests, the left hand balun of a pair is doing 75 to 300 ohms; the right hand balun is doing 300 to 75 ohms.

Your research is so darned well thought-out and practical.
I never could have come up with such a clever and simple method to figure out which ones are best, nor could I have ever guessed different baluns would show so much difference in performance.


The good news is that I'm a pack rat, and I have some old baluns laying around that look a LOT like the original 94444s.



THANKS!
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