Check out Net Gain plots:
http://www.hdtvprimer.com/antennas/comparing.html
http://www.hdtvprimer.com/ANTENNAS/TemporaryPage.html
CM4228 drops off dramatically towards Ch14...it's perhaps 10 dB lower than PR8800
(aka Antennas Direct 8-Bay) and almost that much compared to the new CM4228HD.

Can Ch14 be improved on the old CM4228??? Probably.... Good NEC Student Exercise....
Although Ken Nist tried to improve the new designs, too bad he didn't try to fix the old CM4228.....
Screen Separation??? Add long Reflector Rods....or a bigger Screen??? Tine-to-Tine Spacing???
Longer Whiskers??? Including perhaps Stagger Tuning (Inner and Outer are different)???
Which reminds me....I need to double check Ken Nist's measurements against my REAL CM4228.

I also wouldn't rule out some "minor" surgery to widen the Bowtie Separations....
The 4nec2 files I provided employ SYmbol descriptions, making it easy to vary
parameters. After trying different Screen Separations, change over to NO Reflector
version, cuz the Screen Reflector version runs for many, many minutes.........
(check it after every other station break)...

Hey holl ands.

I tried to send this to you as a private message but was unable to as your box is full. I didn’t want to get in trouble for hijacking this post as we’ve clearly strayed from baluns.

Once again the info you have provided is very interesting. I really don’t want to start messing with my 4228 as they’re becoming impossible to replace. But once someone more capable than I figures it out all bets are off.

ppauper pointed me in the direction of a post he started where they’ve already begun to test the mods on the original CM4228, it can be located here (http://www.digitalhome.ca/forum/showthread.php?t=111068)

I’m also going to do some reading about ganging / stacking dissimilar Antennas, in the hopes that I can tune the second specifically to channel 14. Thanks again for your input.

Combining two dis-similar antennas with a conventional RF Splitter/Combiner will
result in about 4 dB of loss in the Splittter, cuz signals aren't matched in amplitude & phase.

You would need a C-M JoinTenna or Tin-Lee AC-7 Channel Injector for just Ch14:
http://www.tinlee.com/MATV_headend.php?active=4#ANTENNASIGNALINJECTORS

PS: I cleaned out my PM box....

I would like to build a coax balun for VHF channel 11. I've read through most of this topic but don't understand how exactly to make one. Are there step by step instructions anywhere? Currently with a coathanger antenna and a RadioShack balun I can get channel 11 0-10%. I'm hoping by making one of these I'll be able to consistently get the channel. Do I need to worry about losing my other stations which are currently all coming in fine?
Thanks

Snoop, have a look thru this link - a fellow DHC'er (mlord) put it together and provides some good illustrated instructions.

http://rtr.ca/yagi_antennas/index.cgi?z0205655+medium

A few of us have also posted a few photos within this thread which can give you a good idea of what others are doing.

Mlord, any progress to report on your balun construction tips? lol! I believe many of us would really benefit from your expertise and a few of the tips you got from Bob a couple months back when he tested your GH8...

I need a coax balun for dummies guide. :D

I need a coax balun for dummies guide. :D
That would be at the bottom of this K7MEM page (http://www.k7mem.com/Electronic_Notebook/antennas/yagi_vhf_feed.html). :)

Except you really want to have the three coax ends as close together as feasible, for best results. So don't bother with a fancy case, but rather just tape them together into a tight bundle and then make the (very short) connections as shown by K7MEM.

I'm planning on using rg-6 cable that doesn't have copper shielding, maybe it's aluminum?? I used the calculator on http://www.k7mem.com for channel 11 (199.25) and it's giving me a length of 56.4 cm. Is this number correct for channel 11?
Do I need to make a couple loops and twist-tie them together or can I just have 1 big loop? I'm thinking of trying something similar to image 3 on post #381 http://img300.imageshack.us/img300/3...nchrg5978v.jpg to see if it works. If it does I'll make something more permanent. Would I be able to just twist the shielding together even though it's not copper?
Thanks

I'm using my 4228HD for hi vhf as well as uhf. I am going to try the Winegard TV-2900 baluns. I was going to make a set of coax loop baluns but my understanding is that they are not applicable for wider band usage such as the hi vhf / uhf that I need. Is this correct?


