Channel Master OTA Gear & Antennas - Page 2 - Canadian TV, Computing and Home Theatre Forums

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post #16 of 655 (permalink) Old 2005-05-11, 08:21 PM
 
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VHF combo antenna?

Do you think it is worth getting a combo VFH/UHF antenna? This is for the GTA. The antenna installer recommended one. A CM4242. But he doesn't have as much experience with UHF OTA HD.

I'd like to ask people "in the know" here. I would get more stations, but analogue feeds aren't optimal for my 51 inch rptv.

The gain on the 4242 is not as good as a UHF only 4228. http://www.hdtvprimer.com/ANTENNAS/comparing.html

I'm leaning against it. My reasons include analogue quality and potential interference with UHF signals. But maybe it is worth it. I don't have any knowledge here. So it is a bit of a guessing game for me.

Please advise.

thx

kw........
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post #17 of 655 (permalink) Old 2005-06-10, 04:08 PM
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OTA Antenna shootout: CM4228 wins again!

This is from a post at HTS, and the included link below provides a lot more detail on the comparison tests of antennas presented at the PBS 2005 Technology Conference.

Quote:
Kerry Cozad's presentation describes actual on-air range measurements for several of the most popular indoor and outdoor antennas for both the VHF and UHF channel frequencies.

For the few antennas tested, the CM-4228 8-Bay Bowtie was the clear winner, not only in the UHF band, but it also provided 8-9 dBd of gain for CH7-13 and 2 dBd of gain for CH2-6.

http://hdtv.forsandiego.com/messages...6319#POST18823
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post #18 of 655 (permalink) Old 2005-06-10, 11:03 PM
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They didn't test it against a 9032 Now that I'd like to see PBS do!
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post #19 of 655 (permalink) Old 2005-06-11, 10:34 AM
 
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That's interesting: it's what I have been saying about the 4228 for the past 34 years! I have no idea why the 4228 is such a successful design, but who wants to argue with success?
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post #20 of 655 (permalink) Old 2005-06-23, 10:35 PM
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Tips on CM4228

Well, I finally got off my butt and pulled my CM4228 out of the basement. I bought a 3 foot tripod and a 10 foot galvanized fence top rail for the mast. Set it up on the ground quickly and scanned for Digital stations and I only got five (CBC and WNED).

Coincidentally, I tuned into CBC in time to see the Nature of Things in HD. WOW!!!!

I have DirecTv HD (dowrezzed and it shows), Dish Network HD and Rogers HD. The OTA on the 8VSB module of the Dishnet 6000 was awesome.

But I digress. I am now willing to risk life and limb to mount my tripod on the top of my two story home. I am concerned about future leaks in the roof and would appreciate any tips on how I can avoid them. Any other tips would also be appreciated.

I am located in northwest Brampton, BTW.
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post #21 of 655 (permalink) Old 2005-06-23, 11:10 PM
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CM4228 modifications for better gain ?

I read this on http://www.hdtvprimer.com/ANTENNAS/cm4228.html that if you were to Replace the feed lines with two baluns and a splitter would probably yield a higher net gain.

Has anybody tried this ?

Is the Baluns just a 300 to 75 ohm impeadance adaptor if so I might try this and see if I get better results ?

As the 4221 4 bay gives better gain than the 4228 over channel 60.

Scroll down to net gain and you can see by chan 70 its a 3 db gain for a smaller antenna ? http://www.hdtvprimer.com/ANTENNAS/comparing.html

CM4228/9521/7775;F.RmJvc70FH96/8300HDPvr/Dish 612;B.Rm LC52LE810UN/8642HD;Study LG50PK550/Xbox360;
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post #22 of 655 (permalink) Old 2005-06-23, 11:41 PM
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Give it a try and see… but I doubt it. A splitter had a 3dB insertion loss. The way the antenna is made with the two arrays ganged up is the right way… but give it a test and see… let us know!
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post #23 of 655 (permalink) Old 2005-06-24, 09:57 AM
 
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Trick to Extend the High-Frequency Response of the 4228

Although it isn't documented in the literature any longer, you can extend the high-frequency response of the 4228 by as much as 6 db at channel 69 if you modify the antenna as follows:
  1. locate the score marks on each tine of each bowtie
  2. cut them at the score marks using a pair of wire dikes.
  3. this is going to to involve a total of 32 cuts: 4 on each bowtie.
The result is a BIG improvement on UHF channels above 60 while giving up some gain at lower frequencies. This proceedure was documented in the product literature years ago, but after the USA phased out broadcasting above channel 69, I guess that Channel Master figured it was unnecessary. Since a number of Canadian cities plan DTV broadcasting above channel 60, and some US cities have DTV channels up that high (Philadelphia, for one), knowing about this modification can definitely help!
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post #24 of 655 (permalink) Old 2005-06-24, 11:48 AM
 
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Quote:
Originally Posted by tigerbangs
Since a number of Canadian cities plan DTV broadcasting above channel 60, and some US cities have DTV channels up that high (Philadelphia, for one), knowing about this modification can definitely help!
Do you remember if the article discussed what happened to the low end roll off after the modifing "cut's" were applied? Particularly where it occurrs? Right now the 4228 is also a good VHF-High antenna which I shouldn't need in Southern Ontario since as far as I know there will be no digital transmitters in range in that band after the transition is complete. Also Fox Buffalo on 14 will revert to 29 at high power in a few years. That means CBC HD on 20 will be my low marker. I could use the extra high end gain right now to get Toronto 1 on 66 and by next summer OMNI and Global should be on 64 & 65 also at very low power. I've been thinking about getting a 4221 just for that reason. If I knew that clipping the bow ties a little would turn my 4228 into a great UHF only antenna I would go that route.
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post #25 of 655 (permalink) Old 2005-06-24, 12:25 PM
 
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Even without the modification I mentioned earlier, the 4228 is STILL the best all-around UHF antenna in the business: I think that you can be pretty sure that you won't have much of a problem getting what you are looking for with or without the modification.
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post #26 of 655 (permalink) Old 2005-06-24, 03:18 PM
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Caveat about High Frequency Trick

Just one note of caution, if it hasn't occurred to you yet:

Please be aware that the first option that Yaamon presented is reversible, meaning that you can put things back the way they were whenever you like (did you write down how things are before you made the changes?).

The second option about trimming the bowties is NOT reversible. Got that? OK.
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post #27 of 655 (permalink) Old 2005-06-24, 03:41 PM
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Quote:
Originally Posted by stampeder
The second option about trimming the bowties is NOT reversible. Got that? OK.
What? No spot welder??
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post #28 of 655 (permalink) Old 2005-06-24, 03:42 PM
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Quote:
Originally Posted by JohnnyG
What? No spot welder??
Are you volunteering to test that out on one of yours?
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post #29 of 655 (permalink) Old 2005-06-28, 06:26 PM
 
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Quote:
Originally Posted by tigerbangs
Although it isn't documented in the literature any longer, you can extend the high-frequency response of the 4228 by as much as 6 db at channel 69 if you modify the antenna as follows:
I went ahead and made the cuts! all 32 of them. As you said each of the elements had a score mark a little over an inch in from the outside so now they are all a little shorter.

I now get 4 bars on channel 66 (Toronto 1) on the samsung 351 where before I got none. My off axis reception of FOX Buffalo on 14 is not as good as before, but fine when I aim the antenna at grand island. I only watch OTA DTV so I have not checked the impact on VHF high.

Now my problem is multipath on 66 making it hard to get a lock on the 351. I'm fairly sure that 66 is not using the CN tower rather a lower height from the top of first canadian place. Is this location permanent?

I get MUCH better results with CITY at lower power from higher up on the CN Tower.

Also does any one have experence with the difference in multipath rejection capabilities between the sammy 351 vs the LG 4200 at the top of the DTS band (60's)? Anyone here in Burlington got a 4200 to trade with a 351 for a few minutes of testing?
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post #30 of 655 (permalink) Old 2005-06-29, 08:24 PM
 
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What is the hook up on the 4228? 300 ohm twin connector or 75 ohm coaxial (f connector)?

I was under the impression that the CM 0264DSB with its 300 ohm twin input and 75 ohm output is matched to the 4228 while output is on coaxial F connector cable. This as opposed to the 7775 which is f connector input and output (ie, an adaptor is needed)

thx

kw.............
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