Thanks

The most important thing, I would say is:

To keep the output conductors the same width like 300 ohms twin lead.

Also keep the conductors short, maximum 2 inches.

The coax loop baluns have been found to be suitable across the hi vhf/uhf band (see the baluns thread). I have used them and compared them to commercial baluns and have found them to outperform all of them. However, I have not tried the Winegard baluns and have read here that others have found the TV-2900 to outperform the CM ones. I would be curious to see how the coax baluns stack up against them.

Well, sounds like a balun face off :P I have a set of cm 9444, winegard tv-2900, and it looks like I will make a pair of coax loop baluns. what length is recommended for vhf hi / uhf....?

I've tried coax baluns optimized for channels 22, 33 and 58 and didn't really notice much of a difference. Any differences are probably more related to build quality and slight wire spacing/ length differences (all beyone me!). I used coax baluns optimized for channel 33, which is an unshielded section of 16.9 cm. You can try others and see what works best for you (see mlords link to the K7MEM page for the quick length calculator...

Looking forward to the faceoff results!

I'm planning on using rg-6 cable that doesn't have copper shielding, maybe it's aluminum?? I used the calculator on http://www.k7mem.com for channel 11 (199.25) and it's giving me a length of 56.4 cm. Is this number correct for channel 11?
Do I need to make a couple loops and twist-tie them together or can I just have 1 big loop? I'm thinking of trying something similar to image 3 on post #381 http://img300.imageshack.us/img300/3...nchrg5978v.jpg to see if it works. If it does I'll make something more permanent. Would I be able to just twist the shielding together even though it's not copper?
Thanks
Close....but you should use 201 MHz, the center freq for Ch11.

Coiled Coax is ok at low freqs, as in these 1:1 and 1:4 Baluns for FM (above Ch6):
http://www.ham-radio.com/k6sti/balun.htm

I would solder everything together to ensure reliable connection,
which can be a problem if the RG-6 shield is Aluminum...
And if it's outdoors, prevent moisture seaping into unprotected coax ends,
either a WATER-TIGHT box or NON-CONDUCTIVE sealant....

I too have made several coax baluns and compared them with a variety of commercially available ones, and theory aside, they made NO noticeable difference in signal quality, nor did they help "bring in" stations on the edge of reception...

so maybe im doing them wrong...or maybe they only help in certain VERY specific circumstances...

but I can tell you im not the only member here who hasnt noticed any difference!

Here is a cool write up on balun.
www.ycars.org/presentations/baluns.ppt

Wow - I've tried the voltage balun (thank you, mlord), and it works GREAT. I'm hoping to try out this current balun this weekend. I'm thinking that RamKat's method of gutting out a splitter could be exploited. I have to wonder what the best way of dealing with the shields at the antenna end should be - left floating (probably), or twisted together (???). I also wonder about the "at least 1/4 wavelength" - at 470MHz, that's 42 cm or 16-9/16" - does that mean that 6 or 7 feet is OK ??? I guess trial-and-error is again in my future...

Stupid, Stupid dyslexia - make that 10.5cm or 4-9/64" (RG-59 @ 0.66 VOP) - still question 6 or 7 feet.

I've got some rg62a with copper shield braid and a velocity 0.84. This is close to rg11 foam core VF, but its 93ohm impedance. Would this matter for such short pieces?

I made a coax balun for CH 52. It did not give me great results, about the same as a cheap exterior balun.

I found it a bit hard to connect the coax balun to the front of my CM4228.

I could not connector the leads at 90 degrees on the output terminals.

I will try it one more time.

Maybe, also at CH52, you don't get much advantage using a coax balun ?